Anesthesia for Autonomic Dysfunction

AUTONOMIC DYSFUNCTION

Preoperative Considerations

Autonomic dysfunction, or dysautonomia, may be due to generalized or segmental disorders of the central or peripheral nervous system. Symptoms can be generalized, segmental, or focal. These disorders may be congenital, familial, or acquired. Common manifestations include impotence; bladder and gas-trointestinal dysfunction; abnormal regulation of body fluids; decreased sweating, lacrimation, and salivation; and orthostatic hypotension. The lat-ter can be the most serious manifestation of the disorder.

Acquired autonomic dysfunction can be iso-lated (pure autonomic failure), part of a more gener-alized degenerative process (Shy–Drager syndrome, PD, olivopontocerebellar atrophy), part of a seg-mental neurological process (MS, syringomyelia, reflex sympathetic dystrophy, or spinal cord injury), or a manifestation of disorders affecting peripheral nerves (GBS, diabetes, chronic alcoholism, amyloi-dosis, or porphyria).

Congenital or familial dysautonomia occurs most frequently in Ashkenazi Jewish children and is usu-ally referred to as Riley–Day syndrome. Autonomic dysfunction is prominent and is associated with gen-eralized diminished sensation and emotional lability. Moreover, patients are predisposed to dysautonomic crises triggered by stress and characterized by marked hypertension, tachycardia, abdominal pain, diaphoresis, and vomiting. Intravenous diazepam is effective in resolving such episodes. Hereditary dysautonomia associated with a deficiency of dopa-mine β-hydroxylase is described. Administration of α-dihydroxyphenylserine improves symptoms inthese patients.

Anesthetic Considerations

The major risk of anesthesia in patients with autonomic dysfunction is severe hypotension,compromising cerebral and coronary blood flow. Marked hypertension can be equally deleterious. Most patients are chronically hypovolemic. The vasodilatory effects of spinal and epidural anesthe-sia are poorly tolerated. Similarly, the vasodilatory and cardiac depressant effects of most general anesthetic agents combined with positive airway pressure can be equally problematic. Continuous intraarterial blood pressure monitoring is use-ful. Hypotension should be treated with fluids and direct-acting vasopressors (in preference to indirect-acting agents). Enhanced sensitivity to vasopressors due to denervation sensitivity may be observed. Blood loss also is usually poorly tol-erated. Body temperature should be monitored closely. Patients with anhidrosis are particularly susceptible to hyperpyrexia.