Rhabdomyolysis

Today we discussed an interesting case: a 39M on a depot-antipsychotic and benztropine presenting with rhabdomyolysis. This led to a discussion around neuroleptic malignant syndrome as well as electrolytes since his potassium and phosphate were surprisingly low, rather than high as expected.

Interesting points arising from today's discussion:

1. Management of rhabdomyolysis is supportive, with ++ IV fluids and alkalinization of urine (difficult to achieve). Target urine pH is 6.5 or higher but the utility of this has been debated in recent years. Practically, remember that the way to create an alkalinizing infusion is 1 L of D5W, draw out 150mL and discard, and add 3 amps of sodium bicarb (a standard ampule is 50meq in 50mL). Your new solution is isotonic to serum. Remember, run this in ADDITION to the NS "resuscitation" fluids you are running. See here for the National Guidelines Clearinghouse guidelines on management of rhabdo - very practical.

2. Phosphate: hypophosphatemia is cited as a potential etiology of rhabdo, and it is one of the lytes that we very rarely learn about. Causes of hypoPO4 can be classified as due to: 1) Decreased intestinal absorption (eg vit D deficiency, antacid abuse), 2) Internal redistribution (eg refeeding syndrome, sepsis), and 3) increased urinary excretion (ie EtOH abuse, hyperPTH, vit D disorders). See here for a old but very useful article summarizing Mg and PO4 disorders (this is part of a 5-part elytes series that I have found useful in the past). Remember, replacing PO is safer than IV, as the latter runs the risk of causing severe hypocalcemia.

3. Neuroleptic malignant syndrome is a life-threatening medical emergency that is caused by antipsychotic medications. It has been described with both the typical and atypical antipsychotics. It is manifest by fever, autonomic instability, rigidity, and mental status changes. It can result in rhabdomyolysis, renal failure, hypoxia, and metabolic acidosis. Recovery is typically within 7-10 days of discontinuing the drug, although recovery may be prolonged in depot injections. NMS has a broad differential diagnosis (including withdrawal from other Rx , which must be considered carefully - see here for a review.

4. Lastly, we discussed alternatives to statin therapy. There has been some talk about red yeast rice, and there is actually evidence to prove it! The best medicine is usually the one your patient will take. See here for a recent article on this alternative therapy.