A systematic review of morphine equivalent conversions in plastic surgery: Current methods and future directions

Protocols surrounding opioid reduction have become commonplace in plastic surgery to improve peri-operative outcomes. Within such protocols, opioid requirement is a frequently analyzed outcome. Though often examined, there is no literature standard conversion for morphine milligram equivalents (MME) at present, leading to questionable external validity. We hypothesized significant heterogeneity in MME reporting would exist within plastic surgery literature.

Following the PRISMA guidelines, the authors conducted a systematic review of 16 journals. Clinical studies focused on opioid reduction within plastic surgery were identified. Primary outcomes included reporting of morphine equivalents (ME) delivery (IV/oral), operative ME, inpatient ME, outpatient ME, timeline, and method of calculation.

Among the 101 studies analyzed, 73% reported opioid requirements in the form of ME. Among those that used ME, 3% reported IV ME, 41% reported oral, 32% reported both, and 25% gave no indication of either. Operative ME were reported in 19% of studies. Furthermore, 54% of studies reported inpatient ME whereas 32% of studies reported outpatient ME. Only 19% reported the number of days opioids were consumed postoperatively. Moreover, 27% of the studies reported the actual method of ME conversion, with 17 unique methods described. Only 8 studies (8%) reported using the Center for Disease Control and Prevention guidelines for ME conversion.

There is significant variability among the reported ME conversion methodology within plastic surgery literature. Highlighting these discrepancies is an essential step in creating and implementing a single, standard method to mitigate opioid morbidity in plastic surgery and to optimize enhanced recovery protocols.