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Difficulty: HardPhysiological Adaptation

A nurse in the emergency department is evaluating a client who sustained deep partial-thickness burns over 45% of their total body surface area (TBSA) 4 hours ago. The client has not yet received adequate intravenous fluid resuscitation. Which of the following clinical findings represent expected pathophysiological adaptations during this emergent phase of the injury? Select all that apply.

  1. Hematocrit level of 56%Answer
  2. Serum potassium level of 6.1 mEq/LAnswer
  3. C
    Hourly urine output of 65 mL
  4. D
    Serum sodium level of 149 mEq/L
  5. E
    Arterial blood gas showing a pH of 7.48 and HCO3- of 28 mEq/L
  6. Mean arterial pressure (MAP) of 58 mm HgAnswer

Answer

The expected clinical findings are a hematocrit level of 56%, a serum potassium level of 6.1 mEq/L, and a mean arterial pressure (MAP) of 58 mm Hg.
In the emergent phase of a major burn injury (first 24 to 48 hours), a massive capillary leak occurs. This causes intravascular fluid to shift into the interstitial space, leading to hypovolemia (evidenced by a MAP of 58 mm Hg) and hemoconcentration (evidenced by an elevated hematocrit of 56%). Concurrently, the destruction of cells releases large amounts of intracellular potassium into the bloodstream, resulting in hyperkalemia (evidenced by a potassium level of 6.1 mEq/L).

Step-by-Step Solution

1
Analyze the time frame and clinical scenario.
The client is 4 hours post-burn (emergent phase) without adequate fluid resuscitation.
Identifying the phase of a burn injury is critical because fluid and electrolyte shifts vary significantly between the emergent and acute phases.
2
Evaluate the expected fluid shifts during the emergent phase.
Capillary permeability increases drastically, causing plasma to leak into the interstitial space. This leads to intravascular volume depletion (hypotension/decreased MAP) and hemoconcentration (elevated hematocrit).
This pathophysiological mechanism explains the primary hemodynamic changes and early signs of burn shock.
3
Evaluate the expected electrolyte shifts and renal responses.
Cellular destruction releases potassium (hyperkalemia), while sodium follows fluid into the interstitial space (hyponatremia). Decreased renal perfusion leads to oliguria.
Electrolyte imbalances must be anticipated to prevent life-threatening cardiac dysrhythmias and acute kidney injury.
4
Evaluate the expected acid-base balance.
Hypoperfusion causes anaerobic metabolism, leading to lactic acid production and metabolic acidosis, rather than alkalosis.
Understanding tissue perfusion status helps correctly interpret ABG findings in early shock.

Key Concept

During the emergent (resuscitative) phase of a major burn, increased capillary permeability leads to a massive shift of fluid and sodium into the interstitial space, accompanied by the release of intracellular potassium from destroyed tissue. This results in hypovolemia, hemoconcentration, hyperkalemia, hyponatremia, and metabolic acidosis.
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Physiological Adaptation

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