Rhabdomyolysis Flashcards
What is rhabdo? What causes it?
Muscle literally disintegrating. This syndrome arises from loss of integrity of skeletal muscle. Release of contents of muscle cells into extracellular fluid
How straightforward is Rhabdo? Is it usually pretty easy to identify?
Asymptomatic elevation of serum creatine kinase to severe renal failure needing dialysis with multisystem organ failure. There is a diverse spectrum here.
When and what event sparked interest in Rhabdo?
1941 London Blitz = 6 patients under rubble, rescued, seemed fine, progressed to uremia and sudden death after 4-8 days
Discuss the mechanism behind how Rhabdo happens
Muscle injury leads to depletion of ATP within the myocyte
ATP depletion leads to impairment of ion pumps that regulate muscle contraction
Causes unregulated increase in intracellular calcium ions
Leads to persistent contraction and energy depletion with activation of calcium dependent proteases and phospholipases
Ends in muscle fiber necrosis
After the muscle dies in Rhabdo, what happens?
Large amounts of phosphate potassium, myoglobin, CK, and urate leak into the ECF after muscle dies.
Leads to renal tubular obstruction
Discuss myoglobin as it relates to Rhabdo
Myoglobin direct tubular toxicity
Normal serum myoglobin low (0 - 0.003 mg/dL)
If >100g skeletal muscle damaged then serum binding becomes saturated and free myoglobin is filtered by the kidneys
What will we see in the clinic that will point us towards a diagnosis of Rhabdo
Localizing: Muscle pain, swelling, stiffness, weakness, bruising
Compartment syndrome features - Very painful
Neurologic deficit
Can be asymptomatic with dark “coca-cola” urine, decreased urine output
Abnormal labs with electrolyte abnormalities or AKI
Discuss CK as it relates to diagnosing Rhabdo
Elevated CK
Confirms diagnosis
Peaks within 36 hours of rhabdo
Half life is 36-48 hours
Will we see blood in a UA for Rhabdo?
Dark urine due to myoglobinuria in 50% of patients
Urine dipstick positive for blood but with absence or <5 RBCs when urine examined under microscope
Discuss the pH for Rhabdo
Acidic urine pH
What will we see in the urine for someone with Rhabdo?
Tubular epithelial cells, granular casts, dark pigmented casts
Proteinuria presents in 50% of patients
Urine myoglobin positive
Discuss the complication stages of Rhabdo and what we will find at each
Early
Hyperkalemia, hypocalcemia, hepatic inflammation, cardiac arrhythmia, cardiac arrest
Late complications
AKI, DIC, Hypercalcemia a risk during recovery
Early or Late
Compartment syndrome - Timely fasciotomy can salvage tissue
Obvious treatments for Rhabdo
Goals of treatment: Promote increased renal tubular flow to get rid of myoglobin and get their electrolytes back up
Obvious - 200-300 mL/hour goal for urine output via large volumes of fluid intake
Also, alkalization of the urine.
Dialysis as a last resort
Controversial but effective treatment of Rhabdo?
Controversy: Diuretics to increase urinary flow rate
Mannitol. Help or harm?
Decrease cast formation and decrease ECF movement into injured muscle
