Chapter 13

1. After diabetes, thyroid disorders are the second most common endocrine disease. The range of presentation is vast, ranging from subclinical hyperthyroidism to life-threatening thyroid storm, and from subclinical hypothyroidism to myxedema coma with high mortality if not appropriately treated.

2. The current thyroid-stimulating hormone (TSH) assays, along with the free thyroxine (FT4) level, often lead to the correct diagnosis of the thyroid disorder. Although the signs and symptoms of hypo- and hyperthyroidism are quite distinct, with aging, the clinical picture may not be quite as clear. A high level of suspicion, the appropriate use of tests, and careful assessment of coexisting conditions will lead to the correct diagnosis.

3. Patients with mild hypo- and hyperthyroidism may safely undergo elective surgery if proper care is exercised, but patients with thyroid storm or myxedema coma may have significant morbidity with elective surgery.

4. Hypercalcemia places a patient at increased risk for hypovolemia, renal dysfunction, and cardiac dysrhythmias. Hypocalcemia may present with decreased myocardial contractility, tetany, dysrhythmias, and altered response to muscle relaxants, leading to increased perioperative patient risk. Prompt recognition and successful treatment can be lifesaving.

5. The complex interplay between the thyroid, adrenal, and pituitary glands must be considered in anesthetizing patients for surgery. Appropriate corticosteroid replacement will often result in a smooth and stable perioperative course.

6. The major goal in preoperative preparation of the patient with pheochromocytoma is to decrease cardiovascular morbidity and mortality resulting from excess catecholamine secretion. However, the optimal drug for preoperative preparation of the patient with pheochromocytoma is controversial.

7. Central diabetes insipidus characterized by decreased vasopressin secretion may have effects on both intravascular volume and electrolytes. Patients with acromegaly have a higher incidence of airway difficulty, as well as diabetes, hypertension, and cardiomegaly.

8. According to the most recent American Diabetes Association guidelines, both hemoglobin A1C and blood sugar levels can be used to diagnose diabetes mellitus. The most recent consensus conference defines the target hemoglobin A1C levels and outlines a stepped approach to treatment.

9. Diabetes is a disease with a wide impact. Acute diabetic complications include diabetic ketoacidosis, nonketotic hyperosmolar coma, and infection. Chronic complications from diabetes involve the cardiovascular, neurologic, and immune systems. The confluence of diabetes and other diseases and risk factors are components of the metabolic syndrome.

Disturbances in endocrine function increase the complexity of anesthetic care and the risks to the patient. The anesthesiologist must be aware of endocrine abnormalities and their significance in order to optimize patient care and safety. This chapter focuses on the proper preoperative treatment of patients with specific endocrine abnormalities, emphasizing anesthetic-related issues. Chapter 60 discusses intraoperative care of these patients.

### Physiology

The synthesis and release of thyroid hormones occurs as a result of the complex interaction between the hypothalamic–pituitary axis, the thyroid gland, and the thyroid hormones. The hypothalamus controls the release of thyrotropin-releasing hormone (TRH), which is secreted by the hypothalamic neurons and is delivered to the adenohypophysis via the ...

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