Remifentanil infusion in combined general and epidural anaesthesia

K. Papilas, M. Mitselou, L. Papaspyrou, A. Bairaktari, M. Vafiadou. Sismanoglion Hospital, Athens, Greece

Combined general and epidural anaesthesia is a suitable anaesthetic technique for abdominal operations, offering effective postoperative analgesia, as well. We studied whether a remifentanil infusion would allow for easy titration of the general anaesthetic throughout the procedure and prompt recovery.

Material and Methods

Twenty patients scheduled for radical prostatectomy, cystectomy or transperitoneal nephrectomy participated in the study. In all patients, an epidural catheter was placed, at a lumbar interspace.

In the first ten patients (group A), induction in general anaesthesia was performed after the desired dermatomal level of regional anaesthesia was achieved. Following preoxygenation, 0.2 mg kg^-1 bolus remifentanil was administered and an infusion started at 0.05 mg kg^-1 min^-1. One minute later propofol 1.5 – 2.5 mg kg^-1 was administered for induction, followed by the muscle relaxant and tracheal intubation. The patients breathed 30% O₂ in N₂O and the propofol infusion was set at 60 mg kg^-1 min^-1. A CVP catheter was also inserted. The remifentanil infusion was regulated as follows: provided CVP was normal, if MAP < 60 mm Hg or SAP < 100 mm Hg, ephedrine (5 mg) was administered and the remifentanil infusion was decreased by 0.02 mg kg^-1 min^-1. If further reduction was needed, the infusion rate was set to 0.02 mg kg^-1 min^-1. If HR or BP increased more than 20% baseline values, propofol boluses of 20 mg were administered and remifentanil infusion was icreased by 0.02 mg kg^-1 min^-1. Also, a top-up dose of 7.5 –10 mg bupivacaine was administered, if indicated. In general, the epidural anaesthetic was maintained with the administration of 10–20 mg / h of bupivacaine 0.25%. One hour before the end of surgery 2-3 mg morphine were given epidurally.

In the next ten patients (group B), induction was performed as soon as we had tested the position of the epidural catheter and had administered the loading dose of bupivacaine 0.5%. Induction was identical to the previous group, except that initial remifentanil infusion was initially set at 0.2 mg kg^-1 min^-1 and decreased to 0.05 mg kg^-1 min^-1 within the first 45 min, as the epidural spread up to the desired level.

Results

In group A, haemodynamic control was easily achieved with the remifentanil infusion set to 0.03-0.05 mg kg^-1 min^-1, for most of the duration of the operation. In six patients who showed signs of inadequate analgesia, increasing temporarily the remifentanil infusion rate and administering a top-up dose, provided adequate control of the anaesthetic level. In group B, haemodynamic control and adequate analgesia were also achieved following the same algorithm with group A. No patient in both groups reported intraoperative awareness.

In both groups, after the first two and a half hours of the operation, bupivacaine 0.25% did not seem to provide total analgesia, so that remifentanil infusion was increased up to 0.05 mg kg^-1 min^-1, up to the last minute of the operation. Should a higher rate be required, we administered an additional top-up dose. The propofol and remifentanil infusions were switched off at the end of surgery, neuromuscular blockade was reversed and 100% O₂ was administered. The patients were alert and extubated within 3 to 5 min. Analgesia was sufficient in all 20 patients, while all patients were able to move their legs.

Conclusion:

In combined general-epidural anaesthesia, remifentanil infusion 0.02 to 0.2 mg kg^-1 min^-1 with a low dose propofol infusion permits adequate titration of the analgesia and prompt recovery of a pain-free patient.