S10C92 - Rhabdomyolysis

Question 1

Rhabdo: dfn

Answer 1

-acute necrosis of skeletal muscle fibers and leakage of cellular contents into the circulation

Question 2

Rhabdo: common causes

Answer 2

• EtOH, drugs
• meds (statin, antipsychotics, SSRI, colchicine, lithium, antihistamines)
• muscle diseases
• trauma
• NMS (neuroleptic malginant syndrome)
• seizures
• immobility
• infection (legionella, influenza)
• strenuous physical activity
• heart-related illness

-in children: trauma, viral myositis, connective tissue dz

Question 3

Statin induced rhabdo

Answer 3

• rare
• 0.04% with pravastatin and atorvastatin
• 0.19% with lovastatin
• dose related

Question 4

Rhabdo: pathophys

Answer 4

• disruption of NaKATPase pump and calcium transport
• increased intracellular calcium
• subsequent muscle cell necrosis
• myoglobin, CK, LDH, aldolase and aspartate aminotransferase are released

Question 5

Rhabdo: clinical picture

Answer 5

• Sx: myalgias, stiffness, weakness, malaise, fever, dark urine, n/v, abdo pain, tachycardia
• only 1/2 of cases will have muscular symptoms
• can get a urea-induced encephalopathy with mental status changes

Question 6

Rhabdo: dx

Answer 6

• CK is most sensitive and reliable test
• degree of CK change correlates with amt of injury and severity of illness but not dvpt of renal failure
• dx: usually about 5x increase of CK above upper threshold of normal
• CK levels rise 2-12h after muscle injury, peak at 24-72h then decline at 39% per day from previous day’s value
• if Ck does not fall there is ongoing muscle necrosis
• myoglobin: rises before CK and is rapidly cleared by renal excretion, causes red-brown colour, dipstick will show up as RBCs not myoglobin, suspect myoglobin if dipstick + but no RBC on u/a, myoglobin can return to normal w/in 6h post injury
• other tests: lytes, uric acid, calcium, u/a, BUN, Cr, screen for DIC (PTT, PT, fibrin split product, fibrinogen), LDH

Question 7

Rhabdo: complications

Answer 7

• AKI: breakdown product of myoglobin (ferrihemate) is responsible for toxic effect on kidneys in the presence of hypovolemia and aciduria
• DIC
• compartment syndrome
• peripheral neuropathy
• metabolic derangements: hyperca, hyperka, hyperphos, hyperuricemia, hypoca, hypophos (late)
• renal tubular obstruction: occurs from precipitation of uric acid and myoglobin

-hypocalcemia occurs from deposition of calcium in necrotic muscle tissue and as it is mobilized later, hypercalcemia can occur

Question 8

Rhabdo: tx

Answer 8

• ++ fluid resusc to prevent AKI
• bolus to replace any fluid deficit
• then infuse NS 2.5cc/kg/h with goal of u/o for 2cc/kg/h
• only give calcium if indicated for hyperkalemia, or profound symptoms of hypocalcemia
• if hypercalcemia is symptomatic, continue saline diuresis
• treat hyperphosphatemia if >7mg/dL, treat with oral phosphate binders
• hyperkalemia, insulin may not be as effective, try kayexalate, may need dialysis

Question 9

Rhabdo: immunologic causes

Answer 9

• dermatomyositis

- polymyositis

Question 10

Rhabdo: infxs causes

Answer 10

• clostridium
• GAS
• legionella
• salmonella
• shigella
• s. aureus
• strep pneumo

Viral: coxcackie, CMV, EBV, etnerovirus, Hep, HSV, HIV, influenza, rotavirus