Common Complications & Accidents in Veterinary Anaesthesia PDF

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 202...

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?