Hyperkalemia

Hyperkalemia can be fatal! Now that I have your attention, time for some learning…

We recently discussed a case of hyperkalemia in morning report. This is a ‘bread and butter’ internal medicine topic for which trainees have been taught the same approach for eons: pre-renal, renal and post-renal. Instead of focusing on the approach to the many causes of hyperkalemia I will review the acute management.

Stop potassium from coming in

• Low potassium diet
• Stop potassium containing IV fluids - sounds obvious but makes sure to check!
• Also, remember to stop nephrotoxic medications - think about NSAIDs, ACE-inhibitors, etc...

 Stabilize the cardiac membrane

• Calcium gluconate (or chloride) will stabilize the cardiac membrane and (hopefully) prevent a dangerous arrhythmia. But the effect lasts under an hour so give calcium first to buy yourself time to initiate the definitive measures below.

Shift potassium into cells

• Insulin 10-20 units IV to shift potassium into the cells.
• Dextrose D50W 1-2 amps to avoid hypoglycemia from your insulin. The sugar load will also stimulate release of endogenous insulin, thereby further shifting potassium into cells.
• Beta agonists are also effective at transiently lowering serum potassium.
• Sodium Bicarbonate infusion has been shown to cause a small reduction in serum potassium. However, you may not always need to give it if your other measures are successful.

Remove potassium from the body

• Renal: Is the patient producing urine? It is important to address any cause of AKI. Healthy kidneys with a reasonable GFR should eliminate any excess potassium. If the patient is volume overloaded and the clinical situation permits, you can give a loop diuretic to promote renal excretion of potassium. If the patient is pre-renal, perhaps he just needs some IV fluids to start excreting potassium. 
• GI: Resins are often used to treat hyperkalemia (ie. Kayexalate aka sodium polystyrine sulfate) but they are frequently not effective after a single dose and their use has been linked to intestinal necrosis. So if you're going to use a resin, make sure the patient is not post-operative and has no GI problems (ileus/obstruction). Another school of thought is to avoid kayexalate and instead use lactulose to induce a diarrhea which will result in potassium loss. Regardless of your approach, the bottom line is that after you do all (or some) of the above, make sure to follow the serum potassium closely (recheck in 1-2 hours), make sure that one of the methods of potassium excretion is working and address the underlying cause.
• Hemodialysis: If the hyperkalemia is refractory to your management (above) you should consult your friendly nephrologist for consideration of dialysis.

Check out the following review article from CMAJ on Manegement of Acute Hyperkalemia: http://www.ecmaj.ca/cgi/content/citation/182/15/1631