Pre-Anaesthetic Blood Tests
All patients admitted for an operation or procedure requiring a general anaesthetic are offered a pre-anaesthetic blood test.
This test is done to give the vet more information about how your pet’s organs are working. Pre-anaesthetic blood tests are highly recommended in older patients. They are also beneficial in younger patients to confirm all organs have developed correctly and are functioning well.
There are three main benefits to carrying out pre-anaesthetic blood tests -
- Detecting hidden illnesses that may put your pet at risk during anaesthesia and surgery
- Reducing risk by adjusting the approach to anaesthesia and surgery
- Peace of mind for you
The blood sample is taken prior to your pet receiving any medication for their anaesthetic as the results can affect which drugs are given. The sample is taken from the jugular vein which is located on their neck. This means that your pet will come home with a small clipped patch of fur in this area.
There are two parts to a pre-anaesthetic blood test -
Packed Cell Volume (PCV)
This test measures the percentage of red blood cells in the blood. If the percentage of red blood cells is higher than the normal ranges then this may be an indication of your pet being dehydrated and therefore, the vet may decide to put your pet on fluids.
If the PCV is lower than the normal ranges this may indicate that there is an underlying health issue and the surgery may be postponed.
This blood test monitors organ function, in particular the kidneys and liver.
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. The liver has vital roles to play in the body, including metabolising the anaesthetic drugs and producing the factors needed for blood clotting to occur.
To monitor kidney function we look at the blood urea and creatinine levels. Urea and creatinine are usually filtered out of the blood and into urine by the kidneys, keeping their levels in the blood low. When the kidney filter is not working efficiently the levels in the blood build up. Kidney function is important during and after an anaesthetic because if there is a problem it may mean that your pet can not effectively filter the anaesthetic drugs out of their system and therefore, it has the potential to complicate their recovery. If a problem is detected on the blood test, the vet may choose to alter the drugs used in the anaesthetic protocol or put your pet onto a drip.
Biochemistry also measures blood glucose levels. If the glucose is abnormally high this could be an indication of your pet being diabetic or too low can mean that they are hypoglycaemic. Either one can impact your pets surgery.