Paroxysmal Sympathetic Hyperactivity

Paroxysmal sympathetic hyperactivity (PSH) is a syndrome encountered in patients with severe acute neurologic injury. Patients with PSH may have episodic tachycardia, hypertension, tachypnea, fever, diaphoresis, and posturing. Episodes may last minutes to hours and recur several times per day. Features supporting the diagnosis include multiple autonomic symptoms occurring simultaneously, multiple recurrent episodes over several days, and response to specific abortive therapy. The triggering of paroxysms by both noxious and non-noxious stimuli is also an important defining feature of PSH. The pathophysiology of the condition is poorly understood, but impaired descending inhibitory control of excitatory spinal circuits, permitting unregulated sympathetic outflow, is a commonly proposed mechanism. PSH is often seen in severe traumatic brain injury, but may occur with any type of acute brain injury. Historically, terms used to describe this condition include “dysautonomia,” “diencephalic seizures,” “sympathetic storming,” and “paroxysmal autonomic instability with dystonia.” Numerous medications are used to treat PSH, but there is little strong evidence to guide therapy. The most common agents employed in clinical practice are listed in Table 61.1 . Often a combination of agents is necessary to achieve control of PSH episodes.

Table 61.1

Dosing and titration of medications for paroxysmal sympathetic hyperactivity

Acute abortive therapies
	Starting dose	Titration	Maximum dose
Morphine IV	2–4 mg IV q1–2 h prn	2-mg increments	Doses up to 10 mg IV may be needed
Propranolol IV	1–3 mg IV q1–2 h prn	1–2-mg increments	5 mg IV per dose
Labetalol IV	10–20 mg IV q1–2 h prn	10-mg increments	80 mg IV per dose
Midazolam IV	1–2 mg IV q2–4 h prn	1–2-mg increments	10 mg IV per dose

Maintenance/preventative therapies
Oxycodone PO	5–10 mg q4–6 h	5-mg increments	–
β-blockers Propranolol PO Labetalol PO	10–20 mg q8–12 h 100–200 mg q8–12 h	10–20-mg increments 100–200-mg increments	320 mg/day ^a 2400 mg/day ^a
Clonidine PO	0.1 mg q8–12 h	0.1–0.2-mg increments	2.4 mg/day ^a
Gabapentin PO	100–300 mg q8 h	200–300-mg increments	3600 mg/day ^a
Benzodiazepines Clonazepam PO Diazepam PO	0.25–1 mg q12 h 2.5–10 mg q8–12 h	0.5-mg increments 5 mg increments	– –
Bromocriptine PO	1.25–2.5 mg q8–12h	2.5-mg increments	40 mg/day (divided q8–12 h)
Baclofen PO	5 mg q8 h	5 mg/dose every 2–3 days	80 mg/day ^a
Dantrolene PO	25 mg daily	After 7 days increase to 25 mg tid. Titrate dose by 25–50 mg increments weekly.	400 mg/day (divided q6 h)