Why is my Vet Recommending a Pre-Anaesthetic Blood Test?

It is well known that general anaesthesia always involves a certain risk for the patient. In order to minimise those risks and reduce complications after the procedure there are certain diagnostic tools, such as a pre anaesthetic blood test, that we could consider using prior the procedure in order to evaluate if there are any undetected health issues not evident from a physical examination alone.

If your pet is having a procedure that will involve general anaesthesia, it is important to know whether their organs are working properly and they will be capable of processing and eliminating the drugs administered during and after the procedure. By running a blood test we would be able to check for possible diseases that might impact the main organs responsible for detoxifying the body. On the other hand, if the results are within normal limits, they will serve as reference values to compare with future blood tests that your pet might have.

What is Checked in a Pre-Anaesthetic Blood Test?

In a pre-anaesthetic blood test we mainly check the liver (including the gallbladder and biliary ducts) and kidneys. Those are the main organs that metabolise the drugs used during general anaesthesia.

There are different reasons why those parameters might be altered, such as anaemia, inflammation, infection, degenerative diseases, toxicity or even hormonal changes. If any of the parameters are altered at the moment of the pre-anaesthetic blood test, your veterinarian might recommend further testing in order to evaluate the functionality of those organs.

Why Did My Vet Suggest a Full Blood Test Instead of Pre-Anaesthetic Test?

A full blood test is a more comprehensive diagnostic tool. With a full blood test, we will evaluate the complete blood count (CBC), which might give us an idea of possible inflammatory processes, infections, leukaemia or anaemia, among others. The CBC also evaluates the number of platelets in the blood, which are crucial cells for the coagulation process. Knowing the amount of platelets circulating in blood might help us prevent haemorrhages during surgery.

A full blood test also includes electrolytes and hydration status, pancreatic enzymes, thyroid hormone, and SDMA (an early marker of kidney disease that might be altered even before the other kidney parameters are affected). As this is a more comprehensive diagnostic test, we usually recommend it for patients over 7 years old as there’s an increased prevalence of diseases as pets get older.

What Does a Blood Test Involve for My Pet?

In order to get a blood sample, we will collect a small amount of blood from a vein (usually from the neck). To visualise the vein we will clip a small patch of hair and clean the skin. The blood test is run in-house and we will contact you to discuss the results before going ahead with the procedure.

Does My Pet Need a Pre-Anaesthetic Blood Test?

While a pre-anaesthetic blood test is not compulsory for young pets, we strongly recommend it as it might help us to reduce potential risks linked to a procedure under general anaesthesia. On the other hand, if your pet is 7 years or older and hasn’t had a blood test performed in the last 12 months, your pet must have a full blood test prior to the surgery, as senior patients are at a higher risk of underlying chronic diseases.

When is the Best Time to Go Ahead With the Blood Test?

Ideally we should perform the blood test as close to the procedure as possible. In My vet we have a complete in-house laboratory, where we can run blood tests on the same day of the procedure. This not only minimises trips to the vet but also reduces the stress on your pet by avoiding an extra visit to the vet for a blood test.

In geriatric patients, however, we recommend running the blood test at least a few days in advance. This allows us time to plan, initiate medication (if needed), or stabilise the patient before proceeding with general anaesthesia.

What Happens if an Alteration is Found?

In the case of an elective procedure, if any of the blood test parameters are altered, we will contact you to discuss the results. Depending on the obtained results, we might consider delaying the procedure and treating the underlying condition first. Additional complementary exams might be required before going ahead with the procedure.

For urgent procedures, the blood test will be helpful in adjusting the anaesthesia process and potentially making modifications to the anaesthetic protocol.