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Pre-Anaesthetic Blood Tests

Helen GethingWhen you pet goes for an operation under anaesthetic you will normally be offered the chance to have a pre-anaesthetic blood test.  This is done to give the vet more information about how your pet’s organs are working.  It is especially recommended in older animals over the age of 6 years, as they are more likely to have problems.

The test is performed on the morning of the operation as this gives the vet an up-to-date reading on your pet’s condition.  In addition, the sample collected will be of a higher quality because your pet would have been starved, since the night before, in readiness for its anaesthetic and less fat in the sample, tends to give more accurate results.

The test is a very simple procedure.  The blood sample is collected from a vein in the foreleg or neck and this takes only a few seconds. The blood collected is used to check your pet’s blood cells and liver and kidneys as well as for diabetes.

The haematology is the check on the white and red blood cells. If the red blood cells are low it means that your pet is anaemic and this could be a worry if the operation is likely to cause a lot of blood loss. If the red blood cell level is high this is most likely a sign of dehydration so the vet is likely to put your pet on to intravenous fluids prior to the anaesthetic.

A high white blood cell count is usually a sign of infection so your pet may be put on to antibiotics. The liver and the kidneys are the main organs that get rid of the anaesthetic from the body so it is important to know that these are in good working order.

The liver is checked by measuring two enzymes in the blood, which are normally at very low levels.  If there is any damage to the liver cells they release these enzymes into the blood and cause the levels to rise.

 Measuring the level of two toxins in the blood monitors kidney function.  Urea and creatinine are usually filtered out of the blood and into the urine by the kidneys so their levels in the blood are kept low.  When the kidney filter is not working efficiently, their levels build up.

If the operation is urgent, your pet can be placed on a drip to ensure that the kidneys have plenty of blood flowing through them during the anaesthetic.

Most operations are very successful and in most cases, the pet is well enough to go home on the same day.

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