Related Subjects:
Acute Kidney Injury
| Acute Rhabdomyolysis
Rhabdomyolysis is strongly suggested by the fact that urinalysis is strongly positive for blood, whereas urine microscopy is negative for red blood cells.
Conversion
- Calcium: 10 mg/dl = 2.5 umol/L | 12 mg/dl = 3.0 umol/L |14 mg/dl = 3.5 umol/L
- Creatinine: 0.8 mg/dl = 70 umol/L | 1.2 mg/dL = 106 umol/L | 1.4 mg/dl = 123 umol/L
About
- Damage to striated muscle can lead to Myoglobinuria
- Myoglobin precipitating in the kidney can lead to acute renal failure (AKI)
- Acute Rhabdomyolysis can cause AKI, DIC, ARDS and multiorgan failure
- Damaged muscle also releases the enzyme CK
Aetiology
- Myoglobin (Mb) is a globular protein in skeletal muscle
- In 1958, Max Perutz and John Kendrew determined the 3D structure of Myoglobin by X-ray crystallography
- It is a monomeric protein that has 153 amino acid residues and acts a store of oxygen similar to Hb
- Destruction of 100 g of muscle tissue is capable of inducing Rhabdomyolysis
- Release of excessive myoglobin into the plasma overwhelms the capacity of the binding proteins (mainly haptoglobin)
- Myoglobin then gets filtered across the glomerulus, causing tubular damage
- Myoglobin exerts a direct cytotoxic effect through the enhancement of local oxidative stress in the tubular cells
Causes
- Trauma and crush injuries
- Falls and lying on the floor for prolonged periods
- Severe exercise, Generalised seizures
- Neuroleptic malignant syndrome (NMS), Malignant hyperthermia
- Cocaine and heroin, Alcohol, Methanol, Ethylene glycol
- Carbon Monoxide poisoning
- Ischaemic limb with muscle necrosis
- Polymyositis, Statins +/- Fibrates, Hypokalaemia
- Snake bites, Compartment syndrome
- Muscle genetic disorders - carnitine deficiency
- Caffeine, Aspirin, Hypokalaemia, Hypophosphatemia
- Diabetic ketoacidosis and HONK
- Sepsis with bacterial infections
Clinical
- Muscles can be tender and swollen
- There can be skin changes indicating pressure necrosis.
- Muscle pain, weakness and dark urine, Cause may be apparent
- Evidence of trauma or falls, Family history
- Drug history - neuroleptics
- Fever, increased tone, fever - NMS
Investigations
- Urinalysis: positive for blood. Positive urinalysis is caused by myoglobin, a muscle protein released during muscle damage; this appears in the urine and can cause acute renal failure.
- ↑↑ CK x 5 upper limit of normal of above 1000IU/L
- ↑ LDH, AST, Aldolase, Myoglobin and other msucle enzymes
- ↑ Creatinine and Myoglobin in urine
- ↓ Low Calcium
- Magnetic resonance imaging can be useful to identify muscle damage
- ECG and Troponin if myocardial injury suspected
Management
- ABC, treat any hyperkalaemia, hypovolaemia, analgesia.
- Early treatment (ideally<6 hours from onset) is needed with volume expansion to generate a diuresis of all non-overloaded patients along with avoidance of nephrotoxins. There is insufficient data to recommend any specific fluid. The mortality rate ranges from 10% to up to 50% with severe AKI. Myoglobin is normally bound to plasma globulins, and has a rapid renal clearance with a half-life of 2-3 hours. In RML, the level of myoglobin in the serum increases within 1–3 h, reaches its peak in 8–12 h, and then returns to normal within 24 h after the onset of the injury.
- Current guidelines suggest against the routine use of alkalinisation with sodium bicarbonate. The long-term fall in estimated glomerular filtration rate (eGFR) correlated to serum phosphate and myoglobin (>8,000U/L) at admission. Myoglobin which is compatible with convective removal, can be transported to the filtrate by continuous hemofiltration and hemodiafiltration
- Catheterisation may be needed if difficulty passing urine or measuring output or retention and establish a good diuresis (200-300 ml/hr) with IV fluids
- Bromocriptine or Dantrolene in the case of NMS
- Fasciotomy for a compartment syndrome
- Revascularization for limb ischaemia
- Nephrology consult for deteriorating renal function
References