What emergency drug increases myocardial contractility during cardiac surgery?

The correct answer is calcium chloride. During cardiac surgery, maintaining adequate myocardial contractility is crucial for optimal cardiac function. Calcium is an essential ion in the process of muscle contraction, including that of cardiac muscle. Calcium chloride provides an immediate source of calcium ions, which enhance the contractile strength of the heart muscle by increasing the availability of calcium during the contraction cycle.

Calcium chloride can be particularly useful in situations where there is hypocalcemia, which can occur due to various factors during surgery, potentially leading to weakened heart contractions. Additionally, calcium plays a vital role in the excitation-contraction coupling of cardiac muscle cells. The administration of calcium chloride directly supports the heart's efficiency and performance in such critical circumstances.

Dopamine, while also related to cardiovascular function by increasing cardiac output, primarily acts through beta-adrenergic receptors and may not have as direct an effect on myocardial contractility as calcium does. Understanding the specific role of calcium in myocardial contractility helps ensure effective management of the cardiac patient during surgery.