Analgesic Effects of Intrathecally Administered Fentanyl in Spinal Anaesthesia for Lower Limb Surgery

Abstract

Background: Intrathecal opioids as adjuvants to local anaesthetics during spinal anaesthesia have been used to augment the analgesia produced by local anaesthetic agents. The aim of this study is to determine the duration of analgesia following addition of fentanyl to 0.5% hyperbaric bupivacaine during open reduction of lower limb fractures.

Material and Methods: This prospective randomized study is comparing the effect of addition of 25µg of fentanyl to 10 mg of 0.5% hyperbaric bupivacaine intrathecally on sixty consecutive ASA I and II patients scheduled to undergo elective open reduction and internal fixation of lower limb fractures (ORIF) at the UCH, Ibadan. The patients were randomized into their either bupivacaine saline (SB n=30) 10 mg (2 ml) 0.5% hyperbaric bupivacaine or bupivacaine-fentanyl combination (FB n= 30) through a 25-guage Whitacre spinal needle. Quality and duration of analgesia as well as any sequelae were recorded.

Result: Socio-demographic as well as operating data were comparable between the two groups. Fentanyl provided significantly longer duration of complete (239.97 ± 28.58 vs 129.17 ± 11.61), p<0.001 and effective (276.23 ± 26.21 vs 150.80 ± 10.33) analgesia than bupivacaine alone (p<0.001). The pain intensity (visual analog scale [VAS]) at the time to first post-operative analgesic dose in the Fentanyl-Bupivacaine (FB) groups was significantly lower than in the group BS (p<0.001). Eight of the patients in the control group BS (26.67%) group had hypotension whereas six patients (20%) in FB groups had hypotension that required rapid infusion of crystalloid. There was no statistical difference in the level of shivering in the two groups. No patient in either group developed respiratory insufficiency.

Conclusion: Addition of 25 µg of fentanyl to 10 mg of 0.5% hyperbaric bupivacaine intrathecally for open reduction and internal fixation of lower limb fractures significantly prolonged the duration of complete analgesia as well as effective analgesia thereby reducing the need for early postoperative analgesic use without increase in severe adverse effect.