**3. Hyperthermia**

While a reflexive diagnosis of sepsis is tempting for the ill-appearing patient with an elevated temperature, it is important to consider conditions that mimic sepsis which are often both life-threatening and reversible. Unlike the fever associated with sepsis, the majority of these sepsis mimics have elevated temperature as a result of hyperthermia, which occurs secondary to dysfunction of the hypothalamic thermoregulatory system [1]. If an infectious source cannot be found in a seemingly septic patient or the patient is not improving with antibiotics and fluids, it is important to broaden the differential to conditions that cause hyperthermia (**Table 3**).

#### **3.1 Neuroleptic malignant syndrome (NMS)**

NMS is a life-threatening syndrome of altered mental status, autonomic instability, hyperthermia, and muscle rigidity associated with the use of dopaminergic antagonists. "Lead pipe" rigidity is the hallmark physical examination finding in NMS and can be severe enough to precipitate rhabdomyolysis. Most commonly, NMS occurs with the use of dopaminergic antagonists used in the treatment of psychiatric disorders and nausea, but NMS can also be precipitated by may be caused withdrawal from dopaminergic medications, such as those used in the treatment of Parkinson's disease [42, 43]. First generation antipsychotic medications are the most commonly implicated in NMS, with haloperidol and fluphenazine having the highest risk [42]. Risk factors for the development of NMS include higher medication doses, recent or rapid dose escalation, and parenteral medication administration [42].

**25**

of SS [45, 46].

*Evaluation and Treatment of Elevated Temperature in the Emergency Department*

rigidity

Serotonin syndrome Delirium, hyperthermia, tachycardia,

Salicylate toxicity Delirium, hyperthermia, tachycardia,

Thyroid storm Tachycardia, hyperthermia, agitation,

manifestations

Non-exertional heat stroke Fever, tachycardia, neurologic

*Hyperthermic sepsis mimics, their presentation, and their management.*

Anticholinergic toxicity Delirium, tachycardia, dilated

Malignant hyperthermia Hyperthermia, tachycardia,

**Condition Presentation Management**

hyperreflexia/clonus.

hypercarbia, muscle rigidity in the setting of volatile anesthetic or depolarizing muscle relaxants

hyperpnea, gastrointestinal irritation, tinnitus, triple acid–base disturbance

nonreactive pupils, urinary retention,

Delirium, tachycardia, hyperthermia, hypertension, dilated reactive pupils

lid-lag, ophthalmopathy, hand tremor.

anhidrotic hyperthermia

Delirium, hyperthermia, tachycardia,

Supportive, dantrolene sodium, bromocriptine

Supportive, consider cyproheptadine

Sodium bicarbonate

Supportive

steroids

cooling

Benzodiazepines

Beta-blocker, thionamide,

Evaporative and convective

Dantrolene sodium, cooling measures, treatment of hyperkalemia

The highest risk of NMS is within two weeks of medication initiation but this syndrome develop at any time during the treatment timeline [44]. A review of the patient's medications is typically needed to make the diagnosis. The cornerstone of management of NMS is supportive, with discontinuation of the suspected offending agent, support of the cardiopulmonary system, maintenance of normothermia and euvolemia, and prevention of complications including deep venous thrombosis, acute renal failure, and cardiac dysrhythmias [42–44]. In cases of severe muscle rigidity not responding to supportive treatment, intravenous dantrolene sodium or

SS is a syndrome of altered mentation, neuromuscular abnormalities, and autonomic hyperactivity caused by excess serotonin levels [45]. The most commonly implicated medications in SS include linezolid, fentanyl, and selective serotonin reuptake inhibitor (SSRIs) [46]. The neuromuscular abnormalities associated with SS can include hyperreflexia, clonus, or muscle rigidity, and, as with NMS, these may be severe enough to which may lead to rhabdomyolysis [45, 46]. SS is a clinical diagnosis based on patient presentation, and there is no laboratory test or imaging study to confirm the diagnosis [45]. The Hunter criteria for serotonin syndrome is one outline the clinical criteria needed to make the diagnosis [47]. Like NMS, management of SS is primarily supportive. If this is insufficient or ineffective, use of cyproheptadine can be used under the consultation of a toxicologist [45]. If neuromuscular paralysis is need to control neuromuscular rigidity or facilitate intubation, only nondepolarizing agents should be used, as depolarizing agents may exacerbate the hyperkalemia precipitated by the neuromuscular abnormalities

oral bromocriptine mesylate should be considered [44].

**3.2 Serotonin syndrome (SS)**

*DOI: http://dx.doi.org/10.5772/intechopen.94899*

Neuroleptic malignant

Sympathomimetic toxicity or withdrawal from sympathetic

antagonists

**Table 3.**

syndrome

*Evaluation and Treatment of Elevated Temperature in the Emergency Department DOI: http://dx.doi.org/10.5772/intechopen.94899*

