What are the two primary action sites of Vasopressin?

The primary action sites of Vasopressin, also known as antidiuretic hormone (ADH), are indeed the kidneys and blood vessels. In the kidneys, Vasopressin works by promoting water reabsorption in the collecting ducts, which helps concentrate urine and maintain body fluid balance. This action is critical in managing the body's hydration status and thereby regulates blood volume and pressure.

In addition to its renal effects, Vasopressin also acts on vascular smooth muscle, causing vasoconstriction. This increases peripheral vascular resistance and consequently elevates systemic blood pressure. The combination of these effects makes Vasopressin an essential hormone in maintaining hemodynamic stability, particularly in states of hypotension or when fluid balance needs to be carefully managed.

Understanding these two primary action sites is crucial for CRNAs, especially when considering fluid management and hemodynamic support during anesthesia.