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 examination.
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 non-specific 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
Thyroid-stimulating hormone is low; elevated T3 and T4.
Malignant hyperthermia
SIGNS / SYMPTOMS
History of exposure to a potent inhalation anaesthetic or suxamethonium. Usually occurs in the intra-operative period.
INVESTIGATIONS
A therapeutic trial of dantrolene should be considered as soon as the diagnosis is suspected. Resolution of muscle rigidity and the hypermetabolic state with dantrolene confirms the diagnosis.
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.
Serotonin syndrome
SIGNS / SYMPTOMS
History of exposure to a serotonergic drug, overdose, or specific drug-drug interactions.
INVESTIGATIONS
Clinical diagnosis. Specific tests are not readily available.
Drug toxicity
SIGNS / SYMPTOMS
Medicine/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.
Sepsis
SIGNS / SYMPTOMS
Acute deterioration in a patient in whom there is clinical evidence or strong suspicion of infection.
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