CAL: How do we anaesthetise this animal?

Question 1

What ASA category would an animal brought in for elective surgery such as castration, with no underlying health conditions, be put in?

Answer 1

ASA 1 (minimal risk)
Includes animals scheduled for elective surgery, such as neutering, hip dysplasia radiographs and some elective orthopaedic procedures

Question 2

All components of balanced anaesthesia (Unconsciousness, analgesia, muscle relaxation and amnesia) are required for simple castration.
True/false?

Answer 2

True
Castration is a painful procedure and in the dog it would be very difficult to perform the procedure safely without balanced general anaesthesia

Question 3

Why is a T-piece an ideal breathing system for animals under 10kg?

Answer 3

It has minimal apparatus deadspace and resistance to breathing
However it does require a higher fresh gas flow than a rebreathing system

Question 4

What would be an appropriate breathing system for a dog weighing 70kg?

Answer 4

Standard circle system (rebreathing system)
* this would be the most economical option in this scenario as with non-rebreathing systems the required fresh gas flow would be extremely high (and therefore expensive) with a considerable amount of wasted gas.

Question 5

What factors need to be considered when assessing risk of surgery?

Answer 5

• Condition of the animal
• Facilities available, including those for postoperative care
• Experience of the veterinary surgeon
• Whether procedure is elective or emergency

Question 6

How would anaemia affect your anaesthetic plan?

Answer 6

If an animal is anaemic, oxygen content will be reduced and cardiac output will need to be increased to maintain oxygen delivery to the tissues
Most anaesthetic drugs will reduce cardiac output and this may reduce oxygen delivery to a critical level in the presence of anaemia
Blood transfusion may be necessary and will depend on a consideration of the animal’s underlying condition, whether the anaemia is acute or chronic and whether there is ongoing blood loss

Question 7

How might severe hypoalbuminaemia affect the induction of anaesthesia?

Answer 7

Changes in albumin concentrations will affect the amount of free/bound drugs
Many anaesthetic agents are highly protein bound (e.g. propofol is 98% albumin bound) and hypoalbuminaemia will increase the amount of free (unbound) drug, so theoretically a greater response could be seen if a fixed dose is given
The reality is that clinically, anaesthetic drugs are given to effect, so we might not see any changes