A common and unpleasant side effect
Nausea and vomiting after surgery affect about a third of patients who have a general anesthetic, and up to 80% of those at highest risk. Beyond the discomfort, vomiting can strain wounds, delay discharge and lead to dehydration. Anesthetists try to predict who is at risk so they can prevent it rather than treat it.
Four simple risk factors
In 1999, Christian Apfel and colleagues pooled data from centers in Finland and Germany and found that four factors explained most of the risk:
- Female sex
- Non-smoker
- History of postoperative nausea and vomiting, or of motion sickness
- Opioids expected for pain relief after surgery
Each factor counts for one point, giving a score from 0 to 4.
Estimated risk
| Score | Risk of nausea or vomiting in 24 hours |
|---|---|
| 0 | about 10% |
| 1 | about 21% |
| 2 | about 39% |
| 3 | about 61% |
| 4 | about 79% |
Worked example
A woman who does not smoke, with no history of nausea after surgery and no opioids planned, has 2 points. Her estimated risk is about 39%, a moderate risk.
What anesthetists do with it
International consensus guidelines on postoperative nausea recommend matching prevention to the number of risk factors:
- Adults with one or two risk factors are usually given two anti-nausea drugs from different classes.
- Patients with three or more may receive three or four, together with techniques that lower the risk, such as intravenous anesthesia instead of anesthetic gases and opioid-sparing pain relief.
- Some centers now give at least two drugs to everyone, because side effects of these drugs are rare.
Limits
The score was built in adults. Children use a different score, the POVOC score, which includes the type and length of surgery. Other factors, such as long operations, certain types of surgery and young age, also play a part. Mention any past nausea after anesthesia at your pre-operative visit.
This calculator is for general information and education. It is not medical advice and does not replace the judgment of a doctor, nurse or pharmacist who knows the full clinical picture.