Presurgical Preparation and Testing

With modern drugs and sophisticated equipment, the risk associated with general anesthesia and surgeryhas lessened, at least for the healthy pet. However, the potential for complications still exists, and the best way to minimize the risk for your pet is to have a complete pre-surgical evaluation performed before the procedure. This allows your veterinarian to determine if your pet has any underlying problems that might lead to complications, and to make any adjustments necessary 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 the age and health concerns of your pet, and by the nature of the procedure being undertaken.

In general, terms, preparation can be divided into four parts:

  1. pre-operative medications
  2. physical examination,
  3. routine blood testing, and
  4. additional testing.

1. Pre-operative medications:

Depending on the reason for the surgical procedure, your veterinarian may prescribe medications to be started prior to the procedure. For example, a patient undergoing anesthesia for a dental prophylaxis or dental extractions will often be prescribed antibiotics, to be started several days prior to the procedure so that protective levels of antibiotics will be present in the bloodstream, thus minimizing the risk that bacteria can spread throughout the body. A patient that has a pre-existing problem may be prescribed specific medications to stabilize the condition prior to surgery.  

2. The physical examination:presurgical_preparation_and_testing-1

The physical examination includes:

  • a systematic visual inspection of the pet's head, neck, limbs, and body,
  • palpation (feeling with the hands) of the body's outer surface (skin, fur, muscles etc.), and assessment of certain internal abdominal organs through the body wall
  • auscultation (listening with a stethoscope) to the heart and lungs
  • measurement of the heart rate, rhythm, and pulses to ensure the cardiovascular system is stable

3. Routine Blood testing

Routine blood testing typically includes a serum biochemistry profile and an assessment of the cellular components of the blood. These tests provide a wealth of important information about a pet's health status.

Serum Biochemistry Profile - this is a series of tests performed on the fluid component of the blood (the serum). At Blue Cross Animal Hospital, we have several different biochemistry profiles available to us, and the choice of which one to use depends on the individual patient. These profiles range from a pre-anesthetic profile that assesses 10 blood components, to a comprehensive profile that measures 17 components, to a complete wellness profile that measures 25 components. The first two profiles can be performed in-house, while the wellness profile must be sent to an outside laboratory. 

Our pre-anesthetic profile, also known as a 'mini' profile, evaluates the body systems that are most affected by anesthetic drugs. This pre-anesthetic profile provides us with an assessment of the liver and kidney function, as well as the blood glucose level, and is important because the liver and kidneys are the 'detoxifying' organs which are responsible for clearing many drugs and anesthetic agents from the body. liquid component of blood. The pre-ansthetic profile is suitable for young healthy patients that are undergoing elective procedures such as spays or neuters. 

The comprehensive profile provides us with more information about the health of the body, including the function of the liver, kidneys, pancreas, and helps us identify the presence of metabolic diseases (see our handout on Serum Biochemistry). The wellness profile provides us with even more information, and is the most cost-effective testing that we offer. Both the comprehensive profile and the wellness profile are strongly recommended for older animals or animals with some evidence of health issues. The advantage of the comprehensive profile is that the results are available within a short time after the sample is drawn, while the results of the wellness profile are delayed for several days.  

Major abnormalities, especially involving the liver or kidney, or evidence of serious metabolic disease would justify delaying anesthesia and surgery until the underlying problem was controlled or corrected.

PCV or CBC - these simple tests analyse some of the cellular components of blood. The PCV or Packed Cell Volume looks at the percentage of red blood cells in the blood sample. Since the red blood cells carry oxygen to the tissues, this test evaluates the ability of the body to distribute anesthetic agents through the body. The CBC or Complete Blood Count assesses not only the red blood cells, but also the white blood cells and platelets (see our handout Complete Blood Count). The white blood cells fight infection and respond to inflammation, while teh platelets 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 cells, white cells or platelets, or if there are abnormal cells present, then anesthesia and surgery should be delayed, if possible, until the underlying problem is corrected.

4. Additional Testing

A number of additional tests may be recommended by your veterinarian, either as part of routine preparations for a pet that is geriatric or has other problems, or because your veterinarian has identified some irregularity, deficiency or abnormality on the physical examination or routine blood testing.

Urinalysis - examination and analysis of urine is necessary for a complete evaluation of the urinary system. 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 and is especially important whenever there are signs of problems involving the kidney or bladder.

Thyroid testing - The thyroid gland acts as a   "thermostat", setting the metabolic rate of the whole body (See handout Thyroid Testing). Thyroid testing prior to surgery is important for both dogs and cats, but for different reasons. Thyroid testing prior to surgery may be recommended for both dogs and cats, but for different reasons.

In the dog, thyroid disease usually involves a poorly functioning gland (hypothyroidism), and may result in poor wound healing following surgery. In the cat, thyroid disease usually involves an over active gland (hyperthyroidism), which leads to stress on the heart and other organs. Hyperthyroidism should be corrected before proceeding with anesthesia and surgery, due to an increased risk of complications.

Imaging - x-rays, ultrasound, or other imaging techniques may be recommended prior to anesthesia and surgery, especially if abnormalities or irregularities are found on routine testing. If your veterinarian has concerns about your pet's heart function, or needs to know whether a cancer has spread, or wants to evaluate the best approach to the surgery, etc., diagnostic imaging may provide the answers.  

What will my veterinarian do with this information?

Once all the test information has been gathered and analyzed, your veterinarian will make a decision about the advisability to proceed with anesthesia and surgery. The results of the diagnostic testing will be used to determine the most appropriate anesthetic protocol to use for your pet. Sometimes, your veterinarian will decide that your pet's anesthetic risk will be reduced even further by delaying the procedure slightly so that intravenous fluids or other medications can be given before starting the surgery. In some situations, your veterinarian may feel that the risk of anesthesia and surgery is too great at this time, and will recommend delaying the procedure to allow time to treat the underlying problem.

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, and goes a long way towards ensuring your pet has a safe procedure, and a smooth and uneventful recovery.

This client information sheet is based on material written by: Kristiina Ruotsalo, DVM, DVSc, Dip ACVP & Margo S. Tant BSc, DVM, DVSc

© Copyright 2009 Lifelearn Inc. Used and/or modified with permission under license.