Intro to Veterinary Anaesthesia PDF

5711- Introduction to Veterinary Anaesthetic and Surgical Procedures Introduction to Anaesthesia  Cats De-sexing Radiography (x-rays) Dental procedures Reptiles...

5711- Introduction to Veterinary Anaesthetic and Surgical Procedures Introduction to Anaesthesia  Cats De-sexing Radiography (x-rays) Dental procedures Reptiles Dogs Birds What procedures have Fracture repair Grooming YOU seen? Rats and mice Exploratory Laparotomy Guinea Pigs Mass removal Amputation Rabbits What is Anaesthesia? Definitions Anaesthesia - coined from two Greek words: "an" meaning "without" and "aesthesis" meaning "sensation". ‘..refers to the practice of administering medications that block the feeling of pain, memory and other sensations, producing a deep state of unconsciousness. This allows medical and surgical procedures to be undertaken without causing undue distress or discomfort.’ -(ANZCA, 2019) Definitions Local/regional anaesthesia - a technique to induce the absence of sensation and/or pain in a specific part of the body General Anaesthesia (GA) – a state of overall controlled unconsciousness Sedation – patient is unaware of their surroundings, loss of memory, but may still respond to stimulus Intravenous Anaesthesia – anaesthetic drugs (like propofol or ketamine) given intravenously to keep the animal asleep. Inhalational Anaesthesia – use of inhaled anaesthetic drugs (like isoflurane) Analgesia - the reduction or elimination of the patient experiencing pain by medications such as local anaesthetics (which interfere with nerve conduction) opioid medications (which decrease the patient's experience of pain in the central nervous system). Why do we anaesthetise patients? Surgery (elective vs problem) Diagnostics (e.g. endoscopy, biopsy) Handling/transport (e.g. fractious or wild animals) Imaging (Radiographs, Ultrasound, CT, MRI) Pain control Anxiety Seizure control Euthanasia How do we anesthetise patients? Local Sedation Injectable (SQ, IM, IV) and Oral (PO) Light Moderate Heavy General Injectable (IM, IV) Inhalant Combination of the two Anaesthesia Classifications for Veterinary Medicine Adapted from ASA (American Society of Anaesthesiologists) Classification Scheme: I - Healthy patient (routine spey/neuter, routine dental scale and polish) II - Mild systemic disease, no functional limitation (cruciate surgery, lumpectomy, senior/geriatric or neonatal/pediatric animal) III - Severe systemic disease, definite functional limitation (urethral blockage) IV - Severe systemic disease that is constant threat to life (haemorrhaging) V - Moribund patient unlikely to survive 24 hrs with or without surgery (extreme shock, massive tissue damage, severe metabolic issues) E - Is added to the above classifications if the patient is presented on an emergency basis; this denotes an additional risk inherent with rushing into a procedure Why is the classification scheme so important? We want to know what the chances of something bad happening are, so that we can take steps to anticipate and prevent problems, rather than try to correct them after they happen! This includes: Coming up with the best and safest anaesthetic/analgesic plan for that particular patient Addressing the best body position Appropriate fluid plan and/or blood products needed Appropriate airway management Emergency drugs and equipment needed What else do you think? Respiratory system Nervous system How does anaesthesia affect the functions of the body? Renal system Cardiovascular system Respiratory Most anaesthetics decrease the respiratory rate (RR) However, the rate still needs to be in an acceptable range for there to be appropriate levels of both O2 and CO2 in the body Hypoxia - when O2 delivery to tissues is too low If organs become deprived of O2, permanent damage may be caused, including respiratory arrest, cardiac arrest, brain death Cardiovascular Anaesthetics may decrease many aspects of cardiovascular function (and most body systems/vital signs) However, we must monitor this system to avoid significant/detrimental decreases Blood pressure (BP) and heart rate (HR) still need to be within a normal range If blood stops pumping, permanent damage will likely be caused........cardiac arrest, brain death…  Nervous Reduction in nerve transmission at synapses (where nerves meet and communicate) Changes in awareness and perception of sensation Sensory pathways blocked-peripheral to central Muscle relaxation and decreased movement Function of brain depressed-changes in awareness and sensation We want the above things to occur in an anaesthesia to a certain extent! More depressed as anaesthesia deepens Hypotension, hypoventilation, hypothermia occur Decreased threshold to seizures may occur Renal Most anaesthetic drugs are eliminated via the kidneys Anaesthesia makes them work hard! Already reduced renal function may increase elimination time of drugs (may prolong recovery-less drug are needed) Patient may be anaemic Hypertension may occur Electrolyte abnormalities may occur Prevention of Problems Good physical exam prior to anaesthesia is key Assess functionality of body systems Adjust anaesthetic protocols if needed Even a ‘healthy’ animal undergoing routine surgery can experience anaesthetic complications Support the body Avoid hypotension with fluid therapy Avoid hypothermia by using heat pads, Bair huggers Cushioned surgical table (especially larger animals) Provide appropriate analgesia Monitor the patient Summary – Anaesthesia in a ‘Nutshell’ There are many ways to anesthetise patients and for many reasons Many types of patients Can prevent problems with blood tests/urinalysis, checking/maintaining equipment, good supportive care and monitoring Bad things may be happening within the body, even if you don’t see them! Anaesthesia needs to be individualised Many organ systems play a role in and are affected by anaesthesia No machine is a substitute for an attentive veterinary nurse! http://www.vasg.org/ Veterinary Anesthesia Support Group