Risk model predicts illness after ambulatory surgery

By Liam Davenport, MedWire Reporter

A marked proportion of patients undergoing ambulatory surgery suffer postdischarge nausea and vomiting (PDNV), say US scientists who have developed a simplified risk score to identify patients who may benefit from long-acting prophylactic therapy.

Postoperative nausea and vomiting (PONV) occurs in approximately one in four patients, and can have serious consequences. Although risk scores have been developed to manage this outcome in hospitalized patients, there is no risk score for PDNV in ambulatory surgical patients.

Christian Apfel, from the University of California in San Francisco, and colleagues therefore gathered data on 2170 adults who had general anesthesia for ambulatory surgery between 2007 and 2008 and in whom PDNV was assessed from discharge until the second postoperative day. Nausea was measured using the clinical standard 11-point verbal rating scale, with severe nausea defined as a score of 7 or more, while severe vomiting was quantified as three or more emetic episodes during the study period.

The team reports in Anesthesiology that the overall incidence of PDNV was 37.0%, with 36.6% of patients experiencing nausea, 11.9% vomiting, 37.1% nausea and/or vomiting, 13.3% severe nausea, and 5.0% severe vomiting.

On stepwise forward logistic regression analysis, statistically significant independent predictors of PDNV were female gender; age less than 50 years; a history of postoperative nausea, vomiting or both; opioids in the postanesthesia care unit (PACU); and nausea in the PACU, at odds ratios of 1.54, 2.17, 1.50, 1.93, and 3.14, respectively.

Having none, one, two, three, four, or five of the factors was linked to a PDNV incidence of 7%, 20%, 28%, 53%, 60%, and 89%, respectively. In the validation cohort, the area under the receiver operating characteristic curve for the simplified risk score based on these five factors was 0.721.

The researchers conclude: "Based on the results from the validation cohort, the use of our simplified PDNV risk score is useful to identify at-risk patients who are likely to benefit from long-acting prophylactic antiemetics like dexamethasone, aprepitant, palonosetron, and transdermal scopolamine, either alone or in combination. However, the efficacy of these agents for PDNV needs to be confirmed in future studies."

In an accompanying editorial, J Lance Lichtor, from Yale University School of Medicine in New Haven, Connecticut, USA, comments: "As anesthesiologists, although we can't do much about the surgery, we can control the anesthetic as well as treatment modalities. This is a call for action: Let's decrease the incidence of PONV and PDNV."

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