Central Venous Pressure: Just a Blast from the Past or Relevant? A Debate

COMMENTARYare dynamic indices of fluid responsiveness better and less invasive for guiding fluid administration?Central venous pressure (CVP) monitoring is surrounded by controversies and is one of the top matters of debate in critical care.CVP should not be viewed as a mere number but as a trend that can have tremendous importance on the management in critical care. Prerequisite Setup to Minimize Errors in CVP Measurement• Positioning of the CVP transducer: Classical intensive care unit (ICU) teaching dictates placing the transducer at the midthoracic level at the level of the fifth rib.This is said to be the reference point for the right atrium.However, this is only true for supine patients, and the position of the atrium with respect to this reference point changes with changes in posture.A fixed reference point is at a distance of 5 cm below the angle of the sternum, which is at the joining of the sternum and the second rib. 1 • The reference point of pressure measurement: Optimal measurement of the right atrial pressure (RAP) at the end diastole can be done by measuring CVP at the beginning of the V wave, which correlates to the effect of isometric ventricular contraction on RAP and aligns with the Q wave on electrocardiogram.It reflects the atrial pressure just before ventricular contraction, hence represents cardiac preload.At the same time, if there is a tall wave or V-wave, the peak of these waves can have significant hemodynamic effects on the upstream organs like the liver and the kidney. 7• The reference point of the respiratory cycle: In order to estimate the cardiac preload, CVP should be measured at the end of expiration, at which point the effect of the intrathoracic pressure around the heart is minimal. 2 • Consideration of comorbidities: In the event of a high CVP value, one must consider confounding factors like the presence of chronic pulmonary hypertension, dynamic hyperinflation, and restrictive heart diseases. 2The importance of CVP in critical care is given below:• Importance of the value of CVP: The cardiac output (CO) is an interplay of preload, cardiac contractility, afterload, and heart rate.In a state of equilibrium, the CO has to be the same as the venous return into the heart.Hence, a decreased CO can be translated as a decreased venous return.So, low CO due to dysfunction of any of the sides of the heart will invariably lead to increased RAP. 3,4 The RAP, that is, CVP, is a major determinant of CO.The following graph emphasizes the plateau phase of the ventricular function curve (Fig. 1).