Why should pre-anesthetic blood tests be done on my pet?

Pre-anesthetic testing helps veterinarians identify health problems before administering anesthesia. When problems are identified, steps can be taken to minimize the risks either by postponing the procedure, changing medication protocols, or taking other precautions. In addition, appropriate therapy for the problems can be initiated.

The pre-anesthetic evaluation starts with a history. The veterinarian asks questions designed to help identify changes the owner may have noticed. The next step is a physical examination to look for physical problems of concern. For example: a previously unidentified heart murmur suggests that chest radiographs should be taken in an older patient to look for signs of significant heart disease. A fever may suggest that the procedure should be postponed until the immune response has abated.

Many health problems are not apparent during a history and physical exam. Lab work provides information on organ functions. The most important organs evaluated are the bone marrow, liver and kidneys. The bone marrow produces all the cells of the blood. The liver and kidneys are the main organs that remove drugs from the body. For example, the presence of unknown kidney disease can greatly prolong patient recovery. In addition, certain drugs can cause kidney problems, especially when already compromised. Therefore, some drugs will be avoided. Steps to support the kidneys can be taken with prolonged fluid therapy before and after the procedure.

While the risks of health problems increase with age, young animals also benefit from the pre-anesthetic blood screening. Additionally, the information collected serves as a baseline for future comparison and trending. For young animals, most veterinarians strongly recommend blood testing as an option.

As the patient ages, the organs accumulate minor insults. The secondary gradual functional decline makes the blood work more vital for the patient’s safety. Many veterinarians will require pre-anesthetic blood testing in senior patients. Patients are considered seniors at about 75% of their life expectancy. Most pets become seniors between 7 and 8 years of age. Some, like the giant breed dogs, become seniors at about 5 years of age.

Blood work is a tremendously useful tool for identifying health problems. However, additional testing such as radiographs, urinalysis, ECG, or ultrasound, may be recommended. The goal is to make the anesthetic event and procedure as safe as possible and to improve the health and quality of life for the pet.

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