Emergency open cholecystectomy is associated with markedly lower incidence of postoperative nausea and vomiting (PONV) than elective open cholecystectomy: a retrospective cohort study

BACKGROUND During a previous study to define and compare incidence risks of postoperative nausea and vomiting (PONV) for elective laparoscopic and open cholecystectomy at two hospitals in Jamaica, secondary analysis comparing PONV risk in elective open cholecystectomy to that after emergency open cholecystectomy suggested that it was markedly reduced in the latter group. The decision was made to collect data on an adequate sample of emergency open cholecystectomy cases and further explore this unexpected finding in a separate study. METHODS Data were collected for 91 emergency open cholecystomy cases identified at the two participating hospitals from May 2007 retrograde, as was done for the 175 elective open cholecystectomy cases (from the aforementioned study) with which the emergency cases were to be compared. Variables selected for extraction and statistical analysis included all those known, suspected and plausibly associated with the risk of PONV and with urgency of surgery. RESULTS Emergency open cholecystectomy was associated with a markedly reduced incidence risk of PONV compared to elective open cholecystectomy (6.6% versus 28.6%, P < 0.001). The suppressive effect of emergency increased after adjustment for confounders in a multivariable logistic regression model (odds ratio 0.103, P < 0.001). This finding also identifies, by extrapolation, an association between reduced risk of PONV and preoperative nausea and vomiting, which occurred in 80.2% of emergency cases in the 72 hour period preceding surgery. CONCLUSIONS The incidence risk of postoperative nausea and vomiting is markedly decreased after emergency open cholecystectomy compared to elective open cholecystectomy. The study, by extrapolation, also identifies a paradoxical association between pre-operative nausea and vomiting, observed in 80.2% of emergency cases, and suppression of PONV. This association, if confirmed in prospective cohort studies, may have implications for PONV prophylaxis if it can be exploited at a sub-clinical level.