How to perform central venous pressure measurement
Abstract
Central venous pressure (CVP) is an estimate of the blood pressure in the right atrium. CVP refects the amount of blood returning to the heart and the ability of the heart to pump the blood into the arterial system. CVP is directly proportional to the volume of blood in the anterior vena cava and venous tone. This pressure is decreased by hypovolaemia or venodilation and is increased by fluid therapy or venoconstriction. It can be used to guide fluid therapy administration in critically ill patients, or in patients with cardiac disease to help prevent volume overload.
Central venous pressure (CVP) is an estimate of the blood pressure in the right atrium by measuring the pressure in the cranial (or caudal) vena cava (Moses and Curran, 2007). It evaluates three things: the heart's ability to function as a pump; blood volume in relation to volume capacity; and vasomotor tone (indirectly) (Hughes, 2005). CVP measurement is indicated when trying to determine fluid resuscitation end points, as a way of assessing fluid overload, or when heart failure is suspected. CVP measurements can be taken intermittently with a water manometer or continuously with a pressure transducer and patient monitor.
A catheter placed in the cranial or caudal vena cava via the jugular or lateral/medial saphenous vein respectively is required for measurement of CVP. Peripheral venous pressure bears no correlation to CVP. Care must be taken when measuring CVP as consistency is important. For this reason, ideally the same person should take the measurements during the shift; if the patient cooperates all measurements should be taken in the same position.
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