Co-induction for ambulatory surgery.

Abstract

We read with interest the article by Djaiani and Ribes-Pastor (Anaesthesia 1999; 54: 63–7). They conclude that propofol auto-coinduction is a safe alternative to midazolam propofol coinduction. Co-induction refers to the use of two or more drugs. We would suggest that ‘priming’ is a better terminology than ‘auto-coinduction’ since it refers to a small dose of the same drug used to enhance the effects of a subsequent bolus. Co-induction using midazolam and propofol has two main advantages: reduced risk of awareness and reduction in the amount of propofol required for induction of anaesthesia. Reduced propofol consumption is associated with lesser degree of adverse haemodynamic consequences. Midazolam is a potent amnesic in subhypnotic doses unlike propofol which exerts amnesic effects by the degree of sedation it causes [1]. Propofol is unlikely to replace midazolam in producing amnesia. There is no doubt that propofol requirements are decreased by coinduction with midazolam. It is difficult from the present study to prove that there was a significant decrease in the total amount of propofol in the auto-coinduction group. Additional doses of propofol were administered to facilitate LMA insertion in 22%, 17% and 11% in propofol/propofol, saline/propofol and midazolam/propofol groups, respectively. The amount, frequency of and duration over which these boluses were given is not clarified. This is very likely to skew the data for total propofol consumption. Whether small doses of midazolam lead to a significant prolongation of discharge time is controversial. Three studies were quoted in the article by J. G. Whitman [2] which did not show significant delay in the recovery. However, recent studies do indicate some difference in the recovery profile. Further work is required to prove the point that even judicious use of small doses of midazolam does lead to a significant delay in discharging patients. We feel that the advantages of midazolam coinduction outweigh its disadvantages when used in appropriate combination. In view of the insufficient evidence available at present, it would be incorrect to conclude that priming with propofol is a safe substitute to midazolam/propofol coinduction.