Identifying serotonin syndrome

Identifying serotonin syndrome in the emergency department can be difficult without an accurate patient history. Furthermore, the physical symptoms may look similar to many other disorders such as neuroleptic malignant syndrome and anticholinergic toxicity. If you remember the acronym SHIVERS, you can easily recognize the signs and symptoms of serotonin syndrome.

Shivering: Neuromuscular symptom that is unique to serotonin syndrome
Hyperreflexia and Myoclonus: Seen in mild to moderate cases. Most prominent in the lower extremities. This can help differentiate from neuroleptic malignant syndrome which would present with lead-pipe rigidity.
Increased Temperature: Not always present, but usually observed in more severe cases
Vital Sign Abnormalities: Tachycardia, tachypnea, and labile blood pressure
Encephalopathy: Mental status changes such as agitation, delirium, and confusion
Restlessness: Common due to excess serotonin activity
Sweating: Autonomic response to excess serotonin. This symptom can help differentiate from anticholinergic toxicity in which the patients would present with increased temperature but dry to the touch.

Once serotonin syndrome is identified, it is important to discontinue all serotonergic agents, provide supportive care with fluids, and sedate with benzodiazepines. Sedation with benzodiazepines helps to decrease myoclonic jerks which also helps with temperature control. If patients are hyperthermic, they will require intensive cooling. Cyproheptadine, a potent antihistamine and serotonin antagonist, should also be administered. The initial dose of cyproheptadine in serotonin syndrome is 12mg which can be followed by 2 mg every 2 hours as needed for symptom control.