The Inhibition of Acetylcholine-Induced Atrioventricular Block by Potassium*
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Key result
Elevating plasma potassium to ~6 mEq/L markedly inhibits acetylcholine-induced AV block.
- n=7
Why the study?
Does potassium inhibit acetylcholine-induced atrioventricular block in a canine model?
Population
7 mongrel dogs weighing 10 to 14 kg undergoing 11 experiments, anesthetized and vagotomized
Comparison
Potassium to test inhibition of… vs Control observations with acetylcholine alone
Design
Preclinical
Authors
Discussion
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Implication
Does not support clinical use in vagally mediated AV block; leaves open translation of this mechanism to humans.
Structured PICO
Does potassium inhibit acetylcholine-induced atrioventricular block in a canine model?
P
Population
7 mongrel dogs weighing 10 to 14 kg undergoing experimental acetylcholine-induced atrioventricular block.
I
Intervention
Potassium (hyperkalemia) to test inhibition of acetylcholine-induced AV block
C
Comparator
Control observations (4 to 8 consecutive) with acetylcholine alone
O
Outcome
Inhibition of acetylcholine-induced second or third degree atrioventricular (AV) blocksurrogate
This preclinical study investigates the electrophysiological mechanism by which potassium may inhibit vagally-mediated (acetylcholine-induced) AV block.
Limitations
- Animal model (dogs) may not perfectly translate to human clinical scenarios
- The observed inhibition of acetylcholine occurred in a narrow plasma potassium range
- Acute experimental conditions with continuous acetylcholine injections
Cite This Study
Fisch et al. (1963) studied Acetylcholine-induced atrioventricular block (n=7). Potassium phosphate infusion vs. Isotonic buffered sodium phosphate / baseline was evaluated on Number of blocked atrial impulses per injection of acetylcholine. Elevation of plasma potassium from a mean of 3.4 mEq/L to 6.1 mEq/L markedly diminished or completely inhibited acetylcholine-induced atrioventricular block.
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