Differentials
Delirium
SIGNS / SYMPTOMS
Altered attention level.
Not typically associated with elevated core temperature, although patients with heat stroke may have delirium in addition to pyrexia.
INVESTIGATIONS
Diagnostic distinction is typically based on clinical exam.
Significant abnormalities from laboratory investigations are lacking.
Meningitis
SIGNS / SYMPTOMS
Headache, fever, nuchal rigidity, occasional central nervous system alteration.
INVESTIGATIONS
Lumbar puncture is generally abnormal in patients with meningitis.
Diabetic ketoacidosis
SIGNS / SYMPTOMS
Altered level of consciousness or alertness, hyperventilation, and a myriad of other nonspecific systemic symptoms.
INVESTIGATIONS
Plasma glucose is typically severely elevated in patients with diabetic ketoacidosis; ketones in urine.
Hyperthyroidism
SIGNS / SYMPTOMS
Common signs include tachycardia, exophthalmos, hyper-reflexia.
Symptoms are typically of more insidious onset in patients with hyperthyroidism.
INVESTIGATIONS
TSH is low; elevated T3 and T4.
Neuroleptic malignant syndrome
SIGNS / SYMPTOMS
Generally preceded by a typical event, such as receiving antipsychotic agents.
INVESTIGATIONS
Diagnosis is clinical; usually has an elevated creatine kinase.
Drug toxicity
SIGNS / SYMPTOMS
Medication/drug overdose may present with hyperthermia but not be associated with elevated ambient temperature or physical activity.
Often there is a history of drug use or of recent ingestion.
Drugs commonly associated include cocaine, phencyclidines, and salicylates.
INVESTIGATIONS
Blood assays positive for the ingested agent.
Delirium tremens
SIGNS / SYMPTOMS
May present with hyperthermia but not be associated with elevated ambient temperature or physical activity.
Typically associated with history of alcohol abuse without recent ingestion. Often there is a clinical history of prior withdrawal symptoms.
INVESTIGATIONS
LFTs may be elevated.
Exercise-associated hyponatremia
SIGNS / SYMPTOMS
Severe exercise-associated hyponatremia may present similarly to heat stroke, with altered mental status; milder symptoms may present similarly to heat exhaustion. Usually associated with excess hypotonic fluid intake.
INVESTIGATIONS
Plasma sodium is low.
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