Statistical Analysis of the Effect of Extended-Release Epidural Morphine Versus Morphine Sulfate on Postoperative Medical Outcomes

Morphine reduces postoperative pain but may cause adverse events. Statistical analysis is often used to evaluate treatments. In this paper, we compare the effect of extended-release epidural morphine 10 mg dose (EREM 10 mg) and morphine sulfate 4–5 mg dose (MS 4–5 mg) on postoperative medical outcomes. We conduct statistical analysis of research articles published in English before November of 2022. The analysis was done by extracting statistical data, calculating mean differences (MD) between EREM 10 mg and MS 4–5 mg groups for continuous data and risk ratios (RR) for dichotomous data, and analyzing these statistics for important medical outcomes. The results of our analysis favor the EREM 10 mg group over the MS 4–5 mg group in postoperative opioid consumption in morphine equivalents (mg); MD with 95% CI is −13.25 [–26.40, −0.09],
$\mathrm{p}-\text{value}= 0.05$
. However, in postoperative adverse events (no.), the overall effect of the model favors the MS 4–5 mg group over the EREM 10 mg group; RR with 95% CI is 1.29 [1.10, 1.51],
$p-\text{value}=0.002$
. In a subgroup analysis, the model favors the MS 4–5 mg group over the EREM 10 mg group only in pruritus. These results are statistically significant. There were no significant differences between the groups in the incidence of nausea, vomiting, urinary retention, somnolence, and hypoxia. Our analysis shows interesting results: although patients in the EREM 10 mg group consumed 13.25 mg less morphine (on average), they had a higher risk ratio for adverse events compared to patients in the MS 4–5 mg group. This indicates that more randomized controlled trials should be conducted in the future to determine the advantages of each method.