Background and objectives: The aim of this prospective, randomized, double-blind study was to determine the effects of adding two different target-controlled concentrations of remifentanil (1 and 3 ng mL-1) on the desflurane requirement for blunting sympathetic responses after surgical incision (minimum anaesthetic concentration (MACBAR)). Methods: 67 patients, aged 20-50 yr, ASA I, undergoing general anaesthesia for elective abdominal surgery were enrolled and randomly allocated to receive no remifentanil infusion (n = 21) or a target-controlled effect-site concentration of 1 ng mL-1 (n = 24) or 3 ng mL-1 remifentanil (n = 22). All patients were anaesthetized with propofol, cisatracurium and desflurane with a mixture of 60% nitrous oxide in oxygen. Sympathetic responses to surgical incision were determined after a 20-min period of stable end-tidal desflurane and target-controlled remifentanil concentrations. Predetermined end-tidal desflurane concentrations and the MACBAR for each group were determined using an up-and-down sequential-allocation technique. Results: The MACBAR of desflurane was higher in the group receiving no remifentanil (6.25% [95% confidence interval: 5.9-6.5%]) as compared with patients of the groups receiving 1 ng mL-1 (2.7% [2.6-2.8%]; P <0.001) and 3 ng mL-1 remifentanil (2% [1.9-2.2%]; P <0.01). When considering a MAC value in this age population and the contribution of 60% nitrous oxide (0.55 MAC), the combined MACBAR values, expressed as multiples of the MAC, were 1.9, 0.8 and 0.6 MAC, in the three groups, respectively. Conclusion: A target-controlled concentration of 1 ng mL -1 remifentanil results in a 57% decrease in the MACBAR of desflurane combined with 60% nitrous oxide. Increasing the target concentration of remifentanil to 3 ng mL-1 produces a further 26% decrease in the MACBAR values of desflurane.
- Anaesthetics inhalational, desflurane, nitrous oxide, minimum anaesthetic concentration
- Analgesics opioid, remifentanil
- Surgery abdominal
- Sympathetic nervous system
ASJC Scopus subject areas
- Anesthesiology and Pain Medicine