Target-controlled remifentanil in combination with propofol for spontaneously breathing day-case patients

Remifentanil is a new potent opioid with a very short duration of action ir respective of duration of infusion. It may have a role in day-case anaesthe sia as part of a balanced total intravenous anaesthetic technique with prop ofol. We examined the respiratory depressant effects of remifentanil in 20 patients undergoing day-case anaesthesia. The target plasma concentration o f remifentanil was varied while maintaining a constant target-controlled in fusion of 4.5 mu g.ml(-1) propofol. In only 12 patients was satisfactory sp ontaneous respiration maintained. In these patients the median remifentanil target concentration was 1.6 ng.ml(-1) and was achieved with a median infu sion rate of 0.05 mu g.kg(-1).min(-1). The range of target concentrations a ssociated with satisfactory spontaneous respiration was wide and varied ove r a 4.7-fold range from 0.6 to 2.8 ng.ml(-1).