Rhabdomyolysis
Background
- Muscle necrosis and release of intracellular muscle constituents into the circulation
- Recurrent episodes suggests inherited metabolic disorder
- Alcohol and drugs play a role in up to 80% of cases
Etiology
- Trauma or muscle compression
- Crush Syndrome
- Immobilization
- Compartment Syndrome
- Nontraumatic Exertional
- Exercise + hot weather
- Exercise + sickle cell
- Exercise + Hypokalemia
- Hyperkinetic states
- Seizure
- DTs
- Stimulant overdose
- Malignant Hyperthermia
- Neuroleptic malignant syndrome
- Nontraumatic Nonexertional
- Drugs and toxins
- Coma induced by sedatives
- Alcohol
- Coma-induced muscle compression
- Direct toxic effect
- Nutritional compromise increases risk (hypoK, hypoMg, HypoPhos)
- Statins
- Colchicine
- CO Poisoning
- Infection
- Viral myositis - Influenza, Coxsackie, EBV, HSV, HIV, CMV
- Bacterial pyomyositis
- Septicemia
- Endocrine
- Inflammatory myopathies
- Moderate CK elevations only (rhabdo only described in case reports)
- Miscellaneous
- Status Asthmaticus
- TSS
- Mushroom ingestion
- Drugs and toxins
DDx
Clinical Features
- Myalgia, stiffness, weakness, malaise, low-grade fever, dark urine
- Musculoskeletal symptoms may be present in only half of cases
- N/V, abd pain, tachycardia in severe cases
- Mental status changes secondary to urea-induced encephalopathy
Work-up
- Total CK
- UA
- CBC
- Chemistry, including Mag, Phos
- Uric acid
- LFTs
- DIC panel
- Coags, FSP, fibrinogen
Diagnosis
- Total CK
- Most consider rhabdo if 5x or greater increase above upper limit of normal (~2000)
- Serum CK begins to rise 2-12hr after injury, peaks w/in 24-72hr
- Degree of CK elevation correlates w/ muscle injury, but NOT renal failure
- CK-MB
- May be normal or mildly elevated (<5% of total)
- Uric Acid - elevates before CK
- Myoglobinuria
- UA = +blood, no RBCs (Sn ~80%)
- Myoglobin is cleared w/in 1-6hr (often see elevated CK with no myoglobinuria)
- Acute renal failure
- Creatinine increase
- Electrolyte abnormalities
- Hyperkalemia
- Hyperphosphatemia
- Hypocalcemia
- Hyperuricemia
Management
- Aggressive IVF
- Start with NS 1-2 L/hr
- Once diuresis occurs maintain urine output of 200-300 mL/hr
- Frequently need ~10 L/day
- Trend:
- Volume status
- Urine pH
- Chemistry
- CK
- Calcium, phosphorus
- Bicarbonate
- Controversial; no RCT to date have demonstrated benefit
- Consider if CK >5000, severe muscle injury (crush injury), rising CK AND urine pH <6.5
- Contraindications:
- Severe hypocalcemia
- Arterial pH > 7.50
- Serum bicarbonate > 30 meq/L
- Mix 150 mL [3 amps] of 8.4% sodium bicarbonate w/ 1 L D5W
- Infuse at 200 mL/hour; rate is adjusted to achieve urine pH of >6.5
- Arterial pH and serum calcium should be monitored q2hr
- Discontinue if:
- Urine pH does not rise above 6.5 after 3-4hr
- Pt develops symptomatic hypocalcemia
- Arterial pH > 7.5
- Serum bicarbonate >30 meq/L
- Mannitol
- Controversial; no RCT to date has demonstrated benefit
- Mannitol administration can worsen dehydration and oliguria, cause hyperkalemia
- Consider in pts w/marked elevations in CK (>30K)
- Contraindicated if urinary flow is inadequate (<20 mL/hr)
- Add 50 mL of 20% mannitol to each liter of fluid; give at rate of 5g/hr
- Must check plasma osmolaity and plasma osmolal gap q4-6hr
- Discontinue if osmolal gap > 55 mosmol/kg
- Intubation/RSI
- Use Rocuronium
Disposition
- Discharge if:
- Exertional rhabdo
- Otherwise healthy
- No comorbidities (heat stress, dehydration, trauma)
- Downtrending total CK
- Consider admission for CK >30,000
- Otherwise admit to monitored bed
Complications
- Acute Renal Failure
- Neither presence of myoglobinuria nor degree of CK rise is predictive of ARF
- Rare in exertional rhabdo w/o presence of dehydration, heat stress, trauma
- Most commonly oliguric
- Hyperkalemia
- Renal function, not release of K+, is most important determinant
- Treat aggressively; insulin may be ineffective; may require dialysis
- Hypocalcemia (initial phase)
- Treat only if symptomatic or severely hyperkalemic (often have rebound hypercalcemia)
- Hypercalcemia (recovery phase)
- Hyperphosphatemia
- Treat cautiously (treatment may worsen calcium precipitation in muscle)
- Consider oral phosphate binders when level >7
- DIC
- Usually resolves spontaneously w/in several days
- Compartment Syndrome
- Peripheral nerve injury
- Usually resolves w/in few days-weeks
See Also
Source
- Tintinalli
- UpToDate