Febrile Syndrome: Causes, Symptoms, and Management
Febrile syndrome is characterized by an abnormal elevation of body temperature, typically above 36.9°C (axillary) or 37.2°C (oral), due to a pathological condition. Fever is confirmed by a thermometer; however, in its absence, touching the patient’s back or chest with the back of the hand can indicate fever.
Key Physiological Aspects
- Hypothalamic Thermoregulation: The body’s temperature regulation center is located in the hypothalamus.
- Pyrogens: Endogenous pyrogens (e.g., cytokines) or exogenous products trigger fever. Nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin inhibit this effect, acting as antipyretics.
- Antidiuretic Hormone: Acts as an endogenous antipyretic, preventing excessive temperature increases.
Signs and Symptoms
- Signs:
- Flushed and sweaty appearance (initially dry, then wet and red skin)
- Tachycardia (rapid heart rate)
- Tachypnea (rapid breathing)
- Initially cool skin, followed by shivering and piloerection
- Decreased systolic blood pressure
- Systolic ejection murmur
- Scanty, dark urine with possible albuminuria
- Symptoms:
- Chills
- Sweating and hyperhidrosis
- Delirium
- Seizures
- Cold sores
- Malaise, headache, drowsiness, arthromyalgia (joint and muscle pain)
- Thirst
- Anorexia
Fever Intensity
- Mild (Low-grade fever): Below 38°C
- Moderate: 38-40°C
- Intense (Hyperpyrexia): Above 40°C
- Hypothermia: Below 35°C
Effects of Fever
- Metabolism: Increases by approximately 15%.
- Cardiovascular: Increased cardiac output, leading to tachycardia (10-15 beats/min increase).
- Respiratory: Increased respiratory rate (tachypnea) by 4-5 breaths/min.
- Renal: Scanty and concentrated urine with proteinuria due to renal hemodynamic changes.
- Nervous System: Seizures may occur due to cerebral cortex dysfunction.
Important Considerations
- The severity of the illness is not always directly related to the magnitude of the fever.
- Children generally have a greater fever response than the elderly.
- Prolonged high fever can lead to coma and death.
- Distinguish fever from hyperthermia (an increase in body temperature due to environmental factors).
- Fever tends to be higher in the afternoon. An inverted pattern (higher in the morning) may suggest interference with antipyretics (factitious fever).
Onset and Defervescence
- Onset:
- Sudden (e.g., pneumococcal pneumonia)
- Insidious (e.g., tuberculosis, typhoid fever)
- Defervescence (Fever Reduction):
- Sudden with sweating (crisis)
- Insidious (lysis)
Fever Patterns
- Continuous Fever
- Undulant Fever
- Irregular Fever
- Relapsing Fever: Recurrence of fever after a period of convalescence, caused by the *same* organism.
- Reinfection: Recurrence of fever caused by a *different* organism.
Etiology (Causes) of Fever
- Infectious:
- Bacterial
- Viral
- Parasitic
- Rickettsial
- Chlamydial
- Fungal
- Non-Infectious:
- Neoplasms (e.g., lung or pancreatic cancer, lymphomas, leukemias)
- Infarction (cardiac, pulmonary, cerebral)
- Immunologic disorders
- Drug-induced fever
- Hemolysis (hemolytic crisis)
- Acute metabolic disorders (e.g., gout, thyroid crisis)
- Atrial myxoma
- Trauma
Characteristics of infectious origin: Sudden onset, temperature above 39°C, malaise, polyalgia, headache, photophobia, and elevated white blood cell count.
Significance of Fever
Fever is a good indicator of organic disease. It is useful for determining the severity of the illness, monitoring disease progression, and evaluating the effects of treatment. However, fever has deleterious consequences, including increased metabolism, water and salt loss through sweating, and increased cardiac workload. It also serves a defensive function, potentially improving survival.
Treatment
Treatment should be both etiological (addressing the underlying cause) and symptomatic (managing the symptoms).