Improving the Anesthesia Final PDF

26 N. A. Shallik et al. 3.2 Pharmacology Induction GA induction may be done with intravenous (IV) 3.2.1 Introducaito...

26 N. A. Shallik et al. 3.2 Pharmacology Induction GA induction may be done with intravenous (IV) 3.2.1 Introducaiton to Types and/or inhalation agents. Administration of a of Anesthesia sedative-­ hypnotic agent (e.g. Propofol, Etomidate, and Ketamine) and one or more adju- General Anesthesia vant IV agents (e.g. opioids and/or benzodiaze- General anesthesia (GA) is appropriate for most pine, commonly used Midazolam) as well as a major surgical procedures. A reversible state of neuromuscular blocking agent (NMBA) when Stage III surgical anesthesia is established, planning for endotracheal intubation. including the following goals: Maintenance Hypnosis/unconsciousness. Additional agents are required immediately after Amnesia. GA induction to sustain the anesthetic state. Analgesia. Anesthesia is often sustained through the use of a Muscle relaxation or immobility as appropri- primary inhalation technique. Total Intravenous ate for the procedure. Anesthesia (TIVA) is an alternative technique. Autonomic and sensory blockade of responses Most commonly, inhalation and/or IV anesthetic to noxious surgical stimulation. combinations are administered to maintain GA, with the aim of reducing the total dose of any one Anesthesia or sleeping with general anesthe- agent. sia occurs in four stages that may not be observed, If muscle relaxation or complete paralysis is as they can occur very quickly. required to facilitate surgery, then an NMBA is used. Sage I (Analgesia) The patient experiences analgesia or pain loss but remains conscious that Emergence the conversation can continue. GA emergence is the return of consciousness and movement at the end of the surgical procedure, Stage II (Excitement) The patient may have after discontinuing anesthetic and adjuvant delirium or become violent. Blood pressure administration and reversing residual NMBA decreases and the rate of respiration increases. effects. The trachea may be extubated without The administration of barbiturates typically assistance when the patient has sufficient sponta- bypasses this stage. neous ventilation. Stage III (Surgical Anesthesia) The skeletal muscles relax during this stage, and the patient’s 3.2.2 Main Types of Medication breathing becomes regular, eye movements slow in Anesthesia Practice then stop, and surgery can begin. Main types of medications used in general anes- Stage IV (Medullary Paralysis) This stage thesia are as follows: happens when the respiratory centers in the brain’s medulla oblongata, which regulate the Induction medications to produce and main- breathing and other vital functions, cease to oper- tain unconsciousness including intravenous ate. Death can result if the patient is not quick to and volatile agents. be revived. We should never reach this stage. Analgesics to provide pain relief. Careful control of the anesthetic amounts admin- Muscle relaxants to induce muscle relaxation. istered prevents this occurrence. GA has three distinct phases: induction, main- Other medications which are used frequently tenance, and emergence, as described below. in anesthesia field include the following: 3 Pharmacology of the Most Common Anesthesia Drugs 27 medications that produce short-term memory Excretion It is simply removal of the medica- loss or amnesia; tion out the body. “It differs from elimination medications that minimize nausea and vomit- which is removal of the medication out the ing (antiemetics); plasma.” Most of the drugs excreted by bile and medications that counteract the effect of other urine however other possible excretion routs are medications (antagonists); breast milk and tears. and medications that suppress or stimulate Pharmacodynamics: certain nervous reflexes i.e. medications mod- It is defined as the effect of drug on the body, ulate sympathetic and parasympathetic it is simply the mechanism of action of a drug. In response. fact, there are three ways that drug can act in our bodies, these are: Essential Introduction to Pharmacology The difference between pharmacokinetics and 1. depending on the physiochemical properties pharmacodynamics: of the medication, Before we go into further detail, let us differ- 2. binding specific receptors to produce a certain entiate between pharmacokinetics and pharma- effect, codynamics. The difference between 3. binding specific enzymes in order to inhibit/ pharmacokinetics (PK) and pharmacodynamics decrease its activity. (PD) can be summed up pretty simply. Pharmacokinetics is the study of what the body does to the drug and Pharmacodynamics is the 3.2.3 Induction Medications study of what the drug does to the body. Pharmacokinetics: Generally speaking, induction agents could be It is defined simply by how the body is acting intravenous drugs or inhalation agents. towards the drug. It is divided to four stages: Intravenous drugs include but not limited to absorption, distribution, metabolism, and thiopentone, etomidate, ketamine, and propofol. excretion. These drugs easily make patients unconscious when given by intravenous injection. This rapid Absorption It is related to the route of adminis- loss of consciousness makes anesthesia induction tration which can be oral, transdermal, rectal, much more pleasant than before when patients sublingual, inhalational, intramuscular, intrathe- were forced to breathe Ether or Chloroform and cal, and intravenous. necessarily avoiding stage 2 excitement stage as well. Distribution It is related to lipid solubility, pro- tein binding, drug ionization, and molecular 3.2.3.1 Intravenous Anesthetics weight. Thiopentone sodium Generic name: Thiopental sodium (Thiopental) Metabolism Most of the drugs metabolized in Fig. 3.1a: liver through two phases as follows. Form: Injection (powder for solution for Phase 1: It is also known as non-synthetic injection) 0.5-g and 1-g vials. phase. It includes oxidation, reduction, and Uses: induction of anesthesia prior to admin- hydrolysis. istration of inhalational anesthetic; anesthesia of Phase 2: It is also known as synthetic phase. It short duration. includes glucuronidation, sulfation acetylation, Contraindications: inability to maintain air- methylation, and glycination. The main aim of way, cardiovascular disease, dyspnoea or obstruc- this phase is to increase the solubility of the tive respiratory disease; hypersensitivity to metabolized drug. barbiturates “porphyria.” 32 N. A. Shallik et al. Dosage: Morphine: (Fig. 3.3a) Anesthesia: adult and pediatric nitrous oxide Form: Its administration is most often via the mixed with 25–30% oxygen. following routes: orally (PO), intravenously (IV), Analgesia: 50% nitrous oxide mixed with intramuscular (IM), subcutaneous (SC), epidural, 50% oxygen. and intrathecal. Adverse effects: Nausea and vomiting. Uses: adjunct during major surgery; postop- Megaloblastic anemia after prolonged adminis- erative analgesia; pain, myocardial infarction, tration due to depressed white cell formation. acute pulmonary edema. Peripheral neuropathy. Contraindications: acute respiratory depres- Oxygen: In fact, this gas in essential in anes- sion; increased intracranial pressure, head injury thesia practice. The air we inhale contains or brain tumor; severe hepatic impairment; hypo- roughly 21% of oxygen gas. thyroidism; convulsive disorders; acute alcohol- Uses: To maintain an adequate oxygen tension ism, spastic conditions of colon; recent surgery during inhalational anesthesia. on biliary tract; diarrhea due to toxins. Dosage: The concentration of oxygen in inspired Precautions: asthma, heart failure secondary anesthetic gases should never be less than 21%. to chronic lung disease; inability to maintain air- Adverse effects: Concentrations above 80% way; renal impairment. have a toxic effect on the lungs that leads to pul- Dosage: monary congestion, exudation, and atelectasis. Premedication: by subcutaneous or intramus- cular injection 1 h before surgery, adult 150– 200 mcg/kg; by intramuscular injection 1 h 3.2.4 Analgesics before surgery, pediatric 50–100 mcg/kg. Intraoperative analgesia: by intravenous Analgesia medication are varies in their mecha- injection, adult and pediatric 100 mcg/kg, nism of action to produce reducing or elimination repeated every 40–60 min as required. the unpleasant feeling of pain. Opiates or narcotics Postoperative analgesia: by intramuscular are well known painkillers, they are either extracted injection, adult 150–200 mcg/kg every 4 h, pedi- from opium (such as morphine) or synthesized in a atric 100–200 mcg/kg; or by intravenous infusion laboratory (such as pethidine or meperidine, fen- adult 8–10 mg over 30 min, then 2–2.5 mg/h tanyl, alfentanil, sufentanil, and remifentanil). In Adverse effects: respiratory depression; modern practice the concept of multimodal analge- anorexia, nausea, vomiting, constipation; eupho- sia is evolving and many recommends sharing opi- ria, dizziness, drowsiness, confusion, headache; oids with other subtypes of medications. Other dry mouth; spasm of urinary and biliary tract; cir- main targets for analgesia medications include culatory depression, hypotension, bradycardia, cyclooxygenase 1 & cyclooxygenase 2, and palpitations; miosis; allergic reactions; physical N-Methyl-d-aspartic acid or N-Methyl-d-­aspartate dependence. (NMDA) (ketamine). Fentanyl: (Fig. 3.3b) Form: Its administration is most often via the 3.3 Analgesics and Opioid following routes: orally (PO), intravenously (IV), Antagonists intramuscular (IM), subcutaneous (SC), transder- mal as skin patches (TD), intranasally (IN) in the Opioid analgesics, such as morphine, fentanyl, form of a volatile nasal spray, transmucosal, epi- and remifentanil, may be used to supplement dural, and intrathecal. general anesthesia. Repeated doses of intraopera- Uses: 50–100 times more potent than mor- tive analgesics should be given with care, since phine, used as adjunct during minor or major sur- respiratory depression may persist into the post- gery; postoperative analgesia; pain management, operative period. myocardial infarction, acute pulmonary edema. 3 Pharmacology of the Most Common Anesthesia Drugs 33 a b c d e Fig. 3.3 (a) Morphine; (b) Fentanyl; (c) Remifentanil, (d) Naloxone, (e) Paracetamol Contraindications: Fentanyl is relatively con- ium, constipation, narcotic ileus, muscle rigidity, traindicated or can be given with some precautions constipation, addiction, loss of consciousness, in the following conditions: postoperative in biliary hypotension, coma, and even death. tract surgeries, respiratory depression or obstructive airway diseases (i.e., asthma, COPD, obstructive Remifentanil: (Fig. 3.3c) sleep apnea OSA, obesity, liver failure, hypersensi- Form: 2 mg or 5 mg powder concentrate for tivity (i.e., anaphylaxis). solution for injection or infusion. Precautions: asthma, heart failure secondary Uses: Induction and maintenance of anesthe- to chronic lung disease; inability to maintain air- sia, administration by Target-Controlled Infusion way; renal impairment. (TCI). Dosage: Contraindications: Remifentanil is contrain- Premedication: 50–100 mcg IM or slow IV dicated for epidural and intrathecal use in patients 30–60 min prior to the surgery. with known hypersensitivity to remifentanil and Adjunct to general anesthesia: 1–2/kg mcg IV. other fentanyl components of the remifentanil Adjunct to regional anesthesia: 25 mcg IT. and for use as the sole agent for induction of Patient-controlled anesthesia (PCA): 10 mcg/ anesthesia. mL IV infusion, usual concentration 20 mcg Precautions: Use with caution in patients demand dose with 5–10 min lockout time interval with hypovolemia, cardiovascular disease and base rate of ≤50 mcg/h. (including acute MI), or drugs which may exag- Adverse effects: euphoria, confusion, respira- gerate hypotensive effects, bradycardia, and tory depression (which, if extensive and untreated, respiratory depression. may lead to arrest), drowsiness, nausea, visual Dosage: Induction of anesthesia: 0.5–1 mcg/ disturbances, dyskinesia, hallucinations, delir- kg/min. 34 N. A. Shallik et al. Maintenance of anesthesia: 0.05–2 mcg/kg/ Dosage: Opioid-induced respiratory depres- min. sion, by intravenous injection, adult 100–200 mcg, Adverse Effects: Hypotension, bradycardia, repeated every 2–3 min to obtain required headache, nausea and vomiting muscle rigidity, response; pediatric initially 10 mcg/kg, if no respiratory depression, apnea, pruritus, pain at response followed by 100 mcg/kg. the site of injection. Opioid-induced respiratory depression at birth, by subcutaneous, intramuscular, or intrave- Tramadol: (Fig. 3.3d) nous injection, neonate 10 mcg/kg immediately Form: 50 mg/mL Solution for Injection or after delivery. Infusion. Adverse effects: nausea and vomiting, hyper- Uses: tension and hypotension, left ventricular failure, For the treatment and prevention of moderate pulmonary edema, seizures; arrhythmias such as to severe pain. ventricular tachycardia or fibrillation, particu- Contraindications: It is contraindicated in larly in pre-existing cardiac disease. patients with known hypersensitivity to tramadol or any other of its components; in patients with Paracetamol (Fig. 3.3e) epilepsy not adequately controlled by treatment. Paracetamol and nonsteroidal anti-inflammatory Precautions: Intravenous injections must be drugs (NSAD) may be useful alternatives (or given slowly over 2–3 min. adjuncts) for the relief of postoperative pain; they Dosage: do not affect respiration and gastrointestinal 50 mg or 100 mg every 4 to 6 hours by either motility. injection IM or IV routes. The dose should be Form: solution for injection one 100 mL vial adjusted according to the severity of the pain and contains 1000 mg paracetamol. the response. Uses: for the short-term treatment of moder- For postoperative pain: An initial bolus of ate pain, especially following surgery and for the 100 mg is given. During the 60 min following the short-term treatment of fever. initial bolus, further doses of 50 mg may be given Contraindications: every 10–20 min, up to a total dose of 250 mg In patients with hypersensitivity to paracetamol including the initial bolus. Subsequent doses or to propacetamol hydrochloride (prodrug of should be 50 mg or 100 mg 4–6 hourly up to a paracetamol). total daily dose of 400 mg. In cases of severe hepatocellular Adverse effects insufficiency. Nausea, dizziness, constipation, vomiting, Precautions: somnolence, and headache usually occur during Hepatocellular insufficiency, severe renal the initial treatment rather than maintenance insufficiency, chronic alcoholism, and doses of the drug. dehydration. Significant side effects include respiratory Dosage: depression that can lead to death. 15 mg/kg, the maximum daily dose must not exceed 3 g. Adverse effects: 3.3.1 Opioid Antagonists Malaise, hypotension, hypersensitivity reac- tions very rarely. Naloxone Hydrochloride (Fig. 3.3d) Form: solution for injection, 400 mcg/mL. Uses: to counteract respiratory depression 3.3.2 Muscle Relaxants induced by opioids during anesthesia and opioids overdose. These medications work specifically to weaken Precautions: dependence on opioids; cardio- or relax skeletal muscles of the body (voluntary vascular disease. and involuntary skeletal muscles will be relaxed 3 Pharmacology of the Most Common Anesthesia Drugs 35 as well i.e. upper part of esophagus). However, Electroconvulsive therapy (ECT) to control they do not affect the muscles of the heart, nor muscle contractions induced as a result of the smooth muscles (i.e., intestines or bronchial electrical impulses delivered during the tree). Muscle relaxants include two family procedure. groups: depolarizing, i.e., suxamethonium (suc- Adverse effects and contraindications cinylcholine) and non-depolarizing (pan- Hyperkalemia, increased intracranial and curonium, atracurium, cisatracurium, intraocular pressure, malignant hyperthermia, vecuronium, and rocuronium). bradycardia, massive tissue trauma, myopathies, and burn injuries. Dose: 3.4 Muscle Relaxants 1–1.5 mg/kg, average (1 mg/kg). and Cholinesterase Vecuronium bromide Inhibitors It is a non-depolarizing muscle relaxant. Form: Powder for solution for injection Skeletal muscle relaxants are divided into two 10 mg vial. groups according to their mode of action: Uses: For intubation and muscle relaxation during surgery. A. Depolarizing muscle relaxants (e.g., Contraindications: Pulmonary diseases; succinylcholine). dehydrated or severely ill patients, myasthenia B. Non-depolarizing muscle relaxants (e.g. gravis, or other neuromuscular disorders. vecuronium, pancuronium, rocuronium, Precautions: renal impairment, hepatic mivacurium, atracurium, and cisatracurium). impairment; possibly increase the dose in patients with burn injury; electrolyte disturbances, history Succinylcholine (Suxamethonium) (Fig. 3.4a) of asthma, severe obesity, pregnancy, and Indications: breastfeeding. It is the only widely used muscle-relaxing Dosage: for intubation by intravenous depolarizer. It causes sudden, complete paralysis, injection. which is very short-acting and has particular Intubating dose: adults and pediatrics for importance for laryngoscopy and rapid sequence more than 5 months (80–100 mg/kg). intubation and emergency cases. Maintenance: 20–30 mg/kg. a b c d e f Fig. 3.4 (a): Suxamethonium (Succinyl-choline). (b): Rocuronium (c): Atracurium (d): Cisatracurium (e): Neostigmine (f): Sugammadex 36 N. A. Shallik et al. Adverse effects: the minimal release of hista- Uses: for routine tracheal intubation, and to mine (rarely hypersensitivity reactions including provide muscle relaxation during surgery or bronchospasm, hypotension, tachycardia, edema, mechanical ventilation. It is metabolized by non-­ erythema, and pruritus). enzymatic degradation (Hofmann elimination), it can be used in patients with renal and liver Pancuronium Bromide diseases. It is a long-acting non-depolarizing muscle Contraindications: hypersensitivity to atra- relaxant. curium or cisatracurium. Form: 2 mg/mL solution for injection. Precautions: bronchial asthma, neuromuscu- Uses: intubation and muscle relaxation during lar diseases. surgery. Dosage: for Intubation by intravenous Contraindications: hypersensitivity to injection. pancuronium. Intubating dose: 0.5 mg/kg. Precautions: renal and/or hepatic Maintenance dose: 0.1 mg/kg. impairment. Adverse effects: increases plasma histamine Dosage: for intubation by intravenous levels, causing skin flushing, hypotension, and injection. tachycardia. Intubating dose: 0.1 mg/kg. Maintenance dose: 0.02 mg/kg. Cisatracurium (Fig. 3.4d) Adverse effects: prolonged neuromuscular It is an intermediate-acting non-depolarizing blockade in patients with renal impairment. muscle relaxant. Form: 2 mg/mL solution for injection or Rocuronium Bromide (Fig. 3.4b) infusion. It is an intermediate-acting non-depolarizing Uses: for routine tracheal intubation, and to muscle relaxant. provide muscle relaxation during surgery or Form: 10 mg/mL solution for injection/ mechanical ventilation. It is metabolized by non-­ infusion. enzymatic degradation (Hofmann elimination), it Uses: for rapid sequence intubation because it can be used in patients with renal and liver has a faster onset than other non-depolarizing diseases. muscle relaxants and routine tracheal intubation Contraindications: hypersensitivity to atra- and to provide muscle relaxation during surgery curium or cisatracurium. or mechanical ventilation. Precautions: bronchial asthma, neuromuscu- Contraindications: hypersensitivity to lar diseases. rocuronium. Dosage: by intravenous injection. Precautions: renal and/or hepatic impair- Intubating dose: 0.15 mg/kg. ment, neuromuscular diseases. Maintenance dose: 0.03 mg/kg. Dosage: for Intubation by intravenous Adverse effects: Adverse effects are uncom- injection. mon with the use of cisatracurium. Intubating dose: 0.6–1.2 mg/kg. Maintenance dose: 0.15 mg/kg. Adverse effects: prolonged neuromuscular 3.4.1 Reversal of Neuromuscular blockade in patients with renal impairment. Block Atracurium (Fig. 3.4c) Cholinesterase Inhibitor—Neostigmine It is an intermediate-acting non-depolarizing Methylsulfate: (Fig. 3.4e) muscle relaxant. Form: solution for injection, neostigmine Form: 10 mg/mL solution for injection or 500 mcg/mL, 1-mL ampoule; 2.5 mg/mL, 1-mL infusion. ampoule. 46 N. A. Shallik et al. recheck away from theater stress. In addition, dispensing accuracy generally improves admin- istration accuracy. 4.3 Drugs Handling 4.3.1  edication Errors During M Anesthesia, Standardization of the Anesthesia Drug Tray System Medication errors in anesthesia practice is a real Fig. 4.1 Standardized color coding of prefilled syringes concern in fact the accurate prevalence of this problem is not well known however estimation is roughly between 1–5% of administered anes- order inside separate bins, healthcare worker thetic medications this might be due to many of must have a biometric access as a fingerprint to medications error is not noticed and others not pull drugs, by entering the patient name, a page reported. will open showing all the ordered drugs write the Human error occupies a big part of this error needed drugs name a specific bin will open and a in general the literature is lack of evidence in a light blink for guidance. The high alert medica- clear strategic plan to eliminate administration of tions and the narcotics need a second person as a wrong anesthetic medication. witness for safety reason. Medication errors, which can lead to adverse Once the drugs have been loaded in a labeled drug reactions, require clear and unambiguous color-coded syringe with date, dosage, initial definitions, so that patients, prescribers, manu- and patient sticker, a specific tray will take a facturers, and regulators can all understand each place to regroup all those syringes in clear man- other. The classification of medication errors on ner. The used drug’s tray must be removed at the the basis of the underlying psychological mecha- end of each case and replaced by a new drug tray, nisms, based on how errors occur, can suggest later the used drugs are restocked by pharmacy strategies that help to reduce their occurrence. technician. Using a multimodal system reduce documen- Errors usually happen when the intended tation and drug administration errors in anesthe- action intended but could not performed, the sia, customized at site with well-organized reason for this can be divided either due to mis- workspaces, prefilled syringes for the most com- takes (deficiency in planning) or due to slips monly used drugs, large lettered and legible drug and lapses. labels with standardized color coding in purpose Fig. 4.2 demonstrates the errors which can be designed drug drawers, a barcode reader linked reduced by managing the gaps as follows: to a computer, speakers, and touch screen to pro- vide automatic auditory and visual verification of 1. knowledge, a drug immediately before its administration 2. well-built rules, (Fig. 4.1). 3. improve technical supplementation, In our days, many healthcare facilities espe- 4. avoiding lapses and improving memory. cially in ORs starts using technologies to enable smarter, safer medication management known as Currently, there are some features to prevent the automated drugs cabinet. medication errors in anesthetic gases and volatile All anesthetic drugs are placed in a pharmaco- agents which show significant improvement in logic class or from the more to the less usage safe inhalational drugs delivery to the patient. 4 Pharmacy, Drugs Labeling, and Storage 53 Automated dispensing machines is the capa- Table 4.3 Stages of medical aseptic technique bility to track and proactively monitor drug Summary for the Principles of aseptic technique and the usage patterns. rationale behind it Automated dispensing machines enhance The Task Rationale Hand hygiene Remove transient micro-­ first-dose availability and facilitate the timely organisms from the hands administration of medications by increasing Safe storage of Prevent damage to the sterile their accessibility on patient care units. equipment equipment preserve sterility of Automated dispensing machines reduce phar- the equipment and prevent macists’ dispensing time, as inventory man- microbial contamination Cleaning of the Reduce microbial contamination agement is driven by the pre-established procedure trolley minimum and maximum levels and is handled or tray exclusively by pharmacy technicians. Preparation of Prevent microbial contamination equipment of sterile equipment Personnel Aprons provide protection for protective potential contamination from the 4.5 I nfection Control Related equipment health care workers (HCW) to Drugs Use (Aseptic uniform and the procedure and Technique) also protect HCW from potential contamination from the procedure Non-sterile gloves provide Many patients are affected every year by health protection the HCW from care associated infection most of these infections contamination from blood and related to invasive procedure. body fluid that may contaminated Hence intravenous drug administration is con- the hands Sterile gloves protect key sites sidered as one of the possible sources of infec- from potential microbial tion, aseptic techniques should follow during contamination from HCW hands intravenous medications administrations includ- Preparation of the Reduce microbial contamination ing in operating theater. Aseptic technique is environment during the procedure defined as a process or procedure used to achieve Preparation of the Gain informed consent and patient reduce anxiety asepsis to prevent the transfer of potentially Waste disposal Prevent contamination of the pathogenic micro-­organisms to a susceptible site environment that may result in the development of infection. Documentation Provide essential communication Examples of when to use a medical aseptic and meet the standards technique are as follows: Dressing a surgical wound. ment will prone the patient to an avoidable Inserting a peripheral cannula. infection (Table 4.3). Venipuncture. It is recommended before intravenous drug Inserting a urinary catheter. injection not to touch any key part of the cannula Administrating intravenous drugs. and using caps and covers, such as the sterile wrapper of a syringe to protect the key part of the syringe before use. To achieve the main goal ide- 4.5.1 Principles of Aseptic Techniques ally the health care provider should follow the principles summarized in Table 4.1. The fundamental principle of an aseptic tech- nique/ANTT incorporates protecting key ele- Take-Home Message ments of the equipment (usually parts of Familiarity with simple and serious side effects equipment with contact of internal organs or of used medication is essential and a must. blood) that should remain free from micro-­ Minimalizing medications errors is important organisms, contaminating of these parts of equip- to avoid any serious harm to the patient, this 84 N. A. Shallik et al. O2 saturation Uses PaO2 ratio of oxyhaemoglobin to total Measuring the cuff pressure in Endotracheal haemoglobin. Tube (ETT), Laryngeal Mask Airway (LMA), Normally 95–98%. and Laryngeal Tube (LT) in order to ensure safe pressure limit and prevent complications. 6.6 Cuff Pressure Gauge Description Luer attachment to connect to pilot balloon. Overview Rubber hand bulb for cuff inflation. Cuff pressure gauge is known as ETT cuff Pressure display gauge. manometre Fig. 6.5. Pressure release valve on which allow releas- ing air. Ergonomic design to enable inflation and deflation with one hand. Latex free components. Gauges. –– range unit could be in centimetre water or millimetre mercury depends on the brand model usually the range between 0–60 cmH2O and 0–120 cmH2O. –– variable coloured wedge on the gauge according to the recommended pressure limits. Method of insertion/use Firm attachment of the pilot balloon cuffs with pressure gauge Luer connector. To reduce high cuff pressure press release mechanism button. minimal leak technique: inflate ETT cuff, slowly deflate the air until bubbling sound could be heard on inspiration which indicate leak around ETT cuff, gradually re-insufflate cuff until leak disappears then check cuff pres- sure to ensure it is in the safe zone. Complications It gives false reading if not attached properly. Loss of PEEP and micro-aspirate can be hap- pened with over cuff deflation. Fig. 6.5 Cuff Pressure Gauge (Image courtesy Dr. Nabil Shallik) 6 Essential Anaesthesia Monitors and Equipment in the Operating Theatre 85 Cuff size can variably fit in the trachea that is Likelihood of abnormal rhythm to revert in to why the recommended safe zone should not normal rhythm is inversely proportional to always followed blindly and sometimes need time which indicate as early as possible early to perform minimal leak technique in order to defibrillation. avoid serious complications like aspiration or Successful reversion decreases around 7–10% inadequate ventilation. every minute min from onset of VF. Exceeding proper pressure limit can lead to The applied external electrical current causes mucosal necrosis and subsequence tracheal synchronous contraction of cardiac muscle, complications like stenosis or stricture. which allows sinus rhythm to occur after refractory period. Other information Inside the defibrillator, the capacitors make a In general, the pressure for balloon ETT potential difference between two plates and between 20 and 30 cmH2O is safe. can reach up to 8000 V after discharging all In shocked patients pressure limit for currents. mucosal ischemia is lower than healthy patient –– estimated energy is 360 J for external defib as the mucosal perfusion is less. patches while it is 50 J for internal defib which apply directly to the heart muscles. Thoracic impedance inversely proportional 6.7 Defibrillators with number of shocks which means second shock will deliver greater energy and so on. Uses The wave form during energy discharge Applying an electrical current across the heart release can be (monophasic or biphasic). can convert serious cardiac arrythmia (VF/ VT) to sinus rhythm Fig. 6.6. Monophasic Voltage rises rapidly and then returns to base- Description line (0, +ve, 0) consequently. Essential modality in cardiac arrest case management. Biphasic Voltage rises, then reverses its direction below baseline before returning to baseline (0, +ve, 0, −ve, 0) consequently. The effective defibrillation of biphasic and monophasic are similar however the biphasic deliver lower energy. It is smaller than monophasic easy to carry and cheaper in price. Method of insertion and/or use attach paddles to patients as recommended, charge, stand clear, discharge. Fig. 6.6 Defibrillator (Image courtesy Dr. Nabil Shallik) 88 N. A. Shallik et al. Chip at the distal end (CMOS Chip). Complications 5.5- and 4.0-mm outer diameter 2.3- and 1.5-­ mm diameter of the working channel. airway trauma is possible complication espe- Smaller sizes started to appear in the market cially in unexperienced providers, now. in case the inadequate anaesthesia the patient Documentation with pictures and movies. might cough or even bronchospasm might Integrated LED light source. happen, Light weight (385 g). oxygen desaturation might happen during the Excellent overview for intubation (4:3 image). procedure especially in fragile patient and Connected to the high-resolution monitor. high flow nasal oxygen (HFNO) can be used Enables fast switch to the Video Laryngoscope. to prevent oxygen desaturation, Less service – no image fibres! barotrauma, Suitable for intubation (ETT, DLT) and basic bronchoscope damage for example patient bit- bronchoscopy procedure (bronchial lavage ing the scope, and lung exploration). infection transmission could happen between the operator and the patient especially if inad- Checklist before using the fiberscope: equate respiratory precautions taken, accidental extubation while removing the Clean and disinfect every time to use. scope. The movements of the tip before use. The suction port is working. Light source is working. 6.9 Laryngoscope and Blades Defog the tip using anti-fog, alcohol swap. Adjust sharpness of the pic. and white Overview balance. Lubricate the shaft not the tip. A device used during endotracheal intubation Make orientation mark at 12.00 O’clock. to visualize the vocal cords and facilitate intubation. Method of insertion/use Use Make sure to assemble the flexible broncho- scope as recommended by the provider. Facilitate endotracheal tube (ETT) insertion Various techniques can be used to anesthe- by visualization the vocal cords. tized patients’ airway with local anaesthesia Might help in gastric tube and transoesopha- medications and deep sedation might also be geal echocardiography (TEE) probe insertion. used. Make sure the ventilator is ready to use and Description the variables adjusted according to the patient. Connect monitors as recommended by ASA. Blade base. Suction should be ready to use. Hook of blade. Insert a Y connector. Curved (Macintosh) or straight blade (miller). Insert the distal tip. Flange which containing web and light source. Manipulation can be done by flexion exten- Handle tip contains batteries and electrical sion and rotation. connection. 7 Infection Control and Prevention in Operation Theatre 103 by the US Centres for Disease Control and ally recommended policies for their decon- Prevention. After that, they added a new category tamination and/or sterilization, and based on designated as environmental surfaces which is the manufacturers’ advice, should be followed subdivided to housekeeping surfaces and medical and audited. equipment surfaces. Well, it is a fact that anaes- 6. Appropriate infection control precautions thesia providers are a potential vector of cross should be established for procedures such as contamination between medical equipment sur- spinal and epidural insertions, epidural blood faces and patients. patches, blood cultures, and urinary catheters. 7. Anaesthetists should administer antimicrobi- als according to local protocols in order to 7.4 Recommendations preserve their future effectiveness. Association of Anaesthetists of Great Britain and Ireland (AAGBI) have put up the following rec- 7.4.1 Standard Precautions ommendations in their latest guidelines. Most anaesthesia societies recommend adhering 1. There should be a named Lead Consultant in to standard precautions, which is in most cases each Department of Anaesthesia who is are simple Personal Protective Equipment (PPE) responsible for liaising with their Trust (gloves, masks, eye protection shields, and Infection Prevention and Control Team and gown). These are recommended for every patient Occupational Health Department to ensure when contact with bodily fluids including blood, relevant specialist standards are established mucus membranes are anticipated. Special pre- and monitored in all areas of anaesthetic cautions should be taken when there is possibility practice. of splatter of body fluids [9, 10]. 2. Precautions to prevent the transmission of infection between patient and anaesthetist or between patients should be routine practice. 7.4.2 Hand Hygiene (HH) All anaesthetists should comply with local infection control policies, including the safe Hand hygiene is a cornerstone in reducing the use and disposal of sharps. risk of hospital-acquired infection (HAI). 3. When performing invasive procedures, the cor- According to the WHO it should be performed rect skin cleaning solution should be used. For ideally in five crucial moments at a hospital envi- neuraxial procedures, 0.5% chlorhexidine glu- ronment Fig. 7.2: conate in 70% alcohol is recommended. For invasive vascular procedures, 2% chlorhexi- 1. before touching a patient (e.g., attaching the dine in 70% alcohol is recommended. monitor cables); 4. Protocols should be followed to minimize 2. before clean/aseptic procedures (e.g., insert- infection risk associated with indwelling inva- ing CVC, inserting arterial catheters, drawing sive devices. These include correct dressing medications, and spiking IV bags); application, cleaning before access, flushing, 3. after body fluid exposure/risk (e.g., intuba- changing of administration sets, regular tion, inserting LMA, induction, oral and tra- review of device condition, and assessment of cheal suction); continuing need. 4. after touching a patient (e.g.: removing the 5. Single-use equipment should be used wher- body warmer); ever transmission of infective agents is a risk. 5. after touching patient surroundings (after Techniques exist for the reprocessing of some entering/exiting the OR and even removing single-use equipment, in which case nation- gloves). 104 N. A. Shallik et al. 2 Before a procedure 1 Before touching a patient 4 After touching a patient 3 After a procedure or body fluid exposure risk 5 After touching a patient’s surroundings Fig. 7.2 The WHO recommendations for hand hygiene (HH) during patient care 7.4.3 Technique 7. Step 7: Open the palm of one hand and rub the fingers of another hand in circular motion, The following are the steps of proper hand- then repeat with swapping to another hand. washing (Fig. 7.3): 1. Step 1: Wet the hands with lukewarm water Joint Commission International (JCI) is rec- (35–45 °C) and apply soap, create lather. ommending 40–60 s for hand washing with plain 2. Step 2: Rub your palms in clockwise and soap duration, and 20–30 s for hand rub with anticlockwise. alcohol-based hand rub (ABHR) and better to 3. Step 3: Link the fingers and rub the back of follow the manufacturer guidelines.. your hand with palms of second hand, then Applying Alcohol Based Hand Rub (ABHR) alternate. on gloves being worn during a case, instead of 4. Step 4: Put both palms facing together and removing them and performing hand hygiene link fingers, clasp hands, then rub them. between doffing and donning is not advised. 5. Step 5: Cup the fingers keeping one hand over Because, there is no sufficient researches ensuring another, interlock fingers and rub the backs glove’s integrity after application of foam/gel. against palms, alternate hands. Actually, gloved hands are usually assumed to be 6. Step 6: Encircle one hand around the thumb contaminated, however, bare hands are assumed of another, keep rubbing in rotating motion, to be clean following appropriate HH. Indeed, the. then alternate. 7 Infection Control and Prevention in Operation Theatre 105 Fig. 7.3 Steps of proper handwashing 106 N. A. Shallik et al. Centres for Disease Control (CDC) and WHO guidelines recommend removing gloves before performing HH as standard practice. The wearing of the full maximal sterile barrier (full PPE that includes: face mask, cap, sterile gown, sterile gloves) and a large sterile drape, should be used by the anesthesia provider during operation theatre technique before inserting Central Intravenous Catheters (Fig. 7.4). Also, it is a must to use of a cap, mask, sterile gloves, and a small sterile fenestrated drape; in case of plac- ing peripheral arterial lines. Meanwhile, those measures should be followed whenever a catheter is exchanged over a guidewire. 7.5 Cleaning of the Operating Theatre After each patient, the operation theatre should be thoroughly cleaned, applying local protocols for bodily fluids cleaning on the area, including the floor, which should be disinfected in between the cases. Cleaning should also take into account type of identified pathogens, for example, MRSA, VRE, and Clostridia. Regular cleaning schedule should be in place and take into account recom- mendations from infection control team. Fig. 7.4 Full Personal Protection Equipment (PPE) 7.5.1 Anaesthesia Workspace This general rule of cleaning anaesthesia workspace surfaces with hospital approved disin- Parts of current anaesthetic equipment cannot be fectant between cases is applied as well on com- made single use; this increased the risk of cross puter keyboard, mouse, and touchscreen, contamination. Appropriate cleaning and avoid- anaesthesia workstation (including monitors, ing reusing single-use items should be strictly APL valve, knobs, vaporizers, and monitor implemented. cables.) Moreover, disinfection is indicated Anaesthesia workspace surfaces should be whenever there is obvious soiling or wiped between each case including the anaesthe- contamination. sia supply cart (Fig. 7.5). That is why, it is prefer- Indeed, several studies have demonstrated the able to avoid storage supplies on its top surface, potential for contamination of anaesthesia equip- as much as possible. Also, its interior must be ment and workspaces and possible transmission cleaned on a tailored basic period fixed by the of a variety of microorganisms within the anaes- facility. Regarding its drawers and bins, anaes- thesia environment. thesia providers should perform HH before open- Thereby, especially after COVID-19 pan- ing them and handling their contents. demic, facilities are encouraged to consider dis- 7 Infection Control and Prevention in Operation Theatre 107 Fig. 7.6 Disposable plastic coverage of anaesthesia machine particles. To retain heat and moisture, inert, sponge form material is added. Fig. 7.5 Cleaning wipe Actually, Mycobacterium Tuberculosis (TB) can survive for 3 h in soda-lime and 40% of bac- posable coverage anaesthesia machines, as it has teria can pass through it. Therefore, the High- a rational impact on reducing contamination also Efficiency Particulate Air (HEPA bacterial) filters facilitate cleaning and disinfection (Fig. 7.6). must be used in the respiratory circuit or at least On the other hand, internal components of on the expiratory limb because their efficiency is anaesthesia ventilators including Airway not affected during wet conditions. The anaesthe- Breathing System (ABS), reusable soda lime sia provider may add another filter on the inspira- canister and valves, must be cleaned and disin- tory limb if it is not increasing respiratory fected per manufacturer’s instructions and the pressures (for more details, please refer to hospital infection control policies. Filter is usu- the end of this chapter under filter subtitle). ally used to protect anaesthesia machine and cir- Indeed, vials’ rubber stoppers and necks of cuit, which may prevent cross contamination. anaesthesia drugs ampules are not sterile. Hence, it Modern filters allow humidification and heat should be a standard practice of disinfection by exchanged and basically two kinds of designs are scrubbing them with 70% alcohol prior to each use. used. Type one includes mechanical filters, they Aiming to reduce the contamination of periph- stop particles larger than its pores. Second type is eral intravenous tubing stopcocks (triple ways) electrostatic filters which attract and hold charged and injection ports that are used for medication 108 N. A. Shallik et al. administration during intraoperative use, with locking caps due to the possibility of external potential pathogenic bacteria due to lower com- surface contamination [14, 15]. pliance rates of provider HH and higher numbers Meanwhile, multiple-dose medication vials of intravenous medication. It is recommended, to must be used for only 1 patient and should only wipe those ports with alcohol ports for 10–15 s be accessed with both new sterile syringe and followed by a drying time immediately before needle for each entry. each injection. However, during induction and Moreover, the ideal practice is to minimize the emergencies, passive disinfection using sterile time between spiking IV bags and patient admin- alcohol-containing caps is turning out as the most istration and also it is challenging in urgent cir- practical approach. cumstances including lifesaving surgeries which To reduce the risk of bacterial contamination require advanced set-up of IV fluids like Level of the syringe and syringe contents; needleless one. syringes should be capped with a sterile cap that completely covers the Luer connector on the syringe. This technique should be used to admin- 7.5.2 Airway Management ister multiple doses of a drug to the same patient Equipment after each administered dose (Fig. 7.7). The United States Pharmacopeia (USP) 7.5.2.1 Laryngoscopes Chapters which were effective from first Metal laryngoscopes /video laryngoscopes blades December 2019, advise to follow the beyond use are classified as semi-critical items requiring dating of OR intravenous drugs and solutions list sterilization or high-level disinfection (at the classified upon the contamination level risk and minimum) prior to use. Then, stored in appropri- the product stability [9, 10]. ate packaging with tags and preventing recon- Mainly, they recommend to discard prepared tamination. Though handles are classified intravenous medication and solution in the OR, non-critical items, cleaned by 70% alcohol and after each case even not used, especially those 2% chlorhexidine or coco alkyl dimethyl benzyl which have not been prepared in air environment ammonium chloride, studies show shown that less than ISO class 5 (e.g., Pharmacy IV drug 40–50% of laryngoscope handles become con- room). So, they discourage anaesthesia providers taminated with blood during airway management to return back to stock unused commercial pre- (Fig. 7.8). filled syringes even with have intact security Therefore, reusable laryngoscope handles should be disassembled and autoclavable in a monthly basis, plus in case of resistant microor- Fig. 7.8 Washing the laryngoscope handles before Fig. 7.7 Sterile cap for Luer lock sterilization 7 Infection Control and Prevention in Operation Theatre 109 ganism risk. The sterilization process makes their reprocessing potentially costly. That is why, it is recommended to consider using single-use laryn- goscopes due to their performance, costing less than high-level decontamination for reusable laryngoscopes also, with possibility of recycling. Currently, many options of single-use video laryngoscopes are available, for example, the Fig. 7.10 Fibre-optic endoscope ready for sterilization Cobalt GlideScope® video laryngoscope (cGVL). It is composed of reusable video baton and a dis- posable clear plastic blade that is placed over it. bioburden has an opportunity to dry. The second The disposable blade can be discarded after each step is wiping the exterior of the endoscope with use and a new one placed on the video baton for the appropriate fiber optic endoscopes detergent subsequent intubations, eliminating the need for solution (never use alcohol wipes it will destroy disinfection of the cGVL blade and reducing the its membrane). Glutaraldehyde 2% solution is the potential risk of cross-­contamination of infectious recommended agent for chemical disinfection of material between patients. The cGVL video baton fiber-optic bronchoscope and it should be placed must, however, undergo low-­ level disinfection in the solution for 10–30 min. after each patient use, and if it becomes visibly For using gas sterilization, five hours’ expo- contaminated with gross material, high-level dis- sure to Ethylene Oxide (EO) is recommended for infection of the baton must be performed. Other sterilization of instruments (Fig. 7.10). brands of single-use video laryngoscopes are available in the market and each brand has its advantages and disadvantages (Fig. 7.9). 7.6  naesthesia Breathing Circuit A Filters, Types Fig. (7.11) 7.5.2.2 Fiber-Optic Endoscopes After using the fiberoptic endoscopes, preclean- 1. Electrostatic. ing through removing the patient’s secretions is a compulsory step. In fact, it should be performed In electrostatic filters, the use of polarized at the point of use in the operating room, before material in the electromagnetic field, which attracts and captures the charged microbes and viruses, and it holds them within a loosely woven. It has bigger pores comparing to the second type but ensures better air quality with less airway resistance. 2. Mechanical (HEPA). As its name indicates High-Efficiency Particles Air (HEPA), which physically, stops and prevents pathogens from passing through its miniscule pores. It consists on pleated hydropho- bic glass fibres. In fact, HEPA filters tended to outperform Fig. 7.9 Example of disposable video-laryngoscopic electrostatic filters since the latter can lose their blades effectiveness with humidity during the use of a 110 N. A. Shallik et al. Water vapor is given back during Hydrophobic membrane inspiration Water vapor is Hygroscopic component collected By HME during expiration Fig. 7.11 Cross section in filter circle system with active humidification. humidification is mandatory to supply Actually, HEPA filters capture efficiency = 0.01 this missing heat and moisture. micron; meanwhile; the size of SARS HMEF filters capture heat and moisture COV-2 = 0.125 micron. by around 50% of the patient exhaled All filters efficient filters have to be subject of moisture passively to prevent hypother- ISO 23328-1 and ISO 9360-1 standards; by mia, disruption of the airway epithelium, means of standardized test performing a minimal bronchospasm, and atelectasis. Viral Filtration Efficiency (VFE) of 0.3-micron (b) Contraindication. particle challenge. Patients with frank bloody or thick, copi- ous secretions. 3. Heat Moisture Exchanger Filter (HMEF). Patients with an expired tidal volume less than 70% of the delivered tidal volume. These filters (either electrostatic or HEPA) may be modified by inserting sponge material some- Example: times chemically coated to perform additional Those with large bronchopleurocutaneous functions like conservation of heat and moisture fistulas. content of inhaled respiratory and anaesthetic gases Tracheal tube cuff malfunction. and thus function as Heat, Moister Exchanger Presence of uncuffed endotracheal tube. Filters (HMEF) (a) Indications. (c) HMEF Positioning Fig. 7.12: The upper airway provides 75% of the Connection to the expiratory hose: heat and moisture supplied to the alveoli –– It is prohibited to place a filter with HME during invasive mechanical ventilation, characteristics between the circuit and 7 Infection Control and Prevention in Operation Theatre 111 Inspiratory Limb HME Filter Ventilator Patient Expiratory Limb Fig. 7.12 HME Position in Ventilator circuit the soda lime absorber (on the expiratory gas with faster condensation of the water hose) due to the risk of biohazards by trap. creating a microenvironment in circle Breathing circuit filters (without humidifier) absorber systems that predisposes an Positioning. accumulation of carbon monoxide and –– All antiviral and antibacterial filters (either other toxic metabolites such as HEPA or electrostatic) have to be placed Compound A. between breathing circuit and the expira- –– This compound is one of the several prod- tory hose, as a second barrier, to protect the ucts formed when sevoflurane is in the anaesthesia machine from any potential presence of strong bases in soda lime and pathogenic risk during disconnection and/ barium hydroxide lime, especially at higher or replacement of the filter at the patient temperatures. Compound A is the most side. common sevoflurane degradation product –– It is strongly recommended to use HEPA in anaesthesia machines. Unfortunately, filters, because their VFE is not affected by these compounds have been demonstrated wet conditions like electrostatic ones. to be nephrotoxic in mice. However, they may exceed breathing Connection to the Inspiratory hose or resistance. Endotracheal Tube port (ETT): –– HME/filters are designed to retain exhaled moisture on the patient side of 7.7 Ultraviolet Germicidal the HMEF. They can only contribute to Irradiation (UVGI) an effective patient humidification if they are placed directly in contact with ETT UV irradiation produces ultraclean air in opera- port. tion theatres (OT) and highly effective way to –– This assembly is indicated as well, in order reduce microbial contamination in the OT. It is to avoid contamination of the gas measure- much more cost-effective than the laminar air ment unit and consequently the entire system and its efficiency is not less. The most anaesthesia device. commonly used technologies are: low pressure –– If placed in distal position (on the inspira- mercury lamps or pulsed xenon lamps. The effi- tory hose), it will decrease the absolute cacy of disinfection depends on the distance of humidity and temperature of the ingoing the light source and surface, because intensity of  Anesthesia Machines and Anesthetic Breathing System 8 Kemal Tolga Saracoglu, Berk Cimenoglu, Recep Demirhan, Ayten Saracoglu, and Gamze Tanirgan Contents 8.1 Introduction  118 8.2 Basic Components of Anesthesia Machine  118 8.2.1 Oxygen Flush Valve  119 8.2.2 Fail-Safe Systems  119 8.2.3 Safety Systems to Prevent Hypoxic Gas Mixture  120 8.2.4 Causes of Flowmeter Malfunction  120 8.2.5 Vaporizers  120 8.2.6 Factors Affecting the Vaporizer Output  120 8.2.7 Points to Pay Attention in Vaporizers  120 8.3 Carbon Dioxide (CO2) Elimination  120 8.3.1 Ventilators  121 8.3.2 Ventilation Modes  121 8.3.3 Scavenging System  121 8.3.4 Alarm Systems in Anesthesia Machine  121 8.3.5 Monitors of Anesthesia Machine  121 8.4 Anesthesia Machine Calibration and Checklist  122 8.4.1 A  nesthesia Machine Calibration  122 8.4.2 Checklist  122 8.4.3 Checking the Oxygen Cylinder  122 8.5 Breathing Systems  122 8.5.1 C  lassification  122 8.5.2 S emi-Closed Breathing Systems  123 8.5.3 Closed Breathing Systems  123 8.6 Conclusion  123 K. T. Saracoglu (*) A. Saracoglu Department of Anesthesiology and Reanimation, Department of Anesthesiology and Reanimation, Health Sciences University Kartal Dr. Lutfi Kirdar Marmara University Pendik Training and Research Training and Research Hospital, Istanbul, Turkey Hospital, Istanbul, Turkey B. Cimenoglu · R. Demirhan G. Tanirgan Department of Thoracic Surgery, Health Sciences Department of Anesthesiology and Intensive Care, University Kartal Dr. Lutfi Kirdar Training and Marmara University Medical School, Research Hospital, Istanbul, Turkey Istanbul, Turkey © Springer Nature Switzerland AG 2022 117 N. A. Shallik et al. (eds.), Improving Anesthesia Technical Staff’s Skills, https://doi.org/10.1007/978-3-030-88849-7_8 118 K. T. Saracoglu et al. 8.1 Introduction Vaporizers. Breathing circuits. Anesthesia machine provides the control of Ventilator. patient’s gas exchange. In addition, anesthesia Scavenging System. maintenance is carried out by applying inhalation Monitors. anesthetics. Morton identified ether in 1846. In 1912, Gwathwey described continue flow anes- The anesthesia machine can be divided into thetic machine. Then, Boyle modification was three parts as high, intermediate, and low pres- reported in 1917. Anesthesia machine reduces the sure systems. The high pressure system includes pressure of desired gases to a safe level. Volatile cylinders and pressure regulators. Oxygen pres- anesthetics are vaporized into the final gas mix- sure is kept between 2200 and 45 psig. Nitrous ture. It controls the flow of oxygen and nitrous oxide (N2O) pressure ranges from 750 to 45 psig. oxide. Positive pressure ventilation is provided The high pressure system provides more constant by anesthesia machine. The risk of delivering and proper gas transport to the flowmeter. hypoxic gas mixture to a patient is avoided. The intermediate pressure system starts from pressure regulators and continues to the flow con- trol valves. The pressure of gas supplied from 8.2 Basic Components cylinder to the anesthesia machine is 45 psig, of Anesthesia Machine while the approximate pipeline pressure is about (Figs. 8.1 and 8.2) 50–55 psig. The anesthesia machine receives medical gases from piping network and cylin- Gas supply. ders. The cylinders are generally used as a back- Flowmeter. ­up supply in case of pipeline failure. Fig. 8.1 Basic features of anesthesia machine 8 Anesthesia Machines and Anesthetic Breathing System 119 Fig. 8.2 The monitors of anesthesia machine 8.2.1 Oxygen Flush Valve electricity. There could be electronic flowmeters in the low pressure system as well. There are It is located in the intermediate pressure system electronic flowmeters in modern anesthesia with 45–60 psig pressure. It allows the delivery machines. In these machines, the data are dis- of 35–75 L/min of 100% oxygen flow to breath- played graphically or numerically on the screen. ing circuit. Malfunction of oxygen flush valve may result in barotrauma or awareness during anesthesia. It dilutes the anesthetic agent 8.2.2 Fail-Safe Systems concentrations. The hose attachment to the anesthesia machine Fail-safe systems prevent the delivery of a is specific for each supplied gas. Connectors have hypoxic mixture of gas to the patient. These sys- safety features such as non-interchangeable tems include pneumatic and electronic alarm screw thread (NIST). Moreover, there are differ- devices. When the oxygen pressure drops below ent universal colored flexible hoses for each gas a limit set by the manufacturer, it gives an alarm to prevent incorrect connection. within 5 seconds. This is called 2000 ASTM The low pressure system contains the flowme- F1850–00 standard. In addition, the oxygen con- ter tubes, vaporizers, unidirectional valves, and centration in the common gas outlet should not components up to the common gas outlet. The be below 19%. Modern anesthesia machines have low pressure section is the section distal to the many safety equipment. The aim is to minimize flow control valves. Flowmeter and flow control the risk of hypoxic gas mixture. Fail-safe system valves separate intermediate and low pressure is present in all gas lines except oxygen. When systems. Flowmeter regulates the amount of gas oxygen pressure drops, other gases are either that will pass into the low pressure system. completely shut down or their ratio is reduced in The unidirectional valves prevent gas flow proportion to oxygen. Datex-Ohmeda machines back to the vaporizer during positive pressure feature pressure sensor shut off valve. It works on ventilation. The tubes have an antistatic coating the off-or-on principle. North American Drager on both surfaces, preventing the effect of static machines have oxygen failure protection device 120 K. T. Saracoglu et al. (OFPD), which shuts off nitrous oxide or allows anesthetic gas mixture passes through the vapor- its proportional flow. izing chamber. The gas flow directed to the vaporizing chamber is saturated with liquid anes- thetic agent. These vaporizers are agent specific. 8.2.3  afety Systems to Prevent S In flow over vaporizers, the carrier gas passes Hypoxic Gas Mixture over the inhalation agent in vaporizing chamber. There is oxygen/nitrous oxide ratio controller in Datex-Ohmeda Link 25 system. The oxygen gear 8.2.6 Factors Affecting is connected to nitrous oxide gear. When oxygen the Vaporizer Output flow decreases, nitrous oxide flow is directly reduced. This arrangement helps to ensure a min- Flow rate, temperature and characteristics of the imum oxygen concentration of 25%. The disad- volatile agent affect on vaporizer output. The vantage of proportional systems is that their characteristics of the carrier gas are also sensors are not oxygen specific. This poses a risk effective. of incorrect gas connections. Therefore; it is nec- essary to use an oxygen analyzer. 8.2.7  oints to Pay Attention P in Vaporizers 8.2.4 Causes of Flowmeter Malfunction Filling vaporizers with the incorrect anesthetics. They could provide wrong measurements Contamination. because of debris in the flow tube, static elec- Excessive tilting of vaporizers. tricity or sticking inside the tube. Overfilling. Scales may be mixed. Insufficient filling. Filling with multiple agents. Leaks. 8.2.5 Vaporizers Vaporizers are the devices which convert liquid 8.3  arbon Dioxide (CO2) C anesthetics into vapor and deliver volatile anesthet- Elimination ics to the breathing circuit. Vapor pressure is not affected by atmospheric pressure; it only depends The exhaled CO2 is chemically bound with gran- on the characteristics of the volatile agent and the ules consisting of alkaline metal and earth metal temperature. A liquid’s boiling point is the tem- hydroxides. Sodalyme and barolyme are the most perature at which its vapor pressure is equal to the commonly used absorbents. 100 g sodalyme atmospheric pressure. Boiling points at 760 mmHg absorbs 26 L CO2. On the other hand, 100 g are 22.5 for desflurane, 48.5 for isoflurane, 50.2 for barolyme absorbs 18 L of CO2. When the color halothane, 56.5 for enflurane, and 58.5 for sevoflu- change reaches 60–70%, the absorbent is replaced rane. All modern vaporizers are agent specific. (Table 8.1). They are capable of delivering a constant concen- When sodalyme and sevoflurane are com- tration of the agent regardless of temperature bined, Compound A and formaldehyde are changes or flow through the vaporizer. formed. Carbon monoxide formation increases Electrically heated special vaporizers must be with desflurane. New absorbents significantly utilized for desflurane because it boils at room reduce Compound A formation with Sevoflurane temperature. According to the working principle use. Spherasorb does not contain KOH and of agent-specific variable by-pass vaporizers, Amsorb does not contain NaOH and KOH. 8 Anesthesia Machines and Anesthetic Breathing System 121 Table 8.1 Active substances in the structure of CO2 according to lung mechanics. In both VC-SIMV absorbents which play a role in color change and PC-SIMV, the mandatory breaths are syn- Active substance in absorbent Color change chronized with the patients’ breathing effort. Ethyl violet White to purple Cresyl violet Red to yellow Ethyl orange Orange to yellow Mimosa Z Red to white 8.3.3 Scavenging System Phenolphthalein White to pink It consists of two parts: active and passive. In the passive system, gases are discharged with their 8.3.1 Ventilators own pressure. The positive pressure valve is suf- ficient. In the active system, there is a connection Ventilators are classified as single-circuit and to the hospital’s vacuum system. The negative double-circuit systems according to the move- pressure reducing valve protects against the neg- ment mechanism. Modern ventilators are timed ative pressure of the vacuum system. The positive and electronically controlled. In a double-circuit pressure reducing valve protects against the ventilator, the driving gas activates the pneumatic ­positive pressure caused by clogged replaceable system that pushes the bellows. Oxygen or a mix- hoses. ture of oxygen and air are used as pressurized The scavenging system extends the anesthesia gas. Single-circuit ventilators have special elec- circuit. Obstruction in the circuit may occur. In trically driven motors. They can work more pre- case of obstruction, excessive positive pressure is cisely and computer-controlled. This type of applied to the respiratory tract, which may cause ventilator requires no driving gas. An ascending barotrauma. bellows is safer. When the fresh gas flow is cut off, the ascending bellow will collapse; it pre- vents breathing of hypoxic gas mixture. 8.3.4  larm Systems in Anesthesia A Machine 8.3.2 Ventilation Modes There are several safety features in anesthesia machines. These are connected with alarm sys- In order to provide optimum mechanical ventila- tems. Oxygen pressure failure system works as a tion, the pressure, volume, and flow parameters standard to activate an audible alarm when oxy- on the ventilator should be adjusted in accor- gen pressure falls below a safe threshold. The dance with the patient’s respiratory system. oxygen failure safety system detects failure on Modes of mechanical ventilation can be classi- pressure and provides an alarm to warn the low fied according to the control of tidal volume. In level of oxygen. Integral monitor alarms are other this regard, volume controlled and pressure con- types for patient safety. trolled modes are available. Volume controlled modes include Continuous mandatory ventilation (VC-CMV), Synchronized intermittent manda- 8.3.5 Monitors of Anesthesia tory ventilation (VC-SIMV), and Autoflow. On Machine the other side pressure controlled modes are Continuous mandatory ventilation (PC-CMV), The monitors provide valuable information about Synchronized intermittent mandatory ventilation ventilation, oxygenation, hemodynamic parame- (PC-SIMV), Pressure control with volume guar- ters, and temperature. Ventilation monitoring antee (PC-CMV-VG), Pressure support ventila- includes pulse oximeter, end tidal carbon dioxide tion (PC-PSV), Biphasic positive airway pressure measurement, and respiratory rate analysis. (PC-BIPAP), and Airway Pressure Release Electrocardiogram (ECG), non-invasive and Ventilation (PC-APRV). In VC-CMV, there is a invasive blood pressure monitoring give informa- constant flow. Peak inspiratory pressure varies tion about circulation. 122 K. T. Saracoglu et al. 8.4 Anesthesia Machine Table 8.2 The list of items to be completed daily Calibration and Checklist Item to be completed Item #1: Verify auxiliary oxygen cylinder and 8.4.1 Anesthesia Machine self-inflating manual ventilation device are Available & Functioning Calibration Item #2: Verify patient suction is adequate to clear the airway Today, modern anesthesia machines are different Item #3: Turn on anesthesia delivery system and than simple pneumatic devices. Anesthesia work- confirm that ac power is available. station is consist of vital electrical, electronic, Item #4: Verify availability of required monitors, including alarms. and mechanical components such as computer Item #5: Verify that pressure is adequate on the spare equipped microprocessors. Therefore, their com- oxygen cylinder mounted on the anesthesia machine plex structure makes the calibration, mainte- Item #6: Verify that the piped gas pressures are ≥ 50 nance, and cleaning more complicated. The psig calibration includes the physical and electrical Item #7: Verify that vaporizers are adequately filled components of workstation, oxygen supply and and, if applicable, that the filler ports are tightly closed. the monitor, flowmeters, ventilators vaporizers, Item #8: Verify that there are no leaks in the gas and panel connectors. The calibration of oxygen supply lines between the flowmeters and the common sensor should be performed with both 21% and gas outlet 100% oxygen. The control of anesthesia device Item #9: Test scavenging system function. and related equipment should include routine Item #10: Calibrate, or verify calibration of, the maintenance and calibrations by authorized ser- oxygen monitor and check the low oxygen alarm. Item #11: Verify carbon dioxide absorbent is not vices. Weekly maintenance and daily checks exhausted should be performed by nurse anesthetists or Item #12: Breathing system pressure and leak testing. anesthesiologists. It is mostly applied as check- Item #13: Verify that gas flows properly through the lists and should be checked at appropriate time breathing circuit during both inspiration and intervals. exhalation. Item #14: Document completion of checkout procedures. Item #15: Confirm ventilator settings and evaluate 8.4.2 Checklist readiness to deliver ANESTHESIA care. (ANESTHESIA TIME OUT) The American Society of Anesthesiologists (ASA) issued a pre-anesthetic checkout proce- dure in 2008 as a guide. The items are presented the flowmeter is adjusted. Connections to oxy- in Table 8.2. gen delivery devices and oxygen cylinders should be checked for leakage at least once monthly. 8.4.3 Checking the Oxygen Cylinder Oxygen can be dangerous if not used correctly. 8.5 Breathing Systems Therefore, the check of the cylinder has a vital importance for both patients and health care 8.5.1 Classification workers. As oxygen may cause explotion and burns, the safety guidelines should be followed. Open systems. First, the pressure gauge is checked to prevent Semi-open systems. the lack of oxygen. Then, the gauge should be Semi-closed systems. checked when the valve is turned on. Afterwards Closed systems. 8 Anesthesia Machines and Anesthetic Breathing System 123 There is no anesthetic gas reservoir balloon in 8.5.2 Semi-Closed Breathing open systems. There is no rebreathing of exhaled Systems gases. These systems are simple and cheap. No breathing resistance occurs. It is used with insuf- It is the most commonly used breathing system in flation by open drop or mask method. adults and older children. There is CO2 absor- Semi-open systems are flow-controlled, valve-­ bent. Their disadvantage is that they are large, free, and non-rebreathing systems. There are less potable, and more complex. Resistance is types as Mapleson A, B, C, D, E, and F. The higher in spontaneous ventilation due to valves. Mapleson circuits are simple, lightweight, and Humidity is minimized when the fresh gas flow easy to clean. There is low breathing resistance. >5 L/min. Bacteria filter is required. Its advan- The disadvantages are that they require high flow tages are low cost, protection of humidity and rate, there is high heat and moisture loss and heat, reduction in environmental pollution, there is excessive anesthetic agent mixing into increased rebreathing with the decrease of fresh the operating room air. gas flow, and very low levels of fresh gas flow. Mapleson A is named as Magill circuit. It requires very high fresh gas flow to prevent rebreathing in controlled ventilation. Mapleson C 8.5.3 Closed Breathing Systems is named as Waters’ “to and fro” circuit. Mapleson If the fresh gas volume delivered into the system D is Bain circuit. Mapleson E is called as Ayre’s is exactly equal to the amount received by the T-piece. Mapleson F is Jackson modification. patient in a certain period of time, this system is The disadvantage is that it requires high fresh gas called a closed system. The entire volume of flow and waste gas excretion is not sufficient. expiratory gas returns to the patient after CO2 is Advantages are minimal dead space, minimal absorbed. Maintaining sufficient gas volume in resistance to breathing, and economy during con- the system is ensured by the fact that excess gas trolled ventilation. discharge valve is closed and no leak from the Bain circuit has coaxial modification. There is system is present. Closed breathing systems have fresh gas inlet tubing inside breathing tube. some hazards such as giving 02 in unknown and Exhalation occurs via outer tube. During sponta- insufficient concentrations and administration of neous ventilation, a fresh gas flow of 200– potent anesthetic inhalation agent at unknown 300 mL/kg/min is required for normocarbia. On