Efficacy and safety of intrathecal morphine compared to peripheral nerve blocks in patients underwent foot and ankle surgery:  A propensity score analysis

<ns5:p> Background Intrathecal morphine (ITMO) is one of the most effective analgesic techniques in various types of surgery. Spinal anesthesia (SB) is commonly used in lower extremity surgery, thus adding 0.1 mg of morphine is easy. Ultrasound-guided peripheral nerve block requires skill and equipment, and the rebound pain is also our concern. This study aims to compare the efficacy of 0.1 mg ITMO and peripheral nerve blocks in postoperative pain control by using propensity score analysis to look back in real practice decision. Method We include patients who received SB and peripheral nerve blockade (SBPNB) and patients who received SB with 0.1 mg of ITMO (SBMO). Primary endpoint was the proportion of patients who required rescue analgesics during the first 24 hours. Secondary outcomes were mean pain scores at the 6 <ns5:sup>th</ns5:sup> , 12 <ns5:sup>th</ns5:sup> , and 24 <ns5:sup>th</ns5:sup> hours after surgery, side effects from ITMO and peripheral nerve blocks. Propensity score matching was performed and standardized mean difference (SMD) was used to measure the magnitude of differences in clinical characteristics, prognostic factors, and potential confounders. Cox’s proportional hazard regression was used to compare the proportion of patients who required rescue analgesic medication. Mean difference regression was used to compare pain scores at 6 <ns5:sup>th</ns5:sup> ,12 <ns5:sup>th</ns5:sup> , and 24 <ns5:sup>th</ns5:sup> hours. Results After propensity score matching, 52 patients from each group are included. The number of patients required at least one rescue analgesic in SBPNB and SBMO groups were 17/52 (32%) and 5/52 (9.6%), respectively. More patients in SBMO group experienced nausea vomiting compared to SBPNB group but rates of urinary retention were similar. Conclusion From this study, 0.1 mg of ITMO provides effective pain control after FAAS compared to peripheral nerve blocks and reduces postoperative opioid requirements. Adding ITMO to spinal anesthesia is easy especially when spinal anesthesia is planned. Level of Evidence Level III Retrospective comparative study with dramatic effect. </ns5:p>