What laboratory tests are recommended for burn patients?

Laboratory Tests for Burn Patients

For severe burn patients, obtain a complete blood count (CBC), comprehensive metabolic panel including electrolytes (sodium, potassium, chloride, magnesium, calcium), renal function tests (creatinine, BUN), liver function tests (AST, ALT, bilirubin), glucose, lactate, pH, and arterial blood gas analysis during initial assessment and the acute phase. 1

Initial Laboratory Evaluation (First 24-72 Hours)

Essential Tests at Presentation

• Complete Blood Count (CBC) with differential: Monitor for leukocytosis (predictor of transmural necrosis and poor outcomes), thrombocytopenia (associated with poor prognosis), and assess baseline hemoglobin 1

• Comprehensive Metabolic Panel:

  • Electrolytes: sodium, potassium, chloride, magnesium, calcium to detect hyponatremia, hypokalemia, hypocalcemia 1
  • Renal function: creatinine and blood urea nitrogen (BUN) to identify acute kidney injury 1, 2
  • Liver function: AST, ALT, bilirubin (elevated levels predict transmural necrosis and poor outcomes) 1

• Acid-Base Status:

  • pH and serum lactate (severe acidosis and high lactate predict transmural necrosis and mortality) 1, 3
  • Arterial blood gas analysis 1, 4

• Glucose: Monitor closely given profound insulin resistance and stress hyperglycemia in burn patients 1, 5, 3

• Inflammatory markers: C-reactive protein (CRP) and procalcitonin (elevated CRP >20 mg/L suggests complications) 1, 2

Additional Considerations

• β-HCG in women of childbearing age to rule out pregnancy 1

• Blood alcohol levels if intoxication suspected 1

• Hemoglobin A1c and urine ketones to investigate undetected diabetes mellitus 1

Monitoring During Acute Phase (Days 1-5)

Frequency of Testing

Laboratory tests should be individualized based on burn severity, clinical status, and response to resuscitation rather than following rigid protocols. 6 For severe burns (>25% TBSA), monitoring at each shift change is common practice, though studies show most routine tests yield normal results 6.

Key Parameters to Track

• Renal function: Serial creatinine measurements are critical, as serum creatinine ≥100 μmol/L during the shock stage is an independent risk factor for 90-day mortality 2

• Electrolytes: Multiple abnormalities can occur in the first two weeks, requiring frequent monitoring 4

• Lactate and bicarbonate: Declining lactate levels indicate improving perfusion; monitor bicarbonate and base excess for metabolic acidosis 3

• Glucose: Continuous monitoring to manage stress hyperglycemia and avoid excess carbohydrate-related complications 5, 3

• CBC: Persistent red blood cell loss (approximately 8% per day for about 10 days) may necessitate transfusion 4

Specialized Testing Based on Clinical Context

For Suspected Complications

• Blood cultures if patient is febrile or sepsis suspected 1

• Creatine kinase (CK) and CK-MB: Elevated in severe burns; continuous blood purification can help reduce these levels 3

• Cystatin C: Additional marker of renal function in severe burns 2

• Urinalysis: Assess for nephritis, monitor urine output (target 0.5-1 mL/kg/hour) 1

For Inhalation Injury

• Arterial blood gas analysis to confirm diagnosis and guide ventilatory management 4

• Carboxyhemoglobin levels if carbon monoxide exposure suspected 4

Micronutrient Monitoring

In major burn patients, copper levels should be measured whether or not receiving copper supplementation. 1 Additional micronutrient assessment includes:

• Copper status: Measure plasma copper simultaneously with CRP determination 1
• Selenium and zinc: Consider measurement given increased requirements 5
• Iron, magnesium: Monitor to support wound healing and immune function 5

Critical Pitfalls to Avoid

• Over-ordering laboratory tests: Studies show that in pediatric burn patients, only 2% of tests yielded unexpected critical values, and 6% of estimated blood volume was consumed by phlebotomy 6

• Ignoring early renal markers: Microalbuminuria and urinary malondialdehyde appear early (day 0-3) and predict acute renal failure development before creatinine rises 7

• Missing septicemia indicators: Burn size and septicemia are the strongest predictors of acute renal failure; monitor leukocytosis, CRP, and PCT closely 2, 7

• Failing to adjust for fluid resuscitation: Laboratory values must be interpreted in context of massive fluid shifts and hemodilution during the first 48-72 hours 3, 4

• Neglecting continuous monitoring: Use noninvasive monitors when possible to reduce phlebotomy-related blood loss while maintaining adequate surveillance 6