The present guidelines were compiled by a multidisciplinary international panel of individuals with interest and expertise in postoperative nausea and vomiting (PONV) under the auspices of The Society of Ambulatory Anesthesia. The panel critically evaluated the current medical literature on PONV to provide an evidence-based reference tool for the management of adults and children who are undergoing surgery and are at increased risk for PONV. In brief, these guidelines identify risk factors for PONV in adults and children; recommend approaches for reducing baseline risks for PONV; identify the most effective antiemetic monotherapy and combination therapy regimens for PONV prophylaxis; recommend approaches for treatment of PONV when it occurs; and provide an algorithm for the management of individuals at increased risk for PONV.
◊ Reviewed by J. Raeder, MD, PhD
Chairman of Clinical Ambulatory anaesthesia / Professor in Anaesthesiology,
Dept. of Anaesthesia,
Oslo University Hospital, Oslo, Norway
The guidelines are presented in brief below:
1. What are the most important patients’ risk factors for PONV?
These are female gender, non-smoking, and history of PONV or motion sickness. Anesthesia-related PONV predictors are general anesthesia with volatiles or nitrous oxide and the use of intraoperative and postoperative opioids. Long duration of surgery and some surgical procedures per se seem to increase the likelihood of PONV, although the data are inconclusive as per which procedures. In children, nausea is difficult to study, because this is based on subjective reporting. Thus, studies have focused on postoperative vomiting, POV; an increased incidence has been demonstrated by surgery longer than 30 min, strabismus surgery, age of 3 years or older, and patient or near family history of POV. Both in adults and children the risk factors may be summed up and entered into a scoring system which may anticipate any risk of PONV from less than 10% to more than 80%, depending on the type and number of risk factors in the individual patient.
2. How do we reduce the baseline risk factors for PONV?
Use of regional anesthesia will reduce the incidence of PONV in both children and adults, compared with all kinds of general anesthesia. When general anesthesia with propofol for both induction and maintenance is used, the PONV incidence will be lower, whereas use of volatiles or nitrous oxide will increase the incidence. Adequate hydration, minimization of neostigmine reversal and minimization of perioperative opioid dosing will all contribute to a lower incidence of PONV.
3. Which drugs are recommended for prophylaxis in adults at low to moderate risk of PONV?
It is recommended not to use prophylaxis in low-risk patients. Use of prophylaxis should also be influenced by patient preferences, individual consequence of PONV and cost-effectiveness considerations. At medium risk of PONV, one or two different prophylactic principles and in patients with high risk two or more interventions should be used. Recommended drug principles are: 5-HT3 receptor antagonist, dexamethasone, droperidol (or haloperidol), dimehydrinate, and transdermal scopolamine. These seem to have fairly similar efficacy, but there are some differences in effect profile, timing, side-effects and costs. Prochlorperazine, prometazine and ephedrine have also proven protective effects whereas low-dose (i.e. 10 mg) metoclopramid seems to be inefficient. Combinations of two or three different drugs have an additive effect. In addition, non-pharmacological modalities have a proven prophylactic effect on PONV: acupuncture and P6-acupuncture or electrostimulation.
The guidelines do not include specific advice on some new potentially antiemetic drugs, as documentation was sparse or lacking by mid 2006. These promising agents include neurokinin-1 antagonists, low dose naloxone and opioids not crossing the blood-brain barrier such as alvomopan and methylnaltrexone.
Cost effectiveness of prophylaxis may be calculated with numerous endpoints: patient willingness to pay, costs of extra stay and nursing due to PONV, costs of rescue medication weighted against the costs and potential side-effects of prophylaxis. Depending upon differences in these calculations, at least 10-40% risk of PONV may be required for prophylaxis to be cost-effective.
4. Prophylaxis for patients with high risk of PONV:
A combination of droperidol plus dexamethasone plus 5-HT3 antagonist is recommended together with a focus on minimizing the baseline risk factors: regional anesthesia if possible or with general anesthesia: proper hydration, propofol plus remifentanil total IV technique, no neuromuscular block or reversal, optimal non-opioid pain prophylaxis.
5. Prophylaxis in children:
In children, there is probably a higher incidence of POV than in adults. 5HT-3 antagonists should be the first line prophylaxis and dexamethasone the second. Sedation and extrapyramidal symptoms may occur with droperidol in children, thus this drug should be a third-line drug for in-hospital care.
6. Treatment of PONV when no prophylaxis was given or the prophylaxis failed:
Studies on treating PONV are much more difficult to set up than studies of prophylaxis, thus data on treatment are far less abundant than on prophylaxis. The most important principle is to use a drug different from what the patient has received for prophylaxis since it may still act at therapeutic levels. Except of the long-acting dexamethasone and scopolamine patch, any drug can be repeated 6 hours or later from the preceding dose of prophylaxis or treatment. The same drugs seem to be efficient for treatment as for prophylaxis, but usually a smaller dose is sufficient: 5HT-3 antagonists, dexamethasone, or droperidol. An important issue is late PONV or postdischarge PONV, which is quite frequent and not so easy to treat as there patient has no iv access any more. The actions of dexamethasone and of the scopolamine patch may stay on even after discharge. Further PONV may be resolved by ondansetron disintegrating tablets, accupuncture or any commercially available anti-emetic tablet or suppositorium.
These guidelines are very well based on scientific evidence, and very useful for the approach to the problem of PONV. The discussion parts are highly recommendable because they address the dosing, the limitations and many of the relevant controversies in this area. As the whole document has an evidence-based approach, there are shortcomings in areas where evidence is lacking which should not be confused with saying that evidence is negative. Modes of treatment of ongoing PONV are sparsely commented, as well as documentation on new types of drugs. As regional anesthesia is beneficial in terms of causing less PONV, it should also be added that with spinal and epidural anesthesia there is a risk of short lasting perioperative nausea or vomiting due to episodes of hypotension in the awake patient.
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