List the causes, and features of rhabdomyolysis, and outline the principles of management
Aetiology: consider trauma and muscle compression (including immobility), exertional rhabdomyolysis (eg. heat stroke, grand mal seizures), drugs and toxins (via coma/immobility, agitation/hyperthermia, myotoxins eg. HMG-CoA reductase inhibitors, myonecrosis secondary to non-depolarising neuromuscular blockers), infections, inflammatory myopathies (eg. polymyositis), electrolyte abnormalities (esp. hypokalaemia and hypophosphataemia), hyperthermia (eg. malignant hyperpyrexia and neuroleptic malignant syndrome), metabolic myopathies.
Presentation: Consider history of exertion, fitting, drug exposure (including illicit), immobility, family history, and previous episodes. Patient may complain of painful or weak muscles, and pigmented urine. Investigations reveal markedly elevated muscle enzymes (especially CK), acute oliguric renal failure, and electrolyte abnormalities (hyperkalaemia, hyperphosphataemia, hypocalcaemia, hyperuricaemia and metabolic acidosis).
Principles of management: consider general supportive care, adequate fluid resuscitation, forced alkaline diuresis (including mannitol), specific treatment of underlying cause (eg. dantrolene, phosphate replacement, cooling, removal of precipitants, treatment of infection, fasciotomies etc), and correction of electrolyte abnormalities.
The causes of rhabdomyolysis are discussed in Question 26.3 from the second paper of 2013.
A more extensive discussion of rhabdomyolysis can be found among the Required Reading summaries.
To simplify revision, I reproduce the list of differentials below:
A recent meta-analysis of management strategies for rhabdomyolysis has presented the following conclusions:
Dialysis may be commenced to improve the removal of myoglobin, if a high-permeability membrane filter is available. Even if it is not, standard CVVHDF seems to decrease the risk of renal injury.
Holt, S., and K. Moore. "Pathogenesis and treatment of renal dysfunction in rhabdomyolysis." Intensive care medicine 27.5 (2001): 803-811.
Vanholder, Raymond, et al. "Rhabdomyolysis." Journal of the American Society of Nephrology 11.8 (2000): 1553-1561.
Bosch, Xavier, Esteban Poch, and Josep M. Grau. "Rhabdomyolysis and acute kidney injury." New England Journal of Medicine 361.1 (2009): 62-72.
Allison, Ronald C., and D. Lawrence Bedsole. "The other medical causes of rhabdomyolysis." The American journal of the medical sciences 326.2 (2003): 79-88.
Brown, Carlos VR, et al. "Preventing renal failure in patients with rhabdomyolysis: do bicarbonate and mannitol make a difference?." Journal of Trauma-Injury, Infection, and Critical Care 56.6 (2004): 1191-1196.
Scharman, Elizabeth J., and William G. Troutman. "Prevention of kidney injury following rhabdomyolysis: a systematic review." Annals of Pharmacotherapy47.1 (2013): 90-105.
Sorrentino, Sajoscha A., et al. "High permeability dialysis membrane allows effective removal of myoglobin in acute kidney injury resulting from rhabdomyolysis." Critical care medicine 39.1 (2011): 184-186.
Tang, Wanxin, et al. "Renal protective effects of early continuous venovenous hemofiltration in rhabdomyolysis: improved renal mitochondrial dysfunction and inhibited apoptosis." Artificial organs 37.4 (2013): 390-400.