Side effects and complications


Today, it is very safe to have an anaesthetic. Serious problems are uncommon.

Your anaesthetist uses special equipment to monitor you closely throughout your operation. However, there are still risks involved and some people might have side effects or complications.

  • Side effects are secondary effects of medicines or treatment. They are often expected but sometimes cannot be avoided. Side effects include feeling sick or having a sore throat after an operation. They usually only last for a short time and can be treated with medicines if needed.
  • Complications are unexpected and unwanted events because of treatment. An example would be damage to teeth. The risk of complications depends on your medical condition, the type of surgery you have and the anaesthetic used.

If your procedure has specific risks, we will explain these before your operation or treatment.

Side effects of having an anaesthetic

Feeling and being sick (nausea and vomiting), headache, feeling sleepy (drowsy), feeling dizzy, blurred vision

They might be due to the effects of medicines used, the surgery or a lack of fluids. These side effects usually get better within a few hours. We can give you medicines or fluids to treat the problems.

Sore throat

You might have a sore throat if a tube is put in your airway, or an airway device is used to help you breathe freely during the anaesthetic. These symptoms are usually mild and often get better without treatment.

Damage to lips or tongue

Minor damage to the lips or tongue is common.


This might be due to you becoming cold during the operation, some of the medicines you have been given, or anxiety. We give you a hot-air blanket to warm up your body and oxygen until you stop shivering.


This can be a side effect of opioid painkillers (such as morphine). It can be treated with other medicines.

Bruising and soreness

This can happen around injection and drip sites. It normally settles without treatment. If the area becomes uncomfortable, we can change the position of the drip.

Aches, pains and backache

During your operation, you might lie in the same position on a firm table for a long time. We take great care to position you, but some people still feel uncomfortable afterwards.

Injection site pain

Some medicines might cause pain or discomfort when they are injected.

Confusion or memory loss

This is common among older people who have an operation under general anaesthetic. Confusion or memory loss might have several causes. It is usually temporary but can sometimes be permanent.

Chest infection

This is more likely to happen after major tummy (abdomen) or chest surgery, or to people who smoke, are overweight or are older. This is one of the reasons why it is important to give up smoking and lose weight before surgery.

Bladder problems

After some types of operations and after having a regional anaesthesic, men may find it difficult to pee and women may leak pee. To prevent these problems, we might put in a urinary catheter. This is a flexible tube used to empty the bladder and collect urine in a drainage bag.

Muscle pains

You may have sore or painful muscles if you have been given a medicine called suxamethonium. This medicine is mainly used for emergency surgery when your stomach might not be empty.

Damage to teeth

Damage to your teeth is uncommon, but might happen as your anaesthetist places a breathing tube in your airway. It is more likely if you have weak teeth, a small mouth or jaw, or a stiff neck.

Breathing difficulties

Some pain medicines can cause slow breathing or make you feel sleepy (drowsy) after the surgery. If muscle relaxants are still having an effect, the breathing muscles might be weak. We can treat these effects with other medicines. We monitor you closely for this problem.

An existing medical condition getting worse

Your anaesthetist always makes sure that you are as fit as possible before your surgery. However, if you’ve had a heart attack or stroke, it is possible that this might happen again, just as it might even without surgery. Other conditions, such as diabetes or high blood pressure, also need to be closely monitored and treated.

Damage to the eyes

Anaesthetists take great care to protect your eyes. Your eyes might be held closed with sticky (adhesive) tape, which is removed before you wake up. Sometimes the surface of the eye gets damaged from contact, pressure or exposure of the cornea (the transparent front part). This is usually temporary and is treated with drops. Serious and permanent loss of vision can happen but it is very rare.

Serious allergy to medicines

Allergic reactions are noticed and treated very quickly. Very rarely, these reactions lead to death even in healthy people. Your anaesthetist asks whether you or anyone in your family has any allergies. You might be referred to the allergy clinic before your planned surgery.

Nerve damage

When you have a regional anaesthetic, the needle might cause nerve damage (paralysis or numbness). Pressure on a nerve during an operation can also cause nerve damage. The risk of nerve damage depends on the type of anaesthetic you have, but is usually rare or very rare. Most nerve damage is temporary but it can sometimes be permanent.

Brain damage and death

It is very rare for an anaesthetic to cause brain damage and death directly. They usually happen due to complex surgery, complications and an individual's state of health. There are about 5 deaths for every million anaesthetics in the UK.

Equipment failure

We test equipment regularly and monitors give us an instant warning of any problems. We have immediate access to backup equipment.


Awareness is when you wake up and become conscious during part of an operation under general anaesthetic. This happens when you are not given enough anaesthetic to keep you unconscious. We use monitors during the operation to record how much anaesthetic is in your body and how your body responds to it. These monitors normally allow your anaesthetist to judge how much anaesthetic you need to keep you unconscious.

Side effects of having an epidural

You need to be aware of extra possible side effects if you have an epidural.

Difficulty peeing

To avoid this, we put a small tube (catheter) into your bladder while you are in the operating theatre. This drains your bladder.

Low blood pressure

Occasionally, your blood pressure might become low. You have a drip in a vein in your hand or arm. We can give you fluid through the drip to correct this. Sometimes, you might need medicine to increase your blood pressure.


Tell the nurses if you feel itchy. They can give you medicine to help with this.


Rarely, the bag of fluid that surrounds the nerves and spinal cord is punctured when we put in the epidural. This is called a ‘dural puncture’ and might cause a severe headache that could last for days or weeks if it is not treated.

Tell the nurses if you have a headache. They can give you pain relief. Sometimes, you may need specific treatment.

Weak legs

Depending on where the epidural tube is placed, your legs might feel numb or weak while your epidural is working. There is no need to worry and the ward nurse checks on this. When we reduce or stop the pain medicine that we give you, this side effect disappears.

‘Breakthrough’ pain

This is pain that is not controlled by your regular painkillers. It can sometimes be caused by the epidural not working perfectly. To correct this, we can give you extra doses of pain medicine through the epidural. If this does not help, we might need to put in the epidural again or replace it with another type of pain relief.

Nerve damage

When an epidural is put in you might feel a brief pain, ‘twinge’ or tingling, either in your back or down one leg. This is quite common and soon eases. Tell the anaesthetist if you have any of these feelings. They can then change the position of the epidural.

Sometimes a numb patch on a leg or foot, or a weakness in a leg, can last for a few weeks or months before it wears off completely. It is rare to have permanent nerve damage after an epidural that results in muscle weakness, pain, or tingling or numbness down one leg. This happens in 1 in 23,500 to 1 in 50,500 epidurals or spinal injections.


Very rarely, an infection called an epidural abscess can develop around the epidural. This might need treatment with antibiotics or surgery.

Epidural haematoma

Rarely, a blood clot can develop around the epidural. This is called an epidural haematoma. If it happens, an epidural haematoma might cause paralysis. You might need an emergency operation to lower the risk of permanent paralysis. Permanent paralysis or death is very rare and occurs in 1 in 54,500 to 1 in 141,500 epidural or spinal injections.

Resource number: 2737/VER5
Last reviewed: June 2023
Next review: June 2026


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