TERRI JOHNSON, CVT
Chances are if you’ve had any kind of surgical or anesthetic procedure performed, you were required to have some pre-anesthetic blood work done. Most human doctors wouldn’t consider doing any procedure requiring anesthesia without a pre-anesthetic examination and blood tests, and maybe even some additional tests, like an electrocardiogram (ECG), radiographs (X-rays) and urinalysis.
In human hospitals, these tests aren’t just recommended—they’re required. Doctors are keeping your best interests in mind when they order these tests, since people don’t always know if and when they’re sick or developing a disease.
It’s even more difficult to identify illness in animals because their survival instincts mask signs of disease or injury, and many animals are masters at hiding illness. Based solely on a pet’s physical appearance and its activity level, we may not be aware of any underlying problems.
Common Pre-anesthetic Blood Tests
Complete blood cell count provides information about:
- Red blood cells, which carry oxygen to tissues
- White blood cells, which are the body’s primary defense against infection
- Platelets, which are involved in the clotting process
Identifying abnormalities helps to detect:
- Acute or chronic infection
- Bleeding disorders
- Blood parasites
- Dehydration and autoimmune diseases
Comprehensive serum blood chemistry consists of a series of individual tests, which provide information about the kidneys, liver, pancreas, intestinal tract and endocrine diseases:
- Blood urea nitrogen, creatinine and phosphorus—kidney function
- Alanine aminotransferase, alkaline phosphatase and bilirubin—liver function
- Amylase and lipase–pancreas function
- Total protein and globulin—immune system, dehydration
- Glucose—diabetes, insulin tumor (pancreas)
- Cholesterol—hypothyroidism, Cushing’s disease, pancreatitis
- Calcium—kidney disease, hyperparathyroidism, some tumors
- Electrolytes—endocrine diseases, kidney, dehydration
Other tests may be recommended, depending on the results of these initial tests:
- Thyroid function—Hyperthyroidism is common in older cats and can cause hypertension, heart disease and weight loss. Hypothyroidism in dogs can cause problems with metabolism and problems with the coat.
- Urinalysis—Detects kidney disease, diabetes, infection, inflammation and metabolic disorders.
- ECG—Shows the electrical activity of the heart and may identify abnormalities indicating a more serious problem.
Many clinical signs of disease do not develop until late in the disease process. Your veterinarian will recommend or require pre-anesthetic blood work to help identify any possible problems and to decrease the risk of anesthesia-related problems for your pet.
AAHA-accredited hospitals follow standards covering everything from laboratory work and anesthetic monitoring to how things are maintained in the surgical suite. The AAHA standards do not tell your veterinarian how to practice medicine; they focus on having all the right processes and procedures in place to make things run smoothly so your pet will receive the best, most thorough care possible.
Your veterinarian will determine which pre-anesthetic tests should be performed based on your pet’s breed, age and health status, and the requirements for the anesthesia and surgical procedure your pet is having.
Just like us, pets of any age can have problems with their internal organs. Even young, purebred cats and dogs can have congenital liver, kidney and heart problems. As our pets age, their immune system and health can decline, increasing the possibility of having multiple organ problems. Pre-anesthetic blood tests check for anemia, infection, kidney and liver functions, and blood sugar. Even if your pet looks healthy on the outside, there is only one way to determine what’s going on inside: Perform blood tests.
Blood work helps veterinarians “see” what they’re not able to see on a physical exam. Animals are exposed to additional things, like parasites, fleas and ticks, which people aren’t as likely to be exposed to. These can cause problems with your pet’s ability to clot blood properly. For example, a cat can have kidney disease for months to years before developing signs of the disease. And it can actually lose up to 75% of its kidney function before clinical signs develop.
Performing blood tests help identify any changes in kidney or liver function. Identifying possible liver or kidney problems is important because most anesthetic medications are filtered through the liver and/or the kidneys. If the liver or kidneys are not functioning properly, your pet may not be able to clear these medications through its system effectively, causing damage or additional problems.
Early identification can help your veterinarian manage disease and help your pet live a longer and healthier life. That’s why blood work for young pets is a great idea. These first tests provide baseline information and can help identify any problems with the liver or kidney.
Pre-anesthetic blood work helps your veterinarian identify health risks and hidden problems. If your pet is not completely healthy, then potential complications could occur during and after anesthesia and surgery. Your veterinarian may decide to postpone the surgical procedure, change the anesthetic protocol or change your pet’s medication.
Pre-anesthetic blood work doesn’t guarantee that your pet will not have any problems with the anesthesia or surgical procedure, but it can minimize the risk to your pet and provide you peace of mind. Many practices feel so strongly about pre-anesthetic blood work that it is required for all pets undergoing any type of anesthetic procedure.
Age alone should not dictate whether or not pre-anesthetic blood tests should be performed. Talk to your veterinarian and ask questions about what pre-anesthetic tests are right for your pet.
Terri Johnson is an AAHA accreditation coordinator.
This article originally appeared in PetsMatter May / June 2012, published by the American Animal Hospital Association. Copyright © 2012 AAHA. Find out more.