Introduction to anaesthesia Flashcards
Define anaesthesia
loss of sensation resulting from pharmacological depression of nerve function
Define GA
state of unconsciousness produced by controlled reversible drug-induced intoxication of the CNS in which the patient neither PERCEIVES or RECALLS noxious stimuli. AKA ‘reversible death’.
Define local anaesthesia
temporary blockade of sensory nerves (usually with a simultaneous block of motor nerves too)
What are the components of GA? (the Triad of general anaesthesia)
Unconsciousness (‘narcosis’)
Analgesia (i.e. antinociception if anaesthetised)
Muscle relaxation
Define amnesia
no awareness of recall of anaesthesia or surgery
What else is essential to the anaesthetist other than the triad?
homeostasis - especially oxygen delivery to the tissues
What is meant by the trend to ‘lighten up’?
trend in modern anaesthesia. the use of several drugs with selective and complementary actions. The pharmacokinetic properties of these drugs should allow rapid onset, rapid recovery and rapid responses to changes in delivered doses.
Define balanced anaesthesia
use of smaller doses of a combination of drugs to achiev the various components of anaeshtesia, thus reducing the disadvantaages of using large doses of any one drug. It also offers a multi-dimensional approach to pain control - not only does it help to block autonomic responses to surgery and provide analgesia post-op, but may also pre-empt post-op pain hypersensitivity
Side effects -anaesthesia
Excessive physiological depression
Depressed homeostatic mechanisms (baroreflexes, pulmonary hypoxic esponse)
Specific drug effects (NSAIDs –> prostaglandin-mediated renal BF decreased)
What is the pulmonary hypoxic response?
where vessels to poorly ventilated bits of lung constrict and so are diverted to other areas.
Why do pre-op blood tests?
To detect subclinical disease which may influence anaesthetic management. One study this made a difference in 0.2% cases.
INDICATIONS: signalment, history, baseline values
What should be known about renal function and blood tests?
2/3 tissue loss before haematology/biochemistry signs
What are boxers more sensitive to?
Acepromazine
When should anaesthesia be induced in relation to feeding?
In non-emergency cases, wait at least 6 hours after last meal before inducing GA (small animals), 12 hours (horses) or not at all (small birds and rabbits)
What is often the first sign of cardiac disease and often the best test to predict how well an animal will cope with anaesthetic?
exercise tolerance
What may PU/PD indicate?
kidney, liver or endocrine disease, pyometra
What should you be wary of in trauma cases?
multiple injuries
ruptured diaphragm
ruptured bladder
traumatic myocarditis
When do patients die during anaesthesia?
2/3 die during the recovery period –> MONITOR!
What information should be obtained from the patient history? 10
Signalment Time of last meal Previous anaesthetics Cough Exercise tolerance PU/PD V/D Trama Seizures or fainting episodes Concurrent drug treatment
Define CEPSAF
What are the risks of death due to anaesthesia (dog, cat, rabbit, GP)?
Confidential Enquiry into Perioperative Small Animal Fatalities Healthy dog: 1 in 1849 die Healthy cat: 1 in 895 die Rabbit: 1 in 72 die Guinea pig: 1 in 26 die
Outline anaesthetic morbidity
Muscle and nerve damage Cerebral hypoxia--> poor recovery, memory loss and blindness Peripheral nn damage Spinal cord damage Post-anaesthetic cognitive dysfunction Renal dysfunction (due to hypotension)
Define CEPEF
Confidential Enquiry into Perioperative Equine Fatalities. Shows mortality rate in horses to be 1 in 100 or higher if colic.
Why is blindness relatively common after dentals and endoscopy?
entire blood supply in cats to brain is from maxillary artery so decreased BF to brain –> increased risk of temporary or permanent damage.
What factors influence anaesthesia risk?
physical status temperament staff facilities choice of anaesthetic technique.
