The Use of Central Venous Pressure as a Guide to Volume Replacement in Shock

¹ Department of Surgery, Royal Victoria Hospital and McGill University

A prompt hemodynamic diagnosis in shock can be made by measuring the central venous pressure and observing the response to transfusion. Patients with low CVP have either volume deficit or, rarely, peripheral pooling. If transfusion restores

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the CVP and blood pressure to normal, a volume deficit existed. If repeated transfusion fails to restore blood pressure and CVP, strong evidence exists that pooling is occurring in the periphery, probably in the capillaries and venules of the circulation. Patients with a high CVP (over 10 cm. of water) and low blood pressure have a cardiac deficit. Isoproterenol will greatly increase cardiac output and blood pressure at the same or lower CVP in these patients.

Measurement of CVP facilitates prompt treatment of shock, decreases the number of patients taken to surgery with an inadequate blood volume, and is a safe guide to blood volume replacement. Patients can be transfused to a CVP of 15 cm. of water with safety.

Mirroring as it does changes in tone of peripheral blood vessels and volume of venous return to the heart, the CVP represents blood volume as seen from the right side of the heart. In addition, as the cardiac filling pressure, it determines to a large extent the initial stretch of cardiac muscle fiber and thus the force of cardiac contraction. It, therefore, provides the clinician with an inside view of the heart and circulation.

Blood volume measurement, on the other hand, is based on age and weight or surface area of normal subjects. It is a static measurement having little relationship to the minute-to-minute changes in the circulatory dynamics of patients in shock.