One of the questions I am often asked is why we do preanesthetic labwork. That’s a good question considering it could be $50-150 of the procedure price. I have a number of reasons I like to do preanesthetic labwork.
First of all, let me explain the components of the standard labwork. Pretty much any panel, including one for a healthy young animal or one for a sick older patient, is going to contain a CBC and a Chemistry Panel. CBC stands for “Complete Blood Count”. It takes a look at the numbers of red blood cells, white blood cells, and platelets. A certain number of red blood cells are required to carry oxygen to the tissues in the body. Of course, this is important during surgery and just every day. White blood cells are important in infection fighting. Platelets are critical to blood clotting. Changes in any of these values are important to know prior to any anesthetic so that we can either change the anesthetic protocol or, sometimes, even hold off on surgery. For example, an anemic patient might need a blood transfusion or a patient with an infection might need additional antibiotics.
A Chemistry Panel checks the liver, kidneys, protein levels, electrolytes (sodium, potassium and chloride) and blood sugar. In a younger patient, we will likely check a more abbreviated panel. In an older or sick patient, we may do a larger panel that includes tests for the pancreas, expanded tests for liver, more electrolytes, and thyroid level. Again, a Chemistry Panel may make me change what kind of anesthetic drugs I will use. It also may make me want to add intravenous fluids during surgery.
Also in an older or sick patient, we may check a urinalysis. This gives us an idea of any infection in the urine and also can aid us in diagnosing diabetes and kidney disease.
In a patient who is already sick, it is obvious that we want to understand their disease process prior to anesthesia or treatment. But why would we want to check a seemingly healthy pet? Isn’t it likely to be normal? The straight answer to that is YES. The vast majority of young, healthy patients have absolutely normal labwork. The bloodwork can serve as a baseline for that patient for the future. It allows us to know what is “normal” so that we can compare any future labwork. On a rare occasion, I find something on a young healthy patient that is important to that pet’s lifelong health.
Let me give a few examples.
I did preanesthetic labwork on a Chow Chow puppy. She seemed 100% normal. That day, I discovered that she had been born with kidney disease. The bloodwork allowed us to put her on a special diet and monitor her kidneys to help her live as long as possible.
I had another two older patients who were scheduled to have tumors removed. We discovered on their labwork that they had dangerously low platelets. If we had done surgery, they wouldn’t have been able to clot their blood and likely would have died.
So, the take home message? Most of the time, we won’t find anything. But if we do find something, it can make a big difference for those individual patients.