Anaesthesia

Question 1

Define GA

Answer 1

state of unconciousness produced by controlled reversible drug induced intoxication of the CNS so that the patient neither perceives or recalls the noxious stimuli

Question 2

define local anaesthesia

Answer 2

temporary blockage of sensory nerves (usually with simultaneous block of motor nerves)

Question 3

5 components or outcomes of GA?

Answer 3

Aims
> unconsciousness
> analgesia (anti-nociception) 
> muscle relaxation 
Controlling side effects 
- homeostasis
- normal oxygen delivery

Question 4

What is the main side effect of anaesthesia?

Answer 4

• CV and respiratory depression
• homeostatic depression (baroreceptor reflex, pulmonary hypoxic response esp important in horses)
• Specific drug effects (eg. NSAIDs and renal function - PGs needed for vasodilation to maintain blood flow)

Question 5

What may pre-anaesthesia blood tests tell you?

Answer 5

• baseline values
• rarely actually influence anaesthetic protocol
• insensitive for measuring subclinical disease (>2/3 kidney tissue lost before urea^ in blood)
• good for risk animals or before major surgery

Question 6

What is anaemia? Impact on GA?

Answer 6

• low Hbg or PCV
  -> v o2 delivery to tissues (oxygen delivery = CO x o2 content; o2 content =(1.36 x Hb x SaO2%) + (PaO2 x 0.003)
• transfusion triggers:
  5-8g/dL [Hb]
  PCV <20%

Question 7

How may low plasma protein affect anaesthesi? Which drug is this escpecially important for?

Answer 7

• changes in ratio free: protein bound drug (esp. PROPOFOL 98% albumenbound)
• oncotic pressure -> oedema and ow BP

Question 8

How is kidney failure defined by haematology parameters?

Answer 8

• BLood urea >10mmol/l
• creatinine >2–mmol/l
• concurrent acidaemia (^ free drug concentrations, depresses myocardial contractility.. MOER THINGS FIND SLIDE

Question 9

5 reasons for anaesthesia?

Answer 9

• restraint (esp wild animals)
• surgery
• diagnostics
• therapy
• legal requirements

Question 10

What is the triad of anaesthesia?

Answer 10

Unconciousness (narcosis)
Analgesia (anti-nociception)
Muscle relaxation

Question 11

WHat physiological system must be carefully stabilised during anaesthesia? Why?

Answer 11

Cardiovascular (esp in underlying disease)

- with poor analgesia noxious stimuli can cause harmful autonomic responses and involuntary movement

Question 12

What is the main aim of the anaesthetist?

Answer 12

Maintain oxygen delivery to tissues at the same time as prividing the three components of the triad

Question 13

How do modern anaesthetic drugs differ from historical anaesthesia?

Answer 13

“Lighten up” - drugs should allow rapid onset, rapid recovery and rapipd responses to changes in delivered doses

Question 14

Which anaesthetic drug is highly albumen bound?

Answer 14

Propofol >90%

Question 15

Which breed are senstitive to acepromazine?

Answer 15

BOxers

Question 16

Which breeds are more prone to airway obstruction?

Answer 16

brachycephalic

Question 17

which animals may be difficult to estimate weight?

Answer 17

• fluffy breeds! Weigh!

Question 18

How long after a meal should you wait before anaesthesia?

Answer 18

• dogs/cats 6 hours (unless emergency)
• horses 12hours
• birds and rabbits none

Question 19

WHat signs in the patient history may indicate potential anaesthesia risks?

Answer 19

• cough
• excercise intolerance
• PUPD (kidney, liver or endocrine disease, pyometra)
• VD+ fluid and electrolyte imblanaces
• trauma (potential for ruptured diaphragm, bladder, traumatic myocarditis)
• seizures or syncope (CNS disease - may repsond strangely to anaesthetic drugs)
• concurrent drug tx (NSAId, steroids, ACEI, pimobendan)

Question 20

Which way does the eye roll on induction?

Answer 20

Down and medially

Question 21

What are the death rates of anaesthesia in different animals?

Answer 21

• 1/2000 dogs
• 1/1000 cats
• 1/100 rabbits
• 1/25 guinae pigs

Question 22

What is TIVA?

Answer 22

• Total IV anaesthesia

Question 23

MOrbidity asociated with anaesthetic?

Answer 23

• mm and nn damage (esp horses)
• cerebral hypoxia -> poor recovery (esp SA) and post op cognitive dysfunction
  > eg. post-op blindness in cats after dentals due to maxillary a. crushing by jaw hyperextension
• peripheral n damage/CNS damage
• renal dysfunction due to v BP

Question 24

WHat factors influence risk of anaesthesia?

Answer 24

• physical status (ASA grade I-V)
• temperament
• staff available
• facilities available
• what youre used to!

Question 25

What are the exposure limits according to COSHH regulations for anaesthetic gases?

Answer 25

NO 100ppm
Sevoflurane 60ppm
Isoflurane 50ppm
Halothane 10ppm 
> monitor waste gases every 12 months

Question 26

How can gas exposure be minimised?

Answer 26

• machine and vapourisers egularly serviced
• avoid mask and chamber inductions
• ensure endotracheal tube cuff properly inflated
• fill vapourisers at end of day
• caps back on!
• leave patient attached to circuit at end of anaesthesia
• flush circuit with oxygen and dump the bag into the scavenging system
• use low gas flow techniques

Question 27

Define anaesthesia

Answer 27

loss of sensation due to pharmacological depression of nerve function