Which parameter is typically decreased in hypovolemic shock?

In hypovolemic shock, there is a significant reduction in circulating blood volume, which leads to a decrease in both cardiac output and pulmonary artery wedge pressure.

Cardiac output typically decreases due to reduced preload, as low blood volume results in less blood returning to the heart. This diminished preload reduces the stroke volume according to the Frank-Starling mechanism, thus lowering overall cardiac output.

Pulmonary artery wedge pressure, a measure of left atrial pressure and an indirect indicator of left ventricular filling pressure, also decreases. In hypovolemic states, the fluid deficit means that there's not enough blood volume to fill the heart chambers adequately, resulting in lower pressures in the pulmonary circulation.

While systemic vascular resistance may increase in hypovolemic shock due to compensatory mechanisms aimed at maintaining perfusion to vital organs, it is not a parameter that typically decreases. Understanding these physiological changes provides insight into how the body responds to reduced blood volume and the critical importance of fluid resuscitation in managing hypovolemic shock.