PC Stuart^1,2, A Moores², J Sandbach¹, GNC Kenny¹ and D Russell^1,2.

Departments of Anaesthesia, ¹University of Glasgow & ²Southern General Hospital, Glasgow G51 4TF

Background & Goal of Study: Remifentanil is an opioid analgesic that is administered by i.v. infusion. It is metabolised by esterases present in both blood and tissues, is therefore non-cumulative and has a very short 3-4 min half-life which is independent of duration of administration. In clinical anaesthesia remifentanil can be used to provide intense intra-operative analgesia, but this wears off rapidly when infusion is discontinued. When continued into the early postoperative period, administration of remifentanil by bolus and infusion can result in an unacceptable incidence of respiratory depression, apnoea and muscular rigidity[1]. We evaluated the administration of remifentanil by patient maintained analgesia following daycase laparoscopy, using a target controlled infusion system.

Material and Methods: Ethics committee approval was obtained, and 48 patients gave informed written consent. They were anaesthetised with propofol and remifentanil by TCI, intravenous diclofenac 75mg and intra-peritoneal bupivacaine 0.5% with epinephrine 1 in 200,000. The remifentanil TCI system used the pharmacokinetic model described by Minto et al [2]. On completion of surgery, the remifentanil C_T was reduced from 4.0 ng.ml^-1 to 0.6 ng.ml^-1. After emergence, patients who had a verbal rating pain score greater than 4/10, and who in the opinion of the attending nurse required additional analgesia, were given a handset connected to the TCI system. A successful push increased the remifentanil target concentration (C_T) by 0.2 ng.ml^-1,with a lockout period of 2 min. C_T was reduced automatically by 0.2 ng.ml^-1 every 30 min if no analgesic demands were made. Patients were studied for three hours, during which time their sole analgesia was remifentanil.

Results & Discussion: Only 14 out of 48 patients who consented pre-operatively required analgesia. Results are presented below as median, inter-quartile range and range. Pain scores were significantly lower than baseline at all times (*p<0.05, **p<0.01 by Kruskal Wallis test)

Four patients developed significant nausea towards the end of the study period, four had emesis and two received an anti-emetic. The lowest recorded SpO₂ was 93%, and this patient received supplementary oxygen. No other interventions were required on safety grounds, and the main task for the attending anaesthetist was renewing the remifentanil syringe.

Conclusion: In this initial evaluation involving limited numbers of patients, Patient Maintained Analgesia with Remifentanil proved safe and effective and is worthy of additional investigation.

References:

1. Schuttler J et al. Anaesthesia 1997; 52:307-17. 

2. Minto CF et al. Anesthesiology 1997; 6:10-23.