Background: Intraoperative combinations of volatile and opioid agents are used to achieve unconsciousness, hypnotic sparing, haemodynamic stability and uneventful recovery. This study describes the influence of different remifentanil concentrations on these variables when combined with desflurane during abdominal surgery.
Methods: Sixty-one healthy adult patients were randomly allocated to one of five predefined remifentanil target concentrations (3, 5, 7, 10 or 15 ng ml(-1)). Anaesthesia was titrated to maintain mean blood pressure (MBP), heart rate (HR) and BIS trade mark within predetermined values by adjusting desflurane delivery. Postoperative analgesia using propacetamol and morphine was initiated 30-45 min before skin closure, and continued using morphine PCA.
Results: Desflurane requirements adjusted to both BIS and haemodynamics were not significantly modified by the remifentanil concentration (median Fet(DES) 2.7% before incision, 2.5% intraoperatively, and 2.2% during closure), resulting in a calculated drug consumption of 0.22-0.25 ml min(-1) (with 1.5 l min(-1) fresh gas flow). High remifentanil concentration decreased MBP and HR, and reduced the duration of tachycardia, but increased the duration of hypotension. The optimal balance was obtained with a remifentanil concentration of 5-7 ng ml(-1) for intubation, 3 ng ml(-1) until incision, 10 ng ml(-1) during intra-abdominal surgery and 5-7 ng ml(-1) during closure. Post-operative morphine requirements were not significantly modified by intraoperative remifentanil concentrations (median 30 mg/24 h, range [2-88]).
Conclusion: Remifentanil target concentrations from 3 to 15 ng ml(-1) had little influence on desflurane requirements or postoperative morphine consumption, but markedly modified intraoperative haemodynamic stability, suggesting that the target concentration should closely follow the successive noxious stimulations.