Ketamine infusions. Observations on technique, dosage and cardiovascular effects.

A continuous infusion of ketamine, following an initial dose of 1 mg/kg, has been used as sole anaesthetic in over 200 adult patients. The pre-operative use of 4 mg lorazepam has made this acceptable with respect to emergence sequelae and dreams. The technique can be used with neuromuscular blocking drugs and controlled ventilation with air, but here pancuronium is best avoided because of excessive tachycardia and hypertension. Hypertonus was the main problem encountered in the non-relaxant cases. The amount of ketamine required for anaesthesia has been analysed in detail and recommendations on dosage are given. The cardiovascular effects have also been analysed in detail. There is a need for a similar investigation to be carried out in circumstances where inhalation agents are not available and where there is a shortage of anaesthetists.