Sunday, April 5, 2015

The Effect of Calcium on Severe Hyperkalemia

This patient had a K of 8.1 mEq/L and a very low ionized Calcium of 2.4 mg/dl (normal: 4.4 - 5.2). Both were from a blood sample drawn 13 minutes prior to the following ECG (time zero):

ECG time zero:
There is a near sine wave which is pathognomonic for hyperkalemia.  The QRS duration is 254 ms.

3 g of Calcium gluconate was administered and another ECG was recorded 1 minute later:
The QRS is now 190 ms

Another dose of Calcium was given and this ECG was recorded 2 minutes after the 2nd (3 min after the 1st):
The QRS is not 154 ms.

4 minutes after this, another ECG was recorded:
The QRS is wider again, at 190 ms.

There was rapid release of potassium from this very ill patient, and only a transient effect of Calcium

Learning Point:

Calcium has rapid but reversible effects on QRS width in Hyperkalemia.

See this case of Ventricular Tachycardia from Hyperkalemia which required 15 grams of Ca Gluconate for Stabilization.


  1. beautiful use of serial ecgs in an obviously meticulous dr, revealing crucial info

  2. Interesting. Do you know the pH or total calcium?

  3. pH was just slightly low and total calcium is irrelevant, as only ionized calcium affects the myocardium. Nevertheless, it was normal.

    1. Yep, just curious about the interplay considering the two electrolytes here (i.e. was ionized Ca low because of binding or low total quantity). Interesting that total calcium was normal and ionized was low in the setting of normal pH or mild acidosis -- perhaps albumin was high?

    2. Brandon,
      sorry for delayed response. Could be.

  4. Why was calcium gluconate chosen as opposed to calcium chloride, which has about 3 times the elemental calcium per 1 gram?

    - Joe

    1. Joe,
      CaCl has gone out of favor due to sclerosing effects on veins. I disagree with this. It is very ucommon and does not happen with a very good IV.


DEAR READER: We welcome your Comments! Unfortunately — due to a recent marked increase in SPAM — we have had to restrict commenting to Users with a GOOGLE Account. If you do not yet have a Google account — it should not take long to register. Comments give US feedback on how well Dr. Smith’s ECG Blog is addressing your needs — and they help to clarify concepts of interest to all readers. THANK YOU for your continued support!

Recommended Resources