This Invited Commentary accompanies the following original article:
Walldén J, Flodin J, Hultin M. Validation of a prediction model for post-discharge nausea and vomiting after general anaesthesia in a cohort of Swedish ambulatory surgery patients. Eur J Anaesthesiol 2016; 33:743–749.
Postoperative nausea and vomiting (PONV) is still a frequently observed clinical problem in patients undergoing surgery with general anaesthesia, and thus is an issue of ongoing research and debate.1 Approximately, one in three patients with no prior prophylaxis has to face this complication during the first day after an operation. In the majority of cases, PONV occurs during the first 24 h postoperatively with a peak occurring in the immediate postoperative hours.2
What if patients do not spend this time in hospital but at home? And what happens after 24 h? To obtain a reliable prediction of the likelihood of nausea and vomiting after discharge from hospital, Wallden et al.3 conducted a prospective observational study in a cohort of Swedish ambulatory patients from the years 2012 to 2014 with the aim of validating a risk prediction model for post-discharge nausea and vomiting (PDNV). This score was developed by Apfel et al.,4 who conducted a multi-centre study of the occurrence of PDNV in the United States from 2007 to 2008, analysing the perioperative course of 2170 adult patients who underwent general anaesthesia in an ambulatory setting. Based on these data, the authors established a risk prediction score which is very similar to the well known PONV prediction scores for inpatients covering the first 24 h5,6: risk factors for the new extended score are female sex, age less than 50 years, history of PONV, opioid analgesics administered in the post-anaesthesia care unit and the occurrence of nausea in the post-anaesthesia care unit.4 For zero, one, two, three, four or five factors, the estimated risk for the occurrence of PDNV was 10, 20, 30, 50, 60 and 80%, respectively.4 Wallden et al.3 defined the timeframe for PDNV from discharge up to 72 h postoperatively and found that Apfel's simplified risk prediction tool predicted PDNV adequately in their study cohort.
At this point, we would like to ask readers to lean back and reflect. Of course, it may appear elegant to allot individual risk scores to each patient, and thus practise stratified medicine in its classical meaning. But are we not at risk of denying the opportunities we definitely have to prevent (and nearly eliminate) PDNV?
A similar story and very similar issues have been discussed frequently regarding PONV prevention.7,8 The discussion may be viewed from different viewpoints. Although proponents of strictly risk-adapted approaches highlight the capability of the scores and the small (but existing) potential of prophylactically administered anti-emetics to cause adverse effects,8 opponents argue that life could be very simple and anaesthesiologists can virtually eliminate the ‘big little problem’ by trying their best to apply general multi-modal prevention.7 In fact, the difference is a fine one and the approaches may be viewed as two sides of the same coin.9 At the end of the day, anaesthesiologists should be encouraged to put their knowledge of nausea and vomiting prevention to use because its occurrence is a relevant clinical outcome that influences not only postoperative recovery but also patient satisfaction, and it may be associated with secondary complications. PONV is said to be as important to the patient as postoperative pain.10,11
These arguments raise the question of whether we should not simply try to reduce the occurrence of PDNV to an incidence as infrequent as reasonably achievable, and thus eradicate the former ‘big little problem’.12 Because PONV following a surgical procedure performed under general anaesthesia is associated with a considerable recurrence rate of approximately 65%, it may be game playing at the expense of the patient to save anti-emetics for secondary prevention because of a relatively low PDNV score for an individual.13 By using a multi-modal preventive strategy, for example, with dexamethasone, droperidol and ondansetron, clinical trials showed a significant relative risk reduction in PONV.11 Virtually, the same conclusions appear to be valid for treatment, which appears to be more efficacious and associated with a lower recurrence rate if anti-emetics with different targets are combined.14
Such reasoning appears even more substantiated because most of the arguments against a liberal use of preventive or therapeutic administration of anti-emetics (adverse effects, costs, availability, etc.) are no longer valid. The cost issues for new substances, such as Neurokinin-1 antagonists15 or potentially safer D2 antagonists,16 need to be weighed against the considerable willingness of patients to pay for complete elimination of PONV.17,18
We tend to transfer these considerations to PDNV. Risk prediction scores are an important step forward to better understand what is going on and gain a realistic picture (especially for patient cohorts) regarding the likelihood of PDNV. But does another simplified score lead us to the ultimate solution we seem to strive for? Accepting even the baseline risk for PDNV of 10% as predicted by Apfel's PDNV score would be doing things by halves. Do we want to be as good as we can or just ‘moderate’ or ‘acceptable’ in terms of PONV and PDNV?
The approach to individualise patients’ treatment in the clinical setting might be correct and useful in many instances. Nevertheless, there is a responsibility to create the best conditions in therapeutic terms, and it is a fact that patients who undergo ambulatory surgery and anaesthesia will find themselves in a therapeutic environment which does not meet the (luxury) clinical setting. It has to be taken into consideration that there are a lot of difficulties which can be caused by PDNV and patients may find it even more difficult in the ambulatory setting to find relief from these annoying symptoms. Severe consequences may occur [e.g. Boerhaave's syndrome (spontaneous oesophageal perforation), serious subcutaneous emphysema, pneumothorax and rupture of the trachea]11 and there is still a risk of unplanned hospital admission which cannot be judged negligible.19
In our view, these facts underline the necessity to provide multi-modal prevention for all, or at least the majority of, ambulatory patients which is based not only on simplified risk scores but also incorporates the conditions that the patient is exposed to. These conditions, among other factors, are also framed by the support available in the postoperative period, the staffing intensity and awareness of the clinical relevance of the problem among caregivers.
To put things in a nutshell, the prediction model may help anaesthesiologists pre-estimate the likelihood of PDNV. But the exception proves the rule and individual patients may suffer from a strict adherence to scores and numbers. Physicians should be encouraged to offer every patient a wide range of medical treatment, not just to focus strictly on predicted probabilities.
If you already provide liberal anti-emetic prevention, what conclusions can be drawn from Wallden's study on the validation of a prediction model for PDNV? The clinical bottom line may be to use the recovery room as an area for secondary prevention and keep a close eye on patients needing opioids. We think that multi-modal treatment may be a valid option to overcome the recurrence rate after single treatment, although, so far, the evidence in terms of clinical trials for that recommendation is low. Finally, we would like to emphasise a strong caveat in being restrictive with treatment and secondary prevention. Our weakest element in improving clinical practice is still the implementation of interventions that have already proved their benefit. We have learned in PONV prevention that even simple stratified actions may have poor compliance in a busy clinical environment.20–23 We should prevent this happening again in PDNV. Thus, multi-modal prevention and multi-modal therapy (in case of failed prophylaxis) may be the key to success in creating a PONV-free hospital.11
Acknowledgements relating to this article
Assistance with the invited commentary: none.
Financial support and sponsorship: funded by departmental resources only.
Conflicts of interest: PK is a consultant for Acacia Ltd. and has received lecture fees from Fresenius Kabi and Baxter. LE has received honoraria for lectures from Baxter GmbH, Germany; Fresenius GmbH, Germany; Grunenthal GmbH, Germany; Sintetica GmbH, Germany and ratiopharm GmbH, Germany. He is member of the advisory boards of Grunenthal GmbH, Germany and ratiopharm GmbH, Germany.
Comment from the editor: this Invited Commentary was checked by the editors but was not sent for external peer review. PK is an Associate Editor of the European Journal of Anaesthesiology.
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