Preoperative Planning

Chapter 2
Preoperative Planning

Preparation for surgery includes evaluation of the entire patient not just the specific area of concern. Assuring the patient is otherwise healthy for anesthesia and surgery, performing laboratory, and imaging tests all provide a comprehensive assessment of the patient’s health status. Assessing the need for perioperative antibiotic therapy depends on the type of procedure, its duration and the patient’s general condition. Planning for the patient’s pre, intra and postoperative pain control is an essential aspect of patient care. Veterinary technicians play an important role in preoperative planning by performing tests and providing the veterinary surgeon and anesthesia staff with the results. They also follow the veterinarian’s orders by calculating medication dosage, filling prescriptions, and administering medications.

Laboratory Tests

A preoperative assessment is performed on each individual patient to determine its anesthetic risks and general physiologic status. Knowledge of a patient’s condition aids in creating an anesthetic protocol. Common preoperative tests include complete blood count (CBC), serum chemistry panel, and urinalysis. A database of a packed cell volume (PCV), total protein and blood urea nitrogen (BUN—performed with a chemistry strip), and blood glucose via a glucometer provides the minimal information required prior to surgery. A patient’s age, physical condition, and surgical procedure determines the need for more extensive testing. Patients suffering a traumatic event, undergoing a complicated operation or in a debilitated condition also lend themselves to additional laboratory tests. Certain breeds may signify a need for other tests. For example, Doberman Pinschers may carry the trait for von Willebrand disease, indicating the need for a buccal mucosal bleeding time or other clotting tests.

Complete blood count

A CBC measures the actual number and percent of specific blood cellular components: red blood cells (including cell morphology), white blood cells (including all cell types), hemoglobin, hematocrit, PCV, and platelet count/estimate. This test is performed on whole blood collected with an anticoagulant. Normal values are determined for each individual analyzer machine (Table 2.1).

Table 2.1 Complete Blood Count Reference Values

Test Units Canine Feline
RBC ×106/μL 4.95–7.87 5.0–10.0
Hemoglobin g/dL 11.9–18.9 9.8–15.4
Hematocrit % 35–57 30–45
MCV fL 66–77 39–55
MCH pg 21.0–26.2 13–17
MCHC g/dL 32.0–36.3 30–36
Reticulocyte % 0.0–1.0 0.0–0.6
Platelets ×103/μL 211–621 300–800
MPV fL 6.1–10.1 12–18
WBC ×103/μL 5.0–14.1 5.5–19.5
Segs ×103/μL 2.9–12.0 2.5–12.5
Bands ×103/μL 0.0–0.45 0.0–0.3
Lymphocytes ×103/μL 0.4–2.9 1.5–7.0
Monocytes ×103/μL 0.1–1.4 0.0–0.9
Eosinophils ×103/μL 0.0–1.3 0.0–0.8
Basophils ×103/μL 0.0–0.14 0.0–0.2

Adapted from Latimer, K.S. (2011) Duncan and Prasse’s Veterinary Laboratory Medicine: Clinical Pathology, Fifth Edition pg 372 Wiley-Blackwell, 2011.

Reference values are derived from University of Georgia College of Veterinary Medicine only as examples, reference values are not appropriate for interpretation for other laboratories.

Serum Chemistry Panel1

A serum chemistry panel or metabolic panel determines the current level of chemicals within the body. These establish the health of the liver, kidneys, and pancreas as well as the body’s electrolyte status. The test is preferably run on serum but may be performed on plasma. Normal values are determined for each individual analyzer machine (Table 2.2).

Table 2.2 Serum Chemistry Reference Values

Test Units Canine Feline
Albumin g/dL 2.3–3.1 2.8–3.9
ALKP U/L 1–114 0–45
ALT U/L 10–109 25–97
Ammonia µg/dL 19–120 0–90
Amylase U/L 226–1063 550–1458
AST U/L 13–15 7–38
Bile Acids (fasting) µmol/L 0–8 0–5
Bilirubin, total mg/dL 0.0–0.3 0.0–0.1
Calcium mg/dL 9.1–11.7 8.7–11.7
Chloride mEq/L 110–124 115–130
Cholesterol mg/dL 135–278 71–156
CK U/L 52–368 69–214
Creatinine mg/dL 0.5–1.7 0.9–2.2
Globulin, total g/dL 2.7–4.4 2.6–5.1
Glucose mg/dL 76–119 60–120
Iron mg/dL 94–122 68–215
Lipase U/L 60–330 0–76
Magnesium mg/dL 1.6–2.4 1.7–2.6
Phosphorus mg/dL 2.9–5.3 3.0–6.1
Potassium mEq/L 3.9–5.1 3.7–6.1
Sodium mEq/L 142–152 146–156
Total CO2 mEq/L 14–26 13–21
Total protein (serum) g/dL 5.4–7.5 6.0–7.9
Triglycerides mg/dL 40–169 27–94
Urea nitrogen (BUN) mg/dL 8–28 19–34

Adapted from Latimer, K.S. (2011) Duncan and Prasse’s Veterinary Laboratory Medicine: Clinical Pathology, Fifth Edition pg 374 – 375 Wiley-Blackwell, 2011.

Reference values are derived from University of Georgia College of Veterinary Medicine only as examples, reference values are not appropriate for interpretation for other laboratories.

  • Alkaline phosphatase (Alk Phos): an enzyme that may be elevated in certain cancers, muscle, and liver diseases
  • Alanine aminotransferase (ALT) or Serum glutamic pyruvic transaminase (SGPT): an enzyme involved in liver function, elevations indicate liver damage or disease
  • Aspartate aminotransferase (AST) or Serum glutamic oxaloacetic transaminase (SGOT): an enzyme associated with liver parenchymal cells as well as red blood cells and cardiac and skeletal muscle. The ratio of AST to ALT may differentiate causes of liver damage but is also a cardiac marker.
  • Blood Urea Nitrogen (BUN): a by-product of protein breaking down in the body consists of urea compounds containing nitrogen. The kidneys excrete these by-products. Kidney malfunction due to disease or urine blockage causes the compounds to remain in the blood resulting in an elevated BUN. Dehydration can reduce kidney function and cause a rise in this test. Liver disease may demonstrate as a lower than normal blood urea nitrogen.
  • Calcium: an abundant mineral aids in bone growth, muscle contraction, blood vessel expansion and contraction, and secretion of hormones and enzymes.
  • Cholesterol: a lipid or fat produced by the liver, cholesterol is vital for normal body function. Although elevated cholesterol contributes to arteriosclerosis in people, this is not a concern in the small animal patient. Poorly functioning thyroid glands may show an elevated cholesterol level.
  • Creatinine Kinase (CK): an enzyme expressed in many tissues and cells, it helps to evaluate tissue damage particularly in muscles.
  • Creatinine: a by-product of muscle metabolism, it is excreted by the kidneys, elevations of this chemical indicates kidney malfunction.
  • Glucose: a monosaccharide or sugar, carbohydrates convert to glycogen in the body when an animal’s energy level dictates – glycogen converts to glucose. Glucose monitors metabolism and physiology. Low blood sugar (glucose) or hypoglycemia may manifest as weakness, incoordination, or even seizures. High blood sugar or hyperglycemia can come about from stress but in certain disease conditions, particularly diabetes mellitus, excess glucose is excreted in the urine. Blood glucose levels above 180 mg/dl must be investigated further.
  • Magnesium: an electrolyte involved in muscle, nerve and enzyme function, helps to move other electrolytes into and out of cells.
  • Phosphorus: a nonmetallic chemical element, phosphorous helps to build and repair bones, aids in nerve function and muscle contraction. Phosphorus works in combination with calcium: if calcium levels rise, phosphorous levels decline. Phosphorus levels increase in patients with renal dysfunction.
  • Total Bilirubin: a by-product of the breakdown of hemoglobin Elevations occur when excess red blood cells break down, when the liver is diseased and unable to clear the bilirubin or if the bile duct is occluded keeping it from sending bilirubin into the intestine.
  • Total Protein: a combined measurement of albumin (produced in the liver) and globulin (produced in the immune system), these proteins can be elevated or decreased in infectious diseases. They may elevate when a patient is dehydrated.
  • Triglycerides: a type of fat that stores energy and provides energy to the muscles.
  • Electrolytes

    • Sodium: a chemical element, sodium controls the amount of water in the body. The transmission of sodium into and out of cells generates electrical signals. These signals control body processes within the brain, nervous system, and muscles. Increased sodium levels can indicate dehydration and kidney disease. Decreased sodium can be found in patients with liver, kidney, and heart disease.
    • Potassium: a chemical element inside of cells, potassium regulates heartbeat and muscle functions. Increased potassium (hyperkalemia) and decreased potassium (hypokalemia) can be found in patients with kidney disease along with those taking certain medications.
    • Chloride: an ion formed from the element chlorine, it is found in fluid outside of cells, chloride helps to maintain normal fluid balance in the body. Increased chloride levels can be found with diarrhea, kidney disease, and hyperparathyoid conditions. Decrease in chloride can occur with vomiting, adrenal, and kidney disease.
    • Carbon Dioxide (CO2): a chemical compound, it is a by-product of cellular metabolism, it travels through the body with the hemoglobin and leaves the body through the lungs. Poor respiratory function, kidney disease, and metabolic conditions affect its level.


Urine for testing is obtained by free catch, manual expression, catheterization, or via cystocentesis. For samples requiring a culture and sensitivity test to check for bladder infection, cystocentesis is preferred to avoid urethral or catheter contamination. To perform a cystocentesis, the patient may lay in lateral or dorsal recumbency. The sample may also be obtained with the patient standing but this position is difficult for the technician working underneath the dog while cats are not likely to stand still. Samples are easily obtained from female dogs laying in dorsal recumbency. The patient is held comfortably on her back by one or two assistants. Alcohol is poured onto the caudal abdomen to form a “pool” along the midline (Figure 2.1).


Figure 2.1 “Puddle” of alcohol on a female dog prior to performing a cystocentesis. The needle is directed perpendicular to the body through the puddle and into the bladder.

Using a 22-gauge x 1 – 1½″ needle on a 10 ml syringe, the needle is inserted straight perpendicular to the body, directly through the pool of alcohol. Usually, one can feel the needle puncturing the bladder. The syringe is aspirated slightly to check for successfully obtaining urine. If present, the syringe is filled, suction released, and the syringe is removed. If blood is noted in the syringe, aspiration ceases and the needle is withdrawn. (Blood contaminates the sample and may cause a false positive on a urinalysis.) Moving cranially or caudally to the original site depending on the expected size of the bladder may yield success. Full bladders tend to be more cranially located while smaller diameter bladders tend to reside nearer to the pelvis. Palpating the bladder may help in locating it but sometime this is difficult in patients with distended abdomens. Ultrasound is a useful tool for imaging the bladder and obtaining urine samples for all patients.

A similar technique is useful in male dogs; however, the prepuce keeps the alcohol from pooling. The needle is inserted at more of an angle to the body aiming for the midline below the prepuce. Another technique is to move the prepuce to the side and inserting the needle directly perpendicular to midline.

Small dogs and cats have more easily palpable bladders. The patient lays in lateral recumbency with an assistant holding the front and back legs, while the patient is stretched in a comfortable position. Using one hand to palpate the bladder, the hair is smoothed down with alcohol. Keeping the bladder isolated in one hand, the needle is inserted directly perpendicular to the body and into the bladder. Urine is aspirated into the syringe. If blood is seen, the procedure is stopped and tried in another location.

Free catch and expressed samples are acceptable for routine urinalysis without a bacterial culture. Nonabsorbent litter in a plastic litter pan aids in collecting free catch urine from cats.

Urine catheterization is obtained through a variety of catheters. Red rubber and Foley catheters create less urethral trauma and have a decreased risk of bladder perforation than polypropylene catheters. Catheters are inserted using an aseptic technique. The penis or vulva is cleaned with dilute antiseptic of choice. After applying sterile lubricant to the tip of the urinary catheter, the technician (wearing sterile gloves) inserts the catheter. Success is evident when urine flows out of the catheter. If planning for an indwelling (Foley) catheter, the catheter’s balloon is filled with the appropriate amount of media (saline or air) depending upon the manufacturer’s recommendation. For short-term catheterizations, either to obtain a urine sample or to empty the bladder one time, the catheter is removed immediately following the procedure. Urine from a catheter may be used for bacterial testing but may contain urethral contaminants.

Urinalysis tests include the following (Kahn 2011):

  • Specific Gravity (SG) – using a refractometer determines the urine’s concentration. Dilute urine may indicate renal disease, adrenal problems, high calcium, diabetes or hyperthyroidism. High SG may be a sign of dehydration. Normal feline SG range: 1.020–1.040; canine SG range: 1.016–1.060)
  • pH – measures the acidity level of the urine, bacterial infections create alkaluria, struvite crystals form in alkaline urine and cystine crystals in acidic urine. Normal pH values: feline (6.0–7.0) canine (6.0–7.0).
  • Protein – may indicate inflammation, hematuria or glomerular disease. Normal protein values in dogs and cats are “negative to trace.”
  • Glucose – indicates the presence of sugar in the urine, may be indicative of diabetes (perform blood glucose to confirm). Normal urine glucose test for felines and canines is “negative.”
  • Ketones (acetone) – checks for the presence of acetate and acetoacetate, may be present in diabetes or starvation. Normal value for cats and dogs is “negative.”
  • Bilirubin – positive test may indicate liver dysfunction, bilirubin (old blood cells) normally metabolizes through the liver into the colon, when the liver does not function properly, bilirubin is discharged through the kidneys. Normal urine bilirubin value for canines and felines is “trace – 1+” (more often seen in concentrated urine).
  • Blood – indicates hematuria, may be an artifact of cystocentesis or catheterization. Urine sediment confirms or disputes this finding. Normal value for dogs and cats is “negative – trace.”

Urine sediment exam looks for microscopic components in the urine. This may be crystals, casts, red blood cells, white blood cells, epithelial cells, or bacteria. If present, these entities may be indicative of a medical condition and are investigated along with clinical signs and other tests such as bloodwork and urine cultures.

Other Diagnostic Tests

Dec 15, 2022 | Posted by in NURSING & ANIMAL CARE | Comments Off on Preoperative Planning
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