Background and objective: There are anecdotal reports of dysphoria occurring in patients on the first day after anaesthesia with remifentanil. This study was performed to investigate this allegation and to find a possible relationship to postoperative shivering or to nausea and vomiting.
Methods: Patients undergoing otorhinolaryngeal surgery took part in a prospective, randomized, double-blind study comparing total intravenous anaesthesia with propofol (2 mg kg−1 bolus injection then 100 μg kg−1 min−1) and remifentanil (1 μg kg−1 bolus then 0.1–0.5 μg kg−1 min−1) or alfentanil (30 μg kg−1 bolus then 0.16–0.83 μg kg−1 min−1). The patients were carefully insulated and actively warmed by convective heating and rectal temperature was monitored continuously. Postoperative shivering was graded on a three-point scale, and the cumulative incidence of nausea and vomiting were registered at 24 h after surgery. Pre- and postoperative mood was measured with the von Zerssen mood scale (Befindlichkeits-Skala) and changes tested for significance. High scores reflect discontent and dysphoria.
Results: The data of 98 patients (49 in each group, ASA I–II, age 42 ± 13 yr, anaesthesia time 141 ± 60 min; mean ± SD; intergroup P values >0.1) were evaluated. Core temperature did not change perioperatively (before 36.6 ± 0.2°C; after 36.8 ± 0.3°C, inter- and intragroup P > 0.1). The incidence of nausea was the same in each group; vomiting occurred with equal frequency (6/49 vs. 7/49). Shivering was significantly more frequent after remifentanil (41% vs. 10%, P < 0.001). The patients' mood remained stable after remifentanil but worsened after alfentanil (von Zerssen score from 9.3 ± 2.5 to 13.9 ± 3.6; mean ±95% confidence intervals; P < 0.01).
Discussion: Postoperative shivering was more frequent after remifentanil but was unrelated to intraoperative heat loss. Contrary to preliminary informal observations, there was no evidence that remifentanil caused post-anaesthetic dysphoria on the day one after surgery.