Some individuals are just more prone to nausea, but there are many causes for nausea. These include the analgesic drugs used during the anaesthetic and for post-operative pain relief (particularly the morphine-like drugs), the anaesthetic itself and also surgery.
Fortunately there are many drugs that can be used to control nausea, different drugs being more effective in different people. Your anaesthetist will normally have written post-operative orders for drugs to control nausea and vomiting, and you should feel free to tell the ward staff if you are feeling nauseous. If necessary they can contact your anaesthetist to order other drugs if the prescribed ones are not working.
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Nausea and vomiting