Hemodynamic effects of hypovolemia in normal subjects and patients with congestive heart failure.

Five young normal subjects (NS) and six middle-aged patients with chronic, lowoutput, congestive heart failure (HFP) were studied before and after 10 minutes of exposure to hypovolemia induced by negative pressure (30 mm Hg) applied to the lower body. ECG, respirometer, and catheters placed in the subclavian artery and superior vena cava permitted measurements of heart rate (HR), respiration rate, arterial and central venous pressures (CVP), and cardiac output (CO). In the group of NS, systemic vascular resistance (SVR) rose moderately, while CVP fell 4.3 mm Hg; CO, stroke volume (SV), stroke work (SW), and central blood volume (CBV) fell about 20%, whereas blood pressure and HR showed little change. In the group of HFP, control hemodynamic values were generally abnormal. In four patients the response to hypovolemia was similar to that of NS. Two patients with advanced heart failure showed no change or a rise in CO, SV, and SW in the face of a fall in CVP (3.1 and 3.7 mm Hg), no change or a fall in SVR, and a rise in CBV. It is concluded that HFP does not respond to hypovolemia in a consistent manner. Certain patients with advanced failure demonstrated abnormal responses to induced hypovolemia, the causes for which are complex.