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KEY CONCEPTS
Diabetic autonomic neuropathy may limit the patient’s ability to compensate (with tachycardia and increased peripheral resistance) for intravascular volume changes and may predispose the patient to cardiovascular instability (eg, postinduction hypotension) and even sudden cardiac death.
Temporomandibular joint and cervical spine mobility should be assessed preoperatively in diabetic patients to reduce the likelihood of unanticipated difficult intubation. Difficult intubation has been reported in as many as 30% of persons with type 1 diabetes.
Sulfonylureas and metformin have long half-lives and many clinicians will discontinue them 24 to 48 h before surgery. They can be started postoperatively when the patient resumes oral intake.
Incompletely treated hyperthyroid patients may be chronically hypovolemic and prone to an exaggerated hypotensive response to induction of anesthesia.
Clinically hypothyroid patients are more susceptible to the hypotensive effect of anesthetic agents because of diminished cardiac output, blunted baroreceptor reflexes, and decreased intravascular volume.
Patients with glucocorticoid deficiency must receive adequate steroid replacement therapy during the perioperative period.
In patients with a pheochromocytoma, drugs or techniques that indirectly stimulate or promote the release of catecholamines (eg, ephedrine, hypoventilation, or bolus doses of ketamine), potentiate the arrhythmic effects of catecholamines (halothane), or consistently release histamine (eg, large doses of atracurium or morphine sulfate) may precipitate hypertension and are best avoided.
Obese patients may be difficult to intubate as a result of limited mobility of the temporomandibular and atlantooccipital joints, a narrowed upper airway, and a shortened distance between the mandible and sternal fat pads.
The key to perioperative management of patients with carcinoid syndrome is to avoid anesthetic and surgical techniques or agents that could cause the tumor to release vasoactive substances.
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The underproduction or overproduction of hormones can have life-threatening consequences. Therefore, it is not surprising that endocrinopathies affect anesthetic management. This chapter briefly reviews normal physiology and pathophysiology of four endocrine organs: the pancreas, the thyroid, the parathyroids, and the adrenal glands. It also considers obesity and carcinoid syndrome.
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Adults normally secrete approximately 50 units of insulin each day from the β cells of the islets of Langerhans in the pancreas. The rate of insulin secretion is primarily determined by the plasma glucose concentration. Insulin, the most important anabolic hormone, has multiple metabolic effects, including facilitating glucose and potassium entry into adipose and muscle cells; increasing glycogen, protein, and fatty acid synthesis; and decreasing glycogenolysis, gluconeogenesis, ketogenesis, lipolysis, and protein catabolism.
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In general, insulin stimulates anabolism and weight gain, whereas lack of insulin is associated with catabolism, a negative nitrogen balance, and weight loss (Table 35–1).
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