Risks and side effects of anaesthesia

Australia is one of the safest places in the world to undergo surgery. Over the last 50 years, complications from anaesthesia have declined substantially due to both the intensive training of Australian anaesthetists, and improvements in operating theatre technology

Below, we list some common side effects of anaesthesia and rare (but serious) complications.

Side effects related to general anaesthesia 

Nausea and vomiting 

Nowadays this common side effect is much better prevented and treated with modern medications. 

Sore throat 

A tube is placed in your throat under anaesthesia to help you breathe. This can cause temporary discomfort after it is removed. 

Dental injury 

Rarely, ‘teeth grinding’ under anaesthesia or during the insertion of the breathing tube can lead to dental trauma and injury. 


It is normal to feel temporary disorientation for several hours after surgery. In older patients, and after longer operations, this may last for days or weeks.  

General anaesthesia may lead to serious complications 

Allergic reactions 

Contact with drugs and equipment (latex) during anaesthesia can cause allergic reactions that range from mild to life-threatening. It is important to discuss past allergies with your anaesthetist. 

Breathing complications 

It is important to tell the anaesthetist if you have a history of:  

  • Having a ‘Difficult Airway’  

  • Obstructive Sleep Apnoea (OSA).  

These conditions worsen during and after anaesthesia. If you have a continuous positive airway pressure ‘CPAP’ mask for OSA, make sure you bring this with you to hospital. 

Malignant hyperthermia 

Some people inherit this rare but dangerous condition in which fever and muscle contractions develop following exposure to anaesthesia medications. As malignant hyperthermia is inherited, you or your family members may have had heat stroke or suffered from the condition in earlier surgery. If so, please tell your anaesthetist. 

Awareness under anaesthesia 

Dreaming under sedation sometimes occurs. Awareness under deeper general anaesthesia is very rare. 


Some patients are at risk of serious events such as a blood clot, stroke, arrhythmia or heart attack. These patients tend to be: 

  • the elderly  

  • those with complex medical conditions 

  • those having ‘high risk’ surgery. 

Medical advances have seen a dramatic reduction in the risk of death due to anaesthesia, now less than one in 200,000. 

Side effects of spinal or epidural anaesthesia 

After discussion with your anaesthetist, a spinal or epidural anaesthetic may be performed prior to your surgery. This commonly performed procedure is used to reduce pain, nausea and confusion after moderate to major surgery. The procedure is performed under local anaesthetic, and we use a fine needle to inject medication or thread a tiny catheter at the base of the spine. Rare side effects from this include a headache, itch or temporary difficulty in urinating. ‘Bruising’ of a nerve may cause ‘nerve’ pain or tingling that lasts for days to weeks. Permanent nerve damage or paralysis is very rare. 

The overwhelming majority of patients recover from anaesthesia and surgery without problem. Some side effects that occur after surgery may be uncomfortable or frustrating. Most don’t last long though. We cannot cover all patient or procedure specific complications in this information section. We will discuss risks specific to your situation with you in person. You should always ask if you have any questions or concerns. 

Links related to risks and side effects of anaesthesia

Cancer Council

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