Xenon does not reduce opioid requirement for orthopedic surgery

Abstract

Purpose: Is to test the hypothesis that 70% xenon has a relevant opioid sparing effect compared to a minimum alveolar concentration (MAC)-equivalent combination of N2O and desflurane. Methods: In this randomized, controlled study of 30 patients undergoing major orthopedic surgery, we determined the plasma alfentanil concentration required to suppress response to skin incision in 50% of patients (Cp50) anesthetized with xenon (70%) or a combination of N2O (70%) and desflurane (2%). A response was defined as movement, pressor response > 15 mmHg, heart rate > 90 beats·min-1, autonomic reactions or a combination of these. At skin incision, alfentanil was administered at a randomly selected target plasma concentration thereafter the concentration was increased or decreased according to the patient's response. After skin incision, desflurane was adjusted to maintain the bispectral index below 60 and prevent responsiveness in both groups. Results: The Cp50 (± standard error) of alfentanil was 83 ± 48 ng·mL-1 with xenon and 49 ± 26 ng·mL-1 with N2O/desflurane (P = 0.451). During surgery five xenon and 15 N2O/desflurane patients were given desflurane at 1.0 ± 0.5 volume % and 2.5 ± 0.7 volume %. The total age adjusted MAC was 0.97 ± 0.07 and 0.94 ± 0.07 respectively (P = 0.217). The intraoperative plasma alfentanil concentrations were 95 ± 80 and 93 ± 60 ng·mL-1 respectively (mean ± SD; P = 0.451). Patients given xenon were slightly more bradycardic, whereas blood pressure was similar. Conclusion: Xenon compared to a MAC-equivalent combination of N2O and desflurane does not substantially reduce opioid requirement for orthopedic surgery. A small but clinically irrelevant difference cannot be excluded, however.