Pre-surgical Preparation and Testing

By Krista Williams, BSc, DVM, CCRP; Kristiina Ruotsalo, DVM, DVSc, Dip ACVP & Margo S. Tant BSc, DVM, DVSc

Should I worry about general anesthesia and surgery for my pet?

Not really. With modern drugs and sophisticated equipment, the risk associated with general anesthesia and surgery is minimal for a healthy pet.

"The best way to minimize the risk is for your pet to have a complete pre-surgical evaluation before the procedure."

However, the potential for complications still exists, and the best way to minimize the risk is for your pet to have a complete pre-surgical evaluation before the procedure. This ensures there are no unexpected problems that could cause complications, and allows for any last minute adjustments to safeguard your pet's health and comfort.

What is involved in preparation for anesthesia and surgery?

The amount of preparation will be dictated by your pet’s age, existing health concerns, and by the type of surgery planned. In general, preparation can be divided into three stages:

  1. physical examination
  2. routine blood testing
  3. additional or special testing pre-surgical_preparation

1. The Physical Examination. The physical examination includes:

  • a visual inspection of the pet's head, face, eyes, ears, mouth, limbs, and body
  • palpation (feeling with the hands) of the body's outer surface (skin, fur, muscles, etc.), and internal abdominal organs (liver, kidneys, intestines, bladder, etc.)
  • auscultation (listening with a stethoscope) to the heart, lungs, and gastrointestinal system.

2. Routine Blood Testing. Routine pre-surgical blood testing typically includes a complete blood count (CBC) and a serum biochemistry profile; these tests provide important information about your pet's health status (see handouts "Complete Blood Count" and "Serum Biochemistry").

A) Complete Blood Count. This simple test analyzes the cellular components of blood. These include red blood cells, which carry oxygen to the tissues; white blood cells, which fight infection and respond to inflammation; and platelets, which help the blood to clot. The CBC provides details about the number, size, and shape of the various cells types, as well as any abnormalities that may be present. If there are deficiencies in the red blood cells, white blood cells, or platelets, or if there are abnormal cells present, then anesthesia and surgery may need to be delayed until the underlying problem is corrected.


B) Serum Biochemistry Profile. This is a series of tests performed on blood serum, which is the liquid part of blood. These tests give details about how well the organs of the body are working, and whether metabolic disease is present. For example, there are tests to assess the liver, kidney, and pancreas, and tests to identify the presence of diabetes, etc. If serious abnormalities are found, especially involving the liver or kidney, or there is evidence of metabolic disease, then anesthesia and surgery may need to be postponed until the underlying problem is corrected.

3. Additional or Special Testing. Additional or special tests may be done if your pet has an existing problem that needs to be assessed before surgery, or to investigate some abnormality identified on physical examination or routine blood testing. Tests commonly done include: urinalysis, thyroid testing, radiographs (X-rays), and electrocardiogram etc.

urine_jar_updated2017-01A) Urinalysis. This test is necessary for the complete evaluation of the urinary system (see handout "Urinalysis" for more information). Urinalysis provides information about kidney function, inflammation in the kidneys or bladder, some metabolic diseases (e.g., diabetes), and the presence of urinary crystals. Urinalysis is recommended as a part of routine pre-anesthetic testing, especially when a pet has kidney or bladder problems.

B) Thyroid Testing. The thyroid gland acts as a "thermostat", setting the metabolic rate of the whole body (see handouts "Thyroid Hormone Testing in Cats" and "Thyroid Hormone Testing in Dogs"). Thyroid testing prior to surgery is important for both dogs and cats, but for different reasons.

"Thyroid testing prior to surgery is important for both dogs and cats, but for different reasons."

In the dog, thyroid disease usually means the thyroid gland is not producing enough hormone. This leads to low thyroid hormone levels in the blood (a condition called hypothyroidism) and may result in poor wound healing following surgery. Both young and old dogs can be affected, and testing is recommended if there signs of hypothyroidism or as a precaution, especially in an older dog (see handout "Hypothyroidism in Dogs").

In the cat, thyroid disease usually involves an overactive thyroid gland that leads to high levels of thyroid hormone in the blood (a condition called hyperthyroidism). The disease is seen mostly in older cats and causes stress on the heart and other organs. Hyperthyroidism puts a cat at higher risk for complications and the condition should be corrected before undertaking anesthesia and surgery (see handout "Hyperthyroidism in Cats").


C) Imaging. Radiographs (X-rays), ultrasound, or other imaging techniques may be recommended for a variety of reasons. For example, your veterinarian may want to:

  • assess the heart and lungs in more detail
  • see if a cancer has spread before removing a tumour
  • plan the best way to do the surgery
  • evaluate other structures close to surgery site.

D) Electrocardiogram (EKG). An electrocardiogram in pets is similar to the procedure in humans. Small painless electrodes are attached to specific points on the pet's body to detect tiny electrical signals sent from the heart with each heartbeat. The EKG machine records these signals as a graphic printout or "tracing" on a strip of paper. Your veterinarian can examine the tracing to determine if the heart is beating properly.

How will my veterinarian determine if my pet can have anesthesia and surgery?

Once all the test information has been gathered and analyzed, your veterinarian will discuss whether it is advisable to proceed with anesthesia and surgery. In some situations, the risk will be too great, and the procedure will need to be postponed until the underlying problem has been treated. In other cases, your veterinarian may decide that it is safe to proceed as planned. Sometimes adjustments need to be made to minimize risk even further, such as using a different type of anesthetic, administering pre-surgical antibiotics, giving intravenous fluids, or referral to a specialty hospital, etc.

"Once all the test information has been gathered and analyzed, your veterinarian will discuss whether it is advisable to proceed with anesthesia and surgery."

It is important to note that there is a small but unavoidable risk whenever a pet undergoes anesthesia and surgery. Pre- surgical preparation does not eliminate this risk, but it greatly reduces the potential for unexpected complications. It is a simple precaution that helps to ensure your pet has a successful surgery, and a smooth uneventful recovery.

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