Analgesic effect of intrathecal morphine combined with low dose bupivacaine on postoperative analgesia after liver resection: A randomized, controlled prelimary study

Abstract

Purpose: Efficient postoperative pain control plays a vital part in management of patients after major surgeries including hepatectomy. A current method of postoperative pain control envelopes a multimodal approach including intrathecal injection including morphine and a local anesthetic. However, high doses of bupivacaine may inadvertently cause unwanted side effects. The purpose of this study is to compare the effects of intrathecal morphine injection and low dose bupivacaine with morphine injection. Methods: Patients receiving hepatectomy were included and divided into three groups. Each patient received an intrathecal injection immediately prior to induction of general anesthesia based on their group allocation: (1) sham injection for the control group; (2) morphine 400mg for the morphine group (M); (3) morphine 400mcg and bupivacaine 5mg for the morphine and bupivacaine group (M+B). Our primary outcome was time to first rescue analgesic. VAS (visual analogue scale) pain score was compared until POD (postoperative day) 1. Total fentanyl dose administered by patient controlled analgesia was recorded until POD2. Side effects were monitored until POD 3 for any residual effects. Results: Although time to first rescue was significantly shorter in the control group compared to group M and group M+B (p<0.001). both groups were comparable to each other. Although there was a significant decrease in VAS score and total fentanyl administration via PCA (patient-controlled analgesia) in group M and group M+B compared to the control group, there was no difference between the intervention groups. The control group required more rescue analgesic compared to group M and group M+B; however, there was no difference between the intervention groups. Pruritus was more prevalent in M+B group compared to the control group (p=0.023) and tingling was significantly higher in the M+B group compared to the other groups (p=0.010). Conclusion: Addition of 5mg bupivacaine may be insufficient in providing further analgesic benefits; however higher doses may aggravate side effects. Further studies are warranted to investigate optimal regimen for intrathecal postoperative pain control against complications.