The various predictive scoring systems range from fair to only moderately good, according to a new study in the journal Ambulatory Anesthesia. According to the authors multimodal approaches emphasizing prophylactic strategies that incorporate antiemetic medication, intravenous hydration and nonnarcotic analgesia appear promising, having been shown to reduce PONV from a norm of 20-30% to below 10%. The 7 most widely used PONV predicting systems, despite using highly sophisticated methodologies, range from 0.68 to 0.78, based on the area under the receiver operating characteristic curve (AUC ROC) — a statistical evaluation in which a score of 1 represents a perfect test and a score of 0.5 indicates a worthless test.
Patients who’ve had anesthetics and no PONV may have escaped only because they were given antiemetics. Patients who’ve never had anesthetics may be high-risk but not know it.
The best systems for predicting PONV for ambulatory patients, say the researchers, are those of Sinclair (0.78) and Sarin (0.74) , but they’re limited by short follow-up study and more emphasis on nausea than vomiting.
The overall lack of predictability, they say, creates a quandary, because although antiemetics are likely to decrease the incidence of PONV especially when used in combinations gaining an understanding of the full side-effect profiles of those combinations would be daunting. With 8 proven antiemetics, investigating all possible combinations would require 256 study groups.
Additionally, they say, a review of 737 studies involving more than 100,000 patients found that in a population experiencing a 30% incidence of PONV, administering a proven antiemetic helped only 10%, despite exposing all to potential side effects.
Still, many advocate more liberal use of multimodal pharmacoprophylaxis, citing their modest costs and the relatively benign nature of their known side effects, say the authors.