Rhabdomyolysis
Background
- Breakdown of skeletal muscle releasing intracellular contents into the circulation
- Key toxins: myoglobin (nephrotoxic), creatine kinase (CK), potassium, phosphate, uric acid
- Acute kidney injury (AKI) occurs in 15-40% of cases[1]
- Overall mortality ~5%; higher with AKI, DIC, or compartment syndrome
Etiology
- Trauma / Crush injury (most common worldwide)
- Exertional (exercise, seizures, agitation, status epilepticus)
- Drug/toxin-induced
- Statins (especially with interacting drugs)
- Cocaine, amphetamines, MDMA, alcohol
- NMS, Serotonin syndrome, Malignant hyperthermia
- Prolonged immobilization (found down, intraoperative)
- Hypokalemia, Hypophosphatemia, Hyponatremia
- Heat stroke
- Infections (influenza, COVID-19, Legionella)
- Hypothermia, electrical injuries
Clinical Features
- Classic triad: myalgias, weakness, dark urine (tea/cola-colored)
- Full triad present in <10% of cases
- Muscle tenderness, swelling, and stiffness
- May be asymptomatic with only lab abnormalities
- Complications:
- Hyperkalemia (can cause cardiac dysrhythmias) — life-threatening
- Acute kidney injury (oliguria, anuria)
- Compartment syndrome
- DIC
- Hypocalcemia (early), hypercalcemia (recovery phase)
- Metabolic acidosis
Evaluation
- Creatine kinase (CK) — diagnostic marker
- CK >5x upper limit of normal (typically >1,000 U/L) diagnostic
- CK >5,000 U/L: significant risk of AKI
- Peak CK at 24-72 hours; monitor serial levels
- Urinalysis: urine dipstick positive for "blood" but no RBCs on microscopy (myoglobinuria)
- BMP: potassium (may be severely elevated), creatinine, BUN, calcium, phosphate, bicarbonate
- CBC, LDH, uric acid, coagulation studies
- ECG — evaluate for hyperkalemia changes (peaked T waves, wide QRS)
- Consider compartment pressures if clinical concern
Management
Aggressive IV Fluid Resuscitation
- Cornerstone of treatment
- Normal saline at 200-300 mL/hr (or 1-2 L/hr initially if severely hypovolemic)[2]
- Target urine output 200-300 mL/hr until CK trending down and urine clears
- Monitor for fluid overload, especially in elderly and those with cardiac/renal disease
- Bicarbonate drip (150 mEq NaHCO3 in 1 L D5W) may be considered to alkalinize urine (target urine pH >6.5) — evidence is limited
Treat Hyperkalemia
- See Hyperkalemia for detailed management
- Calcium gluconate 10% 10 mL IV for cardiac membrane stabilization if ECG changes
- Insulin 10 units regular IV + D50W 50 mL IV
- Sodium bicarbonate, Albuterol nebulizer, Kayexalate or patiromer
- Emergent dialysis if refractory
Other
- Treat underlying cause (cool if hyperthermic, correct electrolytes)
- Avoid nephrotoxins (NSAIDs, contrast dye, aminoglycosides)
- Compartment syndrome: emergent fasciotomy if pressures >30 mmHg or clinical diagnosis
- Monitor for and treat DIC if present
Disposition
- Admit patients with:
- CK >5,000 U/L
- AKI (elevated creatinine)
- Hyperkalemia or other electrolyte derangements
- Ongoing symptoms or rising CK
- Discharge may be considered for mild rhabdomyolysis (CK <5,000, normal renal function, normal K) with close follow-up and oral hydration