What are the causes of hyperthermia in a patient with a history of diabetes or cardiovascular disease, recently managed for hypothermia?

Causes of Hyperthermia

Hyperthermia in patients with diabetes or cardiovascular disease, particularly those recently managed for hypothermia, most commonly results from infection (94% of cases), but critical drug-induced syndromes, metabolic derangements, and rebound hyperthermia after therapeutic cooling must be immediately excluded. 1

Infection-Related Causes

• Bacterial infections are the predominant cause, accounting for the vast majority of hyperthermia cases, with pneumonia and urinary tract infections being most common in diabetic and cardiovascular patients 2
• Sepsis represents a life-threatening manifestation that requires immediate recognition and antimicrobial therapy 2
• Patients with diabetes are at increased risk due to impaired immune function and autonomic neuropathy that may mask typical fever responses 2, 3

Drug-Induced Hyperthermia Syndromes

Five major drug-induced syndromes must be considered, each requiring specific management:

• Neuroleptic malignant syndrome from antipsychotics or dopamine antagonists, presenting with muscle rigidity, altered mental status, and autonomic instability 4
• Serotonin syndrome from SSRIs, MAOIs, or other serotonergic agents, characterized by neuromuscular hyperactivity and autonomic dysfunction 4
• Anticholinergic poisoning causing hyperthermia with dry skin, mydriasis, urinary retention, and altered mental status 4
• Sympathomimetic poisoning from cocaine, amphetamines, or vasopressors (dobutamine, terbutaline), particularly relevant in cardiovascular patients 2, 4
• Malignant hyperthermia triggered by volatile anesthetics or succinylcholine during procedures, presenting with hypermetabolic crisis, muscle rigidity, and rapid temperature elevation 1, 5

Metabolic and Endocrine Causes

• Hyperglycemic crises (diabetic ketoacidosis or hyperosmolar hyperglycemic state) can present with hyperthermia despite the typical association with hypothermia as a poor prognostic sign 2, 6
• Hypoglycemia in long-standing diabetes can paradoxically cause marked hyperthermia as an excessive reaction to preceding hypothermia, presenting with nausea, vomiting, and impaired consciousness 7
• Thyroid storm should be considered in patients with known or undiagnosed thyroid disease 4

Rebound Hyperthermia After Therapeutic Hypothermia

This is a critical consideration in patients recently managed for hypothermia:

• Rebound hyperthermia following therapeutic temperature management is associated with worse neurological outcomes and increased mortality 2
• Occurs when rewarming is too rapid (>0.5°C per hour) or temperature control is discontinued abruptly 2
• Plasma electrolyte concentrations and metabolic rate change rapidly during rewarming, predisposing to temperature dysregulation 2

Cardiovascular-Specific Causes

• Myocardial infarction can precipitate hyperthermia as part of the inflammatory response 2
• Cerebrovascular accident (stroke) causes hyperthermia in approximately one-third of patients within the first hours after onset, associated with poor neurological outcomes 2
• Intradialytic hyperthermia in patients with cardiovascular disease on hemodialysis results from heat load from the extracorporeal system or increased metabolic rate with volume removal 2

Environmental and Iatrogenic Causes

• Heatstroke (classic or exertional) in patients with impaired thermoregulation due to diabetes, cardiovascular disease, or autonomic dysfunction 8
• Medications affecting thermoregulation: corticosteroids, thiazides, and sympathomimetic agents can precipitate hyperthermia, particularly in diabetic patients 2
• Increased dialysate temperature (>37-38°C) during hemodialysis in cardiovascular patients 2

Critical Pitfalls to Avoid

• Do not assume infection is the only cause despite its 94% prevalence—missing malignant hyperthermia or drug-induced syndromes can be fatal 1, 4
• Do not overlook hypoglycemia as a cause of hyperthermia in diabetic patients, as it presents paradoxically with marked temperature elevation 7
• Do not attribute hyperthermia solely to poor glycemic control—hyperglycemic crises typically present with hypothermia, and hyperthermia suggests infection or another complicating factor 2
• In patients recently cooled, always consider rebound hyperthermia and ensure slow, controlled rewarming at 0.25-0.5°C per hour 2

Diagnostic Approach

Obtain medication history immediately to identify potential drug-induced syndromes, focusing on recent additions of antipsychotics, antidepressants, anesthetics, or sympathomimetics 4

Assess for infection sources with physical examination targeting lungs (pneumonia), urinary tract, skin, and indwelling catheters, obtaining cultures before initiating antimicrobials 2

Check blood glucose immediately in all diabetic patients, as both hypoglycemia and hyperglycemia can present with hyperthermia 2, 7

Review recent temperature management in patients with cardiovascular disease or post-cardiac arrest, as rebound hyperthermia indicates inadequate rewarming protocols 2

Obtain baseline laboratories: electrolytes, creatine kinase (for rhabdomyolysis), arterial blood gases, renal function, hepatic function, and coagulation studies to identify metabolic complications 1