It's all about Conduction: Calcium's Role in Hyperkalemia
Contributor: Dillon Warr, MD
The classic teaching is that calcium’s role in hyperkalemia is that of membrane stabilization. However, what if what we were taught was wrong all along? In this quick-hit, we will discuss the role of calcium in hyperkalemia and a new hypothesis that suggests it may all be about cardiac conduction velocity.
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Take Home Point
*CALCIUM IMPROVES CARDIAC CONDUCTION VELOCITY THROUGH CALCIUM MEDIATED CONDUCTION, RATHER THAN MEMBRANE STABILIZATION*
The Study
The Source:
Beneficial Effect of Calcium Treatment for Hyperkalemia Is Not Due to “Membrane Stabilization”. Crit Care Med. Published online July 24, 2024. [pubmed]
Key Pathophysiology of Hyperkalemia
Elevates resting membrane potential
Slows cardiac conduction (widening intervals)
Shortens action potential duration (peaked T Waves)
This leads to an arrhythmogenic substrate, which can predispose to ventricular arrhythmia and sudden cardiac death
The Key Results:
Data from this Laboratory Study in Dog Myocytes:
Calcium did not restore action potential duration
Calcium did not impact resting membrane potential
Calcium normalized cardiac conduction velocity. This normalization could be blunted by addition of with L-Type calcium channel blocker verapamil, suggesting these channels are important to the underlying mechanism of action.
Why Should I Care about Dog Hearts?
Mechanistic rationale for clinical use of calcium treatment for hyperkalemia only when the ECG reveals slow conduction (i.e., QRS prolongation).
Offers laboratory evidence for why adverse outcomes are not common in those patients with isolated peaked-T waves but are in those with QRS/PR interval prolongation. Begs the question: Do we even need calcium for isolated peaked T-waves?
Indications for Calcium in Hyperkalemia
There is a general consensus that clinical signs and symptoms of hyperkalemia or significant ECG changes warrant early and aggressive therapy as ECG changes are associated with mortality. Some physicians have a “number” that which they treat at. Dr. Warr’s is >6.5 mEq/L, which is a common number reflected in the literature.
Symptoms of Hyperkalemia
Related to poor neuromuscular transmission. Can see 1) neuromuscular weakness, 2) paralysis, 3) sensory changes, 4) paresthesias
ECG Pearls
- Hyperkalemia has been known to cause almost any dysrhythmia.
- The ECG alone is unreliable for the diagnosis and severity categorization of hyperkalemia
- The EKG does not follow the classic progression.
- Plasma potassium concentration often correlates poorly with cardiac manifestations
- Other findings: Regular and/or irregular bradycardias, wide/narrow tachycardias, new fascicular or bundle branch blocks, and ST segment changes
- Sinus or junctional bradycardia may be the only EKG manifestation of hyperkalemia
Administration of Calcium
Calcium Gluconate
- Agent: 10% Calcium Gluconate
- Dose: 3 g IV Push over 2-5 minutes
- Note to provider: May repeat every 5 minutes if no change
- Frequency: As needed if EKG changes present or at request of provider
- Lasts for ~30-60 minutes
Calcium Chloride (Code/Peri-arrest)
- Agent: 10% calcium chloride
- Dose: 1 g IV Push
- Frequency: As needed if EKG changes present or at request of provider
- Repeat EKG after administration of calcium
- Lasts for ~30-60 minutes
Calcium chloride contains 3 times the elemental calcium as calcium gluconate. As a result, it can be corrosive to peripheral vessels and may cause necrosis if extravasation occurs; Therefore, central line administration is preferred. Peripheral IV administration may be used in cardiac arrest. Calcium gluconate is generally preferred for most patients.
References
- An JN, Lee JP, Jeon HJ, Kim DH, Oh YK, Kim YS, Lim CS. Severe hyperkalemia requiring hospitalization: predictors of mortality. Crit Care. 2012 Nov 21;16(6):R225. [pubmed]
- Lasure Ben, Shaver Erica. Hyperkalemia. In: Mattu A and Swadron S, ed. CorePendium. Burbank, CA: CorePendium, LLC [source].
- Palmer BF, Clegg DJ. Diagnosis and treatment of hyperkalemia. Cleve Clin J Med. 2017 Dec;84(12):934-942. [pubmed]
- Montague BT, Ouellette JR, Buller GK. Retrospective review of the frequency of ECG changes in hyperkalemia. Clin J Am Soc Nephrol. 2008 Mar;3(2):324-30. [pubmed]
- Simon LV, Hashmi MF, Farrell MW. Hyperkalemia. 2022 Feb 16. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 [pubmed]
- Helman, A, Baimel, M, Etchells, E. Emergency Management of Hyperkalemia. Emergency Medicine Cases. September, 2016. [source].
- Farkas, J. Hyperkalemia. Internet Book of Critical Care. June 2021. [source]
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