Rhabdomyolysis

First, think about the underlying etiology:
1. Trauma: this can be overt, like a crush injury or a bit more subtle, like immobilization in an elderly person who falls and is unable to get up for some time. Also think about immobilization in patients with a decreased level of consciousness or during prolonged operation.

2. Physical activity: rhabdo may occur in those who either perform excessive physical activity (eg. marathons), in those who are doing significantly more physical activity than they are used to (eg. couch potato who goes on run for 1st time in 10 years), or in situations where hyperthermia may occur (eg. jogging in the Sahara). Also, don't forget seizures as a common etiology.

3. Drugs/Toxins: as always, we should consider prescribed drugs (eg statins, colchicine), and non-prescribed drugs (eg. alcohol, cocaine, ecstasy). There are always a few cases per year of rhabdomyolysis from wild mushroom poisoning.

4. Infections: many viruses (eg. cytomegalovirus, Coxsackievirus, Epstein-Barr, Influenza, adenovirus, HIV), bacteria (eg. pyomyositis), sepsis, and parasitic (Falciparum malaria).

5. Electrolyte: primarily hypokalemia and hypophosphatemia from any cause.

6. Endocrinopathy: mostly in hypothyroidism, but may also be seen in DKA/HONK - probably from hypophosphatemia.

7. Those who are more prone: people who have myopathies may be more prone to developing rhabomyolysis. Think about those with poly/dermatomyositis, malignant hyperthermia, or rare congenital myopathies

What should I watch out for?
1. Hyperkalemia: lots of potassium can be released from muscle cells. Monitor this and the ECGs closely.
2. Renal failure: watch out. Myoglobin is toxic to the renal tubules and can cause acute tubular necrosis.
3. Other electrolytes: hyperphosphatemia (released from muscle cells), hypocalcemia.

Treatment:
This primarily revolves around finding and reversing precipitants, and aggressive fluid administration to prevent myoglobin-induced ATN. There is debate whether the best fluids are saline or if sodium bicarbonate added to D5W works best. Also, keep a close eye on the potassium.

Some good links:
Here's an interesting case
Here's a strange case of Rhabdo from the CMAJ

Tastes like chicken...