Most adults who are at risk for postoperative nausea and vomiting (PONV) after general anesthesia need more prophylactic antiemetics than current guidelines recommend, according to a new study that used a national database.
The large study found that patients who had ambulatory surgery were much less likely to need a rescue antiemetic in the postanesthesia care unit when they intraoperatively received 1 or 2 more prophylactic antiemetics than their total number of risk factors for PONV compared with fewer prophylactic antiemetics.
“Our data show that we need to be more aggressive with antiemetic prophylaxis in [at-risk] adults undergoing ambulatory surgery,” lead investigator Peter Glass, MB, BCh, from Stony Brook Medicine in New York said.
Dr. Glass presented the research findings here at the American Society of Anesthesiologists (ASA) 2013 Annual Meeting.
Without antiemetic prophylaxis, surgical patients have, on average, a 30% risk of experiencing PONV, according to Dr. Glass.
Current Guidelines Based on Patients’ Risk
Current guidelines from the Society for Ambulatory Anesthesia (SAMBA) on management of PONV, published in the December 2007 issue of Anesthesia & Analgesia (2007;105:1615-1618), recommend preoperative administration of antiemetic agents based on the level of the patient’s risk for PONV. According to SAMBA guidelines, the anesthesiologist should give no prophylactic antiemetic medications if a patient is at low risk for PONV (“wait and see”), 1 or 2 antiemetics for moderate-risk adults, and 2 or more antiemetics, using multimodal therapy (a combination of different drug classes), for high-risk patients.
The guidelines assigned a percentage of risk based on the number of Apfel risk criteria for PONV ( Anesthesiology. 1999;91:693-700). Those 4 risk factors are female sex, nonsmoker, history of PONV or motion sickness, and use of opioids.
For most patient risk groups, the guidelines suggest prophylactically giving “at least 1 less antiemetic” than their number of Apfel risk factors, according to Dr. Glass. He said patients with 0 or 1 risk factors fall into the guidelines’ low-risk group, those with 2 risk factors fall into the medium-risk group, and those with 3 or 4 risk factors fall into the high-risk group.
However, his interpretation of the SAMBA guidelines apparently differed from that of the anesthesiologist who led development of the guidelines, Tong Gan, MD, MHS. Dr. Gan, from Duke University Medical Center in Durham, North Carolina, said that, “as a guide,” low risk is defined as no risk factors for PONV, moderate risk is defined as 1 to 2 risk factors, and high risk is defined as 3 or 4 risk factors.
Dr. Glass, who said he was the journal section editor reviewing the manuscript of the SAMBA guidelines, cowrote an editorial that accompanied the guidelines ( Anesth Analg. 2007;105:1528-1529), in which he recommended a more aggressive approach to preventing PONV.
Study Used SCOR Database
To determine whether patients undergoing ambulatory surgery would have better outcomes if they received a greater number of prophylactic antiemetics, Dr. Glass and coworkers retrospectively analyzed data from the SAMBA Clinical Outcomes Registry (SCOR). This US database reportedly had more than 40,000 patients at the time of the analysis.
The researchers included 10,027 patients who had a record of whether or not they received a rescue antiemetic (the primary outcome). All patients had general anesthesia and, for consistency of technique, had received only gas inhalation for maintenance of anesthesia without propofol.
For each patient, the investigators summed the number of Apfel risk factors present and the number of prophylactic antiemetics each received. On the basis of those numbers, they grouped at-risk patients into 5 groups, from the most conservative approach to PONV management (group 1) to the most liberal approach (group 5). The groups were as follows:
1.2 fewer prophylactic antiemetics than the patient’s total number of Apfel risk factors,
2.1 fewer prophylactic antiemetic than the number of risk factors,
3.the same number of prophylactic antiemetics as the number of risk factors,
4.1 more prophylactic antiemetic than the number of risk factors, and
5.2 more prophylactic antiemetics than the number of risk factors.
After excluding patients who could not be classified into one of these groups, the authors analyzed data for more than 9650 patients. Of those, 448 (4.6%) patients needed a rescue antiemetic in the postanesthesia care unit, the data showed. Antiemetics counted included dexamethasone, promethazine, a serotonin 3 receptor antagonist (eg, ondansetron), a neurokinin 1 receptor antagonist (aprepitant), droperidol/haloperidol, scopolamine, and any other antiemetic.
The likelihood of needing a rescue antiemetic decreased incrementally by 23% for each prophylactic antiemetic added intraoperatively for each additional Apfel risk factor, Dr. Glass reported (odds ratio, 0.77; confidence interval, 0.7 – 0.85; P < .01, using logistic regression).
Therefore, he told the audience, the higher the patient’s risk for PONV, the more aggressive the prophylactic antiemesis should be, especially given the low cost of antiemetics and their favorable adverse effect profile.
Kenneth Elmassian, DO, an anesthesiologist from East Lansing, Michigan, who was not involved in the study, agreed with an aggressive approach to preventing PONV in patients at risk for this complication of general anesthesia.
The costs of antiemetic drugs are relatively low compared with [the] consequences. Dr. Elmassian
“We have to look at the consequences of not adequately treating [PONV] prophylactically,” Dr. Elmassian, an ASA board director, said. “Intractable vomiting can require extra time in the recovery room or an overnight stay in the hospital, or even readmission. The costs of antiemetic drugs are relatively low compared with those consequences.”
New Guidelines Due Out
SAMBA’s guidelines on PONV management are being revised and will be published early next year, according to Dr. Gan. He said the revised guidelines will include more information about risk factors, but that the management algorithm will remain risk-based.
Most anesthesiologists adhere to the current SAMBA guidelines, Dr. Gan stated.
However, Dr. Glass disagreed, saying that many anesthesia providers tend to be less aggressive in their PONV prophylaxis than the guidelines recommend.
American Society of Anesthesiologists (ASA) 2013 Annual Meeting: Abstract BOC07. Presented October 15, 2013. Abstract 2300. Presented October 13, 2013.