Rhabdomyolysis: workup and management
Rhabdomyolysis is muscle breakdown with CK usually >5× the upper limit (often >1000 U/L), myalgia and dark urine. The main dangers are AKI, hyperkalemia and compartment syndrome. Find the cause, give goal-directed crystalloid and monitor electrolytes closely.
Working diagnosis
Adult · US guidelines
Draft · awaiting physician review
01Orient
What's new in the evidence
- AAST 2022 consensus: goal-directed crystalloid (about 400 mL/h, range 200–1000) targeting urine output 1–3 mL/kg/h (up to 300 mL/h)
- No routine bicarbonate, mannitol or loop diuretics to prevent AKI
- Lactated Ringer's and saline are both acceptable
Differential diagnoses
- Trauma, crush, prolonged immobilization (fall, overdose)
- Exertional (extreme exercise, heat illness)
- Drugs and toxins: statins (with interacting drugs), cocaine, amphetamines, alcohol, neuroleptic malignant syndrome, serotonin syndrome (can't miss)
- Seizures, hyperthermia, sepsis
- Electrolyte disorders: hypokalemia, hypophosphatemia
- Inflammatory myositis, hypothyroidism, inherited metabolic myopathies (recurrent episodes)
02Assess
Risk scores and decision tools
- McMahon score (≥6 predicts dialysis or death)
- CK trend (peak at 24–72 hours)
- Compartment pressures if suspected compartment syndrome
Key history questions
- Time down after a fall, crush injury, recent intense exercise
- Drugs: statins, antipsychotics, stimulants, alcohol
- Seizures, heat exposure, infection
- Prior episodes, family history of muscle disease
- Urine color and output
Examination findings
- Muscle tenderness and swelling
- Tense compartments, pain on passive stretch (compartment syndrome)
- Hyperthermia, rigidity, clonus (NMS, serotonin syndrome)
- Volume status, pressure injuries
03Investigate
Initial investigations
- CK, BMP (potassium, creatinine), calcium, phosphate, uric acid
- Urinalysis: blood on dipstick without RBCs on microscopy
- ECG for hyperkalemia
- CBC, LFTs (AST rises with muscle injury), lactate
Advanced investigations
- Urine drug screen, TSH
- Compartment pressure measurement
- Genetic or metabolic testing and muscle biopsy for recurrent unexplained episodes
04Treat
Immediate management
- Treat hyperkalemia urgently
- Crystalloid about 400 mL/h (200–1000 mL/h), titrated to urine output 1–3 mL/kg/h
- Emergency fasciotomy for compartment syndrome
First-line treatment
- Stop culprit drugs; treat the cause (cooling, seizure control, NMS or serotonin syndrome treatment)
- Correct hypocalcemia only if symptomatic or hyperkalemic (risk of rebound hypercalcemia)
- Monitor for fluid overload, especially in oliguria or heart failure
Second-line treatment
- Kidney replacement therapy for refractory hyperkalemia, acidosis, fluid overload or uremia
- Bicarbonate only for severe metabolic acidosis, not routinely
Specialist referrals
- Nephrology for AKI
- Orthopedic or general surgery for compartment syndrome
- Toxicology if drug-related
05Disposition
Admission criteria
- CK >5000 U/L, AKI, electrolyte abnormality or ongoing cause
- Unable to drink adequately
Safe discharge criteria
- Mild exertional rhabdomyolysis with normal creatinine and potassium, falling CK, able to hydrate
Follow-up timing
- Repeat CK and creatinine in 2–3 days if discharged
Patient instructions
- Graded return to exercise; hydrate
- Avoid the culprit drug
Monitoring
- CK, potassium, creatinine every 6–12 hours initially
- Hourly urine output
Clinical pearls and pitfalls
- CK level correlates only loosely with AKI risk
- Statin myopathy risk rises with CYP3A4 inhibitors (clarithromycin, azoles) and gemfibrozil
RefGuidelines and landmark evidence
For education only. Typical adult starting points; confirm doses against renal function, allergies, interactions and your institution's protocols. Not a substitute for clinical judgment or senior review.