Comparison ofAnalgesic Effects of Intrathecal Fentanyl and Midazolam in Orthopaedic Lower Extremity Surgery

Abstract

Background: Intrathecal opioids and benzodiazepines 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 was to determine the duration of analgesia following addition of fentanyl and midazolam to 0.5% hyperbaric bupivacaine during open reduction of lower limb fractures. •

Methods: This prospective randomized study compared the effect ofaddition of25 ug offentanyl and 2mg ofmidazolam to 10m,; of 0.5% hyperbaric bupivacaine intrathecally on ninety consecutive American Society of Anesthesiologists (ASA) I and II patients scheduled to undergo elective open reduction and internal fixation (ORlF) of lower limb fractures at the University College Hospital (UCH), Ibadan, Nigeria. The patients were randomized into either bupivacaine saline (SB, n=30) 10 mg (2mls) 0.5% hyperbaric bupivacaine,bupivacaine-midazolam (MB, n=30) or bupivacaine-fentanylcombination (FB, n= 30) through a 25- guage Whitacre spinal needle. Quality and duration of analgesia as well as any sequelae were recorded. Data were entered into statistical package for social sciences (SPSSR)version 17 and analysed by using analysis ofvariance (ANOVA), p value <0.05 was considered statistically significant.

Results: Socio-demographic (age, weight, height) as well as operating data (duration of surgery, times of grade 3 motor block! highest sensory level and highest height of sensory level) were comparable between the three groups. Fentanyl as well as midazolam provided significantly longer duration (minutes) ofcomplete (239.97 ± 28.58 vs. 269.57 ± 26.42 vs. 129.17± 11.61), p<O.OOI and effective analgesia (276.23 ± 26.21 vs. 305.40 ± 14.57vs. 150.80± 10.33)than bupivacaine alone (p<0.001). The pain intensity (visual analog scale [VAS])at the time to first post-operativeanalgesic dose in the Fentanyl-Bupivacaine (FB) and the Midazolam-Bupivacaine (MB) groups were significantly lower than in the group SB (p<0.00 1). Eight of the patients in the control SB (26.67%) group had hypotension whereas six patients (20%) in FB group and five patients (16.67%) in MB group had hypotension that required rapid infusion of crystalloid to treat the hypotension. There was no statistical difference in the level of shivering in the three groups. No patient in all the groups developed respiratory insufficiency, vomited or had neurologic deficit. MB was more effective than FB.

Conclusion: Addition of25 f.l.g offentanyl and 2mg of midazolam to l Omgof0.5% 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, maintained haemodynamic stability thereby reducing the need for early postoperative analgesic use without increase in severe adverse effect. Duration of analgesia by intrathecal midazolam was longer than fentanyl.