Re-Examining Metoclopramides' Role in the Prevention of Postoperative Nausea and/or Vomiting: A Secondary Analysis

Postoperative nausea and/or vomiting (PONV) continue to be two of the most undesirable and distressing complications following general anesthesia, affecting 20-30% of all surgical patients and up to 70% of patients with multiple known risk factors.  Clinical guidelines recommended identifying PONV prophylactic interventions based on risk score.  While the guidelines recommend several antiemetics, metoclopramide was not recommended.  The guidelines were tainted by systematic reviews and meta-analyses that included the work of one widely published researcher that has been discredited.  Therefore, the purpose of this study was to re-examine the use of metoclopramide and describe the incidence of subsequent PONV among adult ambulatory surgical patients.  Secondary data from a 12-center, observational, cohort study of 2170 adult ambulatory surgical patients collected from 2007-2008 were analyzed.  The parent study contained variables of interest that were recoded for this study including demographics, PONV risk factors, antiemetic use, and incidence of PONV.  Descriptive statistics were used to characterize the sample in terms of PONV risk factors and incidence of PONV.  Chi-square was used to determine differences between groups.  Cohen’s d was used to describe the effect size for reduction of PONV for each antiemetic group compared to the expected risk of PONV based on PONV risk score.  Of the 2116 participants with sufficient data to calculate risk scores, participants were on average 49.7 (SD = 15.4) years of age and overweight (body mass index = 28.3, SD = 6.9), and primarily female (N = 1379, 65%).  PONV risk scores ranged from 0-4 with a mean 2.6 (SD = 1.0).  Metoclopramide 10 mg IV alone had a beneficial effect with risk scores of 1 and 2 (0% PONV vs. expected 21% and 39%) and 3 (50% PONV vs. expected 61%, d = 0.22).  Metoclopramide 10 mg IV combined with ondansetron 4 mg IV had a large effect for PONV risk scores of 1 (0% PONV vs. 21%), 2, 3, and 4 (8% vs. 39%, 16% vs. 61%, 36% vs. 79%; d = .78, .97, 90; p = .046, <. 001, .001, respectively).  Metoclopramide 10 mg IV combined with dexamethasone 8 mg IV and ondansetron 4 mg IV had a beneficial effect for PONV risk scores of 1 and 2 (0% vs. 21%, 0% vs. 39%) and 3 and 4 (25% vs. 61%, 35% vs. 79%; d = 0.75, 0.92; p = .025, < .001, respectively).  While this cohort study had limitations, future studies should investigate metoclopramide use based on risk score recommendations and guidelines should be re-evaluated.