During anaphylaxis, how does histamine affect cardiac function?

During anaphylaxis, how does histamine affect cardiac function?

• A. depresses
• B. enhances
• C. no effect
• D. variable

Answer: (A)

Massive histamine release during anaphylaxis drives systemic vasodilation and capillary leakage, which lowers venous return and preload, helping to drop blood pressure. In addition, high histamine levels can directly depress the myocardium, reducing contractility. The combination of decreased preload and impaired cardiac pumping leads to a fall in cardiac output, contributing to shock. While histamine can increase rate via certain receptors, the overall effect on cardiac performance in this setting is a depressed, weakened heartbeat.

Massive histamine release during anaphylaxis drives systemic vasodilation and capillary leakage, which lowers venous return and preload, helping to drop blood pressure. In addition, high histamine levels can directly depress the myocardium, reducing contractility. The combination of decreased preload and impaired cardiac pumping leads to a fall in cardiac output, contributing to shock. While histamine can increase rate via certain receptors, the overall effect on cardiac performance in this setting is a depressed, weakened heartbeat.