CON: Postoperative Nausea and Vomiting Database Research: Limitations and Opportunities

Abstract

Postoperative nausea and vomiting (PONV) has a multifactorial etiology. Some advocate universal combination antiemetic prophylaxis given the high efficacy, relatively inexpensive drug acquisition cost, and favorable side-effect profile of the most frequently used antiemetics.1 However, because many patients will not experience PONV even without prophylaxis, and there are side effects and added costs, albeit low, associated with current interventions, others recommend a risk-adapted strategy for PONV prophylaxis.2 In this context, identification of risk factors for PONV allows the anesthesiologist to tailor the anesthetic management and prophylactic antiemetic administration to patients' underlying risks, with more aggressive prophylaxis being reserved for high-risk patients. However, our current understanding of risk factors for PONV is far from being complete. Numerous studies have identified several patient, anesthesia, and surgical factors that might increase the risk for PONV. A number of scoring systems incorporating those risk factors have also been published. Given the multifactorial etiology of PONV, and the gaps in our understanding of the risk factors, available scoring systems have only shown poor to moderate accuracy with areas under the receiver operating characteristic curve ranging from 0.56 to 0.785 (0.5 being no better than tossing a coin).3–9 In general, there has been agreement about a number of patient-related risk factors, specifically female gender, history of PONV or motion sickness, and smoking status.3 A number of studies also confirmed numerous anesthesia-related risk factors including longer duration of anesthesia and the use of volatile anesthetics, nitrous oxide, and opioids (both intra- and postoperative).10 There has been inconsistency, however, and controversy about the type of surgery as being an independent risk factor for PONV. Although numerous studies have identified the type of surgery as a risk factor,7,8,11–13 the specific procedures implicated as particularly emetogenic did vary and were inconsistent among studies. Types of procedures that were reported as possible risk factors include abdominal, laparoscopic, major gynecologic, orthopedic, ear, nose, and throat, breast, plastic surgery, neurosurgery, and, in children, hernia repair, adenotonsillectomy, strabismus, penile surgery, and orchiopexy. However, only 3 of 8 published PONV risk scoring systems included the type of surgery as one of the risk factors.5,7,9 Some argue the fact that gynecologic surgery has been reported as a risk factor, for instance, is not due to the surgery itself but due to the high risk for PONV of the female patients undergoing this surgery, and that scores considering the type of surgery do not lead to better prediction of PONV compared with procedure-independent models.14 Therefore, there is a clear need for large well-designed studies to address this controversy. In this issue of the journal, Ruiz et al.15 specifically investigated the impact of the surgical procedure on the risk of PONV. They used their electronic anesthesia information system to collect data on all patients who were admitted to the postanesthesia care unit (PACU) over a 2-yr period. Known risk factors for PONV were collected and documented in all patients. In addition to the surgical procedure, they included 9 potential risk factors in the general linear model: gender, smoking status, history of PONV or motion sickness, duration of anesthesia, number of prophylactic antiemetics administered, dose of intraoperative opioids, use of ketorolac, use of an epidural for postoperative analgesia, and use of postoperative opioids. To study the impact of the surgical procedure, they arbitrarily categorized all surgical procedures on the basis of the anatomical site and used a group undergoing integumentary, musculoskeletal, and superficial (IMS) surgeries as a reference group. The end point used was the need for antiemetic administration within the