• J Coquin, N Tafer, M Mazerolles, O Pouquet, R Pfeiff, P Richebé, and G Janvier.
• Service d'anesthésie réanimation 2, CHU de Bordeaux, groupe hospitalier Sud, avenue de Magellan, 33604 Pessac cedex, France.
• Ann Fr Anesth Reanim. 2009 Nov 1; 28 (11): 930-5.

IntroductionRemifentanil is a powerful morphinic agonist often ordered for anaesthesia. The use of peroperative large doses of this opioid increases the risk to develop postoperative hyperalgesia and acute tolerance. But how early these effects can occur? Despite the fact that these effects could be masked during the preoperative time because of general anaesthesia, it seems they could occur precociously. In order to try to describe this time, this study evaluated the acute tolerance under general anaesthesia requiring large doses of remifentanil by using an effective peroperative monitoring of nociception: the continuous pupillary diameter monitoring.Materials And MethodsIn this prospective observational clinical study, a continuous infusion of remifentanil was started at a range of 0.3 microg/kg/min after induction of anaesthesia by using propofol (TIVA), remifentanil bolus and cisatracurium. The pupil monitoring started 10 min later (T+10 min) and lasted until the surgical incision (T+65 min). So, there was no surgical stimulus during this time.ResultsThirty patients undergoing major cardiac or vascular surgery were included in this study. The continuous pupil diameter evaluation showed a significant increase of the pupil diameter from T+45 min. No significant variation of heart rate, blood pressure, bispectral index (BIS) values were observed.DiscussionThe development of acute remifentanil tolerance could possibly explain these results. If evaluations with continuous pupillary diameter monitoring are still limited, these results suggest that the use of powerful opioids such as remifentanil should be associated with a N-methyl-D-aspartate (NMDA) receptor antagonist agent, including short time administrations.

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