The Pre-Anesthetic Evaluation - Part 2
So what is involved in evaluating your patient prior to anesthesia? How do we assign the status number?
A proper evaluation identifies individual risk factors and any physiological issues that may be present that can influence the development of an anesthetic plan. Factors include
- Physical examination
- Type of procedure
- Choice of anesthetic drugs available
The taking of history is usually the technician’s responsibility. Find out the pet’s previous anesthetic experiences and surgeries and any problems with recovery; medication they are on; known medical conditions; any adverse responses to medications. Be sure to ask owners if they have given the pet any medications in the last day – some owners, for example, will give aspirin or a homeopathic substance and not think to offer this information. If the animal is diabetic, make sure the owner has instructions on whether to give insulin that morning or not, and the amount. Then be sure to confirm that on the morning of the procedure, and also give discharge instructions that include feeding and insulin. Any concurrent disease, such as renal impairment, will affect the pet’s anesthetic experience and recovery. Special precautions, such as IV fluids therapy, will often need to be taken. It is important to be aware of previous blood work and trends.
A physical examination that day will reveal any current issues that are unknown, such as a cardiac murmur, lung abnormality or fever, which may affect anesthesia. Being overweight or underweight may alter choice and amount of anesthetic drug. The exam may be done by the veterinarian or technician depending on your hospital’s protocol and your state regulations.
Older pets can be compromised by cardiovascular issues and decreased respiratory function as well as any concurrent diseases. Older pets, especially smaller ones, also get cold very quickly. Very young animals can be affected by hypoglycemia, hypothermia, and decreased drug metabolism.
A fractious animal can limit or make impossible a physical exam. You may not be able to handle an animal for an IV catheter or IV injection. This situation may necessitate alternative anesthetic meds that can be safely given. A quiet, sedate pet may need lower doses or possibly inhalant only.
Be aware of the breathing issues of brachycephalic dogs and cats – plan to leave them intubated longer and monitor their respiratory function on recovery even closer than you would normally do. Persian and Himalayan cats seem to have more undetected cardiac issues and I am always lowering their doses or using inhalant only when possible.
TYPE OF PROCEDURE
Evaluate the level of invasiveness, anticipated pain, risk of bleeding, length of procedure. Will the head be covered? If so you need to think about attaching monitors toward the back of the animal, and you may not be able to physically see its face. Abdominal surgery will cause the pet to lose more heat, as will a longer procedure, so you need to think about warmth. If there is increased risk of bleeding, you need to be ready to address a decrease in blood pressure, be ready to transfuse if your hospital has that ability, and have the suction machine handy. Always assess potential level of pain, decide on a pain management protocol and start it pre-emptively (if you wait until after the pain starts, the medications are less effective).
SEDATION VS GENERAL ANESTHESIA
What level of anesthesia is necessary for the procedure? Pets having shorter, less invasive procedures such as a biopsy of a lump, joint aspirate, wound management, bandaging or casting a limb, radiograph, may need only heavy sedation. These pets still require the same level of monitoring during the procedure and during recovery. Choose an appropriate e-tube and be ready to intubate and provide oxygen if necessary.
Every animal requires an evaluation based on all of these factors, and an individual plan created. The veterinarian may require recent bloodwork (timeframe depending on your hospital protocol), diagnostic imaging, or ECG as part of his or her evaluation. Results of all of the above will determine the anesthetic plan. You as a technician need to be aware of all of these factors as they pertain to your particular patient; you need to be intimately aware of the plan and hopefully play a part in its development as well as implementation. It is your awareness of your patient’s condition at all times, as well as your skilled nursing care that will make the difference for your patient.
***information based on AAHA anesthetic guidelines for dogs and cats