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Department of Anesthesia Torrecardenas Hospital Almeria, Spain
The convenience of the preventive use of ondansetron to diminish the postoperative nausea and vomiting (PONV) gives rise to numerous debates. The favorable results obtained by Sadhasivam et al. (1) persuade them to recommend its prophylactic use. In the discussion section of their article, they disregard less optimistic results shown in the meta-analyses and question their validity. Their statement is grounded on the opinion of experts who consider that the large, randomized, controlled trials (RCTs) remain the gold standard for determining the best choice among different therapeutic options (2). This contention may not be totally accepted. The current trend is for decision making in health care to be determined by what is known as Evidence-Based Medicine. The Centre for Evidence-Based Medicine (http://cebm.jr2.ox.ac.uk/docs/levels.html) classifies the "levels of evidence" accepted for ranking the validity of evidence about the value of preventive maneuvers. On this scale, the systematic reviews (with homogeneity) of RCTs are ranked as a level of evidence "1-a," the individual RCTs (with narrow confidence interval) are classified as type 1-b, and the opinion of experts as type 5. It has been proved that ondansetron is not more effective than droperidol (evidence 1-a) (3), which is why its larger price should limit its use to specific situations (4). Two analyses based on all the existing literature on ondansetron have shown, with different arguments, that its prophylactic administration even in patients with a high emetic risk should be questioned both in regard to its price and its adverse effects (5,6). Furthermore, in the RCT on ondansetron that included a larger number of patients (2199, not selected according to their emetic risk) and the narrowest confidence interval, in which all the patients had been administered a prophylactic dose of 4 mg of ondansetron, an incidence of 36.5% of PONV was observed (7), a figure above what is considered usual (8).
References
Departments of Anesthesia
* Beth Israel Deaconess Medical Center, Harvard Medical School Boston, MA
All India Institute of Medical Sciences New Delhi, India
Postgraduate Institute of Medical Education and Research Chandigarh, India
We recommended the use of prophylactic ondansetron 4 mg at the end of modified radical mastectomy for the prevention of postoperative nausea and vomiting (PONV) until a better alternative was found. This recommendation was based solely on the results of our randomized controlled trial (RCT) (1), which is a grade-A recommendation and 1-b level of evidence proposed by Center for Evidence-Based Medicine (EBM) (2). There is no meta-analysis with homogeneity of RCTs on the antiemetic effects of ondansetron yet, which would have been a grade-A recommendation and 1-a level of evidence of CEBM. Pooling of data in a meta-analysis on PONV from multiple RCTs performed on different patient populations with different PONV risks, with different anesthetic techniques and different antiemetic agents, doses, and timings of their administration ultimately results in loss of homogeneity (3,4). CEBM states that the systematic reviews with worrisome heterogeneity should be tagged with a minus sign ("-") at the end of the designated level of evidence to denote that the level fails to provide a conclusive answer (2). We questioned the validity of published meta-analyses on antiemetics and PONV in our article because:
EBM is not a cost-cutting or clinical-freedom restricting medicine (8). Doctors practicing EBM will identify and apply the most efficacious interventions to maximize the quality of life for individual patients; this may raise rather than lower the (direct) cost of care (8). Improvements in "true" (nonsurrogate) outcome measures of our patients and in global costs of health care (including direct, indirect, and intangible costs) (9) should be our ultimate goals when we make therapeutic decisions.
In this era of EBM and health care cost-containment, we need to have clinical evidences demonstrating improvements in true outcomes and global costs of care to help physicians practice EBM.
References
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