RESUMO
BACKGROUND AND OBJECTIVE: Previous studies have shown that target-controlled infusion (TCI) was associated with increased propofol consumption as compared with manually controlled infusion (MCI). However, most studies lacked an objective measurement of anaesthetic depth. We compared TCI and MCI with regard to propofol dose requirement while monitoring depth of anaesthesia with bispectral index (BIS) and midlatency auditory-evoked potentials (MLAEPs). METHODS: Fifty ASA 1 or 2 patients undergoing elective ENT surgery were randomly allocated to the TCI group (n = 25)or the MCI group (n = 25). BIS, MLAEPs, haemodynamic parameters and propofol plasma concentration were determined at various stages before, during and after anaesthesia. During anaesthesia, BIS values were always maintained between 40 and 60. RESULTS: Anaesthesia significantly increased latency of Pa and Nb compared with when patients were awake (P < 0.01). After extubation, the latency of Pa and Nb significantly decreased and basically returned to baseline level. BIS and latency of both Pa and Nb did not differ between groups.Also, the propofol induction dose (mean WSD: TCI, 2.09 +/- 0.36 mg kg(-1); MCI, 2.06 +/- 0.16 mg kg(-1) and total dose (TCI, 5.57 +/- 0.96 mg kg(-1) h(-1); MCI, 5.79 +/- 0.87 mg kg(-1) h(-1) and measured plasma propofol concentration during anaesthesia did not differ between groups. At 15 min after intubation, the mean predicted plasma concentration (2.2 +/- 0.2 microg ml(-1)) differed significantly from the measured plasma concentration (2.8 +/- 1.2 microg ml(-1)). No correlation was observed between predicted and measured propofol plasma concentrations.
