The clinical presentation is most consistent with paroxysmal sympathetic hyperactivity (PSH). PSH is defined as a syndrome associated with episodes of increased sympathetic activity. The syndrome can manifest as increased heart rate, increased respiratory rate, increased systolic blood pressure, hyperthermia, diaphoresis, and at times with dystonia. PSH is observed more often in younger than older patients and is more common in men than women. Most reported cases of PSH result from traumatic brain injury (TBI), followed by hypoxic brain injury and stroke. The diagnosis of PSH often can be difficult because of the broad differential diagnosis of abnormal vital signs in the patient after brain injury.^1-4

The first step in approaching a patient with this set of disturbances is to investigate the cause of these abnormalities. Although PSH may be the most likely diagnosis, more harmful conditions must be ruled out. The most common etiology for fever and tachycardia in a patient after acute brain injury is infection. Other clinically important considerations include deep vein thrombosis, pulmonary embolism, cardiac events, medication side effects, medication withdrawal symptoms, and neurologic complications. An exhaustive examination for etiologies should be performed. PSH remains a diagnosis of exclusion.

The term “paroxysmal sympathetic hyperactivity” has been adapted and replaces previous terms used to describe the syndrome, such as, episodic autonomic instability, dysautonomia, autonomic dysregulation, central autonomic dysfunction, paroxysmal autonomic instability with dystonia, sympathetic storming, autonomic storming, dysautonomic crises, and diencephalic fits. Recently a consensus statement has attempted to establish standardized diagnostic criteria. The assessment measure is a diagnostic tool that has two components, the first addresses the probability of the diagnosis, which includes clinical features that occur simultaneously, episodes that are paroxysmal in nature, sympathetic overreactivity to normally nonpainful stimuli, features that persist > 3 consecutive days, features that persist > 2 weeks after brain injury, features that persist despite treatment of alternative differential diagnoses, medication being administered to decrease sympathetic features, > 2 episodes daily, absence of parasympathetic features during episodes, absence of other presumed cause of features, and antecedent-acquired brain injury. The second assessment addresses the severity of the clinical features: heart rate, respiratory rate, systolic blood pressure, temperature, sweating, and posturing during episodes. The process requires combination of the two components, which will help estimate the likelihood of diagnosis and severity of the PSH. The assessment tool is designed to assess patients on a daily basis during the intensive care unit (ICU) stay and throughout rehabilitation.⁵

PSH was first described by Wilder Penfield in 1929.³ He called the syndrome diencephalic autonomic epilepsy, which highlighted the initial assumption that these episodic events were epileptic in nature. We now know that these episodes are not epileptic, but the actual cause of the syndrome still remains unknown. Although a number of theories describing the pathophysiology of PSH exist, theories are proposed in the face of a paucity of detailed studies. Theories are mainly focused around a disconnection between the inhibitory cortical pathways and the autonomic nervous system centers in the brainstem.^6-8 This causes an imbalance in the normally exquisite balance between sympathetic and parasympathetic outflow. Episodic bursts of sympathetic outflow causes the symptoms (Figure 7-1).

One of the most important steps in managing PSH is early recognition of symptoms. Because of lack of diagnosis criteria and overlapping symptoms of PSH with other sequelae of acute brain injury, it can become very challenging to identify PSH in a timely manner. Nonpharmacologic treatment modalities play a pivotal role in conjunction with pharmacologic therapies in treating PSH. Symptoms can be triggered by minimal external stimuli, such as touching, turning, or endotracheal tube suctioning. It is important to minimize any triggers that might worsen PSH symptoms without compromising nursing care. Effective clinical management of PSH demands a firm understanding of drug use for appropriate management of symptoms, dosing, and duration of drug therapy. Lack of well-designed studies continues to be challenging in assessing the correct dose or effective medication use. The main goal should be to avoid overmedicating patients or treating symptoms with medications that might worsen the situation. First-choice medications should be targeted to resolve symptoms as soon as episodes are identified. Appropriate medications should be administered based on symptoms presented.

Numerous medications are used to treat PSH. Medications can be classified into abortive medications and preventative medications. No well-designed studies to examine the results or efficacy in a large study have been performed. Treatment recommendations are based on case reports and case series, hindering strong recommendations for specific treatment algorithms.

Medical treatments for PSH include opioids, β-blockers, dopamine agonists, α₂ agonists, GABA ergic agents, benzodiazepines, gabapentin, and muscle relaxants. It is intuitive to initiate medications that can alleviate symptoms during breakthrough episodes with quick onset of action and short half-life. The targets of the abortive medications usually depend on the predominant symptoms: treating hyperthermia with antipyretics, agitation with sedation, and hypertension with antihypertensive agents. Morphine and short-acting benzodiazepines are first-line treatment options for this indication because of their efficacy. Symptom resolution should be immediate and side effects from medications, such as sedation, should be reduced given the short half-life of the medications.

Scheduled symptom preventative medications should be initiated to decrease the frequency and intensity of episodes. These medications include nonselective β-blockers, α₂ agonists, bromocriptine, and long-acting benzodiazepines such as clonazepam. Refractory PSH, in which symptoms do not respond to treatment, can lead to secondary brain injury from hypertension, hyperthermia, and cardiac damage and even result in death. IV medications and/or continuous IV medications such as benzodiazepines, propofol, opioids, or dexmedetomidine drips should be administered (Table 7-1).