Podcast: Which medicines work best to prevent people from being sick (vomiting) after an operation?

Many people experience nausea or vomiting after surgery and dozens of drugs have been tested to prevent it. A new Cochrane review from October 2020 brings together all the trials in a network meta-analysis and we asked senior author Peter Kranke from the Department of Anesthesiology and Critical Care at the University Hospital Wuerzburg in Germany to tell us about the importance of the review and what this vast amount of research tells us.

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Monaz: Hello, I'm Monaz Mehta, editor in the Cochrane Editorial and Methods department. Many people experience nausea or vomiting after surgery and dozens of drugs have been tested to prevent it. A new Cochrane review from October 2020 brings together all the trials in a network meta-analysis and we asked senior author Peter Kranke from the Department of Anesthesiology and Critical Care at the University Hospital Wuerzburg in Germany to tell us about the importance of the review and what this vast amount of research tells us.

Peter: Feeling or being sick is a common adverse effect of anaesthesia and surgery and these bothersome symptoms occur in about a third of patients if they are not given drugs to prevent them. This postoperative nausea and vomiting, or PONV, is a major cause of patient dissatisfaction, and may lead to prolonged hospital stay and higher costs of care due to additional nursing and more severe complications in rare cases. Therefore, identifying which antiemetic treatments are most effective is an important area of research and it might be the one with the most clinical trials in anaesthesia.
Thus, the overall goal of our systematic review, which includes a network meta-analyses is to compare the efficacy and safety of single antiemetic drugs and their combinations. We focused on adults who had undergone surgery with general anaesthesia and sought to determine the effects of the antiemetic drugs, rank them in terms of efficacy and safety, and identify their best dosage or dose-range.
We included a total 585 trials with nearly 100,000 participants. These trials had investigated 44 single drugs and 51 drug combinations. The trials were published between 1965 and 2017, were mostly small and just over half were from Asia. Unfortunately, we found that only about a quarter of all studies had low overall risk of bias but, despite this methodological short coming, there is sufficient evidence available to draw meaningful conclusions.
We found high certainty evidence that five single drugs (aprepitant, ramosetron, granisetron, dexamethasone, and ondansetron) reduce vomiting, and moderate certainty evidence that two other single drugs (fosaprepitant and droperidol) probably reduce vomiting compared to placebo. This means that four of the six substance classes that have been investigated (5-HT₃ receptor antagonists, D₂ receptor antagonists, NK₁ receptor antagonists, and corticosteroids) were represented by at least one drug with important benefit for the prevention of vomiting and this means that there are plenty of options for combining antiemetics when single drug prevention is considered insufficient. Not surprisingly, we also found that combinations of drugs were generally more effective than the corresponding single drugs in preventing vomiting.
Due to poor reporting, we are uncertain about the effect of most drugs on adverse events, but the data available on some do allow us to make comparisons between their beneficial and harmful effects. For example, ondansetron can cause headache and, for every 1000 patients who received it, 111 developed a headache compared to 96 of 1000 if the drug was not used. However, we can contrast this with the effect on vomiting. For ondansetron, the detected decrease in vomiting means that in 1000 patients who receive the drug, 165 will vomit after surgery; but this number would be 300 per 1000 without it.
In summary, therefore, the encouraging message is that if the currently available drugs are used for patients in an appropriate mode and dose, no-one should be considerably sick after surgery anymore.

Monaz: If you would like to learn more about the findings of this review, including the information in its special summary tables of combined efficacy and adverse effects that allow you to find the most appropriate antiemetic at a glance, it's available online. Just go to Cochrane Library dot com and search for 'network meta-analysis of postoperative nausea and vomiting' to find it.

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