AKT · Renal & urology/AKI & rhabdomyolysis

Rhabdomyolysis

Skeletal muscle breakdown → myoglobin, potassium, phosphate, CK released into the circulation

Overview

Breakdown of skeletal muscle releasing myoglobin (nephrotoxic), potassium, phosphate and creatine kinase. Causes include a long lie after a fall/collapse, crush injury, prolonged seizures, extreme exertion, statins, and drugs/toxins. The danger is AKI (myoglobin casts) plus life-threatening hyperkalaemia; treatment is aggressive IV fluids and treating the hyperkalaemia.

Recognise

Muscle pain, weakness and swelling; tea-coloured (cola) urine; a history of a long lie, crush, seizure, immobility, or extreme exertion
Markedly raised creatine kinase; urine dipstick positive for BLOOD but no red cells on microscopy (myoglobinuria)
Hyperkalaemia, hyperphosphataemia, hypocalcaemia, metabolic acidosis; AKI

Red flags

Hyperkalaemia (often severe and early) → ECG + urgent treatment — the immediate killer
Compartment syndrome (cause or consequence of crush) → fasciotomy; rising CK with oliguria → established AKI

Differentials & how to tell them apart

Other causes of AKIno CK rise, no myoglobinuria

Haematuriared cells present on microscopy (rhabdo dip is blood-positive but microscopy-negative)

Myocardial infarction (if CK only mildly up)troponin-specific, cardiac context

Investigations

Creatine kinase (markedly raised — the diagnostic test), U&Es (K up, AKI), calcium (low), phosphate (high), urate; urine dipstick (blood-positive, no RBCs = myoglobin); ECG (hyperkalaemia); VBG; identify the precipitant.

Management

Aggressive IV fluids + urgent treatment of hyperkalaemia; stop the cause

1Confirm with a markedly raised CK and blood-positive/microscopy-negative urine. Give aggressive IV fluids to restore perfusion and flush myoglobin, and stop the precipitant.Gate: Check potassium and the ECG immediately — hyperkalaemia is the early life-threat: calcium gluconate + insulin-dextrose. Suspect/treat compartment syndrome.
2Monitor K/Ca/phosphate, CK trend and renal function; dialysis for refractory hyperkalaemia/acidosis/overload or established AKI.

Aggressive IV fluid resuscitation (crystalloid) — the mainstay — restore renal perfusion and flush myoglobin; titrate to urine output

Treat hyperkalaemia urgently — calcium gluconate (cardioprotection) + insulin-dextrose; monitor closely

Stop the precipitant; treat compartment syndrome — stop statins/offending drugs; fasciotomy if compartment syndrome

Dialysis if refractory — for refractory hyperkalaemia/acidosis/overload or established severe AKI

Key points

Long lie/crush/seizure/exertion + muscle pain + cola-coloured urine + sky-high CK + blood-on-dip-without-red-cells = rhabdomyolysis → aggressive IV fluids and treat the hyperkalaemia (the early killer). Watch calcium (low), phosphate (high) and compartment syndrome.

Monitor & prognosis

CK trend, K/Ca/phosphate, renal function, fluid balance/urine output, ECG.

Good with early fluids; AKI can be severe but is often reversible.

Source: NICE CKS; cross-ref MSK (compartment syndrome)