Preanesthetic evaluation (Proceedings) - Veterinary Healthcare


Preanesthetic evaluation (Proceedings)


Physical Exam

We must do a pre-anesthetic physical exam on every patient! Be consistent in your approach.

Either head to tail or systems approach. The systems that the anesthetists are most concerned with are cardiovascular, respiratory, renal, hepatic, nervous, gastrointestinal, integument as well as overall body condition. When evaluating the patient, know your normal vital signs with various species, breeds as well as age on each of your patients. In evaluating the cardiovascular system, one should have a picture on how well the patient is perfusing his or her tissues. Ascultate for murmurs. Also check to see if pulses are synchronous with heart rate. One can observe rhythm via an electrocardiogram. The capillary refill time can show adequacy of perfusion but is not a real accurate method. Blood pressure monitoring is more ideal. By looking and touching the mucous membranes, one can see how well the patient is hydrated. When evaluating the respiratory system, keep in mind that without normal function, a patient may not get adequate oxygen for the tissues and or a patient may become hypercarbic (high carbon dioxide in the circulating blood). Ascultate all lung fields as well as the upper respiratory tract. If any abnormal sound is heard, a further diagnostic work up may be necessary such as radiographs and or arterial blood gases. Look at the color of the mucous membranes (MM). Normal is pink. Pale MM can be an indication of hypotension, hypothermia, hypoxemia, vasoconstriction (from α2-agonists) and low packed cell volume. A red brick coloring can indicate venodilation, blood sludging, hypercarbia or endotoxemia. Evaluating the renal system can be difficult on physical exam. Palpation of the kidneys should be performed for size and symmetry. Owner history and clinical findings are important as well evaluating the creatinine and blood urea nitrogen on a blood chemistry. A uremic or azotemic (retain nitrogenous wastes in blood- can indicate poor kidney function) patient must be corrected prior to anesthesia as anesthetic drugs can worsen this condition. A low urine specific gravity (USG) will tell you if your patient is concentrating urine normally. A USG less than 1.025 in the dog and 1.035 in the cat may show you early signs of kidney dysfunction prior to finding an azotemia, thus may be the first test you would do on your patient. A patient under general anesthesia must maintain adequate perfusion to support normal kidney function. This can be monitored using blood pressure measurement. If a mean arterial blood pressure of 60 millimeters of mercury is maintained, your patient is perfused adequately. Hepatic function will indicate how well your patient can metabolize and excrete anesthetic drugs. Plasma proteins are also produced in the liver and low total plasma proteins can indicate liver disorders. The liver is also responsible for some clotting factors. Increased alkaline phosphatase (ALK Phos) alanine aminotransferase (ALT), which are liver enzymes can indicate hepatic disease. Animals with portosystemic shunts (PSSs) will often have increased bilirubin, bile acids white blood cell count and sometimes, increased clotting times. It is common with the PSSs or patients with liver disease to see decreased blood glucose, albumin, total plasma proteins and packed cell volume as well. Progressed liver disease may reveal that a patient is jaundice and or lethargic. They may even seizure. The nervous system plays an essential role in anesthesia management as the brain and spinal cord are involved. If a patient has a disorder involving the nervous system such as head trauma or paralysis, a full neurologic exam must be performed by the veterinarian as there are a multitude of concerns one would have to mange the needs of their patient under anesthesia. The nervous system is effect by stress and pain as well and can be altered in these conditions. When evaluation the gastrointestinal system, consider diet and how well the patient has been eating. Do they ever vomit? Do they have normal bowel movements? A patient that has had persistent diarrhea can lose valuable electrolytes such as potassium. If skin infections or ectoparasites are noticed on the integument, this may alter your approach with skin disinfection and or local anesthetic techniques. Look at your patient's overall body condition. What is their weight? Are they cachetic or obese? Is the obesity coming from pregnancy? This will affect your drug choice and dose. Are they hydrated? This will affect uptake, metabolism & clearance. Use skin turgor, eyeball position as well as moisture of mucous membranes. What is your patient's body temperature? This can indicate disease and or stress. Patient's young or old can be presented with disease or trauma. Age is not a disease but geriatrics should be evaluated further as they are more prone to disease. Pain should be scored prior to anesthesia all through the post-op period, therefore wheather an animal is in pain or not, they should always be evaluated for pain and discomfort.


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