Safety & Risks

Anaesthesia has made much of today's surgery possible, and has brought great benefits. 

Today, joints can be replaced, organs can be transplanted, and unhealthy tissue can be removed with a high degree of comfort and safety. The benefit of anaesthesia is that it will remove pain and sensation.

This benefit needs to be weighed against the risks of the surgery and anaesthetic procedure. It is difficult to separate the risks of the anaesthetic from those of your operation and your general health.



The risk to you as an individual will depend on:

• Any underlying health problems you may have
• Personal factors, such as whether you smoke or have weight issues
• The type of surgery that is planned
• The urgency of the situation

Every patient varies in their personal opinions. Shared decision-making between you, your anaesthetist and your surgeon will help you understand the treatment options available and the risks and benefits.

Side effects and complications of anaesthesia

If you feel unwell when you are due to come into the hospital for your operation, the hospital will need to know. Depending on the illness and how urgent the surgery is, your operation may need to be posAnaesthetic risks are thought of in terms of side effects and complications.

Side effects are secondary effects of drugs or treatment. They can often be anticipated but are sometimes unavoidable. Almost all treatments (including drugs) have side effects of some kind. Unpleasant side effects do not usually last long. Some are best left to wear off and others can be treated. Examples would be a sore throat or sickness after a general anaesthetic.

Complications are unexpected and unwanted events due to a treatment. Examples would be an unexpected allergy to a drug or damage to your teeth caused by difficulty in placing a breathing tube.

Common side effects

• Nausea and vomiting after surgery: Some anaesthetic and pain-relieving drugs are more likely to cause nausea or vomiting than others. Vomiting can be treated with medication (antiemetics), but it may last from a few hours to several days. Some operations also are more likely to cause vomiting.
• Sore throat: if you have had a tube in your airway to help you breathe, it may give you a sore throat. The discomfort or pain lasts from a few hours to days and can be treated with pain-relieving lozenges.
• Dizziness, blurred vision: your anaesthetic or loss of fluids may lower your blood pressure and make you feel faint. Fluids or drugs (or both) may be given into your drip to treat this.
• Shivering: This may be due to you getting cold during the surgery, to some drugs, or to stress. You may often be kept warm during the surgery using a hot-air blanket.
• Headache: this may be due to the effects of the anaesthetic, to the surgery, to lack of fluids, or to anxiety. More severe headaches may occur after a spinal or epidural anaesthetic. The headache usually gets better in a few hours and can be treated with pain relievers
• Itching: This is a common side effect of opiates (such as morphine) but can also happen as an allergic reaction to drugs, dressings or skin preparations. If you have itchiness, it can be treated with other drugs.
• Aches, pains and backache: During your operation you may lie in the same position on a firm operating table for a long time. Great care is taken to position you, but some people still feel uncomfortable afterwards.
• Pain during injection of drugs: Drugs may cause some pain or discomfort when they are injected, this is especially common when the drug is injected to put you to sleep.
• Bruising and soreness: This can happen around injection and drip sites. It may be caused by a thin vein bursting, movement of a nearby joint, or infection. It normally settles without treatment, but if the area becomes uncomfortable, the position of the drip can be changed.
• Confusion or memory loss: This is common among older people who have had an operation under general anaesthetic. It may be due to several causes. It is usually temporary, but may last a few days or weeks.

Uncommon side effects and complications

• Chest infection: a chest infection is more likely to happen to people who smoke, and may lead to breathing difficulties. This is why it is very important to give up smoking for as long as possible before your anaesthetic.
• Bladder problems: after certain types of operation and regional anaesthesia (particularly with a spinal or epidural), men may find it difficult to pass urine, and women tend to leak. To prevent problems, a urinary catheter may be inserted at a suitable time.
• Muscle pains: these sometimes happen if you have received a drug called Suxamethonium. This is a muscle relaxant which is given for emergency surgery when your stomach may not be empty.
• Slow breathing (depressed respiration): Some pain-relieving drugs can cause slow breathing or drowsiness after the surgery. If muscle relaxants are still having an effect, the breathing muscles may be weak. These effects can be treated with other drugs.
• Damage to teeth, lips or tongue: damage can be caused to your teeth by clenching them as you recover from the anaesthetic. If your anaesthetist finds it difficult to get the breathing tube in the right place, your teeth may also be damaged. This is more likely if you have limited mouth opening, a small jaw or a stiff neck.
• An existing medical condition getting worse your anaesthetist will always make sure that you are as fit as possible before your surgery. However, if you have had a heart attack or stroke, it is possible that it may happen again as it might even without the surgery. Other conditions such as diabetes or high blood pressure will also need to be closely monitored and treated.
• Awareness: your risk of becoming conscious during your operation will depend on your general health and the type of operation you are having. For example, if you are very ill, the anaesthetist may use a combination of muscle relaxants and a lighter general anaesthetic to reduce the risks to you. However, the risk of your being aware of what is going on is increased. Monitors are used during the operation to record how much anaesthetic is in your body and how your body is responding to it. Some more recent monitors also allow monitoring of brain wave patterns. These normally allow your anaesthetist to prevent your anaesthetic from becoming too light. If you think you may have been conscious during your operation, your anaesthetist should be told about it as soon as possible. He or she will want to know, to help both you and future patients. 

Rare or very rare complications

• Damage to the eyes: anaesthetists take great care to protect your eyes. Your eyelids are held closed with adhesive tape, which is removed before you wake up. However, sterilising fluids could leak past the tapes or you could brush your eyes as you wake up after the tapes have been removed. These could cause damage to the surface of your eye, which is usually temporary and responds to drops.
• Serious allergy to drugs: allergic reactions will be noticed and treated very quickly. Very rarely, these reactions lead to death even in healthy people. Your anaesthetist will want to know about any allergies in yourself or your family.
• Nerve damage: nerve damage (paralysis or numbness) may be due to damage by the needle when performing a regional block, or it can be caused by pressure on a nerve during an operation. Most nerve damage is temporary and recovers within two to three months.
• Death: Deaths caused by anaesthesia are very rare, and are usually caused by a combination of four or five complications arising together. There are probably about five deaths for every million anaesthetics given in Australia.
• Equipment failure: Vital equipment that could fail includes the anaesthetic gas supply or the ventilator. Monitors are now used which give an immediate warning of problems, and these failures rarely have serious effects.