Abstract

1. Experiments have been performed to show the effect of haemorrhage on anaesthetic dosage in animals.

2. The intravenous dose of pentobarbitone required to produce an arbitrarily defined level of anaesthesia in rabbits was not significantly reduced by haemorrhage of 15 c.c./kg., but a reduction of 18% was observed after the loss of 20 c.c./kg. This degree of haemorrhage reduced the dose producing respiratory failure by 24%, but the safety ratio was not altered.

3. Induction of ether anaesthesia in rats was more rapid after haemorrhage. Loss of more than 25% of the blood volume reduced the induction time to 60, 65 and 75% of the normal time in ether concentrations of 7, 8 and 9%. Anaesthesia could be maintained in 50% of the bled rats by an ether concentration of 3 to 4%, while 5 to 6% ether was required to maintain anaesthesia in 50% of normal rats.

4. Recovery times after pentobarbitone anaesthesia in rabbits and after ether anaesthesia in rats were not significantly altered by haemorrhage.