Short Postings Compilation 2020 PDF

SHORT POSTINGS A Legacy Publication of PROJECT B.I.L. © GOLDMINES IN THIS MATERIAL  A perfectly ordered compilation of all the lecture materials for short post...

SHORT POSTINGS A Legacy Publication of PROJECT B.I.L. © GOLDMINES IN THIS MATERIAL  A perfectly ordered compilation of all the lecture materials for short postings.  [Note that, to conserve space, pictures were removed from most of the materials]  Questions and answers for quick revision after reading each topic; set directly from materials, recommended textbooks, past questions and PLAB study material  Guide for reading up topics before or during postings to any unit in the department of Medicine “In life, you cannot eat your cake and have it back. There is a price for every pleasure and leisure enjoyed. There is a prize for every disciplined sacrifice made. The choice is yours!!!”  SHORT POSTINGS 2020 ABOUT PROJECT B.I.L. Project BIL was founded on 17th June 2018 by Asogwa, Chijioke Peter. It was borne out of his passion for bringing innovation into medical education. According to him, “studying medicine is difficult but it does not have to be.” The founding members of Project BIL were medical students of the University of Nigeria Teaching Hospital, Ituku-Ozalla and Enugu State University Teaching Hospital, Parklane, Enugu State. As is expected, Project BIL comprises of highly talented and brilliant medical students that fundamentally have great passion for making professional medical exams much easier. To do this, they collate questions that appear frequently in MBBS examinations and answer them with succinct explanations. Their first publication was “Medical Microbiology: Done and Dusted,” published in 2018. This publication was specially prepared for those who love to read in soft copy; those who love to read anywhere, anytime, both when it is convenient and when it is not – the truly modern students. For people like this, navigation through this compilation was made to be as easy as ABC. Most importantly, we brought innovation into this publication by painstakingly setting revision questions and answers for each topic in the various courses that come under short postings. These questions were set from materials, recommended textbooks, past questions and PLAB study material (for the sake of those who wish to practise beyond the frontiers of this country).  SHORT POSTINGS 2020 CONTRIBUTORS ASOGWA, Chijioke Peter  Founder & Chairman, Project BIL  Multiple Award-Winning Essayist  Director-General, University of Nigeria Essayists Group (2017 – 2019)  Secretary-General, FECAMDS-UNEC (2018/2019 Session)  600 Level Medicine & Surgery, UNTH  Contact: 09034573318 Email: [email protected] UGWUNEBO, Odera Vanessa  Director-General, Project BIL  Distinction in Pathology  Vice-President, Megaminds [2018 – date]  Academic Coordinator II, FECAMDS-UNEC (2018/2019 Session)  Academic Director II, MEDRHUS-UNTH (2018/2019 Session)  600 Level Medicine & Surgery, UNTH  Contact: 08133484208 ENWELUZOR, Chidimma Henrietta  600 Level Medicine & Surgery, UNTH  Contact: 07060716927  SHORT POSTINGS 2020 AMARAH, Goodneess Iruoma  Vice-President, CMDA-UNEC (2018/2019 Session)  600 Level Medicine & Surgery, UNTH  Contact: 08105581788 MBAJIORGU, Adaeze Cleopatra  School Academic Secretary, CMDA-UNEC (2018/2019 Session)  600 Level Medicine & Surgery, UNTH  Contact: 08164821767 IYOKE, Nkemdilim Chelsea  600 Level Medicine & Surgery, UNTH  Contact: 08050733618  SHORT POSTINGS 2020 AYALOGU, Chidimma Vivian  600 level, Medicine & Surger, UNTH  Contact: 07037545943 OSI-OKEKE, UGOCHUKWU  600 Level Medicine & Surgery, UNTH  Deputy Registrar, MEDRHUS (2017/2018 Session)  Registrar, MEDRHUS (2018/2019 Session)  Contact: 08029288059 MBAEZE, Ogechukwu Anastasia  Treasurer, NFCS-UNEC (2016/2017 Session)  Spiritual Coordinator, FECAMDS- UNEC (2018/2019 Session)  Assistant Coordinator, God’s Delight CCRN-UNEC (2018/2019 Session)  600 level, Medicine & Surgery, UNTH  Contact: 08107394151  SHORT POSTINGS 2020 A Sincere Plea: Firstly, note that this is a project by students and for students. We understand that as the years go by, ways of doing things in this department would change: lecturers would change, new topics could be introduced and some topics could be removed. For this, we ask for new members who would carry on with this project. These new members would carry out the work of modifying the publications of Project BIL, for the benefit of their colleagues and that of future generations to come. The only requirement for joining Project BIL is an intense desire to bring innovation into medical education. Should you feel a desire to be a part of this project, please feel free to contact any of the contributors. Most importantly In this compilation, you would discover that some topics have no materials or questions and answers. As you go for lectures and study your books, determine to fill up these lacunae. The ultimate goal is to keep this project ongoing for as many generations of students that would pass through this college. Moreover, an innovative and business-minded person could one day decide to convert this compilation to an app that other universities could use. Finally, should you discover error(s) in this compilation, please do well to reach out to any of the contributors for correction.  SHORT POSTINGS 2020 HOW TO USE THIS MATERIAL EFFECTIVELY Many times, we read materials casually and drop them with an assumption that we understood everything we had read. However, most times when we try recalling, it dawns on us that we can barely recall so much of what we had read. This publication aims to fill this void. With this publication, you are able to revise questions immediately after reading the topics. Click on each topic to read the material for that topic. Alternatively, you could decide to jump to the questions and answers if what you want is a quick revision, either days or hours before an examination. Nevertheless, note that this publication would be most useful only to those who attend lectures, read recommended textbooks, go for Ward Rounds and participate in study groups as well. Happy reading!!! If you don’t feed your mind everyday with success, it will gradually rot with mediocrity!!!  SHORT POSTINGS 2020 LECTURES  Click on Each Unit to Go to its Section or  Click on Each Topic to Go to its Material, Revision Questions & Answers UNITS TOPICS LECTURERS 1 Introduction to anaesthesia / History 2 Stages of anaesthesia 3 Preparation for anaesthesia: Preoperative assessment 4 Premedication & premedicants 5 Induction of anaesthesia: ANAESTHESIOLO Induction agents – intravenous, inhalational, intramuscular GY 6 Muscle relaxants and reversal agents 7 Monitoring in anesthesia: Preoperative, intraoperative, post-operative 8 Anaesthetic equipment – Anaesthetic machines; flow meters; vaporisers; laryngoscopes; endotracheal  SHORT POSTINGS 2020 tubes; gas cylinders 9 Anaesthetic circuit 10 Airway maintenance 11 Basic principles of management i. Full stomach ii. Neonates/Infants iii. Obstetric surgery iv. Thoracic surgery v. Neurosurgery vi. Maxillofacial/ENT 12 Local anaesthetics/anaesthesia 13 Intravenous fluid therapy/Blood transfusion 14 Cardio-pulmonary resuscitation 15 Pain management 16 Introduction to palliative care 1 Introduction to dermatology: Prof. Ozoh Anatomical structure and G. A. O. DERMATOLOGY physiological functions of the skin, history taking, diagnosis and diagnostic tests 2 Fundamentals of dermatologic Dr.  SHORT POSTINGS 2020 therapy: Treatment of skin Onyekonwu disorders, topical and systemic C. L. preparations, surgical therapy 3* Infective skin disorders I: Viral Dr. and parasitic skin infections Onyekonwu 4 Eczemas and dermatitis, Dr. Immunobullous Onyekonwu disorders/diseases of disordered C. L. immunity 5 Papulosquamous skin diseases; Prof. Ozoh Pigmentary skin disorders and G. A. O. disorders of the pilosebaceous glands/cutaneous appendages 6 Cutaneous manifestation of Dr. Ojinmah systemic diseases U. R. 7 Infective disorders 2: Bacterial Dr. Ojinmah and fungal skin infections U. R. 8 Sexually transmitted infections Prof. Ozoh and syndromic management G. A. O. 9 Cutaneous manifestations of Dr. HIV Onyekonwu C. L. 10 Leprosy Dr. Ojinmah  SHORT POSTINGS 2020 U. R. 1 Definition of core concepts in FAMILY family medicine MEDICINE 2 History of family medicine 3 The family physician 4 Family medicine tools 5 Patient-centered clinical methods (PCCM) 6 Biopsychosocial model 7 The Functional and Dysfunctional Family 8 Breaking bad news 9 Referral 10 Integrative medicine 11 NHIS and its operations in different levels of care OPHTHALMOLOG 1 Basic anatomy of the eye and Dr. Obi Y ocular adnexa Okoye 2 History-taking and basic eye Dr. N. examination Nwachukwu  SHORT POSTINGS 2020 3 Cataract Dr. N. Oguego 4 Orbital cellulitis, preseptal Dr. G. cellulitis, chlazion, capillary Onyekonwu haemangioma 5 Introduction to community eye Prof. U. F. health Ezepue 6 Blindness and visual Dr. Onochie impairment: Definition and Okoye common causes 7 Refractive errors, Presbyopia Dr. S. Onwubiko 8 Conjunctivitis including Dr. N. Udeh ophthalmia neonatorum; Differential diagnosis of leucoria 9 The Red eye Dr. F. Maduka- Okafor 10 Glaucoma Prof. C. Chuka- Okosa 11 Ocular trauma Prof. I.  SHORT POSTINGS 2020 Ezegwui 12 Common tropical eye diseases Prof. E. Onwasigwe 13 Systemic diseases and the eye Prof. B. Eze 14 Uveitis, Endophthalmitis Dr. N. Uche 1 Introduction and orientation to Prof. B. C. clinical posting in ENT: Your Ezeanolue curriculum 2 Anatomy and physiology of the Dr. I. J. ear Okorafor 3 Anatomy and physiology of the Dr. Ethel nose and paranasal sinuses Chime 4 Anatomy and physiology of the Dr. James ENT larynx and pharynx Akpeh 5 Techniques of clinical Dr. F. T. Orji examination in ENT 6 Ear infections Dr. I. J. Okorafor 7 Hearing loss Prof. B. C. Ezeanolue 8 Allergy in ENT Dr. Ethel  SHORT POSTINGS 2020 Chime 9 Epistaxis Dr. James Akpeh 10 Emergencies in ENT: An Dr. J. N. overview Nwosu 11 Carcinoma of the larynx Dr. James Akpeh 12 Foreign body impactions in Dr. J. N. ENT Nwosu 13 Inflammatory disease of nose Dr. James and paranasal sinuses Akpeh 14 Congenital malformations in Dr. Ethel ENT Chime 15 Vertigo and dizziness Prof. B. C. Ezeanolue 16 Common neoplasms in ENT Dr. F. T. Orji 17 The obstructed upper airway Dr. J. N. and tracheostomy Nwosu 18 Adenoid and tonsillar disorders Dr. F. T. Orji 19 Diseases of salivary gland Dr. I. J. Okorafor  SHORT POSTINGS 2020 20 Primary and community Prof. B. C. otorhinolaryngology; head and Ezeanolue neck surgery (concepts, principles and practices) PSYCHIATRY 1 Schizophrenia 2 Bipolar disorders I & II 3 Unipolar depression/major depressive disorder 4 Anxiety disorders: Generalised anxiety disorder, panic disorder, dissociative disorders 5 Psychopharmacology: Antipsychotics and anti-anxiety, Antidepressants and Mood stabilisers 6 Geriatric psychiatry/Organic mental disorders 7 Substance use disorders 8 Forensic psychiatry 9 Child and adolescent psychiatric disorders 10 Child abuse & neglect  SHORT POSTINGS 2020 11 Somatic symptoms disorder/Bodily distress disorder 12 Psychosocial methods of treatment 13 Personality disorders 14 Psychiatric emergencies: Suicidal behaviour RADIATION 1 Introduction to principles of MEDICINE radiological techniques and contrast media 2 Principles of radiation biology and radiation protection 3 Chest radiology I (Radiological anatomy and technique) 4 Chest radiology II (Common chest pathologies) 5 Gynaecological and obstetric radiology 6 Cardiovascular radiology 7 Neuroradiology 8 Musculoskeletal radiology 9 Breast imaging  SHORT POSTINGS 2020 10 GIT radiology I (GIT Anatomy/Technique and Acute abdomen) 11 GIT radiology II (Common pathologies of GIT & Abdominal viscera) 12 Urogenital radiology 13 Principles of radiation oncology  SHORT POSTINGS 2020 ANAESTHESIOLOGY  Click on each topic to navigate to the material and/or the revision questions and answers TOPICS 1 Introduction to anaesthesia / History 2 Stages of anaesthesia 3 Preparation for anaesthesia: Preoperative assessment 4 Premedication & premedicants 5 Induction of anaesthesia: Induction agents – intravenous, inhalational, intramuscular 6 Muscle relaxants and reversal agents 7 Monitoring in anesthesia: Preoperative, intraoperative, post- operative 8 Anaesthetic equipment – Anaesthetic machines; flow meters; vaporisers; laryngoscopes; endotracheal tubes; gas cylinders 9 Anaesthetic circuit 10 Airway maintenance 11 Basic principles of management vii. Full stomach viii. Neonates/Infants ix. Obstetric surgery x. Thoracic surgery  SHORT POSTINGS 2020 xi. Neurosurgery xii. Maxillofacial/ENT 12 Local anaesthetics/anaesthesia 13 Intravenous fluid therapy/Blood transfusion  SHORT POSTINGS 2020 HISTORY OF ANAESTHESIOLOGY Dr. Ajuzieogu V, O. Why study the History of Anaesthesia? An understanding of our past guides our future The history of surgery is inextricably linked to the development of appropriate anaesthetic techniques and so the history of surgery follows the history of anaesthesia. History of Anaesthesia Pre-1846 - the foundations of anaesthesia 1846 - 1900 - establishment of anaesthesia 20th Century - consolidation and growth 21st Century - the future Pre-1846: The Foundations of Anaesthesia ……..so the Lord God caused him to fall into a deep sleep. While the man was sleeping, the Lord God took out one of his ribs. He closed up the opening that was in his side……... Genesis 2:21 NIrV Drug methods Alcohol Opium (poppy) Hyoscine (Mandrake) Cannabis (Hemp) Cocaine (New World) Non-drug methods  SHORT POSTINGS 2020 Cold Concussion Carotid compression Nerve compression Hypnosis Blood letting Status of surgery Barber shop surgeons Types of surgery Amputations & dental extractions No antisepsis Appalling mortality Indications Unbearable pain Crippling deformity Imminent death DARK AGES Surgery was a terrifying last resort in a final attempt to save life. Few operations were possible.  SHORT POSTINGS 2020 Surface surgery, amputation, fungating cancers and ‘cutting for stone’ (the removal of bladder stones) were really the only areas in which the surgeon could practice The inside of the abdomen, chest and skull were essentially ‘no go’ areas. Speed was the only determinant of a successful surgeon. Most patients were held or strapped down - some would mercifully faint from their agony - many died either on the table or immediately post-surgery. The suffering was intense. Liston, an eminent surgeon, was once operating for a bladder stone. The panic stricken patient finally broke loose from the brawny assistants, ran out of the room, down the hall and locked himself in the lavatory. Liston, hot on his heels and a determined man, broke down the door and carried the screaming patient back to complete the operative procedure (Rapier HR. Man against Pain London 1947;49). the case was an interesting one of a white swelling, for which the thigh was to be amputated. The patient was a youth of about fifteen, pale, thin but calm and firm. One professor felt for the femoral artery, had the leg held up for a few moments to ensure the saving of blood, the compress part of the tourniquet was placed upon the artery and the leg held up by an assistant. The white swelling was fearful, frightful. A little wine was given to the lad; he was pale but resolute; his Father supported his head and left hand. A second professor took the long, glittering knife, felt for the bone, thrust the knife carefully but rapidly. The boy screamed terribly; the tears went down the Father’s cheeks. The first cut from the inside was completed, and the bloody blade of the knife issued from the  SHORT POSTINGS 2020 quivering wound, the blood flowed by the pint, the sight was sickening; the screams terrific; the operator calm….” Contemporary description of surgery, 1841 WHAT CHANGED 1540: synthesis of ether 1628: circulation of blood 1709: iron formed 1712: first steam engine 1733: flying shuttle 1744: ether inhalation suggested to treat pain (1745: Battle of Culloden) 1769: water frame 1769: Watt steam engine 1770’s: research on CO2 1771: discovery of O2 1771: cotton mills 1772: “Mesmerism” 1773: discovery of N2O 1779: first iron bridge (1789: French Revolution) 1794: gas therapy in illness 1801: first steam carriage  SHORT POSTINGS 2020 INDUSTRIAL AND SCIENTIFIC REVOLUTION Late 1700’s lots of new gases identified attempts to apply gas knowledge to medicine directed at treatment of existing diseases rather than novel use Gases of importance nitrous oxide ether carbon dioxide oxygen Pneumatic Institute, Dowry Square, Clifton, Bristol founded by Thomas Beddoes (1760-1808) in 1794 with equipment designed by James Watt (1736-1819) attempted to use used gas therapy (incl. oxygen, nitrous oxide & ether) to treat diseases incl. asthma, & venereal disease New medical institution. Upper end of Dowry-Square, Hotwells, corner house. Treating incurable diseases. Medical professors at Edinburgh. Many Physicians in England. Asthma, Palsy, obstinate Venereal Complaints. Other incurable diseases. Patients treated gratis. Expectation: Considerable portion of cases will be permanently cured. Methods are not hazardous or painful. Attendance will be given from 11 till 1 o'clock by Thomas Beddoes or Humphrey Davy. Subscriptions for support of Institution received by John Savery, Esq., Narrow Wine Street, Bristol. Bristol Gazette March 21 1799  SHORT POSTINGS 2020 Humphrey Davy (1778-1829) became Superintendant in 1798 continued Priestley’s and Beddoe’s Work Nitrous oxide & Ether Humphrey Davy & the Pneumatic Institute Recognised analgesic properties of N2O and christened it “laughing gas” first tentatively suggested a use during surgery “…as nitrous oxide in its extensive operation appear capable of destroying physical pain it may be used with advantage during surgical operations in which no great effusion of blood takes place …”. Gas Therapy in Illness Nitrous Oxide  SHORT POSTINGS 2020 1800: Davy’s thesis 1834: Colton “anaesthetised” 6 Red Indians by mistake 1844: Horace Wells had his own tooth pulled under N2O - “a new era in tooth pulling” 1845: Wells “failed” to demonstrate N2O at MGH 1540: synthesised and named “sweet oil of vitriol” by Valerius Cordus renamed “ether” by Frobenius 1744: Matthew Turner published essay suggesting its inhalation in certain types of pain late 1790’s: research at Pneumatic Institute Eher 1818: Michael Faraday (1791-1867) described “narcotic effects” of ether 1821: Benjamin Brodie (1783-1862) demonstrated to Royal College of Surgeons that ether inhalation could induce insensibility in a guinea pig -“ ….ether acted like a narcotic poison……” 1842: first use as clinical anaesthetic in USA  SHORT POSTINGS 2020 16th October 1846: first public demonstration of ether anaesthesia in Boston, Mass. FATHER OF ANAESTHESIA William T G Morton “Inventor and Revealer of Inhalational Anaesthesia: Before Whom, in All Time, Surgery was Agony; By Whom, Pain in Surgery was Averted and Annulled; Since Whom, Science has Control of Pain.” Why did Davy not pursue his work? no real concept of “anaesthesia” in late 1700’s / early 1800’s, how can you achieve a state which you assume impossible or cannot envisage achieving. Pneumatic Institute concerned with treatment of disease by “Physicians” - surgery did not have same standing and therefore influence. State of surgery - almost inevitably fatal - why encourage them?  SHORT POSTINGS 2020 Henry Hill Hickman and carbon dioxide Born at Lady Halton, Bromfield, Shropshire matriculated at Edinburgh University 1819, attended lecture “On Asphyxia” by Henry Goldwyer - “a temporary suspension of the vital functions arising from a deficiency of atmospheric air.” and described reversal using artificial respiration & electrical restarting of heart admitted as member of RCS London 1820 set up practice in Ludlow, Shropshire. But before leaving this era we have to consider the work of Henry Hill Hickman, the one man who came closest to creating what we would recognise as Anaesthesia in the early 1800’s. 1821-1824: series of experiments on small animals to induce “suspended animation” semi-asphyxiation due to air starvation or by  SHORT POSTINGS 2020 breathing Carbonic Acid (CO2) gas after unconsciousness was induced Hickman operated on them - amputations, removal of ears, skin incisions - and observed responses to surgery, evidence of pain, amount of bleeding and time to recovery 1824: attempted to bring work to notice of Royal Society “……there is not an individual who does not shudder at the idea of an operation however skillful the Surgeon or urgent the case, knowing the great pain that the patient must endure, and I have frequently lamented, when performing my own duties as a Surgeon, that something has not been thought of whereby the may be tranquillised and suffering relieved …..I have been induced to make experiments on Animals, endeavouring to ascertain the practicability of such treatment on the human subject……I have witnessed results which show that it may be applied to the animal world , and ultimately I think will be used with perfect safety and success in Surgical operations…..I have never known of a case of a person dying after inhaling Carbonic Acid gas if proper means were taken to restore the animal powers …..” As a country doctor, Hickman was well aware from personal experience of the appalling suffering which inevitably accompanied surgery Attempted to bring his work to the attention of the Royal Society by writing a letter to T A Knight of Downtown Castle. This local Squire was a Fellow of the Royal Society of which Davy was now the President and it was well known that Davy often visited Knight to go fishing. 1824: moved to Shifnal  SHORT POSTINGS 2020 1824: “A Letter on Suspended Animation” (W Smith, Ironbridge, 1824) to TA Knight of Downton Castle 1825: having failed to attract attention of Knight, Davy and Royal Society wrote to Shrewsbury Chronicle (dated 3rd June) Anonymous writer (“Antiquack”) responded to “Letter on Suspended Animation” and Shrewsbury Chronicle article in The Lancet 1825 “…can he for a moment suppose that any medical man of sense and judgement will be so far led away by a proposal so utterly at variance with all he has ever heard, saw, or read, of the deleterious effects of respiring the fixed air to believe that that this letter was published with any intention of benefiting mankind... intended to serve as a decoy by which credulous may be induced to give up their senses as well their cash to men…”  SHORT POSTINGS 2020 “…an open and downright quack is superior to a plausible quacking physician… “ “…I sincerely hope, and believe, for the credit of the profession, be utterly impossible to find any surgeon so great a fool, and so unwarrantably bold as to undertake that operation on such terms..” “…I do fervently hope that the letter itself may be a complete hoax, and not written by Dr Hickman; for, in this age of science and gentlemanly acquirement, I feel assured, that no man who has any claim to the honourable appellation of a Doctor of Physic would so far disgrace both his profession and himself by writing such a tissue of quackery, which he himself, and every medical man must know is (to say the least) humbug” signed Antiquack, The Lancet 1825 1828: appeal to Charles X of France - referral to Royal Academy of Medicine in Paris 1829: returned to practice in Tenbury Wells, Shropshire 1830: died; buried in Bromyard churchyard 1847: letters in Lancet by Thomas Dudley of Kingswinford identifying Hickman’s work with reports of “the Letheon” 1912: first modern reference to Hickman Thompson CJS. Brit Med Jour 1912 ; i: 843-845 1930: plaque erected by Section of Anaesthetists of RSM 1846-1900: The Establishment of Anaesthesia General Anaesthesia - Ether : spread to Europe  SHORT POSTINGS 2020 - Nitrous oxide - Chloroform : James Young Simpson, John Snow Local Anaesthesia anaesthesia without sleep - New techniques - early landmarks 16th October 1846: first public demonstration of ether anaesthesia in Boston, Mass. “Gentlemen this is no humbug. We have seen something today that will go round the world” Morton gained the support of many of Boston’s most influential medical men including Warren himself, Henry Jacob Bigelow (became a very famous surgeon) and Oliver Wendell Holmes, Professor of Anatomy and Physiology at Harvard and who later coined the word “Anaesthesia”. Henry Bigelow went on to lecture widely on ether anaesthesia and it was his father Jacob Bigelow (Professor of Materia Medica at Harvard), who sent news of ether to Francis Boott in England (Bigelow Snr and Boott knew each other well as they were both keen botanists). Bigelow Snr sent his letter on 28th November enclosing a letter detailing Morton’s discovery, and described a dental extraction performed on his daughter while under the influence of ether. He also enclosed a copy of the Boston Daly Advertiser of 19th November 1846 containing an article written by his son, Henry. ETHER: THE NEWS SPREADS  SHORT POSTINGS 2020 Letter and other papers from Jacob Bigelow (description of his daughter’s surgery under ether and relevant copy of Boston Daily Adveriser) sent to Francis Boott in London News carried by Cunard paddle steamer “Acadia” leaving Boston 3rd Dec 1846 and arriving Liverpool 16th Dec 1846 17th Dec 1846: Boott received letter and arranged with dentist James Robinson to experiment with ether inhalation 19th Dec 1846: ether administered by James Robinson to a Miss Lonsdale for molar extraction at Boott’s home 21st Dec 1846: Robert Liston, Professor of Surgery at University of London publicly amputated the leg of Frederick Churchill at UCH - “This Yankee dodge beats mesmerism hollow” There is evidence that news of ether anaesthesia had already reached the UK via other means beore Boott received his letter but no-one had chosen to follow it up. Anaesthesia appeared in the UK over a few days at the end of 1846. However, it took much longer for it to become fully established within clinical practice. Its flammable properties were well known and it must have been a challenge using it by candle-light in the short Winter days of 1846/47. Indeed, such was the learning curve for those tried to administer it that many surgeons faced with inadequately anaesthetised patients preferred to continue to work without anaesthesia. Indeed, many went back to working without anaesthesia. Robert Liston tirelessly continued to push the cause of anaesthesia, using it for his surgery and lectured extensively on it. ETHER: THE DUMFRIES CONNECTION William Fraser: Cunard Ship’s surgeon  SHORT POSTINGS 2020 19th December 1946: 1st European use of Ether anaesthesia What case? probably an amputation of a leg in a patient run over by a cart - patient died Some authorities do not believe the Dumfries case actually happened - not even reported locally until sometime later William Fraser - Cunard ship’s doctor - from Dumfries - father was apothecary there and so WF known to Messers Scott and McLaughlin, the surgeons at DRI WF on Arcadia got to hear news from America? Boston Advertiser? Bigelow’s letter and on disembarkation in Liverpool on 16th December headed for his home town. Obviously convinced the surgeons it was worth a try and when a suitable case came in ……... 1847: arrival of Ether Anaesthesia announced in first edition of “The Lancet” of 1847 Letter from Francis Boott Letter to Boott from Henry Bigelow Paper from Boston Medical and Surgical Journal Robert Liston’s own experiences 1847 - following first report there were a number of letters / papers over the ensuing months detailing new uses / experiences of anaesthetic ether. This culminated in attempts by Morton to patent ether anaesthesia under the name “Letheon” - considerable discussion / debate amongst Morton, Jackson, Boott and Bigelow  SHORT POSTINGS 2020 1847: Liston became an increasingly important supporter of ether in the following months at a time when many surgeons tried, then abandoned its use returning to practice without anaesthesia Reasons for possible abandonment attempts to “patent” anaesthesia and so limit its use inadequate anaesthesia excessive secretions vomiting patients risk of explosion and fire (candlelight!) perceived “risks” of rendering patient unconscious for surgery 1847: Horace Wells published paper “A History of the Discovery of the Application of Nitrous Oxide Gas, Ether and Other Vapours to Surgical Operations” 1863: Colton “reintroduced” N2O, primarily for dental surgery 1865: N2O cylinders available in London 1881 pain relief in labour 1887 Hewitt “gas and oxygen machine” Horace Wells gave up dentistry, became a chloroform addict and toured the world with a bunch of performing canaries. Imprisoned for pouring sulphuric acid over a prostitute while recovering from self-administered chloroform and killed himself aged 33 by cutting his femoral artery Paper of 1847 an attempt to identify himself as inventor of anaesthesia  SHORT POSTINGS 2020 CHLOROFORM 1831: Chloroform synthesised 1833: Cynthia Guthrie accidentally anaesthetised herself! 1847: Anaesthetic properties recognised 1847: First clinical use, St Barts, London 1847: James Young Simpson used chloroform for obstetric anaesthesia First use of Chloroform as “Chloric Ether” was at St Barts in Spring 1847 JYS didn’t use it until 6/12 later. Experimented with his friends, then used it clinically JAMES YOUNG SIMPSON Professor of Midwifery in Edinburgh from 1840 Tried chloroform on himself and friends at suggestion of David Waldie, a chemist Secured and popularised chloroform as clinical anaesthetic, esp. in Obstetrics many objections to analgesia for childbirth; religious and moral Genesis 3:16 - “…. The Lord God said to the woman, I will greatly increase your pain when you give birth. You will be in pain when you have children. You will long for your husband. And he will rule over you…….” 1847: John Snow’s regulating inhaler 1847/48: Chloroform eclipses ether  SHORT POSTINGS 2020 1848: Hannah Greener - first anaesthetic death 1858: John Snow “On Chloroform and other anaesthetics” - Born in York in 1813 - became interested in anaesthesia via work in toxicology - apprenticed in Newcastle, then worked in London 1836-1858 until his death - acknowledged as “first full-time” anaesthetist developing ways to improve methods of ether and chloroform administration “Chloroform a la Reine” Prince Leopold: born 7th April 1853 Princess Beatrice: born 14th April 1857 helped to overcome religious and moral objections to analgesia for childbirth “…. administered Chloroform to the Queen in her confinement…. Dr. Locock was sent for about nine o'clock this morning, stronger pains having commenced, and he found the os uteri had commenced to dilate a very little. I received a note from Sir James Clark a little after ten asking me to go to the Palace. I remained in an apartment near that of the Queen……………. At a twenty minutes past twelve by a clock in the Queen's apartment I commenced to give a little chloroform with each pain, by pouring about 15 minims by measure on a folded handkerchief……. Her Majesty expressed great relief from the application, the pains being very trifling during the uterine contractions, and whilst between the periods of contraction there was complete ease. The effect of the chloroform was not at any time carried to the extent of quite removing consciousness. Dr. Locock thought that the chloroform prolonged the intervals between the pains, and retarded the labour somewhat. The infant was born at 13 minutes past  SHORT POSTINGS 2020 one………..consequently the chloroform was inhaled for 53 minutes. The placenta was expelled in a very few minutes, and the Queen appeared very cheerful and well, expressing herself much gratified with the effect of the chloroform…” John Snow Thurs 7th April 1853 John Snow’s description of his part in the birth of Prince Leopold in 1853 Original diary entry handwriting far better than rest of diary - obviously took especial care March 2003 - John Snow voted “greatest doctor of all time” LOCAL ANAESTHESIA IN THE 19TH CENTURY 1884: Cocaine 1885: Spinal analgesia for pain relief - Corning 1890: Oil of cloves (Eugenol) 1891: Tropocaine 1892: Infiltration LA 1898: Spinal anaesthesia for surgery – Bier The introduction of anaesthesia changed all of this. Surgery could slow down - become more accurate and could move into ‘forbidden areas’ of abdomen, chest and brain. The evolution of surgical practice has been dependent on anaesthesia and the concomitant introduction of antisepsis through Lister’s carbolic spray. FROM CHLOROFORM Once ether was used then further inhalational agents were introduced.  SHORT POSTINGS 2020 Chloroform was introduced by the Professor of Obstetrics in Edinburgh, James Simpson, in November 1847. This was a more potent agent but it had more severe side effects. It could precipitate sudden death, particularly in very anxious patients (the first of these incidents happened in early 1848) cocaine - in 1877. Then came local infiltration, nerve blocks then spinal and epidural anaesthesia, which in the 1900s allowed surgery in a relaxed abdomen without the huge ‘depth’ of anaesthesia required by ether and chloroform. Newer, less toxic, local anaesthetic agents were introduced in the early 1900s. The next important innovation was the control of the airways with the use of tubes placed into the trachea. This permitted control of breathing introduced in the 1910s were perfected in the late 1920s and early 1930s. 1865: Lister introduced “Carbolic spray” - antisepsis 1878: first oral ETT - flexible brass, 0.95cm diam 1891: first partial pneumonectomy; no ETT 1894: first anaesthetic charts THE 20TH CENTURY: Consolidation and Growth Whereas in the late 18th / early 19th centuries the Industrial Revolution and sociological change triggered the events which led to the  SHORT POSTINGS 2020 development of Anaesthesia, in the 20th Century increasing prosperity, better medical treatment, increased expectations, transport and modern warfare culminating in two World Wars has driven both the science and speciality of anaesthesia to new heights Intubation and airway advances Anaesthetic equipment Monitoring Drug advances Local anaesthetic advances Speciality advances - ITU & pain General progression of speciality INTUBATION AND AIRWAY DEVICES 1919: Endotracheal intubation (Magill & Rowbotham), Queens Hospital, Sidcup 1928: Blind nasal intubation 1931: first double-lumen tube (Gale & Waters) 1949: Carlens double-lumen tube 1950’s PVC tubes introduced 1980’s PVC finally replaces Red Rubber tubes. Rae (Ring, Adair & Elwyn) tubes & LMA’s introduced McEwan metallic tube described 1978 MONITORING 1901: BP’s recorded on Mass Gen Hosp Anaes chart  SHORT POSTINGS 2020 1911: McKesson added Resp rate & insp O2 concentration to charts (SpO2 described 1913) 1946: paramagnetic O2 analysers 1949: first nerve stimulator 1956: blood-gas monitoring 1960’s: ECG monitoring and capnography 1960’s: CVP and arterial monitoring 1970: “Swan-Ganz” catheter 1980’s/90’s: increasing use of microprocessor-controlled monitoring equipment 1990’s: explosion of new monitoring modalities CO monitoring - CardioQ / PICCO / LidCO SvO2 monitoring pHi monitoring Experimental depth of anaesthesia monitors Perioperative Transoesophageal echocardiography DRUG ADVANCES 1911: Self admin N2O in labour 1911: “Balanced anaesthesia” (Crile) 1934: Cyclopropane, Thiopentone 1934: Minnnitt “gas-air” mix in labour 1941: Trilene  SHORT POSTINGS 2020 1942: Curare 1951: Suxamethonium 1956: Halothane 1964: Introduction of Entonox 1980’s: “New generation” ethers - Enflurane & Isoflurane Opioids - Fentanyl, Alfentanil, (Sufentanil) New methods of analgesia Relaxants - Atracurium / Vecuronium Propofol 1990’s: TCI anaesthesia Opioids - Remifentanil Volatile agents - Sevoflurane & Desflurane Relaxants - CisAtracurium / Mivacurium / Rocuronium By the 1980’s ether was available n a named patient basis only 1904: Stovaine 1929: Cinchocaine 1931: Amethocaine 1943: Lignocaine 1952: Chlorprocaine 1959: Prilocaine 1963: Bupivacaine 1993: Ropivacaine  SHORT POSTINGS 2020 late 1990’s: Levobupivacaine 1907: use of “heavy” spinal solutions - Barker 1908: IVRA - Bier 1909: Sacral block - Stoekel 1921: barbotage and positioning in spinal anaesthesia – Labat 1921: lumbar epidural anaesthesia - Pages 1949: ureteric catheter inserted via Tuohy needle - Curbelo 1979: opioids injected into epidural space 1980’s: eutetic LA mixtures - Lignocaine / Prilocaine (EMLA) for topical use ANAESTHESIA AND INTENSIVE CARE 1929: tank ventilator 1934: ventilation for tetanus 1938: development of Nuffield plywood “iron lung” 1953: IPPR for bulbar poliomyelitis in Denmark (Ibsen) - hand ventilation via tracheostomy PAIN MANAGEMENT C20th: LA techniques 1960: Rudimentary self-controlled analgesia systems in Obstetrics 1967: first Patient-controlled analgesia system 1991: RCA report on Post-op pain - changes course of post-op pain management  SHORT POSTINGS 2020 1990’s: development of Acute Pain Teams and multimodal analgesic strategies incl PCA / Epidural / PC Epidural / combination Rx 1953: Liverpool Centre for Pain relief - cordotomies - acupuncture Anaesthetists involvement in multi-disciplinary chronic team units - Liverpool, Hope (Salford), Norwich, Oxford 21ST CENTURY: THE FUTURE Crystal ball new and better drugs - “anaesthesia” perhaps not priority it was - NDMR version of Suxamethonium - analgesia and PONV more TCI “closing the loop” techniques new airway management techniques new monitoring - anaesthetic depth Staffing and workload issues - increased demand for “anaesthetic services” - questioning of roles outside theatre - questioning of roles within theatre - development of non-medical anaesthetist - pilot sites up and running - how best to integrate with “medical anaesthesia”  SHORT POSTINGS 2020 who to recruit - nurse-based - postgraduate science-based - other background - already raising a number of other training & service issues The future of Anaesthesia is assured - but we may see our roles and how we practice it change INTRAVENOUS AGENTS These were barbiturates which enabled the patient to go off to sleep quickly, smoothly and pleasantly and therefore avoided any unpleasant inhalational agents. Then in the 1940s and early 1950s, there came the introduction of muscle relaxants, firstly with curare (the South American Indian poison!) over subsequent decades a whole series of other agents. Curare in the form of tubocurarine was first used in clinical anaesthesia in Montreal in 1943 by Dr Harold Griffith, first used in the UK in 1946 by Professor Gray in Liverpool. INHALATIONAL AGENTS In the mid-1950s came halothane, a revolutionary inhalational agent, which was much easier to use. PROGRESS All of these groups of drugs have since been refined so there is now much more potent less toxic intravenous agents, inhalational agents, local anaesthetics and muscle relaxants.  SHORT POSTINGS 2020 Anaesthetists are now highly trained physicians who provide a whole range of care for patients - not just in the operating theatre. preoperative period to optimise the patients’ condition High Dependency and Intensive Care Units. obstetric analgesia and anaesthesia, emergency medicine in A&E resuscitation, major accident care, acute and chronic pain management patient transfers between hospitals. Anaesthesia is now very safe, with mortality of less than 1 in 250,000 directly related to anaesthesia in most high income countries. Nevertheless, the anaesthetic profession will continue to strive for improvement over the next years. Revision Questions 1 the pneumatic institute, dowry square, Clifton, Bristol was founded by A Thomas Beddoes 1794 B Thomas hagin 1748 C frank demnn0 1722 D loius frendi 1888 2 who recognized the analgesic property of N2O and named it the laughing gas A Thomas Beddoes  SHORT POSTINGS 2020 B Humphrey Davey C frank demno D loius frendi 3 another name for sweet oil of vitriol is A ether B N20 C Co2 D carbon oxide 4 who described the narcotic effects of ether A Michael faraday B Julius ceaser C campman rotengen D benjamine brochie 5 the first clinical anesthetic us of ether was in A France 1972 B china 1928 C USA 1842 D Egypt 1936 6 Who is the father of anesthesia A William TG Morton B Michael faraday C Benjamin brochie D Julius ceaser 7 when was the first public demonstration of ether anesthesia used A 16th oct 1846  SHORT POSTINGS 2020 B 16th oct 1847 C 16th oct 1848 D 16th oct 1849 8 Who coined the word anesthesia A Oliver Wendell Holmes B William TG Morton C Henry Jacob bigelow D Benjamin brochie 9 who secured and popularized chloroform as a clinical anesthetic especially in obstetrics A James young Simpson B Oliver Wendell Holmes C William TG Morton D Benjamin brohie 10 who was the first full time anesthetist A john snow B William TG Morton C henry Jacob bigelow D Benjamin brochie Answers 1. A 2. B 3. A 4. A 5. C 6. A 7. A  SHORT POSTINGS 2020 8. A 9. A 10. A Back to main outline ↑↑ Back to Anaesthesiology outline ↑↑  SHORT POSTINGS 2020 STAGES OF ANAESTHESIA H. A. Ezike Anaesthesia: A Scientific Phenomena Has empirically determined stages Reproducible Does not vary from patient to patient AS A CLINICAL PHENOMENA Conduct of Anaesthesia has specific stages which if adhered to, results in favourable outcome. EMPERICALLY DETERMINED CASES Stages Respiration Pupils Eye Reflex URT & Resp Reflex 1 Regular Normal ………… ………… Analgesia Small volume 2 Shallow/deep Large Eyelash ………. Excitement Irregular irregular Absent 3 Regular Small Eyelids absent Pharyngeal and Plane I Large volume conjuctiva vomiting center depressed depressed 3 …………. Normal Corneal …………… Plane II size depressed 3 Regular small Little > ……………. Laryngeal Plane III vol diaphragm normal Depressed 3 Irregular small Size 3 …………….. Carina  SHORT POSTINGS 2020 Plane IV vol diaphragm large Depressed 4 Apnea Fully …………… ………….. dilated Clinical Stages of Anaesthesia Preoperative Assessment: Rapport with patient – History taking, physical examination, clinical investigation. Premedication –, Anti-cholinergics: - Atropine, Glycopyrrolate Anxiolytics: - Benzodiazepines, Minor tranquilizers: - Phenothiazines, Major tranquilizers: -Butyrophnones, Phenothizines Sedative/hypnotics: - Barbiturates Narcotic analgesics: - Morphine INDUCTION OF ANAESTHESIA A process by which a patient is put under anaesthesia. It involves the use of two kinds of agents – Inhalational anaesthetics eg Halothane, Isofluorane, Sevoflorane, Desflorane or even Ether. Intravenous anaesthetics eg (ultra – short acting agents) Thiopentone, Etomidate, Propofol, or even the (short – acting agents) ketamine, Diazepam, Midazolam, Narcotics. Endotracheal Intubation  SHORT POSTINGS 2020 This is a process by which a tube is introduced into the trachae to secure the airway. It involves the use of drugs- essentially muscle relaxants eg suxamethonium. These are the short acting relaxants the medium acting relaxants eg atracurium. These agents quickly relax the skeletal muscle and makes it possible for the larynx to be visualizes. Maintenance of Anaesthesia Once the airway is secure, anaesthesia is maintained with one or more agents to ensure continued anaesthesia and analgesia. Balanced anaesthesia is the use of a number of agents to ensure sustained anaesthesia, analgesia and muscle relaxation. These agents work synergistically to produce a state of patient conducive for operative procedures even in their small quantities. Maintenance involves strict monitoring of the anaesthetised patient and replacement of blood or fluid loses. Calories are supplied and patients are protected from cold, injuries etc. REVERSAL AND POSTOPERATIVE CARE At the end of the operation, the anaesthetic agents are turned off and muscle relaxation reversed. Reversal of muscle relaxation involves the use of an anticholinesterase (neostigmine) and an anticholinergic (atropine) to counteract its muscarinic effect. THE ANTICHOLINESTERASE - NEOSTIGMINE  SHORT POSTINGS 2020 The history of anticholinesterase originated from Nigeria in so far as the Calabar man continued to go out witch-hunting. Etu-esere was the galenical (crude preparation). The active agent extracted was physostigmine and marketed as Eserine. Physostimine remains a tertiary amine and therefore crosses all membrane barriers. When converted to quatenary amine, does not cross barrier. Now called neostigmine. POSTOPERATIVE CARE During the postop. Periods, the same monitoring as done during operation is continued. Patient is particularly protected against cold and pain. Analgesics include- Non-steroidal ant-inflammatory drugs Narcotic analgesics Revision Questions 1. The stages of anaesthesia as described by Guedel include all except? a. Excitement b. Analgesia c. Hypnosis d. Surgical anaesthesia e. Apnea 2. About the scientific stages of anaesthesia  SHORT POSTINGS 2020 a. It is made up of 5 stages b. It is reproducible c. The pupils are fully dilated in stage 5 d. All of the above e. None of the above 3. About clinical stages of anaesthesia, the following are premedicants except? a. Atropine b. Diazepam c. Morphine d. Glycopyrrolate e. Etomidate 4. The following are used for induction of anaesthesia except? a. Thiopentone sodium b. Ketamine c. Propofol d. Morphine e. Midazolam 5. Regarding stages of anesthesia, which is correct? a. Stage 2 is surgical anaesthesia b. Stage 1 is excitement c. Stage 3 is analgesia d. Stage 4 is apnea e. Stage 5 is for cardiac anaesthesia 6. An inhalational anaesthetics is? a. Isofluorane  SHORT POSTINGS 2020 b. Thiopentone c. Ketamine d. Diazepam e. Midazolam 7. Balanced anaesthesia is? a. Hypnosis / analgesia / sedation b. Analgesia / muscle relaxation / sedation c. Analgesia / muscle relaxation /anaesthesia d. Analgesia / excitement / anaesthesia e. Hypnosis / sedation /analgesia 8. A drug that can be used for endotracheal intubation is? a. Atropine b. Suxamethonium c. Ketamine d. Midazolam e. Halothane 9. Reversal of muscle relaxation involves the use of? a. Atropine b. Suxamethonium c. Ketamine d. Midazolam e. Halothane 10. Correct placement of endotracheal tube is confirmed by? a. Auscultation b. Direct visualization of the tube passing through the vocal cord  SHORT POSTINGS 2020 c. On the table X-ray of the neck d. Epigastric excursion e. Capnography ESSAYS 1. Write short notes on a. Preoperative assessment for general anaesthesia b. Premedication c. Reversal in anaesthesia 2. List 5 inhalational and 5 intravenous anaesthesia used for induction Answers 1. C 2. B 3. E 4. D 5. D 6. A 7. C 8. B 9. A 10. E Back to main outline ↑↑ Back to Anaesthesiology outline ↑↑  SHORT POSTINGS 2020 PREOPERATIVE ASSESSMENT Dr. Ezike DEFINITION: Preoperative assessment is an overall clinical review of a patient to ascertain degree of fitness for an intended surgery. AIM OF PREOPERATIVE ASSESSMENT Identification of patient Establish rapport with patient Clinical history of patient Physical examination of the patient Review of investigation results of the patient Request for further investigation if necessary Make an overall impression of operative risk PATIENT IDENTIFICATION AND RAPPORT Match patient with name, sex, ward, Doctor. Introduction of oneself and offer of friendship. Explain your mission and sincerity of purpose Assure patient of commitment and support. HISTORY AND PHYSICAL EXAMINATION  SHORT POSTINGS 2020 Bio-data, history of illness, past medical history, drug history, alcohol, tobacco and allergies. General and specific physical examinations. Review of investigation results- C x-ray, laboratory results. Possible requests for further investigations PHYSICAL EXAMINATION Rule out palour, jaundice, oedema, loose or absent teeth, neck mobility, view the larynx. Thoroughly examine each of the systems. Examine the surgical pathology. Note its systemic involvement Note how much activity compromised. OPERATIVE RISK ASSESSMENT American Society of Anaesthesiologists (ASA) Grading A healthy young adult with minor surgical problem, no systemic involvement- ASA1 With associated fever or headache or vomiting /diarrhoea etc. but not limiting activity – ASA 2. With limitation of activity but not incapacitating – ASA 3. When incapacitated – ASA 4 Moribund cases are ASA 5.  SHORT POSTINGS 2020 The prefix E is added when they come as emergency MALLAMPATTI TEST WITH SAMSON AND YOUNG MODIFICATION Examine patients’ oropharynx from opposite patients’ face while patient opens mouth maximally and protrudes tongue without phonating. Faucial pillars, soft palate, uvula visible – 1 Faucial pillars and soft palate seen, uvula tip masked by base of tongue –2 Soft palate only visible – 3 Soft palate not visible – 4 Pugh’s modification of Child’s index- surgical risk assessment for liver disease Mortality Minimal Moderate Marked 50% Bilirubin (molL- 40 1) Albumin (gL-1) >35 30 – 35 6 prolonged) (INR2.3) Ascites none moderate marked Encephalopathy none grade 1&2 grade 3&4 Nutrition excellent good poor FASTING GUIDELINES About 72hrs for food to go through the GIT.  SHORT POSTINGS 2020 About 4- 6hrs for food to leave the stomach. Solid food can take the 6hrs while liquids take less. It is normal to fast adults overnight. Clear liquids can be allowed up to 2hrs before operation in children. PREMEDICATION Administration of drugs- To ensure optimal conditions in a patient coming for surgery. To form an integral part of the anaesthesia technique. AIM These drugs therefore – - Alley anxiety, Dry secretions, - Sedate patients/ provide basal narcosis to ensure stable and cooperative patient, - Could reduce pain, - Tend to reduce the overall anaesthetic demand of patients. - Counteract adverse effects of some agents SPECIFIC PREMEDICATION Strong analgesics for pre-medication in painful conditions. H2 blockers for full stomach patients  SHORT POSTINGS 2020 Major tranquilizers for psychotics B2 agonists for asthmatics PREMEDICANT FAMILY Anti-cholinergics / antisialogogues. Essentially –antimuscarinics and include- Atropine Hyoscine Glycopyronium Benzodiazepines -Diazepam -Lorazepam -Temazepam -Midazolam -Lormetazepam Phenothiazines -Promazine - Promethazine - Chlorpromazine MAJOR TRANQUILIZERS Butyrophenones  SHORT POSTINGS 2020 -Droperidol - Haloperidol And Chlorpromazines GASTRIC pH INCREASING DRUGS H2 blockers– Cimetidine, Ranitidine Proton pump inhibitors– Omeprazole Antacids---- Sodium Citrate (0.3M) ANALGESICS Opoids -- Morphine, Pethidine NSAIDS -- Diclofenac, Paracetamol Prokinetic Drug Metoclopromide Revision Questions Answers Back to main outline ↑↑ Back to Anaesthesiology outline ↑↑  SHORT POSTINGS 2020 PREMEDICATION AND PREMEDICANTS PREMEDICATION These are drugs administered to facilitate the induction & maintenance of Anesthesia. The goal of premedication is to have the patient arrive in the operating room in a calm, relaxed frame of mind while causing minimal interference with breathing and cardiovascular status. Pre-operative medication is given for the following reasons: To sedate the patient and allay his fear and anxiety To reduce secretions To alleviate pain, lessen intra-operative pain, and enhance the hypnotic effect of general anaesthesia. To suppress reflex activity arising from the sympathetic and parasympathetic systems To reduce the incidence of postoperative nausea and vomiting To produce amnesia To reduce gastric volume and increase gastric pH As continuing medication for concomitant diseases -Hypertension, diabetes mellitus The 6 As of premedication: Anxiolysis, Amnesia, Anti-emetic, Antacid, Anti – autonomic. Analgesic  SHORT POSTINGS 2020 Reduction in anxiety and pain (Sedatives and Tranquilizers): Benzodiazepines are ideal agents to reduce anxiety. Short-acting benzodiazepines e.g Midazolam, temazepam are often preferred Benzodiazepine – orally 45 – 90min preop. /iv Diazepam 10-20mg Lorazepam 2-4mg Temazepam 20-30mg Promotion of Analgesia-Analgesics: Opiods- (fentanyl, morphine, pethidine and pentazocin), paracetamol and NSAID. Opiods carry a risk for respiratory depression Reduction in secretions-Antisialagogues: This is achieved with atropine, glycopyrrolate, hyocine or scopolamine They both depress all secretions including tears, sweat, saliva and mucous glands of the respiratory passages and the gut, but have no action on the secretion of bile, milk or urine. They inhibit emptying of the bladder and paralyze the sphincter muscle of the eye, causing dilatation of the pupil. Reduction of volume and Modification pH of gastric Contents-Antacids (to avoid Mendelson’s syndrome)-This is important in patients who are at risk of vomiting or regurgitation e.g. emergency patients with a full stomach. Varieties of drug combination are used to try and increase the pH and reduce the gastric volume:  SHORT POSTINGS 2020 Oral sodium citrate: chemically neutralizes residual acid Cimetidine, ranitidine {H2 antagonists}: reduce acid secretion: Metoclopramide: increases gastric emptying and lowers esophageal sphincter tone. This reduces the potential for regurgitation. An alternative is aspiration of gastric contents via a naso-or orogastric tube. Reduction of postoperative nausea and vomiting-Antiemetics: This is achieved with anti-emetics e.g Dopamine antagonists – metoclopramide, droperidol Serotonin antagonist - Ondansetron Antihistamine- cyclizine, promethazine Reduction of vagal reflexes to intubation: Anti-cholinergic agents, atropine and glycopyrrolate are used to protect against the occurrence of bradycardia. They also prevent excessive secretion of saliva associated with the use of Ketamine. Attenuation of Sympatho-adrenal Response: Sympatho-adrenal response such as tachycardia, hypertension and elevation of plasma catecholamine concentrations may be present at laryngoscopy and intubations To attenuate this response, - B-blocker – Esmolol - Lidocaine – iv  SHORT POSTINGS 2020 - Second dose sodium thiopentone. Promotion of amnesia: Inability to recall events leading up to anesthesia and surgery. Most effective agents are lorazepam and midazolam. Lorazepam is 2 to 5 times more potent than diazepam THE ANAESTHETIC VISIT A pre-anesthetic visit is done to assess a patient’s fitness for anesthesia The purposes of the preoperative visit are to: o Establish rapport with the patient & Development of a professional relationship o Allay anxiety/counseling o Explain in simple terms the anesthetic procedure, measures that will be taken to provide post-operative pain relief and events which occur in the peri-operative period. o Obtain consent ASPECTS OF PRE-ANESTHETIC VISIT HISTORY Check the medical notes & review the patient for the following o General medical and surgical history o Drug therapy – Antihypertensive, antidiabetic, Aspirin o Allergies o History of smoking and excessive alcohol intake  SHORT POSTINGS 2020 o Review of systems: respiratory (cough, shortness of breath, wheezing) & those relating to the CVS- (angina, Orthopnea, etc) o Anesthetics record-Previous anesthetics, and any ill-effect— o Loose teeth, crowns and dentures o Time of last intake of food and drinks PHYSICAL EXAMINATION This will be guided by the surgery and the patient’s medical history General examination: o State of nutrition/malnutrition/obesity o Psychological state of patient o Degree of anxiety Systemic examination AIRWAY ASSESSMENT - Assess the difficulty of airway maintenance and laryngoscope even if intubation is not planned. A) Mallampati scores – A simple classification of the pharyngeal view obtained during maximal mouth opening and tongue protrusion. Patient must fully extend the tongue 1- Soft palate, Uvula and pharyngeal pillars visible SUP 2. Only soft palate, Uvula visible 3. Soft palate only visible  SHORT POSTINGS 2020 4. Soft palate not visible 3 & 4 are predictors of difficult intubations B. Thyromental distance < 6.5cm C. Sternomental distance = 0.5 Dioxide tension  Skin appearance  Color  Temperature  Urine Production  Central Venous CVP 1 – 10 mmHg Pressure PAP 10 – 20 mmHg  Pulmonary Artery (mean) 5 – 15 mmHg Pressure PCWP 75 % SvO2 4.5 – 6 1.Min-1  Pulmonary CO 80 – 120 mmHg Capillary Wedge MAP Pressure  Mixed venous oxygen saturation  Cardiac Output  Mean Arterial Pressure *MAP = DBP + 1/3 ( SBP – DBP )  SHORT POSTINGS 2020 Revision Questions 1. Which of the following is used for monitoring ventilation under anaesthesia? a) Oxygen failure alarm b) Humidifier c) Flow meter d) Capnography e) Vapourizer 2. Correct placement of emdotracheal tube is confirmed by? a) Direct visualization of the tube passing through the vocal cord b) On the table X-ray of the neck c) Capnography d) Epigastric excursion e) Auscultation 3. Inaccurate oximetry readings can be caused by? a) Carbon monoxide poisoning b) Shock c) Warm extremities d) Diathermy e) Patient movement 4. Which of the following statements is correct? a) Capnometry is the continuous display of carbon dioxide concentration in wave form (CAPNOGRAM) b) Capnography is the numerical measurement of the venous carbon dioxide concentration (CAPNOMETRY)  SHORT POSTINGS 2020 c) Capnography is the numerical measurement of the arterial carbon dioxide concentration d) The capnography can be used to identify correct placement of the nasotracheal tube e) End- tidal carbon dioxide levels cannot be used as a predictor of outcome of resuscitation 5. Components of the endotracheal tube include all except? a) Pilot ballon b) Cuff c) Connector d) Pressure sensor e) Radio- opaque line 6. A multi parameter monitor can measure the following except a) Temperature b) End tidal carbon dioxide concentration c) Oxygen flux d) Mean arterial blood pressure e) Electrocardiogram 7. Sources of error in oximetry includes the following except a) Ambient light b) External dyes c) Low perfusion states d) Venous congestion e) Anemia  SHORT POSTINGS 2020 8. Continous temperature monitoring every 15 minutes can be carried out at core temperature monitoring sites which includes the following except a) Axilla b) Tympanic membrane c) Rectal site d) Nasopharyngeal e) Oesophageal 9. According to the American Heart Association’s recommendation, in the measurement of blood pressure using the non invasive blood pressure monitoring technique a) The bladder width should approximate 40% of the circumference of the extremity while the bladder length should encircle at least 80% of the extremity b) The bladder width should approximate 40% of the circumference of the extremity while the bladder length should encircle at least 60% of the extremity c) The bladder width should approximate 20% of the circumference of the extremity while the bladder length should encircle at least 70% of the extremity d) The bladder width should approximate 40% of the circumference of the extremity while the bladder length should encircle at least 80% of the extremity e) The bladder width should approximate 50% of the circumference of the extremity while the bladder length should encircle at least 90% of the extremity Answers 1. D  SHORT POSTINGS 2020 2. C 3. A 4. D 5. D 6. C 7. E 8. A 9. B Back to main outline ↑↑ Back to Anaesthesiology outline ↑↑ THE ANAESTHESIA MACHINE Dr. Ajuzieogu. V. O OCTOBER 6, 1846 TRUIMPH Morton brought “Letheon” to the operating theater at Harvard.  SHORT POSTINGS 2020 Gilbert Abbott had a jaw tumor. “Gentlemen, this is no humbug!” J.C. Warren Morton was running late on the day in questions, waiting for a final modification to his inhaler. He arrived just as Warren was going to start the operation, and reportedly said, “Sir, your patient is ready”. Morton ignored him and went about getting Abbott to breath deeply. IN about five minutes, Morton turned to Warren and said, “Sir, your patient is ready”. The operation took about seven minutes, and at the end, Warren uttered his famous words. SUCCESS OF ETHER Why was ether so successful? Morton’s demonstration was public and dramatic (called it Letheon and had it colored green, inhaler device). Later admitted it was simple ether. Easy to prepare Easy to store in bottles (unlike nitrous oxide) Good physical properties; volatility enabled inhalation Low concentrations meant patients didn’t become hypoxic Very little cardiopulmonary depression Slow induction … safety margin for new learners  SHORT POSTINGS 2020 Easy to administer (towel soaked in ether; later, drop inhalers) CONTROL OF THE AIRWAY Early anesthesia: No definitive airway control Mask anesthesia, inhalers, drop mask techniques were all equally capable of producing an unconscious patient but offered no airway protection or control against apnea or emesis. 1877: Joseph Clover describes jaw-thrust technique for opening airway. Performs surgical airway with metal canula (first cricothyrotomy by anesthesia provider). Frederick Hewitt developed a device for preventing the tongue from obstructing the airway in the unconscious patient. He called this device the “air-way restorer.” Device was a direct precursor to modern oral airways. OBJECTIVES Become familiar with the basic design of an anesthetic machine Become familiar with the design and functioning of anesthetic vaporizers. Become familiar with the design and functioning of the more commonly used breathing circuits  SHORT POSTINGS 2020 CONSIDERATION Anesthetic concentration control Build up of carbon dioxide Consumption of oxygen Atmospheric pollution Airway control GENERIC ANAESTHETIC MACHINE The pressures within the anesthesia machine can be divided into three circuits High-pressure Intermediate-pressure Low-pressure circuit HIGH PRESSURE SYSTEM Receives gasses from the high pressure E cylinders attached to the back of the anesthesia machine (2200 psig for O2, 745 psig for N2O) Consists of:  SHORT POSTINGS 2020 Hanger Yolk (reserve gas cylinder holder) Check valve (prevent reverse flow of gas) Cylinder Pressure Indicator (Gauge) Pressure Reducing Device (Regulator) Usually not used, unless pipeline gas supply is off GAS SUPPLY: PIPELINES OR CYLINDERS PIPELINES primary gas source for the anesthesia machine oxygen, nitrous oxide, and air "normal working pressure" 50 psi DISS (diameter index safety system) CYLINDER SUPPLY reserve E cylinders Color-coded Pin Index Safety System (PISS) high-pressure cylinder source pressure regulator oxygen 2200 psig to 45 psig  SHORT POSTINGS 2020 nitrous oxide 745 psig to 45 psig COLOUR CODINGS OF MEDICAL GAS CYLINDERS AND THEIR PRESSURE WHEN FULL Body Shoulder colour Pressure, kPa colour (at room temp.) Oxygen Black White 13,700 Nitrous oxide Blue Blue 4400 Carbon dioxide Grey Grey 5000 Air Grey White/black quarters 13,700 Entonox Blue White/blue quarters 13,700 Oxygen/helium Black White/brown quarters 13,700  SHORT POSTINGS 2020 Diagram showing the index positions of a cylinder valve. Oxygen: 2 & 5 Nitrous oxide: 3 & 5 Air: 1 & 5 CO2: 1 & 6 O2, and medical compressed air (5 bar) used for life support and respiratory therapy. N2O is an analgesic gas used in anesthesia machine.  SHORT POSTINGS 2020 Vacuum (technically not gas), negative pressure to to do suction AGSS (Anesthesia Gas Scavenging System), to take out N2O and filter it before being outdoors. Compressed air (8 bar) or Nitrogen, to operate pneumatic surgical tools. CO2 used for insufflations. Xenon new inert gas Medical Gas Pipeline products are used in Hospitals, Universities and Research Labs, to process and monitor the delivery of medical gases from source systems to various operating and care areas of the facilities. Medical Gas Pipeline Products include, Air Compressors, Vacuum Systems, Medical Gas Outlets, Alarms, Manifolds, Zone Valves and Zone Valve Boxes. The Architectural Products include a variety of wall or floor mounted Headwall Systems designed and installed to continue the delivery of the medical gases and electrical services for delivery of these essential services in the high acuity areas of the facilities. These systems feature rail profiles which allow extremely effective equipment management concepts to better utilize floor space and provide flexibility in equipment movement. Since the ventilator is concerned to supply a mixture of air and oxygen, we will concentrate on oxygen supplies especially. MEDICAL GAS PIPELINE SYSTEM  SHORT POSTINGS 2020 A pipeline system is a system that includes: The pipeline network, The control unit and The terminal units where the medical gases or anesthetic gas scavenging disposal systems may be required. OXYGEN SUPPLYING SYSTEM Oxygen may be supplied as follows: Gas in cylinders Cryogenic liquid in mobile vessels or stationary vessels GAS IN CYLINDERS A cylinder manifold system shall have two banks (groups) of cylinders or cylinder bundles The banks alternately supply the pipeline, Each bank having its cylinders connected to a common header with a separate manifold pressure regulator. The secondary bank comes into operation automatically when content of the primary bank becomes exhausted. CRYOGENIC LIQUID SYSTEM  SHORT POSTINGS 2020 Cryogenic tanks systems hold liquefied cryogenic gases (oxygen, nitrogen, argon, hydrogen or helium) and dispense these gases in the form of a liquid or gas as required by the customer. Cryogenic tanks pressure vessels manufactured with an inner and outer vessel to hold cryogenic liquefied gases that have condensation points less than -150 ºC. OXYGEN SYSTEM COMPOUNDS Pressure regulators Pressure relief valve HANGER YOLK Hanger Yolk: orients and supports the cylinder, providing a gas-tight seal and ensuring a unidirectional gas flow into the machine Index pins: Pin Index Safety System (PISS) is gas specific prevents accidental rearrangement of cylinders (e.g. switching O2 and N2O) PRESSURE REDUCING DEVICE Reduces the high and variable pressures found in a cylinder to a lower and more constant pressure found in the anesthesia machine (45 psig) Reducing devices are preset so that the machine uses only gas from the pipeline (wall gas), when the pipeline inlet pressure is 50 psig.  SHORT POSTINGS 2020 This prevents gas use from the cylinder even if the cylinder is left open (i.e. saves the cylinder for backup if the wall gas pipeline fails). Cylinders should be kept closed routinely. Otherwise, if the wall gas fails, the machine will automatically switch to the cylinder supply without the anesthetist being aware that the wall supply has failed (until the cylinder is empty too). INTERMEDIATE PRESSURE SYSTEM Receives gasses from the regulator or the hospital pipeline at pressures of 40-55 psig Consists of: Pipeline inlet connections Pipeline pressure indicators Piping Gas power outlet Master switch Oxygen pressure failure devices Oxygen flush Additional reducing devices Flow control valves  SHORT POSTINGS 2020 PIPELINE INLET CONNECTIONS Mandatory N2O and O2, usually have air and suction too Inlets are non-interchangeable due to specific threading as per the Diameter Index Safety System (DISS) Each inlet must contain a check valve to prevent reverse flow (similar to the cylinder yolk) At this point mention that in Sudbury Ontario in the 1970s 23 people died because the N20 and O2 pipelines were crossed over during repairs. Ask them what they would do in this situation? Backup oxygen cylinder turned on Pipeline supply must be disconnected (necessary because the machine will preferentially use the pipeline supply as per the high pressure system regulator design). OXYGEN PRESSURE FAILURE DEVICES Machine standard requires that an anesthesia machine be designed so that whenever the oxygen supply pressure is reduced below normal, the oxygen concentration at the common gas outlet does not fall below 19% A Fail-Safe valve is present in the gas line supplying each of the flowmeters except O2. This valve is controlled by the O2 supply pressure and shuts off or proportionately decreases the supply pressure of all other gasses as the O2 supply pressure decreases  SHORT POSTINGS 2020 Historically there are 2 kinds of fail-safe valves Pressure sensor shut-off valve (Ohmeda) Oxygen failure protection device (Drager) PRESSURE SENSOR SHUT-OFF VALVE Oxygen supply pressure opens the valve as long as it is above a pre-set minimum value (e.g. 20 psig). If the oxygen supply pressure falls below the threshold value the valve closes and the gas in that limb (e.g. N2O), does not advance to its flow- control valve. OXYGEN FAILURE PROTECTION DEVICE (OFPD) Based on a proportioning principle rather than a shut-off principle The pressure of all gases controlled by the OFPD will decrease proportionately with the oxygen pressure OXYGEN SUPPLY FAILURE ALARM The machine standard specifies that whenever the oxygen supply pressure falls below a manufacturer-specified threshold (usually 30 psig) a medium priority alarm shall blow within 5 seconds. OXYGEN FLUSH VALVE (O2+)  SHORT POSTINGS 2020 Receives O2 from pipeline inlet or cylinder reducing device and directs high, unmetered flow directly to the common gas outlet (downstream of the vaporizer) Machine standard requires that the flow be between 35 and 75 L/min The ability to provide jet ventilation Hazards May cause barotrauma SECOND STAGE REDUCING DEVICE Located just upstream of the flow control valves Receives gas from the pipeline inlet or the cylinder reducing device and reduces it further to 26 psig for N2O and 14 psig for O2 Purpose is to eliminate fluctuations in pressure supplied to the flow indicators caused by fluctuations in pipeline pressure LOW PRESSURE SYSTEM Extends from the flow control valves to the common gas outlet Consists of: Flow meters Vaporizer mounting device Check valve  SHORT POSTINGS 2020 Common gas outlet FLOWMETER ASSEMBLY When the flow control valve is opened the gas enters at the bottom and flows up the tube elevating the indicator The indicator floats freely at a point where the downward force on it (gravity) equals the upward force caused by gas molecules hitting the bottom of the float VAPORIZERS A vaporizer is an instrument designed to change a liquid anesthetic agent into its vapor and add a controlled amount of this vapor to the fresh gas flow CLASSIFICATION OF VAPOURIZERS Methods of regulating output concentration Concentration calibrated (e.g. variable bypass) Measured flow Method of vaporization Flow-over  SHORT POSTINGS 2020 Bubble through Temperature compensation Supplied heat FACTORS THAT INFLUENCE VAPORIZER OUTPUT Flow Rate: The output of the vaporizer is generally less than the dial setting at very low (< 200 ml/min) or very high (> 15 L/min) flows Temperature: Automatic temperature compensating mechanisms in bypass chambers maintain a constant vaporizer output with varying temperatures Back Pressure: Intermittent back pressure (e.g. positive pressure ventilation causes a higher vaporizer output than the dial setting) C’ = concentration at the new atmospheric pressure C = the concentration at the old atmospheric pressure (i.e. the concentration dialed into the vaporizer) P’ = the barometric pressure for which c’ is being established P = the barometric pressure for which the vaporizer is calibrated (i.e. at the old atmospheric pressure) Atmospheric Pressure: Changes in atmospheric pressure affect variable bypass vaporizer output as measured by volume % concentration, but  SHORT POSTINGS 2020 not (or very little) as measured by partial pressure (lowering atmospheric pressure increases volume % concentration and vice versa) Carrier Gas: Vaporizers are calibrated for 100% oxygen. Carrier gases other than this result in decreased vaporizer output. ADJUSTABLE PRESSURE LIMITING (APL) VALVE User adjustable valve that releases gases to the scavenging system and is intended to provide control of the pressure in the breathing system Bag-mask Ventilation: Valve is usually left partially open. During inspiration the bag is squeezed pushing gas into the inspiratory limb until the pressure relief is reached, opening the APL valve. Mechanical Ventilation: The APL valve is excluded from the circuit when the selector switch is changed from manual to automatic ventilation SCAVENGING SYSTEM Protects the breathing circuit or ventilator from excessive positive or negative pressure. Mention that the ventilator relief valve is the same thing as the overflow valve mentioned in the previous slides Revision Questions 1. Which of these is not an essential part of anaesthetic machine? a. Calcium hydroxide b. Sodium hydroxide flow meter  SHORT POSTINGS 2020 c. Vapourizer d. Oxygen alarm e. Flow meter 2. Which of the following equipment is used for monitoring ventilation? a. Capnography b. Humidifier c. Pulse oximeter d. Vapourizer e. Flow meter 3. The following equipments are used as monitors except? a. Pulse oximeter b. Capnography c. Humidifier d. Electrocardiogram e. A urinary catheter 4. The airway could be maintained using? a. Bag valve mask device b. Laryngoscope c. Ventilators d. Endoscope e. Guedel’s device 5. The part of an anaesthetic machine responsible for delivering a given concentration of volatile anaesthetic agent is? a. Flow meters b. Breathing circuits  SHORT POSTINGS 2020 c. Reducing valves d. Sadalime canisters e. Vapourizers 6. The pulse oximeter absorbs oxygenated blood using? a. Red LED b. Infra-red LED c. Blue LED d. None of the above e. Green LED 7. About spinal needles, the following are correct except? a. They are used to inject anaesthesia directly into the CSF b. It can also be used to collect CSF for diagnostic purposes c. The needle is inserted at the level of L2 d. A 27G needle is thinner than a 25G needle e. None of the above 8. Safety features of the anaesthetic machine include all except? a. Colour coding of gas cylinders b. Oxygen supply failure alarm c. Pressure reducing valve d. Vapourizers e. Circuit breakers 9. A multiparameter monitor can measure the following except? a. Oxygen flux b. Mean arterial blood pressure c. Electrocardiogram d. End-tidal carbon dioxide concentration  SHORT POSTINGS 2020 e. Temperature 10. Uses of endotracheal tube includes all except? a. For airway management in the setting of general anaesthesia b. As a route for administration of drugs like salbutamol c. Used to deliver oxygen in higher concentration than air d. Visualizing the airway e. Maintenance of airway 11. The size of spinal needle used for subarachnoid block includes a. 12G b. 14G c. 18G d. 40G e. 23G ESSAYS 1. Enumerate the safety features of an anaesthetic machine 2. List 5 anaesthetic equipment and their uses Answers 1. B 2. A 3. C 4. E 5. E 6. B 7. C 8. D  SHORT POSTINGS 2020 9. A 10. D Back to main outline ↑↑ Back to Anaesthesiology outline ↑↑  SHORT POSTINGS 2020 BREATHING CIRCUIT IN ANAESTHESIA Dr. Ajuzieogu. V. O DEFINITION A breathing system is defined as an assembly of components which connects the patient’s airway to the anaesthetic machine creating an artificial atmosphere, from and into which the patient breathes. IT PRIMARILY CONSISTS OF a) A fresh gas entry port/delivery tube through which the gases are delivered from the machine to the systems; b) A port to connect it to the patient’s airway; c) A reservoir for gas, in the form of a bag or a corrugated tube to meet the peak inspiratory flow requirements; d) An expiratory port/valve through which the expired gas is vented to the atmosphere; e) A carbon dioxide absorber if total rebreathing is to be allowed and f) Corrugated tubes for connecting these components. Flow directing valves may or may not be used. REQUIREMENTS FOR A BREATHING SYSTEM Essential: The breathing system must a) deliver the gases from the machine to the alveoli in the same concentration as set and in the shortest possible time; b) effectively eliminate carbon-dioxide;  SHORT POSTINGS 2020 c) have minimal apparatus dead space; and d) have low resistance. Desirable: The desirable requirements are a) economy of fresh gas b) conservation of heat c) adequate humidification of inspired gas d) Light weight e) convenience during use f) efficiency during spontaneous as well as controlled ventilation g) adaptability for adults, children and mechanical ventilators h) provision to reduce theatre pollution. MANY CONFIGURATIONS No Soda Lime Soda Lime Uni Non-Rebreathing Circle System Circle System  SHORT POSTINGS 2020 Classification Examples Bi a) Afferent reservoir Waters Canister systems. Mapleson A, B & C Lack’s system. b) Enclosed afferent reservoir systems Miller’s (1988) c) Efferent reservoir systems Mapleson D, E & F Bain’s system d) Combined systems Humphrey ADE THE MAPELSON’S SYSTEMS  SHORT POSTINGS 2020 Open No boundary and no dead space Oxygen tubing near patient, Nasal canula Semi- Partial boundary between airway Schimmelbusch open and atmosphere mask Semi- Fully bounded. Prevents entry of Mapleson systems closed atmospheric air but vents excess fresh gas Closed No venting of excess gas Circle systems at low flows THE COMPONENTS OF THE BREATHING SYSTEM Adjustable pressure-limiting valve Reservoir bag Tubing ADJUSTABLE PRESSURE LIMITING VALVE Spill valve, pop-off valve, expiratory valve, relief valve. Designed to vent gas during positive pressure. Pressure of less than 0.1 kPa activates the valve when open. COMPONENTS 3 ports: inlet, patient and exhaust port- latter can be open to atmosphere or connected to the scavenging system Lightweight disc sits on a knife-edge seating- held in place by a spring  SHORT POSTINGS 2020 Tension in the spring and therefore the valve’s opening pressure is controlled by the valve dial. RESERVOIR BAG Antistatic rubber or plastic Ellipsoid in shape Standard adult size is 2 l (range from 0.5 to 6 l) MECHANISM OF ACTION Accommodates fresh gas flow during expiration acting as a reservoir available for the following inspiration. Acts as a monitor of patient’s ventilatory pattern during spontaneous breathing and also a very inaccurate guide to tidal volume Used to assist or control ventilation TUBING Corrugated or smooth Different lengths depending on system being used Allow humidification of inspired air Parallel and coaxial arrangements available MAPLESON’S CLASSIFICATION Mapleson classified breathing systems in 1954 into 5 types. BIDIRECTIONAL FLOW a) Afferent reservoir systems. Mapleson A  SHORT POSTINGS 2020 Mapleson B Mapleson C Lack’s system. B) Efferent reservoir systems Mapleson D Mapleson E Mapleson F AFFERENT LIMB Is that part of the breathing system which delivers the fresh gas from the machine to the patient. If the reservoir is placed in this limb as in Mapleson A, B, C and Lack’s systems, they are called afferent reservoir systems (ARS). EFFERENT LIMB Is that part of the breathing system which carries expired gas from the patient and vents it to the atmosphere through the expiratory valve/port If the reservoir is placed in this limb as in Mapleson D, E, F and Bain systems, they are called efferent reservoir systems (ERS). BIDIRECTIONAL FLOW Systems with bi-directional flow are extensively used. These systems depend on the FGF for effective elimination of CO2. Understanding these systems is most important as their functioning can be manipulated by changing parameters like Fresh gas flow, alveolar ventilation, apparatus dead space, etc. FRESH GAS SUPPLY  SHORT POSTINGS 2020 Fresh gas flow (FGF) forms one of the essential requirements of a breathing system. If there is no FGF into the system, the patient will get suffocated. If the FGF is low, most systems do not eliminate carbon-dioxide effectively, and if there is an excess flow there is wastage of gas. So, it becomes imperative to specify optimum FGF for a breathing system for efficient functioning. If the system has to deliver a set concentration in the shortest possible time to the alveoli, the FGF should be delivered as near the patient’s airway as possible. ELIMNATION OF CARBONDIOXIDE Normal production of carbon-dioxide in a 70 kg adult is 200 ml per minute and it is eliminated through the lungs. Normal end-tidal concentration of carbon-dioxide is 5%. Hence, for eliminating 200 ml of carbon-dioxide as a 5% gas mixture, the alveolar ventilation has to be: 200 x 100 = 4,000 ml. 5 This 4000 ml is the normal alveolar ventilation. Any breathing system connected to an adult’s airway should provide a minimum of 4 litres per minute of carbon-dioxide free gas to the alveoli for eliminating carbon- dioxide. If the alveolar ventilation becomes less than 4 litres per minute, it would lead to hypercarbia. APPARATUS DEAD SPACE It is the volume of the breathing system from the patient-end to the point up to which, to and fro movement of expired gas takes place.  SHORT POSTINGS 2020 EXTENT OF DEAD SPACE IN VARIOUS SYSTEMS In an afferent reservoir system with adequate FGF, the apparatus dead space extends up to the expiratory valve positioned near the patient. If the FG enters the system near the patient-end as in an efferent reservoir system, the dead space extends upto the point of FG entry. In systems where inspiratory and expiratory limbs are separate, it extends upto the point of bifurcation. IMPORTANCE OF FGF The dynamic dead space will depend on the FGF and the alveolar ventilation. The dead space is minimal with optimal FGF. If the FGF is reduced below the optimal level, the dead space increases. The whole system will act as dead space if there is no FGF. Increasing the FGF above the optimum level will only lead to wastage of FG. MAPELSON A Corrugated rubber or plastic tubing: 110- 130 cm in length Reservoir bag at machine end APL valve at the patient end. Tube Volume > Tidal Volume (550mls) MAPELSON ‘A’/MAGILLS SYSTEM: FUNCTIONAL ANALYSIS Spontaneous breathing:  SHORT POSTINGS 2020 The system is filled with fresh gas before connecting to the patient. When the patient inspires, the fresh gas from the machine and the reservoir bag flows to the patient, and as a result the reservoir bag collapses. The expired gas, initial part of which is the dead space gas, pushes the FG from the corrugated tube into the reservoir bag and collects inside the corrugated tube. Expiratory pause – Fresh gas washes the expired gas out of the reservoir tube, filling it with fresh gas for the next inspiration. CONTROLLED VENTILATION To facilitate IPPV the expiratory valve has to be partly closed. During inspiration, the patient gets ventilated with FG and part of the FG is vented through the valve after sufficient pressure has developed to open the valve. During expiration, the FG from the machine flows into the reservoir bag and all the expired gas (i.e., dead space gas and alveolar gas) flows back into the corrugated tube till the system is full. During the next inspiration the alveolar gas is pushed back into the alveoli followed by the FG. When sufficient pressure is developed, part of the expired gas and part of the FG escape through the valve. This leads to considerable rebreathing, as well as excessive waste of fresh gas. Hence these systems are inefficient for controlled ventilation. Fresh Gas Flow of >20l/min is required to prevent rebreathing in controlled respiration MAPLESON A – LACK SYSTEM Coaxial modification of Magill Mapleson A  SHORT POSTINGS 2020 1.5 m length FGF through outside tube (30mm), exhaled gases through inner tube. Inner tube wide in diameter (14 mm) to reduce resistance to expiration(1.6 cms H2O). Reservoir bag at machine end APL valve at machine