oa Southern African Journal of Anaesthesia and Analgesia - A study to compare continuous epidural infusion and intermittent bolus of bupivacaine for postoperative analgesia following renal surgery : original research
Background Extradural administration of local anaesthetics, opioids or a combination of both is now a well-established technique for managing postoperative pain following upper abdominal, pelvic and thoracic procedures or orthopaedic procedures on the lower extremities. There are two techniques of administration of drugs via epidural catheter - one is by continuous infusion and the other is by intermittent boluses. At present there is controversy in the literature regarding the analgesic effects of the techniques.
Methods This study was conducted in a prospective, randomised manner on 60 patients of either sex of ASA class I or II, scheduled to undergo elective renal surgery. The general anaesthetic technique was standardised. The patients were divided randomly into two groups of 30 each. The patients in group 1 received a continuous infusion of 0.166% bupivacaine, while the patients in group 2 received intermittent boluses through epidural catheter. The efficacy of postoperative analgesia was assessed using pulmonary function tests up to 12 hours. The generated data were analysed statistically.
Results There were no significant changes in pulse rate and arterial pressure at different time intervals from the preoperative values. Respiratory rates in both the groups were found to be significantly higher than the preoperative values in the two groups (p < 0.05). Forced vital capacity (FVC) and peak exploratory flow rate (PEFR) were significantly lower than the preoperative values at all points in time in both groups, but the drop was greater in group 2 and pain scores on movement were also found to be significantly higher than those in group 1 at the times when the effect of the bupivacaine bolus was wearing off (p < 0.05). Pain scores at rest were found to be comparable in both groups postoperatively.
Conclusions We conclude that continuous infusion of bupivacaine (8.3 mg / h) provides better analgesia at rest and on movement than intermittent boluses, and is not associated with fluctuations in the level of analgesia. Incidences of adverse effects are similar and not insignificant with both schedules.
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