Hyperthermia in a Patient on Polypharmacy

Case Study

A rapid response event was initiated by the bedside nurse for a patient who developed severe hyperthermia. Upon the arrival of the rapid response team (RRT), the patient was noted to be a 45-year-old male admitted to the hospital for severe depression. The bedside nurse informed the RRT that his temperature had been normal on morning vital signs. The patient had reported a racing heart to the nurse, who checked his vitals and found him to have elevated temperature. A review of his chart showed that he was taking sertraline for depressive disorder. Buspirone had been added to the patient’s regimen that morning. He had also received his usual dose of trazodone the evening before, which he was taking for insomnia. The patient denied taking any illicit substances. He was not on any other prescription or over-the-counter medications or supplements.

Vital Signs

Temperature: 105 °F, axillary
Blood Pressure: 180/90 mmHg
Heart Rate: 102 beats per min (bpm), sinus tachycardia on the monitor
Respiratory Rate: 22 breaths per min
Pulse Oximetry: 98% saturation on room air

Focused Physical Examination

A quick exam revealed a middle-aged male, awake and alert, and answering questions. His face was flushed, and there was visible perspiration on his forehead. He appeared agitated. Visual tracking was intact without evidence of nystagmus. His cranial nerve exam was unremarkable. There was evidence of rigidity with passive movement of his extremities, and his patellar reflexes were noted to be 3+ bilaterally. A cardiac exam revealed tachycardia without evidence of murmurs. His lung exam was unremarkable, and his abdominal examination revealed hyperactive bowel sounds.

Interventions

A cardiac monitor and pacer pads were attached to the patient immediately. Blood sample for stat laboratory tests was drawn, which included a complete blood count (CBC), comprehensive metabolic panel (CMP), creatine phosphokinase (CPK), lactate level, and blood cultures. A urine drug screen was also ordered. Then, 1 g of intravenous acetaminophen was administered immediately, which had no effect on the patient’s temperature. Ice packs were placed along his neck, axilla, and groin. The patient’s labs were later reported and showed elevated CPK level, elevated lactate level, and mild acute renal insufficiency. With relevant history and laboratory examination, a presumptive diagnosis of serotonin syndrome was made. Intravenous fluids were started, and the patient was immediately given 2 mg of IV lorazepam to induce mild sedation and decrease muscle activity. The orders for the patient’s sertraline, buspirone, and trazodone were discontinued, and a consult was placed for psychiatry to evaluate the patient’s medication regimen. The patient was transferred to the intensive care unit (ICU) for further management and possible need of further sedation, neuromuscular blockage, and mechanical ventilation.

Final Diagnosis

Hyperthermia secondary to serotonin syndrome.

Severe Hyperthermia

Hyperthermia is the elevation of core body temperature above 38.5°C or 101.3 °F. Severe hyperthermia is the elevation of core body temperature to greater than 40°C or 104 °F. The various mechanisms underlying the development of hyperthermia are discussed in Table 50.1 .

Table 50.1

Mechanisms of hyperthermia

Mechanism	Example
Increased environmental heat load	Heatwave Humidity
Increased heat production	Overexertion Thyroid storm Pheochromocytoma Malignant hyperthermia Neuroleptic malignant syndrome Serotonin syndrome Delirium tremens Illicit drugs such as MDMA Anticholinergic toxicity Hypothalamic dysfunction – hemorrhage or stroke
Decreased heat dissipation	Humidity Poor sweat production Anticholinergic toxicity

The underlying pathophysiology of hyperthermia is different from fever. Fever is mediated by the release of cytokines, whereas hyperthermia is mediated by a failure of thermoregulation. Clinical differences between fever and hyperthermia are discussed in Table 50.2 .

Table 50.2

Clinical comparison of fever and hyperthermia

Fever	Hyperthermia
Temp generally lower than 104 °F	Temp higher than 104 °F
Improves with acetaminophen	Antipyretics have no effect
The patient may have rigors, no changes in muscle tone or reflexes	The patient may exhibit rigidity or clonus if hyperthermia is caused by medication side effect