How much blood is gravitationally transferred to the right heart during the PLR maneuver?

The PLR (Passive Leg Raise) maneuver is commonly used in critical care practices to assess a patient's fluid responsiveness. During this maneuver, the legs of the patient are elevated to create a gravitational shift of blood from the lower body to the thoracic cavity, which increases venous return to the heart.

Research indicates that this maneuver can lead to an increase in right heart filling volume, typically around 300 mL. This volume is significant enough to have a measurable impact on cardiac output and blood pressure, reflecting the patient's ability to respond to fluid resuscitation.

While other volumes might be associated with different contexts or maneuvers, the 300 mL figure has become a standard reference point within the context of the PLR maneuver in clinical practice, highlighting its effectiveness in gauging volume responsiveness in critically ill patients.