What is the role of lab studies in the diagnosis of electrical injuries?

Updated: Mar 09, 2020
  • Author: Tracy A Cushing, MD, MPH, FACEP, FAWM; Chief Editor: Joe Alcock, MD, MS  more...
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In all patients with more than a trivial electrical injury and/or exposure, the following tests should be considered:

  • CBC count: Obtain values for hemoglobin, hematocrit, and white blood cell count.

  • Electrolytes: Assess sodium, potassium, chloride, carbon dioxide, blood urea nitrogen, and glucose.

  • Creatinine: There is a high risk of rhabdomyolysis/myoglobinuria in electrical injuries; mortality in one study was 59% for patients with acute renal failure. [31]

  • Urinalysis: Obtain values for specific gravity, pH, hematuria, and urine myoglobin if the urinalysis is positive for hemoglobin.

  • Serum myoglobin: If urine is positive for myoglobin, a serum level should be obtained.

  • Arterial blood gas: This is obtained for patients needing ventilatory support or those with severe rhabdomyolysis who require urine alkalinization therapy.

  • Creatine kinase (CK) levels: This level may be extremely elevated in patients with massive muscle damage from high-voltage injuries. Normal CK values published by the laboratory may be low for typical construction and electrical workers whose vocation involves heavy exercise. Some evidence suggests that initial CK levels may help predict which patients could benefit from early fasciotomy to prevent subsequent amputations. [10]  CK-MB subfractions are also often elevated in electrical injuries, but their significance in the setting of electrical injuries is not known. [3] CK-MB fractions and troponin should be checked if the current pathway involved the chest/thorax, if the patient has any signs of ischemia or arrhythmia on ECG, or if the patient has specific complaints of chest pain. One retrospective review created a decision rule for clinical identification of patients likely to have rhabdomyolysis. [32] Multivariate modeling revealed that high-voltage exposure, prehospital cardiac arrest, full-thickness burns, and compartment syndrome were associated with myoglobinuria. Defining "positive" as two or more of these findings has a sensitivity of 96% and negative predictive value of 99%. Initial CK and myoglobin levels correlate with burn size, ventilator days, hospital length of stay, need for surgical intervention, sepsis, and mortality. [33]

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