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FEVER - Exam-Oriented Notes

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1. DEFINITION

One-liner: Rectal > oral > axillary (in terms of accuracy and temperature reading).

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2. DIURNAL VARIATION (One-liner Q)

• Lowest: Midnight to 6 AM
• Highest: 5-7 PM

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3. THERMOMETERS - KEY FACTS

Exam tip: Forehead strip = NOT recommended. Infrared = closely approximates rectal.

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4. ETIOPATHOGENESIS

All insults → Production of endogenous pyrogens (IL-1, IL-6, TNF-α, IFN-β, IFN-γ, Prostaglandin E2) → Alter temperature set point in anterior hypothalamus → Elevation in body temperature

• Interleukin-1 (IL-1)
• Interleukin-6 (IL-6)
• TNF-α
• Interferon-β, Interferon-γ
• Prostaglandin E2 (lipid mediator)

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5. FEVER vs. HEAT ILLNESS (MUST KNOW DISTINCTION)

• Hyperthyroidism
• Anhidrotic ectodermal dysplasia
• Drugs: Anticholinergics, Phenothiazines
• Heat stroke
• Malignant hyperthermia

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6. ADVERSE EFFECTS OF FEVER (Exam favorite)

• Paradoxical suppression of immune response
• Increased insensible water losses
• Cardiopulmonary stress
• Triggering febrile seizures in predisposed patients

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7. WHEN TO PRIORITIZE FEVER REDUCTION

1. Past/family history of febrile seizures
2. Critically ill patients
3. Cardiorespiratory failure
4. Disturbed fluid and electrolyte balance
5. Temperature >40°C (104°F)

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8. ANTIPYRETICS - HIGH-YIELD DRUG TABLE

• Aspirin - adverse effects
• Nimesulide - adverse effects
• Mefenamic acid - adverse effects

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9. FEVER WITHOUT FOCUS (FWF) - AGE-BASED APPROACH

A. Neonates (<1 month)

• High risk of serious bacterial infection (SBI)
• May look well and still have SBI
• Management:
  • Basic evaluation: Blood counts + CRP
  • Send cultures
  • If septic screen positive: Lumbar puncture → CSF examination → IV antibiotics
  • If septic screen negative: Observe + repeat screen at 6-12 hours
  • Continue observation till afebrile and culture reports available

B. Infants 1-3 Months

• Risk of SBI: ~10% (bacteremia risk: 2-3%)
• May look well and still have bacterial disease
• Toxic/ill-appearing: Manage same as <1 month
• Well-looking infant: Complete sepsis evaluation:
  • Leukocyte + platelet counts
  • Band cell count
  • C-reactive protein
  • Urinalysis + urine culture
  • Blood culture
  • Smear for malarial parasite (if indicated)
  • Chest X-ray
  • CSF examination (if no other focus found)
• Negative screen criteria (can observe at home):
  • WBC <15,000/cu mm
  • Band count <20%
  • CRP negative
  • Urine WBCs <10/HPF
  • Reliable caretakers + agree to reassessment at 24 and 48 hours

C. Children 3-36 Months

• Risk of SBI: ~5%
• Toxic child: Hospitalize + evaluate + treat
• Non-toxic, fever <39°C: Observe only
• Non-toxic, fever >39°C:
  • Do leukocyte count + malarial parasite smear
  • WBC >15,000/cu mm → Blood culture + IV ceftriaxone (inpatient or outpatient)
  • WBC <5000/cu mm → Suspect viral infections, dengue, enteric fever

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10. FEVER OF UNKNOWN ORIGIN (FUO)

Definition Clue:

History Points to Cover:

• Duration and pattern of fever (distinguish from recurrent fever)
• Symptoms referable to all organ systems + weight loss
• History of recurrent infections, oral thrush
• Joint pain, rash, photosensitivity
• Contact with tuberculosis and animals (brucellosis)
• Travel to endemic zones (kala-azar, rickettsia)
• Drug history - especially anticholinergics (drug fever)

Physical Examination:

• Document fever; assess general activity, nutrition, vitals
• Head-to-toe exam after removing all clothes
• Repeat examination daily (new findings may emerge)
• Keep Kawasaki disease in mind - diagnosis before Day 10 of fever is critical to prevent coronary complications

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11. FUO - INVESTIGATIONS (TWO-TIER APPROACH)

First-Line (All patients):

1. Complete blood counts + peripheral smear
2. Malarial parasite
3. C-reactive protein + ESR
4. Blood culture
5. Widal test
6. Chest X-ray
7. Tuberculin test
8. Urinalysis + culture
9. Liver function tests + serum creatinine
10. Abdominal ultrasound

Second-Line (Based on clinical clues):

1. HIV ELISA
2. Contrast-enhanced CT chest and abdomen
3. CT of paranasal sinuses
4. 2D echocardiogram
5. Complement levels
6. ANA + Rheumatoid factor
7. Bone marrow histology + cultures (if indicated)
8. Tissue biopsies
9. Brucella serology + EBV serology
10. Hepatitis B surface antigen

Limited value tests (Exam trap): Quantiferon Gold + serology for M. tuberculosis

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12. FUO MANAGEMENT FLOWCHART

Diagnosis established → Appropriate treatment

No diagnosis → Reassess clinically + second-line investigations
                ↓
         Consider IV Ceftriaxone empirically
         (Enteric fever is an important cause of FUO in India)
                ↓
         If still no diagnosis after exhaustive workup + sick patient
                ↓
         Empirical ATT (4 drugs × 4 weeks)
                ↓
         Empirical steroids → AVOIDED

Key exam facts:

• Lymphoma, Systemic-onset JRA may not surface immediately - periodic reassessment needed
• Some FUO cases self-resolve over time
• Empirical steroids should be AVOIDED

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QUICK REVISION BOX - One-liners

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Source: Ghai's Essential Pediatrics, Chapter 11 - Infections and Infestations (Tanu Singhal, Rakesh Lodha, Sushil K Kabra), pp. 205-208