Nausea and vomiting are some of the most unpleasant symptoms after an operation. They are also relatively common with large studies showing that they occur in more than one third of operations. There are a number of predisposing factors:
Laparoscopy, gynaecological operations and breast surgery have a higher incidence of nausea and vomiting. It is more common in women than men and also more common with obesity. It is more common in patients who suffer from motion sickness and historically has been related to the duration of surgery although this is probably less relevant with modern anaesthetics.
Post-operative nausea and vomiting is multifactorial and not only the result of the anaesthetic. Any surgical incision or invasive procedure will result in a stress response where the body releases a myriad of chemicals and hormones which contribute to nausea. Nevertheless there has been considerable interest and research in modifying anaesthetic techniques to avoid nausea and vomiting. Avoiding nitrous oxide and using a totally intravenous technique may reduce symptoms although this is not always possible and in many cases may introduce other difficulties. Newer anaesthetic drugs such as propofol have a lower risk of causing nausea and newer narcotic agents allow us to avoid or minimise the use of muscle relaxants or paralysing agents which also increase the risk of nausea and vomiting. As a result, we can say that the risk of nausea and vomiting with a modern anaesthetic technique is probably lower than it was some years ago.
There is only one known protective factor – smoking – but please remember that the risk of smoking far outweighs any benefits. There are a number of drugs which reduce nausea and vomiting but a major breakthrough was the development of serotonin 4 –HT3 receptor antagonists of which the commonest is ondansetron. These drugs were developed when doctors at St Bartholomew’s Hospital noticed that very large doses of another antiemetic called metoclopramide reduced nausea in patients receiving chemotherapy. They identified the receptor and ondansetron was one of the first so-called designer drugs where a drug was developed for a specific receptor. As such it has very few side effects and in my practice it is given routinely to all patients because it is unique in preventing these symptoms after anaesthesia.
There is a subgroup of people who suffer from perioperative nausea and vomiting or PONV. This is classified as nausea and or vomiting occurring after every operation without exception. It is commonest in northern Europeans with fair hair and fair complexion. It occurs between puberty and the menarche and is common in women. In order to make the diagnosis a patient has to have more than one operation and ideally more than two, and experience the same degree and duration of nausea and vomiting in every case.
The good news is that about half these patients are helped significantly by ondansetron and if it works on one occasion it will work with future operations. For this reason it is very important that patients who suffer nausea and vomiting keep a record of its severity and duration and also ask for a written record of what drugs they have been given to help it.
In order to help patients avoid nausea and vomiting it is vital to have an accurate history and my questionnaire on this website does just that. We design the anaesthetic technique not only in relation to the operation and any other illnesses that the patient has, but also to minimise nausea and vomiting in those operations or patients where it is identified as being more likely. As well as ondansetron we can use secondary drugs such as cyclizine but it is important not to give too many drugs as this can be counter-productive. Adequate intravenous fluids and arranging for patients to stay overnight, minimising the use of narcotic drugs by local anaesthetic blocks and nonnarcotic analgesics as well as techniques to ensure normal gut activity can all be used to minimise these symptoms. Good communication and preplanning often results in patients being surprised at how little nausea and vomiting they have. A small amount of nausea for the first 30 minutes or so in recovery is a feasible objective in the vast majority of sufferers.

About the author

Dr Aubrey Bristow is a consultant anaesthetist in central London. These articles are his personal views and reflect individual issues of interest to patients. They are not a comprehensive review of the subject nor a substitute for a consultation with your anaesthetist.