crush syndrome, rhabdomyolysis
Reading File
Finding Sources
Searching PubMed
"rhabdomyolysis" AND "acute kidney injury"
Reading File
Reading File
Finding Sources
Reading File
Reading File
Reading File
Reading File
Reading File
Reading File
I now have comprehensive information to provide a thorough response. Let me compile it.
Crush Syndrome & Rhabdomyolysis
Definition
Rhabdomyolysis is the dissolution and disintegration of striated (skeletal) muscle, releasing intracellular contents — myoglobin, CK, potassium, phosphorus, calcium, aldolase, LDH, organic acids — into the systemic circulation. It is an acute, potentially fatal syndrome.
Crush syndrome is a specific, severe form of traumatic rhabdomyolysis arising from reperfusion injury after prolonged muscle compression. First described in victims of the London Blitz, it is classically seen in earthquake, mining, and battlefield casualties.
Pathophysiology
Common Final Pathway
Regardless of cause, the terminal event is disruption of the Na⁺/K⁺-ATPase pump and calcium transport:
- Intracellular Ca²⁺ rises → activates phospholipase A2, proteases, and free oxygen radical production → muscle cell necrosis
Crush Syndrome Specifically
- Reperfusion injury — prolonged ischemia followed by rescue/extrication releases myoglobin and vasoactive mediators into circulation
- Fluid sequestration — damaged muscle sequesters litres of fluid → ↓ intravascular volume → renal vasoconstriction and ischemia
- Myoglobinuria → renal tubular obstruction and direct nephrotoxicity
AKI Mechanism (Three Pathways)
| Mechanism | Detail |
|---|---|
| Renal vasoconstriction | Hypovolemia + vasoactive mediators |
| Proximal tubular injury | Oxidant stress from heme-iron in myoglobin (Fe²⁺) |
| Intratubular obstruction | Myoglobin + uric acid precipitate in distal tubules (worsened by acidic urine) |
Macrophage extracellular traps activated by platelets have also been identified as pathogenic in myoglobin-induced AKI.
Causes
Traumatic / Compression
- Crush injury, earthquakes, building collapse
- Prolonged immobilization (coma, anesthesia, bariatric surgery)
- Limb compression from unconsciousness
Increased Exertion / Environment
- Strenuous exercise (especially eccentric/high-force contractions — strength training > aerobic exercise)
- Seizures, delirium tremens, dystonia, psychosis
- Heat stroke, neuroleptic malignant syndrome, malignant hyperthermia, hypothermia
Drugs & Toxins
- Statins (0–2.2 cases/1000 person-years; highest risk with cerivastatin; polypharmacy with cyclosporine or macrolides ↑ risk)
- Cocaine, heroin (~20% of cocaine overdoses), amphetamines, MDMA, PCP, ethanol
- Antipsychotics, propofol, colchicine, isoniazid, corticosteroids
Infections
- Viral: Influenza A/B, Coxsackievirus, EBV, CMV, HIV, HSV, SARS-CoV-2
- Bacterial: Streptococcus, Staphylococcus aureus, Legionella, Clostridium, Mycoplasma
Genetic / Metabolic
- Disorders of glycolysis/gluconeogenesis (e.g., McArdle disease — myophosphorylase, PYGM)
- Fatty acid oxidation disorders (CPT2, ACAD9)
- Mitochondrial disorders
- RyR1 mutations (ryanodine receptor — also links to malignant hyperthermia susceptibility)
- Electrolyte disorders: hypokalemia, hypophosphatemia, hypocalcemia, DKA
Clinical Features
Symptoms
- Classic triad: myalgias + weakness + dark/cola-colored urine (but muscle symptoms absent in ~50% of cases)
- Malaise, low-grade fever, nausea, vomiting, abdominal pain, tachycardia
- Mental status changes (urea-induced encephalopathy in severe cases)
Signs
- Swelling and tenderness of involved muscle groups (postural muscles of thighs, calves, lower back most common)
- Skin hemorrhagic discoloration (uncommon)
- Compartment syndrome — especially in lower leg, forearm, thigh (fascially enclosed groups): pain on passive stretch → sensory changes → loss of pulse (late)
Life-threatening Complications
| Complication | Mechanism |
|---|---|
| Acute kidney injury | See above; occurs in 13–67% of rhabdomyolysis cases; accounts for 5–10% of all AKI in the US |
| Hyperkalemia | Massive K⁺ release from necrotic muscle |
| Hypocalcemia (early) | Ca²⁺ influx/deposition into damaged muscle |
| Hypercalcemia (late) | Release of sequestered Ca²⁺ during recovery |
| Metabolic acidosis (anion-gap) | Organic acids released from necrotic muscle |
| Arrhythmias | Hyperkalemia + hypocalcemia + acidosis |
| DIC | Myocellular contents trigger coagulation cascade |
Diagnosis
Key Lab Markers
| Marker | Notes |
|---|---|
| Serum CK (CK-MM) | Most sensitive and reliable; peaks 2–5 days post-insult; >5× ULN consistent with rhabdomyolysis; >15,000–20,000 U/L associated with AKI |
| Urinary myoglobin | Most specific but clears rapidly — not always detected; urine dipstick positive for blood without RBCs on microscopy is a key clue |
| Pigmented granular casts | On urine microscopy |
| Serum K⁺, phosphate, Ca²⁺ | Monitor for electrolyte crises |
| Serum creatinine, BUN | Assess AKI |
| ABG | Anion-gap metabolic acidosis |
Important: CK levels >5× normal + appropriate clinical presentation = acceptable diagnostic threshold. Baseline CK is higher in African American males and young athletic men, so context matters. AKI risk is lower when CK < 20,000 U/L but can occur at ≥5,000 U/L when coexisting sepsis, acidosis, or volume depletion are present.
Management
1. Aggressive IV Fluid Resuscitation — the cornerstone
- Start before extrication in crush syndrome when possible
- Normal saline: 1,000–1,500 mL/h in adults
- Continue until myoglobin is no longer detectable in urine
- Target urine output: 200–300 mL/h
2. Mannitol-Alkaline Diuresis
- Once urine flow established → mannitol + urinary alkalinization
- Maintain urinary pH > 6.5 (reduces myoglobin and uric acid precipitation)
- Up to 8 L/day diuresis can be maintained
- Rationale: both myoglobin and uric acid have less nephrotoxicity in alkaline urine
3. Electrolyte Management
- Hyperkalemia: urgent treatment (ECG changes, cardiac monitoring)
- Hypocalcemia: treat only if symptomatic or severe (do not over-correct — exacerbates tissue calcification)
- Monitor and correct acidosis
4. Fasciotomy
- Early fasciotomy decompresses compartments and prevents irreversible ischemic damage (nerve/muscle injury if >6–8 hours untreated)
- Late fasciotomy (>12 hours of entrapment) — generally avoided: risks massive myoglobin release and wound infection in dead tissue
5. Renal Replacement Therapy (RRT)
- Required in up to 20% of AKI from rhabdomyolysis
- Indications: uncorrectable metabolic acidosis, life-threatening hyperkalemia, volume overload, uremia
6. ICU Care
- Close fluid balance monitoring
- Treat underlying cause (e.g., stop offending drug, treat infection)
Crush Syndrome Summary (Bailey & Love)
- Arises from reperfusion after muscle crushing
- AKI and renal failure from myoglobinuria is the key complication
- Treatment must start before extrication
- Late fasciotomy makes outcomes worse, not better
Key Numbers to Remember
| Fact | Value |
|---|---|
| AKI incidence in rhabdomyolysis | 13–67% |
| Rhabdomyolysis share of all AKI cases (US) | 5–10% |
| Annual US hospitalized cases | ~26,000 |
| RRT needed in rhabdomyolysis-AKI | ~20% |
| CK threshold for AKI risk | >15,000–20,000 U/L (lower if comorbidities) |
| Fasciotomy time limit | Avoid after >12 h entrapment |
| Compartment syndrome irreversible damage | >6–8 hours untreated |
Sources: Bailey and Love's Short Practice of Surgery 28e; Goldman-Cecil Medicine; Tintinalli's Emergency Medicine; Comprehensive Clinical Nephrology 7e
Recent evidence: A 2026 systematic review (PMID 41928063) on crush injury syndrome in earthquakes confirms high complication rates; a 2025 meta-analysis on pediatric rhabdomyolysis (PMID 41146051) highlights viral myositis and trauma as leading pediatric causes. No major contradictions to current management guidelines were found.
This is a shared conversation. Sign in to Orris to start your own chat.