Between deciding to have surgery and getting a date there is a step that strikes many people as bureaucracy: the list of tests. It is not. Each one looks for something specific, and what they look for is exactly what can turn a planned operation into a problem.
What each one looks for
- Full blood count. Anaemia above all. Operating on someone with a low haemoglobin narrows the margin against the normal blood loss of surgery, and anaemia often goes unnoticed.
- Clotting profile. If blood takes longer than normal to clot, the risk of a haematoma rises. It is the test that most often changes a plan.
- Glucose and, where appropriate, glycated haemoglobin. High blood sugar compromises healing and increases infection. The glycated figure tells you how the last three months have gone, not just this morning.
- Liver and kidney function. They matter because the liver and the kidney are what process the anaesthetic and the medication you will take afterwards.
- Electrocardiogram. From a certain age, or with cardiovascular history. It picks up rhythm disturbances that are worth knowing about before putting someone to sleep.
- Chest X-ray, depending on the case and the type of anaesthesia.
- Pregnancy test in women of childbearing age. It is routine and it is not skipped.
- Surgical risk assessment. Not a test but a judgement: a doctor reviews all of the above alongside your history and authorises, or does not authorise, surgery under that type of anaesthesia.
For major surgery, or with a specific history, an assessment by another specialty is added: cardiology, endocrinology, respiratory medicine or haematology, according to what has come up.
What is not on the list and matters just as much
Two things never show up in any test result and are worth bringing written down:
Your medication, all of it. Including contraceptives, supplements, vitamins and anything "natural". Some common herbal products affect clotting, and that will not appear in the profile if they were taken last week.
What happened with previous anaesthetics. Severe nausea, a difficult wake-up, a reaction. It is information the anaesthetist cannot deduce from any piece of paper.
How long results stay valid
Blood tests are usually valid for around three months and the surgical risk assessment for a shorter period. If surgery is postponed, some of the tests have to be repeated.
That is why it is not a good idea to do them too early: the sensible moment is when a date is already in sight, not the day you decide to go ahead.
The surgeon reviews the results before confirming a date. If something comes back abnormal, surgery waits until it is corrected.
And if something is wrong, is the surgery off?
Almost never off. Delayed.
Most findings are correctable: anaemia is treated, uncontrolled blood sugar is adjusted, an underactive thyroid is compensated, an anticoagulant is managed with the doctor who prescribed it. What changes is the calendar, not the possibility.
What does happen sometimes is that a routine test finds something unrelated to the surgery that nobody was looking for. It happens more often than people imagine, and it is one of the quiet benefits of this step.
Where to have them done
At any accredited laboratory. It does not have to be a particular one, nor does the clinic have to arrange them, and it is worth being wary of anyone who insists otherwise: the tests are yours, so are the results, and they are just as valid for any second opinion you want to seek.
All that matters is that they are complete, current and reviewed before anyone gives you a date.