Anesthetizing cardiac patients (Proceedings)
Veterinary technicians are the veterinary hospital's mainstay when it comes to carefully and successfully anesthetizing critical patients. A large number of elderly canine and feline patients are affected by cardiac disease, and knowledge of how to safely monitor, anesthetize, and problem solve cardiac patients makes for a less stressful anesthesia for both the patient and technician.
Preanesthetic evaluation should include a thorough physical exam and a complete history, including what medications the patient is on. If they are currently on cardiac medications such as diuretics or ACE inhibitors, a serum biochemistry profile and electrolyte panel is even more important than usual, as these drugs can cause azotemia and changes in electrolyte levels. If arrhythmias are ausculted, they should also be characterized with an ECG prior to anesthesia. Further diagnostic testing may be necessary to evaluate the cardiac disease. As a general rule, it is much more risky to anesthetize a patient in congestive heart failure than one who is stabilized. A recent set of chest radiographs will indicate whether the patient has pulmonary edema or pleural effusion. It will also help evaluate the cardiac silhouette for enlargement. An echocardiogram may also be indicated to further characterize heart disease and evaluate severity.
Ideally, the equipment available would include blood pressure monitoring, either invasive or non-invasive; ECG; capnography; and pulse oximetry. Technicians should be familiar with the equipment in order to expedite induction and set up of the monitoring equipment. With a critical patient, it is also ideal to have a technician solely dedicated to anesthesia monitoring. Anesthesia monitoring forms should be utilized to record anesthesia dosing, track trends in blood pressure, heart rate, respiratory rate, etc. The anesthetist should also remember that monitoring equipment cannot replace their own senses, and that no one piece of equipment will give all the information about their patient's status.As a general rule, the safest anesthetic agent for any patient is the one which the anesthetist is most familiar. However, there are a few basic guidelines for cardiac patients.
First, the patient should have a peripheral catheter placed. As with any patient, this allows the technician to deliver medications quickly in case of changes in the patient's status. The anesthetist may also wish to place an arterial catheter. This allows invasive, and therefore more accurate, blood pressure monitoring, as well as access to arterial blood to evaluate changes in respiratory status.