Are Preanesthethic Blood Tests Really Necessary?

By September 20, 2016Cat Health, Dog Health

Are Preanesthetic Blood Tests Really Necessary?

This is a question we hear a lot, especially from owners who have a young, healthy pet that is in for routine spay or neuter surgery.  First of all, our top concern is making sure your pet has a successful and uneventful anesthetic and surgical procedure.  So, in our opinion, yes, it is in your pet’s best interest to have preanesthetic blood tests, and here’s why:

  • If everything on the test is within normal range, your pet is not only a good candidate for anesthesia and surgery, but you also have baseline normal blood values for your pet to compare to in the future.  You also have peace of mind, knowing they are healthy on the inside and the outside.
  • If some levels are not in normal range, but the doctor feels they can still safely proceed with surgery, it allows us to change the medications we use based on that information.
  • If some levels are not in normal range, it allows us to postpone surgery and look into why they are abnormal, and start treatment before the pet even shows outward signs of illness.  Catching abnormalities early allows for the best possible outcome for treatment and recovery.

What Kind of Blood Tests?

The two main tests we run are a blood chemistry and a complete blood count (cbc).  If any of those are abnormal, we may recommend further tests before proceeding with surgery.

  • Chemistry: This tests the blood levels of both the kidneys and liver, which are the main organs that metabolize and filter medications and anesthetics.  It also tests protein and glucose levels in the blood.
  • CBC:  This test looks at the cells within the blood itself, like red blood cells, white blood cells, and platelets.  Looking at these will tell us if there is anemia, an infection, or other illness, or a clotting problem going on in your pet.


Our patient, Dexter, is a great example of the importance of preanesthetic blood testing.  He came into the hospital the morning of his scheduled neuter surgery, a seemingly  healthy, young Great Dane. Dexter passed his presurgical exam with flying colors.  His blood sample was drawn, and we ran his sample on our in-house laboratory equipment.  We were very surprised to find that Dexter’s kidney values were high.  Surgery was postponed and further testing was done.  Had we not done the testing, we would not have caught the kidney abnormalities, and the medications and anesthesia could have damaged his kidneys further.  With that information, we were able to get Dexter started on a treatment course that would help keep him healthy and put less stress on his kidneys.  Dexter’s mom was happy to have us share his story about the importance of blood tests prior to surgery.  It literally saved his life.

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Dexter at one of his recheck exams