The Case
A 24-year-old man sits on the floor after his first high-intensity workout in months, his thighs so swollen that standing makes him grimace. His urine in the specimen cup is the color of black tea, while his pulse is fast and his mouth is dry. He says his muscles are “tight,” but his abdomen is soft and he is speaking normally. The creatine kinase result is pending, and the fluid strategy has not yet begun.
Before You Read
- Which history and laboratory pattern should make rhabdomyolysis likely?
- Who needs aggressive fluid therapy and who is at risk from indiscriminate fluids?
- What complications must be screened for immediately?
Why It Matters
Rhabdomyolysis releases myoglobin, potassium, phosphate, and intracellular enzymes, potentially causing dysrhythmia, acute kidney injury, and compartment syndrome. Early recognition is more reliable than waiting for the classic triad, which is uncommon.
When to Think of It
Suspect rhabdomyolysis with muscle pain, weakness, swelling, dark urine, or unexplained AKI after crush injury, extreme exertion, seizure, hyperthermia, prolonged immobilization, ischemia, infection, toxins, or medications. The diagnostic anchor is CK elevation, typically more than five times the upper limit of normal, with serial testing because CK may peak 1–3 days after injury. Urine dipstick positive for blood with few or no red cells suggests myoglobin, but a negative result does not exclude disease.
Sick or Not Sick
The key fork is
complication burden and volume tolerance: dysrhythmia or hyperkalemia, shock, oliguria/anuria,
pulmonary edema, severe acidosis, compartment syndrome, or rapidly rising CK requires monitored care and possible ICU/nephrology involvement. CK alone does not determine disposition; renal function, potassium, urine output, cause, and comorbidities do.
The First Fifteen Minutes
- Place on cardiac monitoring; obtain IV access, ECG, glucose, CBC, CMP, calcium, phosphorus, magnesium, CK, urinalysis, and pregnancy testing when relevant.
- If hypovolemic or at risk for AKI and not volume overloaded: begin lactated Ringer’s or 0.9% saline 1 L IV, then 200–500 mL/hour, titrated to urine output approximately 1–3 mL/kg/hour; fluids dilute nephrotoxins and preserve renal perfusion. Check local protocol when CK is extreme or cardiac/renal disease limits volume.
- If potassium is ≥6.0 mEq/L, rapidly rising, or with ECG changes: calcium gluconate 10% 10 mL IV over 5–10 minutes, because it stabilizes the cardiac membrane but does not lower potassium.
- For significant hyperkalemia with ECG changes or marked elevation: regular insulin 10 units IV plus dextrose 25 g IV; insulin shifts potassium intracellularly, while dextrose prevents hypoglycemia.
- If severe hyperkalemia with acidemia or as a bridge: albuterol 10–20 mg nebulized; it promotes intracellular potassium shift. Do not give bicarbonate routinely for rhabdomyolysis alone.
- Treat hyperthermia with active external cooling and benzodiazepines for agitation/seizures: lorazepam 2–4 mg IV, repeated cautiously; dosing varies with age and respiratory status.
Definitive Care & Disposition
Identify and stop the cause: remove offending drugs, treat seizures or hyperthermia, address ischemia, and evaluate for compartment syndrome. Trend CK, potassium, calcium, phosphate, bicarbonate, creatinine, and urine output. Admit patients with AKI, electrolyte abnormalities, oliguria, significant muscle injury, unreliable follow-up, or ongoing cause; selected mild cases with normal renal function, normal electrolytes, improving symptoms, reliable hydration, and follow-up may be discharged after observation. Dialysis is for standard indications—refractory hyperkalemia, severe acidosis, pulmonary edema, or uremic complications—not CK level alone.
How This One Kills
The lethal miss is focusing on the dark urine while overlooking evolving hyperkalemia or compartment syndrome. A normal initial creatinine does not protect against delayed AKI.
The Atypical Presentation
Patients may have painless CK elevation, isolated AKI, or no visible pigmenturia. Older adults, people with neuropathy, and patients found down may not report muscle pain. In a patient with unexplained creatinine elevation, hyperkalemia, or a blood-positive/RBC-negative urine dipstick, ask directly about exertion, seizures, immobilization, heat, medications, and substance exposure.
Back to Our Patient
Back to the 24-year-old: severe exertional muscle pain, tea-colored urine, dehydration, and a likely blood-positive/RBC-negative urinalysis make exertional rhabdomyolysis the leading diagnosis. He is currently hemodynamically stable, but he requires ECG, electrolytes, CK, creatinine, and serial urine-output assessment before disposition. He receives an initial liter of crystalloid followed by goal-directed fluids; no bicarbonate or mannitol is added routinely. His CK is markedly elevated, potassium is normal, creatinine is normal, urine output improves, and repeat labs remain stable, so after observation and reliable follow-up he is discharged with strict hydration, no strenuous exercise, repeat laboratory testing, and return precautions—while admission would be appropriate if potassium, renal function, or urine output worsened.
Patient Presentation to Attending
“This is a 24-year-old man with severe bilateral thigh pain and tea-colored urine after an unusually intense workout, concerning for exertional rhabdomyolysis. He has dry mucous membranes and tachycardia but is alert, normothermic, without chest pain, dyspnea, focal neurologic deficit, or a tense compartment. I’m placing him on cardiac monitoring and sending CK, renal function, electrolytes, urinalysis, calcium, phosphorus, and magnesium. I’ll begin goal-directed crystalloid, monitor urine output and serial potassium and creatinine, and evaluate him urgently if compartment findings develop. If labs remain reassuring and he maintains urine output with reliable follow-up, he may be discharged; otherwise he needs admission and possible nephrology consultation.”
Study Directive
- Memorize the hyperkalemia sequence: ECG → calcium for toxicity → insulin/dextrose → adjunct shifts → definitive removal.
- Work three cases using urine output, potassium, creatinine, and volume status to choose disposition.
- Review your institution’s rhabdomyolysis fluid protocol and write the target urine-output range.
- Practice identifying causes from a medication, exertion, seizure, and immobilization history.