Use of a target-controlled infusion system for propofol does not improve subjective assessment of anaesthetic depth by inexperienced anaesthesiologists

Abstract

Background and objectives: Target-controlled infusion, via the calculated effect compartment concentrations, may help anaesthesiologists to titrate anaesthetic depth and to shorten recovery from anaesthesia.

Methods: In this prospective, randomized clinical study, we compared the performance of six inexperienced anaesthesiologists with <1 yr of training when using target- or manually controlled infusion of propofol, combined with manual dosing of fentanyl. Ninety-two premedicated ASA I-III patients undergoing minor elective urological or gynaecological surgery were assigned to the manual- or target-controlled infusion group. Bispectral index was recorded in a blinded manner. Subjective assessment of anaesthetic depth on a 10 point numerical scale (1 = very deep anaesthesia, 10 = awake) was asked at regular intervals and the correlation with the blinded bispectral index was analysed using the prediction probability, PK. The propofol concentration profile was calculated post hoc.

Results: Propofol administration was similar in both groups with no significant difference for the administered amount and concentrations of propofol. Recovery times were also not different. In both groups, a large percentage of the bispectral index data points recorded during surgery showed bispectral index values below the recommended value of 40, but in the target-controlled infusion group there were significantly less bispectral index values above the recommended upper limit of 60 (2.5% vs. 5.1%).

Conclusions: A target-controlled infusion system does not help inexperienced anaesthesiologists to assess anaesthetic depth or to shorten recovery times, but may reduce episodes of overly light anaesthesia and thus help to prevent awareness.