Tourniquet use for limb surgery

Regarding the use of tourniquets in the theatre environment, the following statements

are true EXCEPT which one?

a) Exsanguination and tourniquet inflation is associated with immediate rise in

central venous pressure, arterial blood pressure and heart rate

b) After two hours’ inflation time, a significant decrease in core temperature can be

expected on deflation of the tourniquet

c) Pre-inflation, ketamine 0.25 mg/kg intravenously can prevent the hypertensive

response to tourniquets

d) When using a double-cuff tourniquet for intravenous regional anaesthesia the

proximal cuff is the first to be used

e) If the continuous tourniquet inflation time exceeds two hours, the ischaemic cell

damage and lesions associated with acidosis are irreversible

Answer: e

Explanation

The use of a tourniquet for prevention of haemorrhage during limb surgery requires a

pneumatic cuff of width at least half the diameter of the limb. The limb is exsanguinated

and the cuff inflated to 50mmHg greater than the systolic blood pressure for the

upper limb or 100mmHg greater than the systolic blood pressure for the lower limb.

Exsanguination causes an autotransfusion of blood volume to the central compartment

with consequent increase in central venous pressure, heart rate and blood pressure.

This is exacerbated by the acute increase in systemic vascular resistance. The temperature

of the ischaemic limb drops and metabolites accumulate in it. It is the release of

these metabolites, and cold to the circulation, which causes the physiological changes

seen on deflation. After about one hour of cuff inflation, characteristic resistant hypertension

is seen. This may be avoided with pre-inflation ketamine as described or

regional anaesthesia. An arbitrary inflation duration limit of two hours is often applied

but some centres use in excess of this and at two hours’ duration, cell lesions secondary

to local acidosis are reversible. During intravenous regional anaesthesia the proximal

cuff is inflated first before the local anaesthetic is injected in order that the site of the

distal cuff is rendered insensate before the distal cuff is inflated such that tourniquet

pain is avoided.

Reference

Malanjum L, Fischer B. Procedures under tourniquet. Anaes Intens Care 2009; 10(1):

14–17.