Ca in hyperkalemia

Q; Which of the following increases the cardiotoxicity of hyperkalemia? (select one)

A) Hypercalcemia

B) Hypocalcemia

Answer: B

Hypocalcemia increases the cardiotoxicity of hyperkalemia; that's why calcium is usually the first line of action in an unstable patient with EKG changes and 'near code.' Ca directly antagonizes membrane actions of hyperkalemia. Hyperkalemia induces depolarization of cardiac muscles' resting membrane potential and leads to sodium channel inactivation. This decreases membrane excitability. Ca prevents this effect of hyperkalemia.

Calcium works within 5 minutes and can be repeated in 5 minutes if EKG changes persist in such patients. The effect lasts for 30 to 60 minutes. Usually, this management is combined with other modalities such as 'Insulin with glucose' and bicarbonate infusion. Many clinicians may forget the caveat that bicarbonate should be administrated after calcium infusion, as post-bicarb calcium may combine with already administrated bicarbonate and form calcium-carbonate in the body. Calcium should be given first and bicarbonate afterwards. It is important to understand that all these measures are temporary and meant to buy time till definite treatment can be employed to resolve hyperkalemia.

#electrolytes

#cardiology

References:

1. Long B, Warix JR, Koyfman A. Controversies in Management of Hyperkalemia. J Emerg Med 2018; 55:192.

2. Winkler AW, Hoff HE, Smith PK. Factors affecting the toxicity of potassium. Am J Physiol 1939; 127:430.

3. Lindner G, Burdmann EA, Clase CM, Hemmelgarn BR, Herzog CA, Małyszko J, Nagahama M, Pecoits-Filho R, Rafique Z, Rossignol P, Singer AJ. Acute hyperkalemia in the emergency department: a summary from a Kidney Disease: Improving Global Outcomes conference. Eur J Emerg Med. 2020 Oct;27(5):329-337. doi: 10.1097/MEJ.0000000000000691. PMID: 32852924; PMCID: PMC7448835.