In a 42-year-old man with a history of traumatic brain injury–related seizures, hypertension, and chronic alcoholism who presents post-ictal after a witnessed tonic-clonic seizure with elevated creatinine and abnormal urinalysis, what is the next step in his work-up?

Workup for Post-Ictal Patient with Elevated Creatinine and Abnormal Urinalysis

The next step in workup is to check serum creatine kinase (CK) to evaluate for rhabdomyolysis, as the combination of seizure activity, urinalysis showing 2+ blood with minimal RBCs (suggesting myoglobinuria), elevated creatinine, and proteinuria strongly indicates muscle breakdown requiring immediate assessment and aggressive management to prevent acute kidney injury. 1, 2, 3

Primary Diagnostic Priority: Rhabdomyolysis Assessment

• Serum creatine kinase (CK) is the confirmatory test for rhabdomyolysis, with diagnosis established when CK exceeds five times the upper limit of normal 1, 2
• The urinalysis findings are highly suggestive of myoglobinuria: 2+ blood on dipstick with only 3-5 RBCs on microscopy indicates the dipstick is detecting myoglobin rather than hemoglobin 4
• Seizures are a well-established cause of rhabdomyolysis, accounting for 2-5% of all acute renal failure cases in intensive care settings 1
• The elevated creatinine (1.6) in this context likely represents early acute kidney injury from myoglobin-induced nephrotoxicity 5, 3

Additional Laboratory Studies to Order Immediately

• Serum potassium, calcium, and phosphate to identify life-threatening electrolyte derangements that commonly accompany rhabdomyolysis 1, 2, 3
• Serum uric acid should be checked, as hyperuricemia after seizures may indicate severe muscle damage and is a risk factor for kidney dysfunction in rhabdomyolysis 5
• Liver function tests to assess for hepatic involvement, as severe rhabdomyolysis can cause liver injury 2
• Arterial or venous blood gas to evaluate for metabolic acidosis 3

Critical Management Considerations While Awaiting Results

• Aggressive intravenous fluid resuscitation is the cornerstone of treatment, with a goal urine output of 300 mL/hour to prevent acute renal failure 2, 3
• Normal saline is the appropriate initial fluid choice for volume resuscitation 3
• Bicarbonate-containing fluids and mannitol lack strong evidence for improved outcomes beyond aggressive crystalloid hydration alone 1, 2, 3
• Loop diuretics should only be considered after achieving euvolemia or hypervolemia, not as initial therapy 1

Important Clinical Pitfalls to Avoid

• Do not dismiss the urinalysis findings as simple hematuria - the discrepancy between heavy dipstick positivity for blood and minimal RBCs on microscopy is pathognomonic for myoglobinuria 4
• Hyperkalemia is a potentially life-threatening complication requiring immediate ECG and continuous cardiac monitoring 2, 3
• The presence of darkly pigmented granular casts in urine sediment, if present, would further confirm myoglobinuria 4
• Factors that worsen outcomes include hypovolemia (which this patient may have from inadequate oral intake), hyperthermia, and pre-existing electrolyte disorders 1

Monitoring and Disposition

• Early initiation of renal replacement therapy may be necessary if acute kidney injury progresses despite aggressive hydration 1
• Serial CK measurements should be obtained to track the trajectory of muscle breakdown 4
• Most patients with rhabdomyolysis require hospital admission for aggressive fluid management and monitoring 2
• The goal is to maintain high and alkaline diuresis to prevent progression to acute renal failure requiring dialysis 4