Haemodynamic, endocrine and nociceptive response to gynaecological procedures under epidural local anaesthesia during continuous epidural infusion or bolus epidural fentanyl dosing

Abstract

This study aimed to evaluate the analgesic effects and hormonal responses of a single epidural bolus compared to continuous epidural infusion of fentanyl as supplements to intraoperative local epidural anaesthesia for major gynaecological surgery. Forty patients undergoing total vaginal hysterectomy were randomised to receive in a double blind fashion either 1.5 μg kg−1 fentanyl epidurally (group A) or saline (group B) as bolus injections followed by epidural infusion of saline or fentanyl (0.7 μg kg−1h−1) respectively at a rate of 10 ml h−1. Postoperative pain intensity was assessed by visual analogue scale (VAS). Prolactin and cortisol plasma levels were used as stress markers. The onset of anaesthesia was significantly shorter in group A (p<0.05) but the duration of T10 blockade was significantly longer in group B (p<0.01). Pain intensity was significantly higher in group A at 90, 105 and 120 minutes after skin incision (p<0.001). There was no intraoperative difference in heart rate or mean arterial pressure between the two groups nor was there any difference in the incidence of adverse effects such as nausea, vomiting or shivering. Both groups had a progressive decrease in serum cortisol and prolactin concentrations 30 and 60 min after skin incision, but cortisol and prolactin concentrations were higher in group A (p<0.05) 120 minutes after skin incision. Our observations suggest that perioperative continuous epidural infusion of fentanyl begun intraoperatively attenuates the endocrine stress response, but a bolus dose of fentanyl given along with bupivacaine lacks this protective effect. A possible explanation for these findings is that an infusion begun intraoperatively, just after administration of epidural bupivacaine, prolongs the duration of sensory blockade and provides a better quality of analgesia, and thereby attenuates the endocrine response triggered by regression of the intraoperative level of anaesthesia.