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Musculoskeletal & Integumentary · Topic 1 of 11

Rhabdomyolysis

Musculoskeletal · muscle breakdown

Rhabdomyolysis

Muscle breakdown with CK above 5 times normal: check potassium first, then give early, aggressive IV fluid to protect the kidneys.

Key numbers
CK > 5× upper limit of normalCK > 5× ULN
IV fluids to urine 200–300 mL/hUO 200–300 mL/h
CK above 5,000 U/L raises AKI riskCK > 5,000 U/L
01 · Defined byCK > 5× upper limit of normal

Rhabdomyolysis is confirmed by a CK above 5 times the upper limit of normal (typically > 1000 U/L) in the right setting; the classic triad of myalgia, weakness and dark urine appears in under 10%.

02 · DoIV fluids to urine 200–300 mL/h

Start isotonic crystalloid as early as possible — ideally within 6 hours of the muscle injury — and titrate to a urine output of about 200–300 mL/h, watching closely for volume overload.

03 · RiskCK above 5,000 U/L raises AKI risk

Pigment AKI occurs in about 15–55% of patients; the risk is higher with CK above 5,000 U/L and higher still above 15,000 U/L, especially with dehydration or sepsis.

01

Causes & risk factors

Why it happens
Causes: crush, seizures, drugs, heat, immobilizationCommon causes: crush injury, compartment syndrome, electrical injury, seizures, prolonged immobilization, extreme exertion, statins, cocaine, amphetamines, alcohol, NMS, malignant hyperthermia, heatstroke, hypokalemia and hypophosphatemia.
02

Presentation

What you'll see
Dipstick positive for blood, no RBCs on microscopyMyoglobinuria makes the urine dipstick positive for blood with few or no red cells on microscopy; myoglobin clears quickly, so clear urine or a normal myoglobin does not exclude rhabdomyolysis.
Rising CK: suspect ongoing injury or compartment syndromeA CK that keeps rising or fails to fall suggests continuing muscle injury or a developing compartment syndrome — re-examine the limbs and measure compartment pressures if suspected.
03

Diagnosis & monitoring

Work-up
Expect high K, phosphate, urate; low calcium earlyExpected labs: hyperkalemia, hyperphosphatemia, hyperuricemia, early hypocalcemia with late hypercalcemia during recovery, anion gap metabolic acidosis, rising creatinine and sometimes thrombocytopenia or DIC.
Trend CK: peaks at 24–72 hoursCK rises 2–12 hours after injury, peaks at 24–72 hours and then falls about 39% a day; trend CK, potassium and creatinine, and keep up fluids until CK is falling and the urine clears.
04

Do right now

In this order
First moves
1
Hyperkalemia: get an ECG and potassium now
→
2
IV fluids to urine 200–300 mL/hUO 200–300 mL/h
→
3
Treat the cause; fasciotomy for compartment syndrome
→
4
Trend CK: peaks at 24–72 hours
Why each step
Hyperkalemia: get an ECG and potassium nowHyperkalemia is the most life-threatening early complication: get an ECG and potassium at once and, with ECG changes, give 10% calcium gluconate 10–20 mL IV, then shift and remove potassium.
IV fluids to urine 200–300 mL/hStart isotonic crystalloid as early as possible — ideally within 6 hours of the muscle injury — and titrate to a urine output of about 200–300 mL/h, watching closely for volume overload.
Treat the cause; fasciotomy for compartment syndromeTreat the cause alongside fluids: stop offending drugs such as statins, cool hyperthermia, treat infection, and get an early fasciotomy when compartment syndrome is the trigger.
Trend CK: peaks at 24–72 hoursCK rises 2–12 hours after injury, peaks at 24–72 hours and then falls about 39% a day; trend CK, potassium and creatinine, and keep up fluids until CK is falling and the urine clears.
05

Management

Orders
No routine bicarbonate, mannitol or loop diureticsDo not routinely alkalinize the urine with sodium bicarbonate or give mannitol or loop diuretics to prevent AKI; no benefit is proven. Use bicarbonate only to treat significant metabolic acidemia.
Stop pushing fluid once oliguric AKI sets inIf oliguric AKI develops and fluid balance is positive, more fluid only causes harm; manage volume and electrolytes and start dialysis for refractory hyperkalemia, acidosis, volume overload or uremia.
06

The rules

Know these
No calcium for asymptomatic early hypocalcemiaEarly hypocalcemia is common as calcium enters injured muscle; give IV calcium only for hyperkalemia with ECG changes or symptomatic hypocalcemia — extra calcium may worsen muscle injury and later returns as hypercalcemia.
07

More detail

Reference
Show 5 reference facts
Renal replacement therapy is not used to prevent rhabdomyolysis AKI; conventional intermittent hemodialysis does not remove myoglobin, while continuous hemofiltration can, without proven mortality benefit.
The McMahon score (age, sex, cause, and admission creatinine, calcium, phosphate and bicarbonate) predicts the need for dialysis or death better than the CK level; a score of 6 or more marks higher risk.
Statin-associated rhabdomyolysis is usually defined by a stricter cutoff — CK above 10 times the upper limit of normal with muscle symptoms or kidney injury.
No crystalloid is proven superior (lactated Ringer's vs normal saline), and crystalloids are suggested over colloids; choose the fluid by acid–base and electrolyte status.
Myoglobin causes AKI through renal vasoconstriction, tubular cast formation in acidic urine and direct oxidant injury; injured muscle also sequesters fluid (third-spacing), adding hypovolemia.
Pearl

Blood on the dipstick but no red cells under the microscope — think myoglobin, and start the fluids.

Sources · Merck Manual Professional — Rhabdomyolysis (full review Feb 2026) · Chavez LO et al. Beyond muscle destruction: a systematic review of rhabdomyolysis for clinical practice. Crit Care 2016;20:135 · Gupta A et al. Rhabdomyolysis: Revisited. Ulster Med J 2021;90:61–69 · Michelsen J et al. Prevention of rhabdomyolysis-induced acute kidney injury — a DASAIM/DSIT clinical practice guideline. Acta Anaesthesiol Scand 2019;63:576–586 (abstract via Europe PMC) · Long B, Koyfman A, Gottlieb M. An evidence-based narrative review of the emergency department evaluation and management of rhabdomyolysis. Am J Emerg Med 2019;37:518–523 · WikEM — Rhabdomyolysis · Yang BF et al. Advances in rhabdomyolysis: a review of pathogenesis, diagnosis, and treatment. Chin J Traumatol 2026;29:21–31 · Merck Manual Professional — Hyperkalemia · Bosch X, Poch E, Grau JM. Rhabdomyolysis and acute kidney injury. N Engl J Med 2009;361:62–72 (treat early hypocalcemia only if symptomatic or with severe hyperkalemia — confirmed via HKSCCM review summary) · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).