INTRODUCTION TO VETERINARY ANAESTHESIA AJADI ADETOLA DEPARTMENT OF VETERINARY MEDICINE AND SURGERY

ANAESTHESIA: HISTORY 16 th October, 1846: Prof. William Morton administered sulphuric ether to a patient with congenital vascular tumor 19 th December, 1846: Ether anaesthesia was first administered in England 21 st December, 1846: Robert Liston administered sulphuric ether on a patient named Frederick at the Chicago University College Hospital In 1847: Prof. James Simpson introduced chloroform In 1877: The first local anaesthetics was introduced Knowledge of airway control and endotracheal intubation became known toward the end of 19 century The first intravenous agent was introduced around the 1920’s The first muscle relaxant was introduced around the 1940’s

ANAESTHESIA: DEFINITION The use of drugs and techniques to produce in a subject Behavioural depression Unconsciousness Suppression of reflex activity Analgesia Muscle relaxation While at the same time maintaining normostasis

OVERVIEW OF THE DRUGS Anticholinergics α 2 adrenergic agonists Benzodiazepines Phenothiazine Opioid analgesics Cyclohexylamines Barbiturates Alkyl phenol Carboxylated imidazole Muscle relaxant Volatile anaesthetic agents Local anaesthetics Miscellaneous drugs

ANAESTHETIC TECHNIQUES Sedation: the use of drug to induce in a subject a state of calmness with some degree of drowsiness Local anaesthesia: the use of drug (majorly amide) to achieve a reversible loss of consciousness (pain) around the area where it is administered Regional anaesthesia: Administration of a drug (opioids, amides, etc.) at a site to obtain loss of consciousness at the adjourning region of the body General anaesthesia: use of drugs to produce reversible loss of unconsciousness involving the whole body

DEFINITIONS Tranquilization: A state of calmness without drowsiness Sedation: A state of calmness with some degree of drowsiness Hypnosis: Reversible unconsciousness characterized by a sleep-like state.

USES OF ANAESTHESIA Patient restraints Surgery Treatment of CNS disorder Transportation of animal Euthanasia

USES OF ANAESTHESIA IN PATIENT RESTRAINT Physical examination Diagnostic imaging Dentistry Obstetrical manipulations Endoscopy Patient manipulation

USES OF ANAESTHESIA IN SURGERY Immobility of operative site Pain control Muscle relaxation Unconsciousness

ANAESTHETIC USES IN CNS DISORDER Convulsion Familial epilepsy Local anesthetic overdose Treatment of poisoning CNS diseases

EUTHANASIA Behavioural problem Terminal or incurable illness Public health reasons Economic reasons

TRANSPORTATION OF ANIMALS Prevention of motion sickness Reduction of transportation stress Prevention of injury due to fight

CHOICE OF ANAESTHETIC PLANS: CRITERIA Temperament of patient Physical status of patient Specie, breed, size and age Duration and type of intended procedure Amount of personnel available Knowledge and skill of personnel Type of equipment

PATIENT EVALUATION: AIM Determine the physiological status of patient Determine the need of patient Determine the need of anaesthetist Evaluate and predict the risk involved in anaesthesia

PATIENT EVALUATION: COMPONENT History Physical examination Laboratory examination Ancillary examination

PHYSICAL EXAMINATION Patient record Previous and concurrent medication Known adverse reactions Clinical signs observed Recent food and water intake Reason for anaesthesia

PHYSICAL EXAMINATION Bodyweight and body condition Cardiopulmonary status CNS activity Hepatic functions Renal functions Musculoskeletal status Skin and other external appendages Others

LABORATORY EXAMINATION Packed cell volume Complete blood counts Serum total proteins Liver function test Blood urea nitrogen and creatinine Serum glucose Lipid profile Urinalysis Serum electrolytes

ANCILLARY EXAMINATION ECG EEG EMG

CLASSIFICATION OF PHYSICAL STATUS CATEGOR Y CONDITIONSDEGREE OF RISK IHealthy animal for elective caseminimal IINo clinical sign of disease but patient have altered body condition e.g. obesity, geriatrics, neonates Slight IIIModerate signs of system disease e.g. fever, anaemia Moderate IVLife threatening disease e.g. shock, ureamia, toxemia Severe VMoribund patient: advanced organ diseases or failure Grave

PATIENT PREPARATION FOR ANAESTHESIA Food restriction for 6-12 hours to empty the gut Allow water free-choice up to the time of premedication Use emetics to empty full stomach Administer enema to evacuate colon Correct dehydration, anaemia, electrolyte and acid-base imbalance Prepare for unexpected events!