A neurologic disorder, narcolepsy is a derangement of the normal sleep-wake cycle characterized by episodes of excessive daytime sleepiness (EDS), cataplexy, hypnagogic and/or hypnopompic hallucinations, and sleep paralysis, all of which represent inappropriate intrusions of sleep into the awake state. Onset of this disorder may be at any time, from as young as 10 years of age through the fifth decade. There is no known cure at the present time.

Narcolepsy is found worldwide without regard to race or ethnic group. Some groups appear to be more prone to develop narcolepsy; in Japan the estimated incidence is 1:600, in the United States the estimated prevalence ranges from 1:1000 to 1:10,000, and in Israel the estimated prevalence is 1:500,000. The estimated prevalence rates for the United States, alone, may account for 10,000 to 20,000 to as many as 100,000 to 200,000 patients.

The cause of narcolepsy has not been delineated. The disease does seem to appear in families.

The classic symptoms of narcolepsy include EDS, cataplexy, sleep paralysis, and hypnogogic or hypnopompic hallucinations, which are referred to as the “narcolepsy tetrad.” When a patient reports EDS that is accompanied by one of the other three parts of the tetrad, the diagnosis of narcolepsy is highly suspected. Only 20% to 25% of patients with narcolepsy display all four parts of the tetrad.

Narcolepsy is incurable. Occasionally, some patients are able to treat EDS by scheduling nap periods over the course of the day. More frequently, patients with narcolepsy must depend on pharmacologic support to treat symptoms. EDS/sleep attacks are treated using central nervous system stimulants. Cataplexy may be treated with tricyclic antidepressants (TCAs)or possibly fluoxetine.

Complications that may arise do so from increased risk of injury resulting from excessive daytime sleepiness or cataplexy.

The major anesthetic implications of narcolepsy revolve around medication interactions. Enzyme induction with a patient who has narcolepsy can be expected secondary to treatment with CNS stimulants and/or tricyclic antidepressants. The CNS stimulants and tricyclic antidepressants used for symptomatic treatment are metabolized by the liver.

Most of the CNS stimulants employed are noncatecholamine sympathomimetic amines. Long-term administration of amphetamines may reduce the anesthetic requirements.

Response to ephedrine or phenylephrine may be exaggerated. Response to atropine may be exaggerated in patients taking tricyclic antidepressants.

Sedation from sodium thiopental is prolonged in the patient taking a TCA. Acute hypertension and cardiac dysrhythmias may occur with the administration of ketamine.

Cataplexy, a state of paralysis in which the patient is fully conscious but unable to move, is triggered by extremes in emotion, excitement, stress, surprise, or startle. All these factors may be experienced in a patient emerging from anesthesia. Other potential causes of immobility must be investigated before concentrating on the possibility of an episode of cataplexy being the cause of immobility. In the event that cataplexy is the cause, support and calm reassurance are the most appropriate measures to take. The anesthetist should communicate understanding of the situation at hand and may administer a small dose of an IV sedative to alleviate any anxiety the patient may be experiencing.

Hypnopompic hallucinations may occur during emergence from general anesthesia or any situation in which the patient has received heavy sedation. This patient may act out or act on the event he or she perceives. The patient may be inordinately frightened and/or combative during the emergence process. Calm yet firm reassurance combined with small increments of IV sedation will help the patient through such an episode.

Sleep paralysis may occur during emergence from general anesthesia, during a regional anesthetic, or during a monitored care case. This symptom is very similar to cataplexy but may be distinguished from cataplexy by the patient’s ability to open his or her eyes spontaneously. As with the other symptoms of the narcolepsy tetrad, calm reassurance and possibly a small amount of IV sedation may be the best course of action to aid and comfort the patient.