Ontario Paramedic Practice Exam

What does increased heart rate and contractility due to adrenaline result in?

1. Decreased blood pressure

2. Improved cardiac output

3. Lower oxygen demand

4. Reduced risk of cardiac arrest

The correct answer is: Improved cardiac output

Increased heart rate and contractility due to adrenaline, also known as epinephrine, leads to improved cardiac output. Cardiac output is the volume of blood the heart pumps per minute, and it is a product of heart rate and stroke volume (the amount of blood pumped with each heartbeat). When adrenaline is released, it stimulates beta-adrenergic receptors in the heart, resulting in an increase in both the heart rate and the force of contraction (contractility). As the heart beats faster and more forcefully, the amount of blood pumped out with each contraction increases, thus enhancing the overall cardiac output. This is particularly important in situations of stress or emergency, where the body requires more blood flow to vital organs and tissues to respond effectively to a threat or to support physical activity. In contrast, decreased blood pressure would not result from increased heart rate and contractility but rather could occur in scenarios of vasodilation or severe blood loss. Lower oxygen demand typically does not occur with increased heart activity; rather, the heart’s activity increases oxygen consumption. Lastly, while improved cardiac function can lower the risk of cardiac arrest overall, it does not directly translate to an immediate reduction in risk in the context of acute physiological changes caused by adrenaline. Hence,