A Study on the Analgesic Effects of Two Different Doses of Morphine Added to Intrathecal Levobupivacaine in Cesarean Section: A Randomized Double-Blind Study

TL;DR

This study compared two doses of morphine added to spinal anesthesia for cesarean sections and found the higher dose provided better pain relief without more side effects.

Contribution

The study provides new evidence that 100 µg of intrathecal morphine is more effective than 50 µg for post-cesarean analgesia without increasing adverse effects.

Findings

Both 50 µg and 100 µg of morphine provided effective and safe postoperative analgesia.

The 100 µg dose reduced the need for supplemental NSAIDs compared to 50 µg.

No significant differences in maternal or neonatal adverse effects were observed between the two doses.

Abstract

Introduction: Intrathecal morphine is considered the gold standard for post-cesarean analgesia. However, opioid-related adverse effects, especially with larger doses, limit its uniform adoption in clinical practice. We aimed to compare the analgesic efficacy and safety profile of two doses of morphine (50 µg and 100 µg) added to intrathecal hyperbaric levobupivacaine in parturients undergoing elective cesarean section.

Materials and methods: This prospective randomized double-blind study included a total of 76 parturients scheduled for elective cesarean section under spinal anesthesia, who were randomized to receive 10 mg of 0.5% hyperbaric levobupivacaine with either 50 µg (Group A) or 100 µg (Group B) of intrathecal morphine. Other outcomes that were assessed include postoperative pain scores, requirement for additional analgesics, and maternal and fetal adverse events.

Results: Following the exclusion of two patients from Group A, 74 patients were included in the statistical analysis (Group A, n=36; Group B, n=38). Demographic characteristics and perioperative hemodynamics were comparable between the two groups. The median time (minutes) to the first analgesic request was similar in both groups (Group A: 363 (interquartile range (IQR): 207-442) vs. Group B: 365 (IQR: 200-445), P=0.931). However, a significantly higher proportion of patients in Group A required supplemental nonsteroidal anti-inflammatory drugs (NSAIDs) during the assessment period. The incidence of maternal adverse effects, such as pruritus (33.3% vs. 21.1%, P=0.234) and postoperative nausea and vomiting (PONV) (13.8% vs. 14.3%, P=0.462), was comparable between the two groups, and none of the patients developed respiratory depression or hypoxia. Perioperative hemodynamic parameters and neonatal outcomes assessed by Apgar scores were similar between groups.

Conclusion: In this study, both 50 µg and 100 µg doses of intrathecal morphine provided effective and safe postoperative analgesia following elective cesarean section. However, the 100 µg dose demonstrated superior analgesia in terms of a reduced requirement for supplemental NSAIDs, rather than a difference in the time to first analgesic request. As this benefit was achieved without an increase in opioid-related side effects, 100 µg of intrathecal morphine may be the preferred dosage for post-cesarean analgesia.

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