Rhabdomyolysis: Expected Electrolyte Abnormalities
The correct answer is B) 2,4,5 (hyperkalemia, hyperphosphatemia, and hypocalcemia), as these are the classic electrolyte derangements seen in acute rhabdomyolysis with acute kidney injury.
Clinical Presentation Analysis
This patient presents with the classic triad of rhabdomyolysis:
- Muscle pain and extreme fatigue indicating muscle breakdown 1
- High-colored (dark) urine representing myoglobinuria 1, 2
- Acute kidney injury (creatinine 4.0 mg/dL) with hypotension (BP 80/60 mmHg) 1
Electrolyte Abnormalities in Acute Rhabdomyolysis
Hyperkalemia (Option 2) - PRESENT
Hyperkalemia is a hallmark finding in rhabdomyolysis due to massive release of intracellular potassium from damaged myocytes 3. This represents one of the most life-threatening complications requiring immediate recognition and treatment 1, 2. The combination of muscle destruction and acute kidney injury creates profound hyperkalemia that can cause cardiac arrhythmias 3.
Hyperphosphatemia (Option 4) - PRESENT
Phosphate is released in large quantities from injured muscle cells, leading to marked hyperphosphatemia in the acute phase 3. This occurs because phosphate is a major intracellular constituent that floods the circulation when the muscle membrane is disrupted 1. The hyperphosphatemia can worsen kidney injury through calcium-phosphate complex deposition in renal tissue 4.
Hypocalcemia (Option 5) - PRESENT
Hypocalcemia occurs during the oliguric phase of rhabdomyolysis-induced AKI 5. The mechanism involves calcium deposition in damaged muscle tissue as calcium-phosphate complexes, effectively sequestering calcium from the circulation 5, 3. This hypocalcemia is characteristic of the acute phase and can be severe 3.
Why Other Options Are Incorrect
Hypokalemia (Option 1) - ABSENT in Acute Phase
Hypokalemia does NOT occur in acute rhabdomyolysis. Instead, the opposite occurs with life-threatening hyperkalemia 3. Hypokalemia only develops later during recovery or with aggressive dialysis treatment 4.
Hypophosphatemia (Option 3) - ABSENT in Acute Phase
Hypophosphatemia does NOT occur acutely. The acute phase is characterized by hyperphosphatemia from muscle breakdown 3. Hypophosphatemia may develop later during recovery or with intensive kidney replacement therapy 4.
Hypercalcemia (Option 6) - ABSENT in Acute Phase
Hypercalcemia does NOT occur during the acute oliguric phase. While severe hypercalcemia can develop during the recovery/diuretic phase of AKI (as calcium is mobilized from muscle deposits), the acute presentation described in this case would show hypocalcemia 5.
Critical Management Considerations
Immediate priorities include:
- Aggressive fluid resuscitation to restore renal perfusion and increase urine flow 1
- Continuous cardiac monitoring for hyperkalemia-induced arrhythmias 4, 3
- Urgent treatment of hyperkalemia if severe (>6 mmol/L) with insulin/glucose, calcium, and potentially dialysis 4
- Close monitoring of all electrolytes given the potential for life-threatening derangements 4, 6
Common pitfall: Failing to recognize that the electrolyte pattern in acute rhabdomyolysis mimics tumor lysis syndrome (hyperkalemia, hyperphosphatemia, hypocalcemia) due to similar pathophysiology of massive cellular destruction 4, 3.