Anaesthetic Complications

To assist you in understanding how often complications occur, please consider these definitions:

  • Common side effects (>1%),

  • Uncommon complications (< 1%)

  • Rare but serious complications (<0.1%)

Most complications resulting from anaesthesia fall into the following categories:

Drug reactions and side effects
All drugs have side effects that may be unpredictable and potentially damaging. Anaesthetic drugs are particularly powerful and carry with them potentially dangerous and unpredictable reactions. In order to use these drugs safely, anaesthetists train for years in order to reduce these risks to acceptable levels.

It is common to experience some side effects from your anaesthetic. Common side effects include nausea and vomiting, amnesia, dizziness, itch and mild rash. Your anaesthetist tries to choose the best drug for you whilst minimizing the side effects. These side effects will go away when the drug is stopped.

Uncommon complications include excessive sleepiness and depressed breathing with narcotics such as morphine and kidney damage from anti-inflammatory drugs. These complications can limit how much of these painkillers can be used. Major drug reactions such as anaphylaxis, malignant hyperthermia or local anaesthetic toxicity are rare but potentially serious. Anaesthetists are trained and experienced in managing these complications.

Rarely, a drug may have less effect than expected. This may result in awareness and very rarely pain or a failed nerve block. Your anaesthetist will take steps to reduce this risk and address such a problem quickly.

Airway and Breathing

Most anaesthetics will involve some assistance from the anaesthetist in keeping your airway clear. This will be required whenever sedation or general anaesthesia is used, or if there is an emergency.

Common side effects from airway management include sore throat, hoarse voice, abrasions. Uncommon complications include damage to teeth, particularly if they are in poor condition or have had dental treatments such as caps and crowns. Uncommonly, it is possible to inhale vomit during an anaesthetic. This is why you need to follow your fasting instructions.

Rare but serious complications with airway management include loss of the airway and inability to maintain breathing. Anaesthetists in Australia rehearse this scenario regularly to ensure you have the most trained person possible looking after your airway.

Positioning and lying still
In order to have an operation it is important that you are very still and that you are in the right position for the surgeon. Your anaesthetist provides these conditions for as long as it is required to complete the surgery. Surgery that takes a long time or requires an unusual position is more likely to be associated with problems.

Common side effects from positioning include sore muscles, stiffness and bruising. Sore or dry eyes can occur due to reduced tear production and loss of blinking reflex. Uncommon complications from positioning and immobility include deep venous thrombosis, nerve damage and pressure sores. In some positions, such as face down, swelling of the face and eyes can cause unpleasant irritation.

Rare but serious complications include blindness during prolonged face down or head down position or stroke from marked head up position. Such complications are extremely rare <0.01% and difficult to predict.

Nerve blocks and epidural/spinal block complications
Your anaesthetist may recommend a block for part or all of your anaesthetic. Complications from nerve blocks are dealt separately on this website.

It is important to understand that whilst there are risks from nerve blocks, there are also benefits such as improved pain relief, reduced bleeding, reduced thrombosis and reduced risk of opioid excess/overdose.

Often your anaesthetic will be much safer if it includes a nerve block. Your anaesthetist will discuss these pros and cons with you.

Pre-existing disease
The risk of an anaesthetic is partly dependent on your own underlying medical condition. An emergency operation, age greater than 70 years and ASA3 status are independent risk factors for complications.

Some medical conditions can be accentuated as a result of anaesthesia and surgery. Some of these conditions may be previously unknown to you. Your anaesthetist is experienced in managing patients with serious health problems. Whilst there are risks that an anaesthetic may make your pre-existing health problem worse, sometimes you need the operation more. The key is to let your doctors and surgeons know as soon as possible so that they can help manage this risk.