Preanesthetic evaluation (Proceedings) - Veterinary Healthcare


Preanesthetic evaluation (Proceedings)


Pre-Anesthetic Diagnostics

Pre-anesthetic laboratory tests should be performed on each patient in order to eliminate unexpected complications. If stabilizing is necessary, this will guide your therapeutic techniques.

Every hospital will have different policies depending on cost, available testing as well as environmental concerns for that particular town/state/country. Lab tests for a young patient (< 6 yrs) should include PCV, TPP, USG, & BUN. If the patient is compromised or over 6 yrs, a full CBC, chemistry profile as well as other diagnostic tests may be required.

PCV (packed cell volume)

This is a slight indicator of hydration. It will give you information on the body's oxygen carrying capacity.

Minimum PCV for pre-op is 27-30%. The minimum Intra-op is 20%. The maximum is 60% (patient's cardiac output is cut in half if blood viscosity is double what it should be).

If PCV is low; consider stabilizing patient. Check hemoglobin as this is a more precise way of measurement of tissue oxygenation as well as arterial blood gas. Keep in mind that delivery of fluids will dilute PCV further. A whole blood transfusion may be necessary. You may want to consider pre-oxygenation and or intermittent positive pressure ventilation (IPPV) if improved oxygen tissue deliver is required.

TPP (total plasma protein)

The TPP will affect the patient's protein binding ability. A patient with a low TPP (hypoproteinemia) will have more drugs to bind to receptors thus increasing the potency. An increase in TPP may indicate dehydration in a patient.

CBC (complete blood count) - whole blood

This will include PCV, TPP, and Hemoglobin but also provide information about the white blood cells. An alteration may indicate stress or infection. This should also include a count of platelets which will reveal information about clotting.

Chemistry Profile- serum

There are a variety of tests that will assess organ function & disease. Listed below are some of the tests available. Each test should be considered based on each individual patient as well as disease.

Additional diagnostics are available for particular concerns of the patient such as serum electrolytes, clotting tests, arterial blood gases, urine specific gravity or full urinalysis, electrocardiogram, ultrasound, CAT scan, and magnetic resonance imaging.

ASA- American Society of Anesthesiologists

Now that you have all your pertinent information on your patient, you can develop an anesthetic plan....based on their ASA status! This is a status that the ASA developed to help the anesthetist determine what anesthetic approach is the best based on a variety of factors.

Category Class (RISK): I- minimal risk of a normal healthy patient, II- slight risk of a slight to mild systemic change, III- moderate risk & systemic change w/ some clinical alterations, IV- high risk with preexisting disease that is severe in nature and V- extreme risk where patient will probably die with or without surgery. An E, for emergency can be attached to each class if it is an emergency.

ASA Status- Examples of Various ASA

A healthy dog for castration or cruciate repair would be considered as a patient that is a class I.

An example of a class II patient would be an obese cat for a castration or a mild anemia in a dog that is being spayed. For examples of class III; a depressed dog presented for pyometra or a cat with mild cardiovascular disease presented for esophageal endoscopy. A class IV patient might be a dog with severe dehydration presented with foreign body removal or a peg tube placement on a cat that has liver failure. A class V example would be a dog with multiple organ failure leading to circulatory failure such an advanced gastric dilatation volvulus (GDV). Another example would be a trauma severe in nature such as hit by car (HBC) on shocky dog undergoing exploratory with massive abdominal hemorrhage.


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