Basic Ultrasonography PDF

Basic Ultrasonography Shona McIntyre BVMS MRCVS Learning Outcomes To understand the generation and delivery of ultrasound and the difference between the standard probes To be able to describe an ultrasonographic image in terms of image quality and positioning in relation to tissues of int...

Basic Ultrasonography Shona McIntyre BVMS MRCVS Learning Outcomes To understand the generation and delivery of ultrasound and the difference between the standard probes To be able to describe an ultrasonographic image in terms of image quality and positioning in relation to tissues of interest To describe potential imaging faults and the means to avoid, identify and account for such faults Discuss the relative advantages and disadvantages of abdominal ultrasound and radiography 2 Basic Ultrasound Principals Ultrasound uses transmission of sound waves through tissue to produce an image A current is applied to the piezo-elements in the transducer This causes the crystals to change shape and oscillate, producing an ultrasound wave Returning sound waves are received at the transducer, causing compression of the crystals and thus an electric voltage This signal is then amplified, converted, and displayed as a dot on the screen 3 Interaction with tissues 1. Reflection – a wave is reflected back to the transducer and called an echo 2. Refraction - the change in direction of a wave due to differing velocities of tissues 3. Diffraction – change in direction of a wave through an opening or around a barrier. Allows sound waves to be detected around a corner 4. Attenuation – loss of energy of the wave due to scatter or absorption 4 Interaction with tissues Reflection Refraction 5 Interaction with tissues Diffraction Scatter 6 Ultrasound Probes Linear Array Curved Array Phased Array Crystals in a line Crystals in a curve Crystals in a line Rectangular image Fan shaped image Fan shape – greater depth No near field Some near field Steered artefact artefact electronically Large footprint Smaller footprint Smaller footprint 7 Basic Ultrasound Principles Frequency High Frequency Low Frequency Good axial resolution Poor axial resolution More rapid beam Less rapid beam attenuation attenuation Poor penetration Better penetration Axial resolution The ability to determine two points along the path of the beam 8 Axial Resolution 9 Basic Ultrasound Principles Depth 10 Basic Ultrasound Principles Gain Changes the overall brightness of the image If Gain too high – Increase in “noise” 11 Basic Ultrasound Principles Time Gain Compensation Echoes from deeper tissues are weaker due to attenuation TGC controls brightness at different levels though the tissue 12 Basic Ultrasound Principles Focus / Focal Zone Area where image is optimised by focusing the sound wave Most often shown by triangular marker Keep region interest in focal zone Improves lateral resolution Lateral Resolution The ability to determine 2 points perpendicular to the beam Determined by beam width Narrow beam = better lateral resolution 13 Lateral resolution 14 Ultrasound Artefacts Reverberation Cause parallel bright lines Mirror Image At curved reflective surface Acoustic Enhancement Caused by lack attenuation, i.e. through fluid Bright area deep to fluid structure Poor Probe Contact Often insufficient clipping or not enough gel 15 Ultrasound Artefacts Reverberation Mirror Image 16 Ultrasound Artefacts Acoustic Enhancement 17 Ultrasound Artefacts Acoustic Shadowing If meet highly reflective interface get complete reflection and distal shadow (if gas get a comet tail) Edge Shadowing Acoustic shadow distal to lateral aspect cystic structure Slice thickness Part of beam is wider than a cystic structure Mimics tissue interface 18 Ultrasound Artefacts Distal acoustic shadow Slice thickness 19  Describing an ultrasound image Echogenicity Normal organs and tissues are displayed as shades of grey Isoechoic - structures the same shade of grey Hypoechoic - Describes a structure that is a darker shade of grey Hyperechoic - Describes a structure that is a lighter shade of grey Anechoic - Describes a structure that is black 20 Describing an ultrasound image Echotexture The image is made up of large (coarse) or small (fine) dots. These contribute to echotexture Homogeneous - a uniform distribution of grey shade (echogenicity) or dot size (echotexture) Heterogeneous - a non uniform distribution of grey shade (echogenicity) or dot size (echotexture) 21 Describing an ultrasound image Describing a lesion Roentgen Signs Number Size Shape Margin Location Echogenicity and echotexture Artefacts LEMONS Location, Echotexture, Measurements, Outline, Number, Size 22 Abdominal Ultrasound 23 Abdominal Ultrasound Indications Elective Any condition involving an abdominal organ Identifying and describing abdominal tumours Staging of neoplasia Intra-abdominal biopsy System specific investigation – Reproductive tract 24  Abdominal Ultrasound Indications Emergency POCUS scan Used to identify free fluid, often following trauma Where to scan: DH: diaphragmatic hepatic HR: hepato-renal SR: spleno-renal CC: cysto-colic 25 Benefits of Abdominal Ultrasound Non-invasive and safe General anaesthesia not required Excellent morphological information and good resolution Information from all major organs Real-time sampling of tissues possible Relatively inexpensive 26 Disadvantages of Abdominal Ultrasound Limited functional information Diffuse disease more difficult to detect Sampling required to classify disease Patient needs to be clipped Sedation often required Gas interferes with sound transmission Technically demanding to get good results Images cannot be interpreted by a specialist as taken in real-time 27 Patient Preparation Withhold food – ideally 8 hours – allow water to drink Extensive clipping Wash patient down to remove stray hairs Apply liberal amounts coupling gel Sedation as required Lateral recumbency 28 Patient Preparation Allow plenty of time for examination Use a darkened, quiet room Ensure table at correct height Vet bed or similar for comfort of patient Sufficient assistance from nurses 29  Abdominal Ultrasound A systematic approach is required so as not to miss anything Right lateral recumbency Left lateral recumbency Left Liver Right liver Gastric fundus and body Biliary system Spleen Pylorus Left limb pancreas Duodenum Left kidney and adrenal Right pancreas Small intestine Right kidney and adrenal Colon Urinary bladder (+/- prostate) 30  Abdominal ultrasonography Ultrasound Guided Techniques Ultrasound guidance improves target acquisition Abdominocentesis Cystocentesis – providing sterile sample for C&S Needle + FNA, Trucut mass, liver, spleen Syringe Transducer Tissue Samples can be obtained for cytology and histology Must aseptically prepare skin Mass lesion Ultrasound Apply spirit to skin beam Protect probe in glove with copious gel 31 Echocardiography 32 Echocardiography Indications Heart murmurs ECG abnormalities Radiography abnormalities Hypertension Dyspnoea Syncope Arterial thromboembolism Identification phenotypically normal animals prior to breeding 33  Patient Preparation Clip right and left side over the apex beat Patient in lateral recumbency on a table with a cut out Heart falls towards thoracic wall to allow visualisation through lung window R side 3rd to 6th intercostal space L side 5th to 7th intercostal space 34 Echocardiography Standard Views Right parasternal long axis view Right parasternal short axis view Papillary muscle Chordae tendinae Mitral valve Aortic valve Subcostal view Left apical 4 and 5 chamber view 35 Echocardiography Right parasternal Long Axis view 36 Echocardiography B mode M Mode Doppler - Colour flow doppler Pictures courtesy of A. Denning 37 Thoracic ultrasound Arrow = Normal lung surface. Smooth hyperechoic line * = Rib. Hyperechoic line with distal acoustic shadow Images courtesy of BSAVA Manual of canine and feline ultrasonography 38 TFAST Thoracic Focused Assessment with Sonography for Trauma Used to examine for pleural space disease and pericardial effusions. 5-point scan Chest tube site (CTS) (x2) Pericardial site (PCS) (x2) Diaphragmaticohepatic view (DH) Fluid = hypoechoic effusion present Air = absence of the ‘glide sign’ 39  Vet BLUE assessment - assessment of pulmonary parenchyma Evaluation of the thorax in 4 areas Caudodorsal lung lobe region (cdll) Middle lung lobe region (mdll) Perihilar lung lobe region (phll) Cranial lung lobe region (crll) Cole,L. Pivetta,M. Humm,K. JSAP (2021) 62,178-186 40 41 Summary Understand basic ultrasonographic principles Recognise commonly encountered artefacts Patient preparation Benefits of abdominal ultrasound over radiography Have a basic understanding of use of ultrasound in thorax 42  COMMON C O M P L I C AT I O N S & ACCIDENTS IN VETERINARY ANAESTHESIA Hanna Machin Dip ACVAA, Dip SIAV, MVetMed, MRCVS Lecturer in Veterinary Anaesthesia at the University of Surrey 4th October 2024 LEARNING OBJECTIVES Describe approaches to the prevention and management of adverse events commonly occurring during anaesthesia in domestic species Outline common risk factors associated with anaesthetic related morbidity and mortality  R E S P I R ATO R Y C O M P L I C AT I O N S Oral masses, inability to open mouth, fractures… DIFFICULT INTUBATION Pre-oxygenation! ≠ sizes of ET Tubes available Use a stylet /bougie to guide your ET Tube Change position Check for adequate plane of anaesthesia Use topical anaesthetic (cats: laryngeal spasm) Flexible fibre-optic endoscope Image from: https://www.theveterinarynurse.com/Review/article/how-to- manage-a-difficult-airway R E S P I R ATO R Y C O M P L I C AT I O N S DIFFICULT INTUBATION R E S P I R ATO R Y C O M P L I C AT I O N S ALTERNATIVE WAYS of SECURING THE AIRWAYS Image from: https://www.researchgate.net/figure/Tracheotomy-with- tube-tracheostomy-in-dog_fig1_347767131 Image from: https://bvajournals.onlinelibrary.wiley.com/doi/epdf/ 10.1136/inp.j133?saml_referrer= TEMPORAL TRACHEOSTOMY RETROGRADE INTUBATION PHYSIOLOGY RECAP  ANAESTHETIC DRUGS have a depressant effect on: Respiratory centre Central & peripheral chemoreceptors Intercostal muscle & diaphragm  POSITION  HIGH O2 CONCENTRATIONS → ↓ Functional Residual Capacity → Atelectasis → Hypoventilation & Hypercapnia → Hypoxaemia R E S P I R ATO R Y C O M P L I C AT I O N S HYPERCAPNIA ↑ ETCO2> 45mmHg Image from: https://www.atdove.org/sites/atdove.org/files/publicFiles/ETCO2- Causes: %20What%20Every%20Tecnician%20Should%20Know%20Lecture%20Notes.pdf METABOLISM PULMONARY ALVEOLAR TECHNICAL ERRORS PERFUSION VENTILATION ↑ Fever ↑ Cardiac Hypoventilation Exhausted CO2 absorber ETCO2 Hyperthermia Output Rebreathing Inadequate fresh gas flow Malignant hyperthermia ↑ Blood Faulty valves Seizures pressure Ventilatory settings: Hyperthyroidism hypoventilation R E S P I R ATO R Y C O M P L I C AT I O N S CONSEQUENCES of HYPERCAPNIA  Up to 60 mmHg…. Stimulation of SNS (mild tachycardia, hypertension)  60- 90mmHg: Vasodilation Tachycardia Central nervous system depression → apnoea Respiratory acidosis ↓ cardiac contrac lity Arrhythmias  > 90 mmHg: CNS & Cardiovascular system depression, arrhythmias, death R E S P I R ATO R Y C O M P L I C AT I O N S HYPERCAPNIA Treatment: Treat underlying cause Decrease depth of anaesthesia (if possible) Manual ventilation Mechanical ventilation R E S P I R ATO R Y C O M P L I C AT I O N S REBREATHING of CO2 Inspiration of CO2 (FiCO2) Causes: ↑ dead space NON-REBREATHING systems: Inadequate fresh gas flow Insufficient expiratory time (High RR) Leak inner tube Bain system REBREATHING system: Exhausted carbon dioxide absorber Inspiratory/expiratory valves dysfunction R E S P I R ATO R Y C O M P L I C AT I O N S AIRWAY OBSTRUCTION ET Tube occlusion (mucous, blood, mass, regurgitation.…) → “Shark fin” appearance → Suc on, re-intubation Bronchoconstriction (asthma) Kinked ET tube Images from: https://derangedphysiology.com/main/cicm-primary-exam/required- Obstruction in expiratory limb of breathing system reading/respiratory-system/Chapter%205593/abnormal-capnography-waveforms-and- their-interpretation  R E S P I R ATO R Y C O M P L I C AT I O N S REGURGITATION → risk of ASPIRATION PNEUMONIA Causes: To prevent/minimise: Inappropriate fasting times Adequate fasting time Drugs Rapid sequence induction + cuffed ET tube Hiatal hernia, gastroesophageal reflux.. ET tube slightly cuffed on extubation Lighter plane of anaesthesia Suction ready Change of position Adequate depth of anaesthesia Avoid changes of position Drugs: Metoclopramide, Maropitant, Omeprazole R E S P I R ATO R Y C O M P L I C AT I O N S REGURGITATION Treatment: Head down Suction +/- lavage with saline/tap water Measure PH of regurgitated material: if acidic instil sodium bicarbonate diluted with water into oesophagus Careful with sedation R E S P I R ATO R Y C O M P L I C AT I O N S HYPOXAEMIA Low concentration of O2 in arterial blood (PaO2) PaO2 (partial pressure of 02 in arterial blood) < 80 mmHg (SPO2 10 mcg/kg/min Up to 1 mcg/kg/min) VASODILATION ↑ INOTROPY, HR ↑ INOTROPY + ↑ INOTROPY, HR + VASOCOSTRICTION (dopaminergic) VASOCOSTRICTION VASOCOSTRICTION ↑ INOTROPY (beta) HR ↑ or ↓ VASOCOSTRICTION (alpha) CONSTANT RATE CRI BOLUS CRI CRI INFUSION 0.1 mg/kg IV (CRI) C A R D I O VA S C U L A R C O M P L I C AT I O N S HYPERTENSION ↑myocardial work & O2 demand → myocardial ischemia, arrhythmias Retinopathy, blindness, renal failure Causes: Pain/nociception Light plane of anaesthesia Hypercapnia, metabolic acidosis, hypoxaemia (initial stimulation of SNS) Underlying cardiac or renal disease (i.e. CKD) Pheochromocytoma C A R D I O VA S C U L A R C O M P L I C AT I O N S HYPERTENSION Treatment: Identify and treat the cause: (i.e. depth of anaesthesia, administration analgesia..) Use drugs that will cause vasodilation: - ↑ concentration of anaesthetic agents + Adjunct analgesic - Acepromazine - Beta adrenergic blockers (e.g., Esmolol, Propanolol) HAEMORRHAGE ↓ plasma volume, haemoglobin concentration, ↓ 02 carrying capacity of the blood Body response: ↑CO, minute volume and O2 tissue extraction… up to a certain level → then hypoxaemia, lac c acidosis, hypotension.. Blood volume: 60 ml/kg cat, sheep, cattle, rabbit Calculate before surgery, measure PCV/ TP 90 ml/kg dog, horse Consider transfusion if loss >20%, clinical signs (tachycardia, hypotension, change in Et CO2 values, increase lactate…) Replace with whole blood, packed red blood cell, haemoglobin-based O2 products HYPOTHERMIA Temperature heat production Image from Plateau: heat production= heat loss Kristen G. Cooley, Rebecca A. Johnson (2018) : Veterinary Anesthetic and Monitoring Equipment HYPOTHERMIA Consequences: Decrease metabolism Prolonged recovery Vasoconstriction ↑O2 consump on Shivering Hypoventilation ↑ wound infections Impaired coagulation ↑ intraoperative blood loss ↑ hospitalization & £££ Death HYPOTHERMIA How to prevent/treat: Minimal clipping Prewarming ↑ room temperature Avoid/minimise alcohol-based products for scrubbing Warm fluids Close monitoring Low gas flow Active rewarming I N A D E Q U AT E D E P T H O F A N A E S T H E S I A Clinical signs: Sudden increase in heart rate, arterial blood pressure Change of respiratory rate/ pattern Change of eye position Presence of strong palpebral reflex Change in jaw tone (Sudden) movement Image from: Clarke, Trimm and Hall (2014) Veterinary Anaesthesia (Eleventh Edition), Saunders Important to differentiate from NOCICEPTION ↑ Inhalational agent level, propofol, alfaxalone, ketamine.. THE 7 H OF ANAESTHESIA Hypothermia Hyperthermia Hypercapnia Hypocapnia Hypotension Haemorrhage Hypoxaemia/Hypoxia C O N F I D E N T I A L E N Q U I R Y I N TO P E R I O P E R AT I V E S M A L L A N I M A L FATA L I T I E S ( C E P S A F ) Risk factors for peri-anaesthetic mortality Data from many sedation & anaesthesia records Increase Odds of Death: Increasing ASA Status Urgent or Emergency procedure Major (v. minor) procedure Age > 12 years Interpret with caution! Weight < 5 Kg (dogs), < 2 Kg or > 6 Kg (cats) & BCS Inhalant Induction (& maintenance) Intermittent positive pressure ventilation (IPPV) Sedation alone Endotracheal Intubation in cats? Fluid therapy in Cats ? C O N F I D E N T I A L E N Q U I R Y I N TO P E R I O P E R AT I V E S M A L L A N I M A L FATA L I T I E S ( C E P S A F ) BRODBELT, D. C. 2006. The Confidential Enquiry into Perioperative Small Animal Fatalities. PhD, Royal Veterinary College, University of London, UK. BRODBELT, D. C., PFEIFFER, D. U., YOUNG, L. E. & WOOD, J. L. N. 2007. Risk factors for anaesthetic-related death in cats: results from the confidential enquiry into perioperative small animal fatalities (CEPSAF). British Journal of Anaesthesia,99,617-623. BRODBELT, D. C., BLISSITT, K. J., HAMMOND, R. A., NEATH, P. J., YOUNG, L. E., PFEIFFER, D. U. & WOOD, J. L. N. 2008a. The risk of death: the Confidential Enquiry into Perioperative Small Animal Fatalities. Veterinary Anaesthesia and Analgesia,35,365-373. BRODBELT, D. C., PFEIFFER, D. U., YOUNG, L. E. & WOOD, J. L. N. 2008b. Results of the Confidential Enquiry into Perioperative Small Animal Fatalities regarding risk factors for anesthetic-related death in dogs. Journal of the American Veterinary Medical Association,233,1096-1104. REFERENCES REFERENCES Hung Wan-Chu, Ko Jeff C., Weil Ann B., Weng Hsin-Yi (2020) Evaluation of Endotracheal Tube Cuff Pressure and the Use of Three Cuff Inflation Syringe Devices in Dogs. Frontiers in Veterinary Science, 7: 39 https://www.frontiersin.org/article/10.3389/fvets.2020.00039 Vieitez V, Ezquerra LJ, López Rámis V, Santella M, Álvarez Gómez de Segura I. Retrograde intubation in a dog with severe temporomandibular joint ankylosis: case report. BMC Vet Res. 2018 Mar 27;14(1):118. doi: 10.1186/s12917-018-1439-7. PMID: 29587754; PMCID: PMC5872398. THANK YOU FOR YOUR ATTENTION. ANY QUESTIONS?  FLUID THERAPY Hanna Machin Dip ACVAA, Dip SIAV, MVetMed, MRCVS Lecturer in Veterinary Anaesthesia 4th October 2024 LEARNING OBJECTIVES Be able to: Describe the normal distribution of fluid within the body Define hypovolaemia and dehydration Describe the different types of intravenous fluids available and their relative indications Describe normal fluid requirements and suggest a treatment plan for maintenance Suggest a treatment plan for a hypovolaemic and/or dehydrated patient Identify the patient at risk of iatrogenic fluid overload TOTA L B O D Y WAT E R ADULTS Dry matter NEONATES (% of Body weight) 20% 40% Total Body Water (% of Body 80% 60% weight) F LU I D C O M PA RT M E N TS ADULTS (% of Body Mass) 40% Dry Matter Total 40% Intracellular (2/3 of TBW) Body Water Interstitial fluid (3/4) (TBW) 20% Extracellular (1/3 of TBW) Intravascular (1/4) TOTA L B LO O D V O L U M E Dog/Horse : 8-9% body mass (i.e. 80-90 mL/kg) Cat/Cattle/Sheep: 6-7% body mass (i.e. 60-70 mL/kg) T H E B O D Y ’ S F L U I D C O M PA R T M E N T S Semi-permeable Capillary walls Cell membranes Fluids move between compartments depending on: Tonicity of fluid Tonicity of extracellular compartment (Na+) Size macromolecules in the fluid Movement across endothelial membranes: Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff Condition of capillary membrane E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 Hydrostatic pressure, colloid osmotic pressure & vascular permeability Water & electrolytes (ECF loss): Vomiting, diarrhoea, diuresis Blood TYPES of FLUID LOSS Protein rich ECF loss: Pure water Transudate, exudate, effusion, High RR (hyperthermia, severe enteritis, protein losing pneumonia), water deprivation, enteropathy/nephropathy excessive water loss FLUID BALANCE SENSIBLE LOSSES Urine output GAINS INSENSIBLE LOSSES Faeces Water intake (food & Respiration water) Saliva Metabolic water Cutaneous (i.e., Sweating) production (10%) Respiratory tract MAINTENANCE REQUIREMENTS Losses Gains To maintain balance Sensible Losses + Insensible Losses must = 25 mL/kg/day + 25 mL/kg/day = Losses = ~ 50 mL/kg/day GOAL DIRECTED FLUID THERAPY Restore homeostasis: euvolemia & hydration Correction of acid base & electrolytes imbalances Where are/is the deficit(s)? Which fluid type is the best to replace the deficit(s)? Calculate fluid dose & rate Monitor patient’s response & potential complications Reassessment of therapy Image from: BSAVA Manual of Canine and Feline Anaesthesia and Analgesia Chris Seymour, Tanya Duke-Novakovski (eds), Blackwell Publishers, 2016  Adapt plan to patient’s needs  Goal: zero balance  FLUIDS ARE DRUGS…  Are IV fluids indicated?  Correct drug  Correct dose/volume  Administration (rate/bolus)  Patient considerations (Hypotension? Causes? Contraindications?)  Monitoring  Side effects H Y P O V O L E M I A v s D E H Y D R AT I O N Hypovolaemia: Decrease fluid volume within the VASCULAR space → ↓ ssue perfusion Loss of blood and/or fluid & electrolytes If persist can affect other compartments Rapid replacement therapy Dehydration: Decrease fluid volume within the interstitial compartment It can affect all other compartments causing also hypovolaemia Images from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Water & electrolytes imbalance (especially Na+) Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Slower, sustained replacement Assoc. 2024  A S S ES S I N G I N TR AVA S C U L A R S PAC E D E F I C I TS (HYPOVOLAEMIA) History: (V+, D+, anorexia, fever, haemorrhage, oedema, ascites …) Physical examination:  Altered mentation including depression, inactivity & recumbency  Tachycardia/ arrhythmias  Change CRT & paler MM (vasoconstriction)  Weak peripheral pulses (vasoconstriction), low BP  Cold extremities  Tachypnoea Laboratory tests: ↓ PCV, ↓TS, ↑ lactate, metabolic acidosis, anaemia, electrolytes abnormalities, ↓ urine output, ↑ urine specific gravity PHASES OF HYPOVOLEMIC SHOCK Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 A S S E S S I N G D E H Y D R AT I O N Images from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 A S S E S S I N G I N T R A C E L L U L A R S PA C E Sodium concentration Free water deficit Na-K-ATPase pumps Na+ is a membrane-impermeant solute Water moves freely Dehydration: hypernatremia and hypertonicity Image from: https://testbook.com/chemistry/electrolytes Free Water Deficit (L)= [ (Patient Na/ Desired Na) – 1] X 0.6 X Weight (kg) TYPES OF FLUIDS AVAILABLE Crystalloids Colloids Oxygen- carrying solution (covered in another lecture) Blood products (covered in another lecture) C R Y S TA L L O I D S Solutions prepared by dissolving crystalline compounds (electrolytes +/- sugar) in water, usually contain buffers (acetate, lactate, gluconate) to maintain body acid base status Classification: tonicity in comparison to plasma (290–310 mOsm/L) Isotonic: ~ osmolality Hypotonic: ↓ osmolality Hypertonic: ↑osmolality Image from: https://flexbooks.ck12.org/cbook/ck-12-biology-flexbook- 2.0/section/2.12/primary/lesson/osmosis-bio/ I S OTO N I C C R Y S TA L LO I D S ~ composition to ECF → stay into ECF → REPLACEMENT/RESUSCITATION Redistribution from Intravascular Space to Interstitial space within 30-60’ Only 25% (1/4) remains in intravascular space Image from: Yunos, N.M., Bellomo, R., Story, D. et al. Bench-to-bedside review: Chloride in critical illness. Crit Care 14, 226 (2010). https://doi.org/10.1186/cc9052 SALINE SOLUTION (0.9% NaCl ) Not balanced Acidifying solution → Hamburger shift Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 Care with heart or renal disease (Na+ +++) AKI risk in human (+++ Cl-) Uses:  Hyponatremia  Hypercalcemia  Hypochloremic metabolic alkalosis (pyloric obstruction: V+++→loss of HCl) HARTMANN'S SOLUTION Balanced solution Most used for Replacement/resuscitation & peri-operative fluid therapy Alkalinising solution (contain bicarbonate precursors: lactate) Liver: Lactate converted into glucose: 2 H+ consumed (less H+ in blood) “ HCO3- sparing effect” Oxidative metabolism: HCO3- production Careful with blood transfusion:clots (Ca2+)  with urethral obstruction, hyperkalaemia.; (NaCl 0.9% makes acidosis worst) H Y P E R TO N I C C R Y S TA L LO I D S Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 RESUSCITATION (hypovolemia) Rapid intravascular volume expansion (3X volume infused), transient effect (1-3h): → Draws water from ICS, ISS, RBC (osmotic gradient) into IVS →  dehydration: Administer WITH isotonic crystalloids to address TBW deficits + to prolong duration of action Inotropic effect, increase CO Vasodilation due to hypertonicity ( coronary & cerebral perfusion)→ do not administer fast! Dose: 4-5 ml/Kg (NO administer faster than 1ml/kg/min)  H Y P OTO N I C C R Y S TA L L O I D S MAINTENANCE fluids (often now substitute with isotonic crystalloids)  pure water loss treatment Often Dextrose added to ↑ tonicity to avoid damage to RBC Water in excess to electrolytes (↓ Na+ content, ↑ K+ like inside cells) Water from extracellular space to intracellular space Hypernatremia treatment No boluses! Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024  COLLOIDS Macro-molecules suspended in a crystalloid solution (protein, sugars, starches) Colloid osmotic pressure: drawn fluid from ISP, ICS → volume expansion (> than volume infused) Longer lasting in intravascular space compared to crystalloids (hours)  Hypoproteinaemia Natural: blood products (plasma, whole blood, albumin) Synthetic: Dextrans & hydroxyethyl starches (HESs): hetastarch, tetrastarch & pentastarch → Controversial use: Adverse effects: Coagulation impairment, Acute Kidney Injury, Death… FLUIDS CAN BE HELPFUL FOR… RESUSCITATION (i.e. Hypertonic Saline, Hartmann’s solution, Blood products..): to correct intravascular volume deficit (hypovolemia) REPLACEMENT (i.e., Hartmann’s solution): to replace lost body fluids & electrolytes that cannot be compensated by oral intake ~ to ECF: [Na+ & Cl- ]~ to ECF Often used also for short term maintenance (supplemented with K+ & dextrose) MAINTENANCE (i.e. Hypotonic crystalloids): to cover daily basal requirements of water, electrolytes, glucose ↓ Na+, > K+ than replacement fluids Suitable for long term therapy SUBSTITUTE LIKE with LIKE  T R E AT M E N T P L A N F O R H Y P O V O L E M I A ( R E S U S C I TAT I O N ) Rapid correction intravascular deficits & address underlying causes Always IV/IO Buffered Isotonic crystalloids: boluses over 15-30’ Only 25% (1/4) remains in intravascular space after 30-60’ Dog: 15-20 mL/kg Cat: 5-10 mL/kg Monitor closely Assess clinical response & repeat if necessary +/- Hypertonic crystalloids: If haemorrhage: consider blood products  Dog: 4-6mL/kg  Cat: 1-4 mL/kg +/- Colloids: Remain in intravascular space for hours  2.5-5 mL/kg  Max amount: 20mL/kg dog; 10-15mL/kg cats T R E AT M E N T P L A N F O R D E H Y D R AT I O N Balanced isotonic crystalloids IV, IO If not severe: PO (voluntary oral intake, orogastric tube), SC ( poor absorption, poor peripheral perfusion, small amount can be given at time) Calculate Total fluid deficit (L)= Body weight (kg) X % dehydration (as a decimal) Administer over 12-24h Maintenance fluid requirements & ongoing losses should be added to the volume calculated for dehydration Continuous monitoring If end points returned back to normal: → Con nue with oral administration (if possible) → If not: maintenance fluid plan Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024  T R E AT M E N T P L A N I F H Y P O V O L A E M I A & D E H Y D R AT I O N A R E B OT H P R E S E N T Address hypovolemia 1st THEN rehydration (account for ongoing losses) + maintenance rate T R E AT M E N T P L A N F O R M A I N T E N A N C E Hypotonic crystalloids (or balance isotonic crystalloids + K & dextrose short term) Daily fluid requirements in hydrated & euvolemic patients that are unable to maintain fluid homeostasis through oral ingestion Dog: 60 mL/kg/day → ~ 2mL/kg/hr Cat: 40 mL/kg/day Paediatric patients: Dog: 3 X adult dose → ~ 5mL/kg/hr Cat: 2.5 X adult dose Over 24h FLUID APPROACH IN ANAESTHESIA RESTRICTED APPROACH PREVIOUS APPROACH: Administration large volume of crystalloids Fluid administration according to (10 ml/kg/hr) as: patients needs Peri-operative fasting 3ml/kg/hr (cats) Insensible losses: 5ml/kg/hr (dogs) - Evaporation If normal cardiac & renal function - Dry anaesthetic gases 3rd space losses?? Recommended: to counteract ↓ Cardiac output & vasodilation caused by inhalational agents & other drugs To maintain IV canula patency  GOALS OF FLUID THERAPY DURING ANAESTHESIA O2 delivery & tissue perfusion Macro circulation Micro circulation Maintain/ correct electrolyte composition & acid balance Stabilise before anaesthesia Monitoring Maintain adequate blood pressure INFUSION EQUIPMENT Intravenous canula Intraosseous catheters Fluids of choice Giving set +/- Fluid pump/ syringe driver +/- Pressure bag  GIVING SETS FOR FREE FLOW FLUID A D M I N I S T R AT I O N 20 drops/ml 60 drops/ml (adult set) Gate-clamps or squeeze-clamps Micro dripper (paediatric set) Spike Roller clamps Injection port Gravity assisted Risk of fluid overload Risk of air embolism Sometimes inaccurate (change of patient’s position, blood clots)  field anaesthesia, MRI  F L U I D R AT E C A L C U L AT I O N S U S I N G A G I V I N G SET From mL/kg/hr drops/second Giving set type (drops/mL) Patient body mass (kg) Info needed Desired administration rate (mL/kg/hr) mL/kg/hr x body mass (kg) → mL/hr Image from: mL/hr ÷ 60 → mL/min https://picryl.com/media/questions- demand-doubts-emotions-2ea8c6 mL/min ÷ 60 → mL/sec mL/sec x drops/mL (giving set) → drops/sec (1 ÷ drops/sec → # seconds per drop)  INFUSION PUMPS & SYRINGE DRIVERS RATE of infusion: ml/hr VTBI (Volume To Be Infused): Total ml of fluid you would like the pump to deliver VI (Volume Infused): amount of fluid already infused. Should be zeroed before starting. Improve accuracy & consistency Boluses administration Audible alarms (i.e., air bubbles)  FLUID THERAPY MONITORING Start treatment and monitor for changes in… Clinical signs: Heart Rate Arterial Pressure Pulse rate & quality Laboratory findings: Capillary Refill Time & MM colour Urine specific gravity Core-peripheral temperature gradient Haematocrit Respiratory rate & effort Total protein Mentation Lactate Urine Output Electrolytes Skin turgor Body weight Signs of oedema Values should trend towards normal… F L U I D T H E R A P Y C O M P L I C AT I O N S Common adverse effects: Fluid overload/ intolerance (heart or kidney disease) →Interstitial oedema & tri-cavitary effusion Electrolytes & acid-base imbalances Dilution coagulopathy (from excessive administration of crystalloids) Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 FLUID OVERLOAD THERAPY Image from: Pardo M, Spencer E, Odunayo A, Anim Hosp Assoc. 2024 Image from: Pardo M, Spencer E, Odunayo A, Ramirez ML, Rudloff E, Shafford H, Weil A, Wolff E. 2024 AAHA Fluid Therapy Guidelines for Dogs and Cats. J Am Anim Hosp Assoc. 2024 REFERENCES REFERENCES REFERENCES Asim M, Alkadi MM, Asim H, Ghaffar A. Dehydration and volume depletion: How to handle the misconceptions. World J Nephrol. 2019 Jan 21;8(1):23-32. doi: 10.5527/wjn.v8.i1.23. PMID: 30705869; PMCID: PMC6354080 Malbrain, Manu & Mekeirele, Michaël & Raes, Matthias & Hendrickx, Steven & Ghijselings, Idris & Malbrain, Luca & Wong, Adrian. (2023). The 4-indications of Fluid Therapy: Resuscitation, Replacement, Maintenance and Nutrition Fluids, and Beyond. 10.1007/978-3- 031-42205-8_8 Langston C., Gordon D. Effects of IV Fluids in Dogs and Cats With Kidney Failure, Frontiers in Veterinary Science, Vol 8 (2021) URL=https://www.frontiersin.org/journals/veterinary science/articles/10.3389/fvets.2021.659960DOI=10.3389/fvets.2021.659960 T H A N K Y O U F O R Y O U R AT T E N T I O N ! ANY QUESTION? Interpretation, image quality and faults Georgina Catlow BVSc MRCVS Learning objectives To be able to describe a radiographic image in terms of quality, radiographic positioning and adequacy of exposure in relation to the tissues of interest To describe potential imaging faults and the means to avoid, identify and account for them To discuss the relative advantages and disadvantages of digital and film radiography with regard to image faults #universityofsurrey 2 Simplified Radiographic Report Description Radiographic Diagnosis Differential Diagnosis Recommendations Patient name Description of image Prioritise list Further recommendations Signalment Most significant Imaging History Incidental findings Surgery Diagnostics Area imaged Identify variations from Ongoing management Projections normal Quality Summary of findings Exposure Positioning Technical faults #universityofsurrey 3 How do I remember what to comment on??? P: Positioning C: Centering C: Collimation E: Exposure L: Labelling A: Artefacts ‘Pink Camels Collect Extra Large Apples’ #universityofsurrey 4 Area Imaged / Positioning Name area of interest The area of interest will determine projections required Minimising non-pathological variation Standard views Standard positioning Standard exposure settings #universityofsurrey 5 Radiographic Projections Named according to the direction the primary beam penetrates the body part (from point of entrance to point of exit) Lateral radiographs are named by the side in which the patient is lying on #universityofsurrey 6 Patient positioning Principles of radiographic positioning Minimising geometric distortion Magnification Orthogonal views Centering #universityofsurrey 7 Geometric distortion #universityofsurrey Images courtesy of BSAVA manual of radiography and radiology 8  Object-focus distance #universityofsurrey Magnification object Focal Spot Object-film distance Film-Focal distance Object-film distance object Focal Spot Object-focus distance 9 Orthogonal views Always take orthogonal views to identify abnormalities in ‘3D’ #universityofsurrey 10 Centering Centre to the anatomical area of interest using bony landmarks Allows close collimation to avoid scatter Centring corresponds with the cross on the light diaphragm when the collimator light is switched on #universityofsurrey 11 Collimation Accurate collimation reduces radiation dose, scatter and improves contrast and image quality Bisgaard et al Front.Vet.Sci.14 Dec 2021 #universityofsurrey 12 Exposure #universityofsurrey 13 Exposure Film/Screen Digital Too dark Quantum mottle Over exposed Under exposure (Over developed) ‘grainy’ appearance Too white Under exposed Under developed #universityofsurrey 14 Exposure Under exposed – increase KV Over exposed – decrease KV #universityofsurrey 15 Labelling Radiographs should be labelled with: L / R marker Marker should be visible on image Should not be underneath a body part Can be added electronically on digital images Dental radiography often uses a dot on the film to indicate side Patient name/date often not directly on image in digital systems Other labelling requirements exist for canine health schemes (elbow and hip) #universityofsurrey 16 Viewing a radiograph Lateral views o Rostral part of animal to viewer’s LEFT Ventrodorsal/Dorsoventral o Rostral part of animal pointing UP and LEFT of animal to viewer’s RIGHT Lateromedial/mediolateral extremities o Proximal limb UP o Cranial/dorsal limb to viewer’s LEFT Craniocaudal/Caudocranial extremities o Lateral aspect limb to viewer’s LEFT #universityofsurrey 17 Image orientation –which is correct? #universityofsurrey 18 Image orientation – which is correct? #universityofsurrey 19 Quality – Artefacts Common to digital and film/screen radiography Incorrect/no labelling (name, date, L/R marker) Poor positioning Poor collimation Movement blur Fogging Double exposure Radiopaque artefacts on the patient (mud, wet coat, syringe under patient!) #universityofsurrey 20 Fogging and Scatter radiation Focal Spot Scatter causes random blackening of the image Reduced by o Using grids Patient o Appropriate collimation Grids o Use if tissue is over 10cm Grid o Placed between the cassette and Black = lead patient White = plastic o Placed on top or under table in DR system Film #universityofsurrey 21 Film/Screen Faults Over exposed Fogging Over developed Incorrect storage Fogging Old film Under developed Under exposed Poor washing of fixer Under developed Prolonged storage #universityofsurrey 22 Digital Faults Post exposure faults Partial erasure of image and fading White specks and lines Moire artefact Workstation faults Incorrect algorithm Incorrect cropping Uberschwinger artefact #universityofsurrey Images courtesy of BSAVA manual of radiography and radiology 23  Description of the image #universityofsurrey 24 Röentgen signs Roentgen signs Change Possible cause Size Increased Hypertrophy, hyperplasia, neoplasia, torsion, cystic change Decreased Atrophy, hypoplasia, congenital anomaly Shape Localised or diffuse Neoplasia, necrosis, ulceration Number Increased Accessory ossification centre, congenital anomaly Decreased Congenital anomaly Position Displacement Torsion, ectopia, hernia Opacity Increased Calculi, mineralisation, fluid/ST in a gas filled structure Decreased Abnormal gas, osteopenia Margination Periosteal reaction, protruding mass, surrounding fluid/gas #universityofsurrey 25 Opacity Radiolucent Radiopaque #universityofsurrey Image courtesy of Thrall. Textbook of Veterinary Diagnostic Radiology 26 Tell me about opacities…… #universityofsurrey 27 Border effacement Also known as Silhouette Sign Two structures of same opacity are in contact Cannot distinguish margins of two structures Pathological causes Right middle lobe pneumonia Pleural effusion Peritoneal effusion #universityofsurrey Image courtesy of Thrall. Textbook of Veterinary Diagnostic Radiology 28 Finishing the report Identify abnormalities Summarise findings Consider differentials Things to avoid o DAMNITV Bias Satisfaction of search Further diagnostics #universityofsurrey 29 Let’s have a go……. P C C E L A #universityofsurrey 30 31  MONITORING IN VETERINARY ANAESTHESIA Hanna Machin Dip ACVAA, Dip SIAV, MVetMed, MRCVS Lecturer in Veterinary Anaesthesia at the University of Surrey 4th October 2024 OBJECTIVES Explain the importance of the monitoring of the anaesthetised patient Describe the use and interpretation of physical examination findings in the assessment the anaesthetised patient Identify the clinical signs used to assess anaesthetic depth Describe the use and interpretation of electronic equipment in the physiological monitoring of the anaesthetised patient, specifically electrocardiography, pulse oximetry, capnography and arterial pressure measurement Discuss the potential sources of error associated with the various physiological monitors and their influence on the interpretation of global patient status Understand the importance of the anaesthetic record as a legal document AIM OF MONITORING Maintain adequate depth of anaesthesia Assess adequacy of analgesia Maintain function of different body systems as physiologically normal as possible Identify changes/issues Evaluate response to treatment Safety of patients & staff Legal purposes HOW? Complete patient overview The 5 Human senses Monitoring equipment Anaesthetic record Image from: https://cpaexamcoach.com/use- your-five-human-senses-for-cpa-exam-success ANAESTHETIC RECORD Legal document Must be filled in its entirety Recording at least q 5’ (but monitor continuously) Any important event occurred should be recorded! Source of info for future anaesthetics  MONITORING OF THE CENTRAL NERVOUS SYSTEM HOW DO WE MONITOR? Species differences Eye position & movement, palpebral reflex, lacrimation, nystagmus Jaw tone Laryngeal & pharyngeal reflexes Physiological parameters (Heart Rate, Respiratory Rate, Blood Pressure…) Anal tone? Pedal reflex Righting Reflex Evaluate trends  MONITORING OF THE CENTRAL NERVOUS SYSTEM To assure adequate anaesthetic level Often inconsistent signs Species differences (i.e. Horses, Ruminants) Drugs effects (i.e. Ketamine) Aim during anaesthesia: stage III, plane 2 Image from: Clarke, Trimm and Hall (2014) Veterinary Anaesthesia (Eleventh Edition), Saunders E X A M P L E S O F A N A E S T H E T I C P L A N E S ( D O G S & C AT S ) Eyes central position Eyes central position Eyes rotated No palpebral reflex Palpebral reflex + (ventromedial position) No jaw tone Mild/ strong jaw tone + palpebral reflex → no No movement palpebral reflex Possible movements RR & HR usually decrease Relaxed jaw tone LIGHT PLANE SURGICAL PLANE DEEP PLANE LIGHT PLANE OF ANAESTHESIA M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M Respiratory Rate (RR) & Rhythm Capnography Pulse Oximetry Mucous Membrane Colour Tidal Volume Blood Gas Analysis M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M RESPIRATORY RATE (RR) & RHYTHM Observe: Chest movements Reservoir bag movements RR on monitor (Capnography) Auscultation Change in respiratory rate & pattern → change in the depth of anaesthesia ↑ RR: light plane of anaesthesia, nociception/pain, hyperthermia, hypercapnia.. ↓ RR: deep plane of anaesthesia, hypothermia Apnoea: rapid administration of drugs, overdose of anaesthetic, breath holding (light plane of anaesthesia) M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M CAPNOMETRY Breath by breath analysis of Expired CO2 (End-tidal CO2- ET CO2) RR FiCO2 (inspired CO2 levels) CAPNOGRAPHY Graphical representation of CAPNOMETRY throughout the respiratory cycle Image from: https://kidocs.org/2013/11/much-hot-gas- etco2-non-anaesthetists/ M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M END EXPIRATION CAPNOGRAPHY Waveform: Pressure vs time plot Expressed as % or partial pressure (mmHg) Normal ET CO2 values: 35 - 45 mmHg PHASE Hypocapnia: < 35 mmHg, hypercapnia > 45 mmHg  Non-invasive, continuous EXPIRATION INSPIRATION  Early issue detection NORMAL capnograph trace Image from: https://www.nuemblog.com/blog/capnography M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M CAPNOGRAPHY Image from: ikolaus Gravenstein, Michael B. Jaffe. Capnography, Anesthesia Equipment (Third Edition),W.B. Saunders,2021, Pages 239-252 M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M CAPNOGRAPHY Estimates arterial CO2 (PaCO2, Partial pressure of CO2 in the arterial blood) Ventilation/perfusion mismatch PaCO2 ] ALVEOLAR DEAD SPACE Image from: https://airwayjedi.com/2017/01/06/ventilation-perfusion- mismatch/ M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M CAPNOGRAPHY/CAPNOMETRY Gives info on: METABOLISM CARDIAC OUTPUT → CPR ALVEOLAR VENTILATION ANAESTHETIC EQUIPMENT RESPIRATORY RHYTHM M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M SIDESTREAM vs MAINSTREAM capnography Image from: Marshall, M A. “Capnography in Dogs.” Compendium on Continuing Education for The Practicing Veterinarian 26 (2004): 761-777.  M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M METABOLISM CAPNOGRAPHY PULMONARY PERFUSION ALVEOLAR VENTILATION TECHNICAL ERRORS ↓ Hypothermia ↓ Cardiac output Hyperventilation Disconnection ETCO2 Hypothyroidism Hypotension Asthma Sampling leaks or blockage Drugs/anaesthetic depth Hypovolemia Apnoea ET tube obstruction Pulmonary embolism ET tube cuff deflated Cardiac pulmonary Ventilatory settings: arrest hyperventilation ↑ Fever ↑ Cardiac Output Hypoventilation Exhausted CO2 absorber ETCO2 Hyperthermia ↑ Blood pressure Rebreathing Inadequate fresh gas flow Malignant hyperthermia Faulty valves Seizures Ventilatory settings: Hyperthyroidism hypoventilation Image from: Marshall, M A. “Capnography in Dogs.” Compendium on Continuing Education for The Practicing Veterinarian 26 (2004): 761-777. M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M PULSE-OXIMETRY Use recommended in ≠ studies AAHA guidelines on monitoring Decreases odds of anaesthetic death in cats (Broadbelt at al. 2007)  Early problem recognition (especially with capnography) M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M SPO2 value PULSE-OXIMETRY Pulse rate Measure the degree of saturation of Haemoglobin (Hb) with O2 Calculates the amount of Oxy-Hb as a % of Total Hb Normal range 98-100% Pulse waveform Hypoxaemia if Sp02 < 90- 95% Easy to use, non-invasive Continuous measurements Detects hypoxaemia earlier than human eye Can be positioned on tongue, ears, prepuce, vulva, lips, toe web, skin flap… Audible signal for each pulse with ≠ pitch A B R I E F R E C A P... 98-99% of O2 in blood is carried in RBCs in combination with Hb (SaO2) 1-2% O2 dissolved in plasma (PaO2) O2 saturation: % of Hb molecules saturated with O2 Image from: https://stock.adobe.com/uk/images/oxygen-transport-oxygen-binds-to- hemoglobin-and-is-released-by-red-blood-cells-gas-exchange-mechanism/565825079 One Hb molecule carries maximum 4 X O2 molecules (fully saturated with O2) Image from: Thomas C., Lamb A. Physiology of Haemoglobin Continuing Education in Anaesthesia, Critical Care & Pain | Volume 12 Number 5 2012 A BRIEF RECAP… BOHR effect: O2 - HEMOGLOBIN DISSOCIATION CURVE O2 released into ssues with High CO2, ↓ PH ( ssue & organs) O2 is bound to Hb in ssues with ↓ CO2, ↑PH (lungs) HALDANE effect: De-O2 Hb greater ability to carry CO2 O2-Hb less able to carry CO2 O2 of blood in the lungs displace CO2 from Hb Normal range 98-99% Hypoxaemia if Sp02 < 90- 95% (PaO2 < 60mmHg) Image from: https://partone.litfl.com/oxygen_storage.html  A B R I E F R E C A P... O2 - HEMOGLOBIN DISSOCIATION CURVE Reluctance O2 unloads > to release easily O2 from Hb Image from: https://x.com/silmerrillon/status/1269260948990119943/photo/1 M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M HOW PULSE-OXIMETRY WORKS PULSE PLETHYSMOGRAPHY to detect pulse waveform INFRARED SPECTROSCOPY to detect absorption of light (red & infrared) by tissue under probe 02-Hb absorbs > INFRARED light De-02-Hb absorbs > RED light Only measured from arterial blood (pulsatile) Images from: How equipment works.com M O N I TO R I N G T H E R E S P I R ATO R Y S Y S T E M PULSE-OXIMETRY If quality of signal is poor calculation of Hb saturation might be wrong: “SEE PLETH BEFORE O2” Interference Movement Hypoperfusion & peripheral vasoconstriction Species related inaccuracies Pigmentation (Sp02 overestimation) Carboxyhaemoglobin/ Methaemoglobin Image from: https://ccforum.biomedcentral.com/articles/10.1186/cc341  M O N I TO R I N G T H E R E S P I R ATO R Y & CARDIOVASCULAR SYSTEM PULSE-OXIMETRY (PLETHYSMOGRAPH) Additional info on: Vascular tone Perfusion Fluid responsiveness Pulse deficits/variation during arrhythmias Image from: https://corom.org/embrace-the-full- power-of-your-spo2/ Image from: Mohanty, Pankaj. (2014). Early detection and management of critically sick newborn in neonatal intensive care unit using perfusion index and pleth variability index in advanced pulseoximetry. Indian journal of child health. 1. 158-159. MONITORING THE CARDIOVASCULAR SYSTEM Monitor tissue O2 delivery Maintain cardiac output & SaO2 Heart Rate (HR) & Rhythm Blood Pressure Image from: Mathis, A. (2016), Practical guide to monitoring anaesthetised small animal patients. In Practice, 38: 363- Mucous Membrane Colour 372. https://doi.org/10.1136/inp.i3947 Peripheral Pulses Palpation (rate, quality, synchronicity with heart beats) Pulse Oximeter Capnography/Capnometry MONITORING THE CARDIOVASCULAR SYSTEM HEART RATE & RHYTHM PALPATION of the APEX BEAT AUSCULTATION (stethoscope, oesophageal stethoscope) ECG  Graphic representation of changes of electrical activity on the heart measured at the surface of the skin  Monitor HR & rhythm  Electrolytes disturbances  Myocardial hypoxia AMPLITUDE (mV) Not a measure of contractility TIME (sec) Careful about artifacts Image from: https://www.bhf.org.uk/informationsupport/tests/ecg MONITORING THE CARDIOVASCULAR SYSTEM ECG LEFT DEPOLARISATION BUNDLE VENTRICLES BRANCH REPOLARISATION ATRIAL DEPOLARISATION VENTRICLES RIGHT BUNDLE BRANCH Image from: Beyrami Enanlou, Hamed & Lotfivand, Nasser. (2017). Shannon’s Energy Based Algorithm in ECG Signal Processing. Computational and Mathematical Methods in Medicine. 2017. 1-16. 10.1155/2017/8081361 MONITORING THE CARDIOVASCULAR SYSTEM ECG 3 LEADS (+, - & ground lead) usually positioned on BOTH arms and LEFT LEG Paws, axilla + inguinal region, ears… Adhesive patches, crocodile clips… +/- gel ≠ trace appereance depending on leads placement (relatively to the heart) Most common: lead II (right shoulder, left leg) To look at the electricity of the heart from a 360 degree angle  EINTHOVEN’s TRIANGLE MONITORING THE CARDIOVASCULAR SYSTEM HOW to DESCRIBE an ECG  Look at the HEART RATE: Is it FAST or SLOW for this SPECIES & BREED?  Is RHYTHM regular or irregular? Look at R-R intervals Are P waves and QRS complex regular?  Is there a P wave in front of every QRS?  Is there a QRS following every P wave?  Are QRS normal (tall & narrow) or abnormal (wide & bizzarre) MONITORING THE CARDIOVASCULAR SYSTEM BLOOD PRESSURE MEASUREMENT Pressure = Force of blood flow/Area (arterial wall) Blood Pressure = Cardiac Output X Systemic Vascular Resistance Stroke Volume X HR Preload, Afterload, Contractility MONITORING THE CARDIOVASCULAR SYSTEM BLOOD PRESSURE MEASUREMENT ≠ Values for ≠ species & breeds Systolic Mean Diastolic SAP MAP DAP < 50 mmHg >150 mmHg > 100mmHg > 90 mmHg Blood pressure values under anaesthesia Image from: Canine and Feline Anesthesia and Co- Existing Disease, First Edition. Edited by Lindsey B.C. Snyder and Rebecca A. Johnson. © 2015. MONITORING THE CARDIOVASCULAR SYSTEM WHY DO WE CARE ABOUT MAP? Indirect indicator of Tissue perfusion Anaesthetic drugs depress autoregulatory mechanisms Start treatment if MAP< 70 mmHg & SAP oral), anaphylaxis rare in veterinary species Bacterial resistance – bacterial β-lactamases breakdown the β-lactam ring (also other resistance mechanisms). Tuesday, 24 September 2024 14  β-lactam antibiotics Penicillins Tuesday, 24 September 2024 15  β-lactam antibiotics Cephalosporins Tuesday, 24 September 2024 16  β-lactam antibiotics Class D Natural penicillins e.g. procaine benzylpenicillin Aminopenicillins e.g. amoxicillin, ampicillin Anti-staphylococcal penicillins e.g. cloxacillin Class C Aminopenicillins in combination with β-lactamase inhibitors e.g. amoxicillin + clavulanic acid 1st or 2nd generation cephalosporins e.g. cefalexin, cefapirin Tuesday, 24 September 2024 17  Penicillin antibiotics - example Amoxicillin is licenced for treatment of primary infections of the urogenital tract, e.g. pyelonephritis and infections of the lower urinary tract, endometritis and vaginitis Urinary tract infections Class D Amoxicillin Tuesday, 24 September 2024 18  Protein synthesis Taken from: https://socratic.org/questions/580e5702b72cff43cca22ec6 Tuesday, 24 September 2024 19  Tetracycline antibiotics Tetracyclines inhibit protein synthesis in susceptible bacteria Bacteriostatic Time-dependent Broad spectrum of activity, effective against Gram +ve and Gram -ve bacteria and mycoplasma and protozoa. Generally well-tolerated. Associated with oesophageal erosion. Can interfere with gut flora (use in horses largely abandoned). Use with caution in young animals (binds to calcium). Widespread resistance, but still first-line treatment Class D Doxycycline, oxytetracycline, chlortetracycline Tuesday, 24 September 2024 20  Tetracycline antibiotics - example Doxycycline is licenced for treatment of rhinitis and bronchopneumonia in cats and dogs caused by Bordetella spp. and Pasteurella spp. Kennel cough Class D Doxycycline Tuesday, 24 September 2024 21  Responsible use - EMA Tuesday, 24 September 2024 22  Responsible use - EMA Tuesday, 24 September 2024 23  Sulfonamides, DRIs and combination antibiotics Sulfonamides and dihydrofolate reductase inhibitors interfere with the production of folic acid and thereby purine synthesis - usually combined (TMPS) Bactericidal Time-dependent Broad spectrum of activity, effective against Gram +ve and Gram -ve bacteria and antiprotozoal Serious side effects are uncommon with TMPS Wide variety of adverse events, including hypersensitivity, inappetence, gi disturbance Widespread resistance, still first-line treatment Class D Trimethoprim-sulfadiazine Tuesday, 24 September 2024 24  TMPS - example TMPS is relatively cheap and easy to administered to horses, used to treat infections of the upper respiratory tract, the urogenital system and wound infections Wound infections Class D Trimethoprim-sulfadiazine Tuesday, 24 September 2024 25  Nitroimidazoles Inhibit nucleic acid function by preventing DNA repair Bactericidal Concentration-dependent Active against Gram +ve and Gram –ve anaerobes and protozoa Antiinflammatory effect (see GI therapeutics lecture) N.B. not licenced for use in food producing animals (metabolites in ruminants shown to be carcinogenic in humans) Class D metronidazole Tuesday, 24 September 2024 26  Metronidazole - example Metronidazole is licenced to treat gastrointestinal tract infections caused by Giardia spp. and Clostridium spp. (i.e. C. perfringens or C. difficile) GI infections Class D Metronidazole Tuesday, 24 September 2024 27  Aminoglycosides Aminoglycosides inhibit protein synthesis Bactericidal Concentration-dependent Narrow spectrum - Gram -ve aerobic bacteria Poorly absorbed from gi tract Associated with nephrotoxicity and ototoxicity – plasma levels may require monitoring Some resistance Combined with penicillins to broaden spectrum but …. Class C gentamicin, streptomycin, amikacin Tuesday, 24 September 2024 28  Aminoglycosides - example Gentamicin is included in combination with other antimicrobials and a steroid in some ear drops – used to treat otitis externa Ear infections Class C Gentamicin (in combination with a steroid and an antifungal) Tuesday, 24 September 2024 29  Macrolides & lincosamides Macrolides and lincosamides inhibit protein synthesis Bacteriostatic (later generations bactericidal) Time-dependent Gram +ve bacteria and Mycoplasma, though later generations have activity against Gram -ve Generally well tolerated but can be painful on injection. Avoid in horses (irreversible diarrhoea) Resistance is common Class C Macrolides: erythromycin, tylosin, tilmicosin Lincosamides: clindamycin Tuesday, 24 September 2024 30  Macrolides and lincosamides - example Clindamycin is licenced for the treatment of infected wounds and abscesses and infected mouth cavity and dental infections in cats and dogs Cat bite Advanced abscess peridontitis Class C Clindamycin Tuesday, 24 September 2024 31  Amphenicols Amphenicols inhibit protein synthesis Bacteriostatic Time-dependent Broad spectrum – Gram +ve and Gram –ve and some mycoplasmas Large animal – may cause transient reduction in food intake. Small animal – use limited to topical treatment eye infections Class C florfenicol (mainly LA), chloramphenicol (topical) Tuesday, 24 September 2024 32  Amphenicols - example Florfenicaol is licenced for the treatment of respiratory tract infections in cattle caused by florfenicol susceptible Mannheimia haemolytica, Pasteurella multocida and Histophilus somni. Respiratory tract infections Class C Florfenicol Tuesday, 24 September 2024 33  Fluoroquinolones Inhibit DNA synthesis Bactericidal Concentration-dependent Narrow spectrum – active for Gram –ve and good penetration for otherwise difficult to treat infections Few classes licenced for exotics – fluoroquinolones are, but N.B. Class B antibiotics – treatment of last resort. VMD consider it is justified to prescribe an antibiotic on the cascade in the interests of minimising development of resistance Class B Enrofloxacin, marbofloxacin, danofloxacin Tuesday, 24 September 2024 34  Fluoroquinolones - example Enrofloxacin is licenced for use in pet rabbits, rodents, birds and reptiles e.g. for the treatment of Pasteurella multocida in rabbits. Infections of respiratory and gastrointestinal tract infections Class B Enrofloxacin Tuesday, 24 September 2024 35  Responsible use of antimicrobials Tuesday, 24 September 2024 36  Key Points LO - Describe the pharmacological and therapeutic characteristics of the main classes of antimicrobials used in veterinary medicine – Give common examples from each class β-lactam antibiotics (penicillins and cephalosporins) – interfere with transpeptidation of bacterial wall synthesis - effective against Gram +ve and Gram -ve bacteria, but spectrum ranges from narrow to broad dependent on particular drug amoxicillin, ampicillin, procaine benzylpenicillin, cloxacillin amoxicillin + clavulanic acid, cefalexin, cefapirin Tetracyclines inhibit protein synthesis in susceptible bacteria - broad spectrum of activity, effective against Gram +ve and Gram -ve bacteria and mycoplasma and protozoa doxycycline, oxytetracycline, chlortetracycline Tuesday, 24 September 2024 37  Key Points LO - Describe the pharmacological and therapeutic characteristics of the main classes of antimicrobials used in veterinary medicine – Give common examples from each class Sulfonamides and dihydrofolate reductase inhibitors interfere with the production of folic acid and thereby purine synthesis - usually combined (TMPS) - Broad spectrum of activity, effective against Gram +ve and Gram -ve bacteria and protozoa trimethoprim-sulfadiazine Nitroimidazoles - inhibit nucleic acid function by preventing DNA repair - active against Gram +ve and Gram –ve anaerobes and protozoa metronidazole Tuesday, 24 September 2024 38  Key Points LO - Describe the pharmacological and therapeutic characteristics of the main classes of antimicrobials used in veterinary medicine – Give common examples from each class Aminoglycosides inhibit protein synthesis - narrow spectrum - Gram -ve aerobic bacteria gentamicin, streptomycin, amikacin Macrolides and lincosamides inhibit protein synthesis - Gram +ve bacteria and Mycoplasma, though later generations have activity against Gram –ve Macrolides: erythromycin, tylosin, tilmicosin Lincosamides: clindamycin Tuesday, 24 September 2024 39  Key Points LO - Describe the pharmacological and therapeutic characteristics of the main classes of antimicrobials used in veterinary medicine – Give common examples from each class Amphenicols inhibit protein synthesis - broad spectrum – Gram +ve and Gram –ve and some mycoplasmas florfenicol (mainly LA), chloramphenicol (topical) Fluoroquinolones - inhibit DNA synthesis - Narrow spectrum – active for Gram –ve and good penetration for otherwise difficult to treat infections enrofloxacin, marbofloxacin, danofloxacin Tuesday, 24 September 2024 40  Key Points LO - Demonstrate a logical approach to empirical prescribing using common examples BVA 7-point plan for responsible antibiotic use: 1. Work with clients to avoid the need for antimicrobials 2. Avoid inappropriate use 3. Choose the right drug for the right bug 4. Monitor antimicrobial sensitivity 5. Minimize use 6. Record and justify deviations from protocols 7. Report suspected treatment failure to the VMD Tuesday, 24 September 2024 41 Physics of radiography and radiation safety Georgina Catlow BVSc MRCVS Learning objectives To describe the generation of x-rays from standard equipment To describe the requirements for safe operation of radiographic equipment To understand the legal requirements for protection of personnel involved in radiographic exposure To describe the steps to prepare animals for radiographic exposure #universityofsurrey 2 X-ray generation Generator Photons Patient Film #universityofsurrey 3 X-ray generation – the X-ray tube Tungsten target Vacuum Glass envelope Anode Cathode + - Collimators #universityofsurrey 4 Exposure Settings What can you alter to affect the image obtained? KV mA Time (seconds) Film focal distance #universityofsurrey 5 KV KVp = peak voltage across cathode and anode Controls kinetic energy of electrons Increased KVp o More photons o Increased energy o More penetrating #universityofsurrey 6 mA and time mA = tube current to cathode filament Controls number of electrons Increased mA o Increased heat in cathode filament o Increased number electrons o Increased number photons mAs = mA x time (s) o Measure of intensity of beam o Intensity = total number and energy of all x-ray photons #universityofsurrey 7 Film focal distance (FFD) FFD = distance between the focal spot on the anode and the detector under the patient X-ray beam diverges from focal spot Quantity of radiation at any point is proportional to 1/(FFD)2 FFD Santé’s rule kV = (patient width in cm) x2 + (FFD in inches) #universityofsurrey 8 Interaction of X-rays with matter Attenuation Absorption o Removed energy transferred to the patient o Increases with increasing atomic number o Creates contrast between tissues Scatter o Removed energy emitted away from patient o Worse with increasing KV o Hazard to radiographer o Causes loss of contrast due to fogging #universityofsurrey 9 Interaction of X-rays with matter Transmission and interaction with film-screen detector = FILM BLACKENING mAs kVp Adapted from Thrall Veterinary Radiology 5th Ed #universityofsurrey 10 Interaction of X-rays with matter Tissue/Matter Appearance on radiograph Gas Fat Soft tissue/Fluid Bone Metal Contrast = Shade of grey #universityofsurrey 11 Recording and displaying the image Emulsion Produces image Silver bromide crystals Photon + silver bromide crystal = silver atom deposited (Latent image) Latent image Not visible to naked eye Must undergo chemical processing #universityofsurrey 12 Intensifying screens and cassettes Base Advantages Reduced dose Reflective layer Shorter exposure time Less motion blurring Phosphor Less scatter Disadvantage Protective layer Loss some resolution Film #universityofsurrey 13  Digital radiography – Computed Radiography (CR) The cassette contains a storage-phosphor image plate containing The image plate is then photostimulable crystals exposed to intense white light to delete the latent image and allow reuse X-ray energy absorbed and temporarily stored during an exposure to create a latent image Photodiodes capture the light emitted and Cassette put into processer convert to a digital where the image plate is signal removed and scanned by a laser which sets the stored energy as visible light #universityofsurrey 14 Digital radiography – Direct Radiography (DR) Uses flat panel detectors to convert x-rays into electrical charge Can be either direct or indirect converting systems Detectors either sit underneath the x-ray table or on the tabletop and can be used with grids Signal from the detector to the computer can be wired or wireless. Image from BSAVA Manual of Musculoskeletal imaging #universityofsurrey 15 Digital radiography Advantages Disadvantages Greater tolerance to sub-optimal High initial set up cost and ongoing exposure factors maintenance Images can be manipulated Overexposures can be overlooked Images can be shared Interpretation can be limited if computer monitors not of adequate quality Quicker Easier storage No replacement film costs (although initial set up expensive) #universityofsurrey 16 Radiation Safety #universityofsurrey 17 X-ray interaction with tissue Deterministic o Threshold levels for effects exist o Severity proportional to dose received Stochastic o No threshold level of radiation exists o Probability proportional to dose received Hereditary o Stochastic effect which occurs in offspring of exposed #universityofsurrey 18 Principles of radiation protection 1. Radiography should only be undertaken if there is a definite clinical justification for the use of the procedure 2. Any exposure to personnel should be kept to a minimum. (ALARA – As low as reasonably achievable) 3. No legal dose limit should be exceeded #universityofsurrey 19 Principles of radiation protection Radiation protection supervisor Radiation protection adviser Local rules Controlled area o Defined by physical boundary o Walls must be shielded o Warning light and sign #universityofsurrey 20 Limiting occupational exposure #universityofsurrey 21 Limiting occupational exposure 1. Time Rotate staff Record exposure involving staff Exposure chart Electronic timer #universityofsurrey 22 Limiting occupational exposure 2. Distance Stay outside controlled zone I1/I2 = D22 / D12 Use a protective shield Glass should have a lead equivalent of >0.5mm I1 = Intensity at D1 Avoid horizontal beam radiography I2 = Intensity at D2 D = Distance from source #universityofsurrey 23 Limiting occupational exposure Patient Restraint Image courtesy of CardioAcademy Cevalearn #universityofsurrey 24 Limiting occupational exposure 3. Shielding Structural shielding in walls Lead cover to table Persona