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Rare but potentially very serious complications

Dental damage


Wound infection

Heart attack

Deep Vein Thrombosis (DVT)

Blood transfusion

Spinal headache

Wrong site anaesthesia




Dental damage

Whenever we put anything in the mouth, there is a potential for us to damage teeth.  I am always very aware of this risk and very careful, but once every few years it does happen.

Things that we put in people’s mouths include breathing tubes, rubber “bougies” for some types of stomach surgery, and surgical instruments for some types of mouth or throat surgery.

People will be at more risk of dental damage if they have loose teeth, missing teeth, very brittle teeth, have caps, crowns, bridges, or veneers, or if they have difficulty opening their mouth wide.  It will also depend on the type of surgery.

If teeth do get inadvertently damaged, we make a plan to manage the damage.





Pneumonia (lung infection) is a common infection even without surgery, and anaesthesia and surgery does several things to you that may precipitate pneumonia.

Firstly, while you are anaesthetised you do not cough.  Coughing is a protective reflex that protects the lungs from infection.

Similarly, after the anaesthetic you may need opioid analgesia (such as morphine) for pain relief, and this suppresses the cough reflex.  Depending on the surgery it may be painful to cough (for example, abdominal surgery), and so you may “hold back” your cough even though you feel that you want to.

“Microaspiration” events probably occur frequently during your normal life – every time something “goes down the wrong way” and you suddenly cough and splutter.  They rarely progress to pneumonia as the protective mechanisms of your lungs usually clear the germs before they take hold.  Microaspiration events probably occur during anaesthesia too – we would never know.  Rarely people can develop a pneumonia days or even weeks after anaesthesia and surgery, and this may be due to a microaspiration event.

People at more risk of pneumonia are people having painful surgery or abdominal surgery, and people who are overweight, immunosuppressed (diabetes, renal failure, or take immunosuppressive medication), elderly, or have lung disease.




Wound infection

Although technically speaking this is a surgical rather than an anaesthetic complication, the patient who suffers an infection does not care whose complication it is.

This is a very broad term, and its incidence and significance will vary greatly between types of surgery.  For example, it is relatively common to suffer a skin wound infection after bowel surgery, but it usually gets better with antibiotics.  It is quite rare to suffer a joint infection after a joint replacement, but it is a long and difficult process to try to clear the infection.

Smokers have approximately double the chance of all types of wound infection that non-smokers do.  Other people at higher risk, similar to those at higher risk of pneumonia, are the elderly, people who are overweight, and people who are immunosuppressed (diabetes, renal failure, or take immunosuppressive medication).




Heart attack

The stress of anaesthesia and surgery may precipitate a heart attack.

Heart attacks rarely occur during the surgery itself – they usually occur in the days afterwards.  Often they occur without any chest pain, and are only discovered when they are suspected and the appropriate tests are ordered.

The risk of a heart attack is almost zero in most people, but may be 10% or higher in extremely high-risk people (such as people who have had a previous heart attack or who have severe coronary artery disease that has not been fixed).  The risk-profile of the individual undergoing surgery is much more important than the type of surgery in predicting who may be at risk of a heart attack.

People who have a heart attack in the days after surgery are at higher risk of other complications, including death.




Deep vein thrombosis (DVT)

When your blood is stagnant, it tends to clot.

One place where the blood may become stagnant during a hospital admission is in the veins in the hip, that drain the blood from the leg back to the heart. 

When you are walking up a steep hill, the muscles of the legs receive many litres per minute of blood flow, so the arteries and veins of the leg must be big to carry all of this blood.  When you are resting, the whole leg only receives a few hundred millilitres of blood flow per minute, and so the blood then only moves very slowly through these wide vessels.  Add to this the stress of surgery, and on occasion a clot can from in the vein.

A clot in the vein is not a tremendous problem in itself – it becomes a problem if it becomes loose and flows through the bloodstream, flowing through the heart and lodging in the arteries of the lungs, blocking them (a pulmonary embolus or PE).  It can sometimes cause sudden death.

The hospital system takes this potential risk very seriously, and measures such as compression stockings, calf compressors, blood thinning injections, and early physiotherapy are all aimed at reducing the risk of DVT/ PE.




Blood transfusion

I am rarely required to administer a blood (or blood products) transfusion, but on occasion it is necessary.

Most young and healthy people can tolerate significant anaemia without the need for a transfusion.  If they are actively bleeding (for example, severe motor vehicle trauma), it is often the plasma with the coagulation factors that they need more than the red blood cells.

People with heart disease or suspected heart disease are a different story – often they can only tolerate mild anaemia before the maximum flow through their coronary artery, which is already vastly reduced, does not carry enough oxygen to supply a portion of their heart.  I have a much lower threshold for transfusing these people, as anaemia greatly increases their risk of a heart attack (see above).

Blood products are not completely harmless.  The risk of contracting contagious disease such as HIV or Hepatitis B or C is, in Australia, absolutely tiny.  There is always a risk though of the next disease that we haven’t discovered yet.  And there is a risk of introducing bacterial infection – particularly with platelet transfusion as these must be kept warm.

The biggest risk with transfusion of blood products is their effect on the immune system.  They suppress some parts of the immune system and activate other parts, depending on the product and the recipient.  If somebody who has had a blood transfusion gets pneumonia 3 days after the surgery, we will never know if it was because of the blood transfusion or not, but it will happen more often than to people who have not required a transfusion.  That being said, severe anaemia also makes one prone to infections – particularly surgical wound infection.

In conclusion, requirement for a blood transfusion is rare, it is often but not always partly predictable, it is not without risk, but sometimes it is essential for the safety or even the survival of the patient.




Spinal headache

Sometimes a spinal or epidural anaesthetic can cause a headache.

Spinal headache may be as high as 2% in Caesarean sections, but falls to well below 1% for older people having joint replacements or prostate surgery.  Younger people appear much more prone to getting a headache.

Spinal headaches, when they do occur, are fairly typical.  They tend to be related to posture – they come on over 10 minutes or so when you are standing up, and then when you lie down they get better over 10 minutes or so.  Rarely they are associated with other symptoms, such as double vision.

As a general rule, about half of spinal headaches resolve each week.  This means that after one week, 50% of people will still have a headache, and after one month 6% of people will still have a headache.

If the headache is severe, we can perform a procedure called and “epidural blood patch” to try to fix the spinal headache.  This will fix about half of the spinal headaches that wouldn’t have fixed themselves, ie, one week after the “epidural blood patch” procedure, 25% of people will still have a headache, compared with 50% without the procedure.




Wrong site anaesthesia.

Anaesthetists are (unfortunately) humans, and most of us have a story about one time when we have put the wrong arm to sleep, or blocked the wrong eye for cataract surgery, or something similar.

If we manage to do this to you, it may mean that you have more pain or that your surgery may be postponed, which will all be highly inconvenient and not the best possible outcome, and it also means that we will be extremely embarrassed.

I include this because it is possible, and if you think that I am doing something to the wrong body part, please tell me!