What is the primary purpose of measuring central venous pressure (CVP) in critically ill patients?

The primary purpose of measuring central venous pressure (CVP) in critically ill patients is to assess the patient's intravascular fluid volume status and right ventricular function. Central venous pressure is the pressure of blood in the vena cava near the right atrium of the heart. It reflects the amount of blood returning to the heart and the ability of the heart to pump the blood back into the circulation. CVP is used as an estimate of right atrial pressure, which is a determinant of right ventricular preload (the degree of stretch on the right ventricle at the end of diastole). A high CVP may indicate fluid overload or impaired right ventricular function (such as in right heart failure or pulmonary hypertension), whereas a low CVP may indicate hypovolemia (low blood volume). Although CVP is no longer considered a reliable sole indicator of fluid responsiveness (the likelihood that the patient's cardiac output will increase with fluid administration), it is still useful when interpreted in the context of the patient's overall clinical picture, including urine output, blood pressure, and other hemodynamic parameters. Trends in CVP measurements are often more informative than single values. For example, a rising CVP may indicate worsening fluid overload, while a falling CVP may suggest improved fluid status after diuresis. More advanced hemodynamic monitoring techniques, such as pulmonary artery catheterization and echocardiography, provide more comprehensive assessments of cardiac function and fluid status, but CVP monitoring remains a common and readily available tool in critical care settings.