Intro to Anaesthesia

Question 1

What is general anaesthesia?

Answer 1

Greek word ‘insensibility or ‘loss of sensation’.
A reversible production of a state of unconsciousness required to perform surgery and diagnostic testing.
Relies on provision of the elements of the anaesthesia triad.
Produced by anaesthetic agents w/ absence of pain sensation over the entire body.

Question 2

1. What is regional anaesthesia?
2. What is local anaesthesia?

Answer 2

1. Insensibility caused by an interruption of the sensory nerve conduction in any region of the body. e.g. whole leg.
2. Lack of sensation in a localised part of the body. e.g. around hernia.

Question 3

Reasons for anaesthesia.

Answer 3

Facilitate surgical / diagnostic / and other procedures.
Prevent pain / suffering.
Research.
Immobility.

Question 4

1. What is sedation?
2. What is anxiolysis?
3. What is analgesia?
4. What is premedication?

Answer 4

1. The allaying of irritability or excitement (a method often used for the minor procedures / imaging etc.)
2. Reduced anxiety.
3. Reduced sensibility to pain.
4. A drug or combination of drugs, given prior to the induction of general anaesthesia.

Question 5

Why do we pre-med?

Answer 5

Calms patient.
Aids restraint.
Provides pre-emptive analgesia (dept. on drugs used).
Allows a reduction in induction drugs and maintenance drugs (for gaseous agents, we call this ‘MAC sparing’). – MAC = Mean alveolar concentration.
Contributes to a smooth induction AND recovery.

Question 6

Basic sequence of events for anaesthesia.

Answer 6

Owner conversation / consent.
Pre-operative examination.
Check list / ASA classification.
Pre-med.
Induction.
Maintenance.
Recovery and post-operative care.

Question 7

1. What happens to the state of the patient in the induction phase?
2. Give examples of induction agents.
3. Give examples of what could be used to secure the airway in this phase.

Answer 7

1. From conscious t anaesthetised.
2. Propofol / Alfaxalone.
3. ET tube, V-gel, Laryngeal mask airway device, face mask.

Question 8

1. How can anaesthesia be induced in animals?

Answer 8

1. Injectable – administering an incremental dose of induction agent i.e. Propofol or Alfaxalone.

Injectable – May involve giving a set dose of drugs to induce and maintain anaesthesia –common for feline neutering.

Gaseous – Using a volatile gas to ‘gas down’ the patient, via either a close fitted face mask or a gas chamber.

Question 9

1. What may maintenance phase involve placement of?
2. Methods of maintenance of anaesthesia?

Answer 9

1. Placement of local / regional blocks where applicable.
2. TIVA (total intravenous anaesthesia).
   – setting up and administering a set dose of drug i.e. propofol via a syringe driver or pump to maintain anaesthesia.

Injectable – giving a set dose of a combination of drugs to induce and maintain anaesthesia – common for feline neutering.

Gaseous (most common) – placing an airway device (or close-fitted face mask – not first choice) to deliver continued volatile gas within oxygen. Depth easily changed.

Question 10

Recovery phase.

Answer 10

Procedure finished and patient ready to be recovered.
Cessation of maintenance agent.
Antagonism of injectable drugs where required.
Removal of airway device when safe.
Move to recovery area (well ventilated / quiet / calm).

Question 11

1. What are the 3 elements of the anaesthesia triad.
2. Define balanced / multi-modal anaesthesia.

Answer 11

1. Narcosis.
   Analgesia.
   Muscle relaxation.
2. Anaesthesia produced by smaller doses of two or more agents considered safer than the usual large dose of a single agent.

Question 12

1. Which sp. out of dogs, cats and rabbits has the lowest overall risk in anaesthesia?
2. ” “ highest overall risk in anaesthesia?

Answer 12

1. Dogs.
2. Rabbits.

Question 13

CEPSAF Enquiry.

Answer 13

Complications were looked at in the 48 hr post op period.
50% of deaths occurred within 3 hours of recovery.
Sick animals had higher risk than healthy animals.
Risks sig. higher during GA compared to sedation.
Cats had a twofold increase in risk compared to dogs.
ET tube intubation has been associated w/ increased mortality in cats but not in dogs (larynx sensitivity).
Still behind human medicine / dated.
Of all animals died, only 10% went for post mortem.

Question 14

1. Equine anaesthesia risks for overall, colic, non-abdo.
2. What was the risk increase in animals undergoing urgent procedures compared to animals undergoing routine / elective procedures?
3. ” “ in older (5 to 9yrs old) animals compared to younger (6m to 1.5yrs) animals?
   – “ “ in animals >9yrs old?
4. ” “ in long-skulled animals compared to animals with medium length skulls.

Answer 14

1. Overall – 2.1%
   Colic – 11.7%
   Non-abdo – 0.9%
2. 13.6X.
3. 4.9X.
   – 12.8X.
4. 3.7X.

Question 15

1. How can the long-nosed animal risk increase be explained?

Answer 15

1. May be as we pay much more attention / vigilance to how they are managed, and we may reduce our concern of other breeds.
   There may be an additional risk pathway that is specific to dolichocephalic dogs that we do not fully understand.

Question 16

Spp-specific problems seen in dogs, cats and rabbits.

Answer 16

• Extremes of size: 500g to 100kg – need to provide a wide range of equipment or more staff.
• Hyper/hypothermia – some animals VERY hairy, some not. Ranges in body surface area. Some animals at risk of becoming very hot and some at risk of losing body temp. v quickly.
• Differences in temperaments
  – Risk of injury – cannot perform pre op exam, may need extra equipment / owner assistance.
  – Stress from handling.
  – May need to rely on drugs that are not ideal for that animal.
  – May need to extubate early / remove IV lines.
• Drug sensitivities in some breeds – Some larger breed dogs may need lower mg/kg.
• Obesity.
  – IM inj. difficult.
  – Can easily overdose.
  – Ventilatory compromise.
  – Increased CV workload.

Question 17

Breed specific problems…
1. Brachycephaly.
2. Boxers.

Answer 17

1. BOAS – Airways / GOR (gastro-oesophageal reflux) / ocular (dry eye, ulcers) / skin (IV placement, clipping and cleaning, LA blocks) / skeletal e.g. corkscrew tails, spinal deformities, disc prolapses (impacts positioning, management, restraints).
2. – Acepromazine (ACP) sensitivity (more prev in UK bred boxers than US bred boxers). – can see bradycardia and hypotension. ACP CANNOT BE ANTAGONISED!
   – Cardiomyopathy – ventricular tachycardia / arrhythmia / syncope. Can be seen in otherwise healthy dogs.

Question 18

…
1. MDR1 gene.

Answer 18

1. Multi drug resistance.
   – Collies / sheepdogs / shepherds.
   – MDR gene = responsible for removing some drugs from the brain.
   – If mutation present, then defect in P-glycoprotein which is important for transport of these drugs, meaning it cannot transport toxins away and so they build up which can cause neuro symptoms.
   – Genetic test available for this gene.
   – Drugs include Ivermectin (antiparasitic), Butorphanol (opioid/sedation), ACP (sedative).

Question 19

…
1. Greyhounds.
2. Dobermans.
3. Mini Schnauzers.

Answer 19

1. Lack cytochrome P450 (important clearance mechanism) – thiopental (not UK licensed anymore) / Propofol.
   Low body fat (17% vs 35%): Slow recovery / dose to effect / keep warm / padded (pressure sores etc).
2. – Von Willebrand factor (clotting factor) – Buccal mucosal bleeding time.
   – Dilated cardiomyopathy in 50% of >6yr olds. (can be asymptomatic).
3. Mostly females affected by sick sinus syndrome (westies can also be affected).
   – Sinus node works poorly so there is a large gaps between beats – Maybe perform ECG.

Question 20

1. Legislation relating to anaesthesia.
2. According to this legislation what is it illegal to carry out without anaesthetic?

Answer 20

1. Protection of Animals (Anaesthetics) Act 1964. (Amended from 1954)
2. • Castration of a male animal (except under circumstances laid out in the 1954 act).
     - The de-horning of cattle.
     - The dis-budding of calves (except by chemical cauterisation during first week of life.
     - Docking of lambs’ tails by using rubber ring or other tourniquet after first week of life.

Question 21

1. Another legislation relating to anaesthesia.
2. What does this legislation state must be done with drugs?
3. What schedule of drug must be kept in DD cupboard and what schedule of drug is it sensible to keep in DD cupboard?

Answer 21

1. Misuse of Drugs Act and Misuse of Drugs Regulations 1971 (and subsequent amendments 2001).
2. • Kept in a locked / bolted to the wall cabinet.
     - With limited key holders (RVNs can be key holders).
     - Have a bound register to record use / disposal / arrival.
     - Have regular stock checks / audits.
3. Must – Schedule 2.
   Sensible – Schedule 3.

Question 22

1. Give examples of schedule 2 drugs.
   – Why are these subject to the most restrictions.
2. Give examples of schedule 3 drugs.
   – What are these drugs subject to?
3. Give examples of schedule 4 drugs.
4. Give examples of schedule 5 drugs in vet med. – locked away? – why?

Answer 22

1. Full mu agonist opioids i.e. Methadone, Morphine, fentanyl, Ketamine.
   – Potential for abuse.
2. Barbiturates, Tramadol, Gabapentin, Pregabalin, some benzodiazepines.
   – Subject to special prescription requirements and sometime special storage requirements.
3. Part 1 – benzodiazepines.
   Part 2. – anabolic / androgenic steroids.
   (No special requirements).
4. Codeine based. e.g. Pardale-V. – no – produce contains such low quantities of the drug so v low risk.

Question 23

Delegation to VNs re anaesthesia. (RCVS advice).

Answer 23

• Inducing anaesthesia by administration of a spec. amount of med directed by VS may be carried out by RVN, or SVN with supervision, but NOT any other suitably trained person.
• Administering med incrementally or to effect, to induce and maintain anaesthesia may only be carried out by VS.
• Maintaining anaesthesia is responsibility of VS, but suitably trained person may assist by acting as the surgeon’s hands e.g. by moving dials.
• Most suitable person to assist VS to monitor and maintain anaesthesia = RVN, or SVN under supervision.

Question 24

1. What does AVA stand for?
2. Who are they?

Answer 24

1. Association of Veterinary Anaesthetists.
2. An active group of vets, nurses, researchers, technicians etc with a common interest in animal anaesthesia, analgesia and welfare.