Hypomagnesemia and Hypokalemia

Hey team:
We discussed yesterday the clinical pearl that you cannot correct hypokalemia in the face of hypomagnesemia. This is useful to remember especially in ICU patients.

The question came up as to the underlying pathophysiology of this phenomenon and I am happy to provide some evidence that indeed it seems to be related to ATP!  In addition it seems that hypomagnesemia itself increases potassium excretion in the ascending loop of Henle.  These changes result in potassium loss in the urine that is refractory to  potassiumsupplementation.

Physical exam evidence

Hey team:

We discussed the evidence for examining for airway obstruction today.  Check out the Tangents blog post on this.

This week we also talked about the JAMA paper on deciding whether a patient is ECF volume contracted.  Here is the key article from JAMA 1999.  Note that the findinmg of postural dizziness and increase in HR>30 is only sensitive to hypovolemia from blood loss.

I will be posting EBM stuff we discuss in this blog so feel free to subscribe.