Chapter 12
Induction Techniques for the Really Sick Patient
Do you have any other options?
Berit L. Fischer
Anesthesia Director, Animal Medical Center, New York City, USA
- Q. What constitutes a “really sick patient”?
- A. A really sick patient is any patient who has an illness or injury that impacts homeostasis to such a degree that there is a constant threat to life. Patients in this category include those suffering from any type of shock (hypovolemic, cardiogenic, obstructive, distributive), severe upper or lower airway diseases (e.g., acute respiratory distress syndrome [ARDS], upper airway obstruction), those that have severe metabolic or electrolyte derangements (e.g., diabetic ketoacidosis or uremia), and patients with severe neurologic disease who may be obtunded or at risk of brainstem herniation.
- Q. Does my critical patient require general anesthesia?
- A. This depends on the procedure that needs to be performed and why the patient is sick. Consider other options, where practical, such as mild sedation and a block using local anesthetic. This can work well, for example, in blocked cats who are azotemic with electrolyte abnormalities. Systemic butorphanol, hydromorphone, or methadone can be combined with a coccygeal epidural to allow placement of a urinary catheter [1]. On the other hand, some patients may require general anesthesia despite minimally invasive procedures because the effects of sedatives could create more problems. An example is the patient with suspected increased intracranial pressure (ICP), as might occur in a dog hit by car with head trauma. Depending on the level of sedation, patients may hypoventilate, leading to hypercapnia, which can increase ICP. Induction of anesthesia allows the anesthetist to establish an airway and ventilate the patient in order to prevent this from occurring.
- Q. If general anesthesia is required, how should I prepare?
- A. First things first! Make sure your patient is as stable as possible at the time of anesthesia. This includes ensuring adequate circulating blood volume, administration of blood products to anemic patients (∼PCV < 20%) to improve oxygen carrying capacity, correcting acid-base and electrolyte derangements, when possible, and optimizing systemic blood pressure (mean arterial blood pressure (MAP) > 60 mmHg) with fluid support, colloids, and possibly inotropic agents such as dobutamine or dopamine (see Chapter 17).
Unfortunately, some patients may be so ill that stabilization is not possible due to how rapidly their status is declining. A good example is a patient suffering from septic peritonitis that requires an emergency exploratory laparotomy. In these situations, stabilization measures should be ongoing while you are preparing for anesthesia induction.
- Q. Do specific diseases require special preparation?
- A. Yes! When preparing for each case, you should be thinking about everything that could go wrong at induction and how you can either prevent it or treat it if it occurs. Often, this requires knowing the pathophysiology of the disease and how different anesthetic drugs can affect it.
In general, there are some basics that should be done prior to inducing any critically ill patient:
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- Q. If general anesthesia is required, how should I prepare?
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