RESPONSES OF THE HUMAN UPPER EXTREMITY VASCULAR BED TO EXERCISE, COLD, LEVARTERENOL, ANGIOTENSIN, HYPERTENSION, HEART FAILURE, AND RESPIRATORY TRACT INFECTION WITH FEVER

Modulation of vascular capacitance by angiotensin and nitroprusside: a mechanism of changes in pericardial pressure

The aim of the present study was to test the hypothesis that vasoactive drugs may modify left ventricular diastolic function by shifting blood between the systemic vascular bed and the heart, thereby changing pericardial and left ventricular pressure. The experiments were done in 10 open-chest, anesthetized, previously splenectomized dogs in which changes in pericardial surface pressure in response to intravenous sodium nitroprusside and angiotensin were related to changes in blood volume in the abdominal region. Blood volume was determined by blood pool scintigraphy (99mTc) and regions of interest were drawn in the liver and in the mesenteric area. Angiotensin was infused at rates that were adjusted to increase mean aortic pressure by 20 and 30 mm Hg, and nitroprusside was infused at rates to decrease mean aortic pressure by 30 and 50 mm Hg. Angiotensin increased pericardial pressure by 3 and 5 mm Hg at the respective doses and there were increments in left ventricular end-diastolic pressure (LVEDP) and left ventricular diameter (sonomicrometry). Angiotensin decreased blood volume in the mesenteric region by 14% and 17%, but did not significantly change blood volume in the liver region. Angiotensin increased portal venous pressure and decreased mesenteric blood volume, suggesting decreased mesenteric venous compliance. Nitroprusside had opposite effects: pericardial pressure was decreased by 5.5 and 6.5 mm Hg by the respective doses. The doses of nitroprusside increased blood volume in the mesenteric region by 14% and 20%, but did not significantly change blood volume in the liver region.(ABSTRACT TRUNCATED AT 250 WORDS)

The contribution of local factors to the elevated venous tone of congestive heart failure

Since the concept of an elevated venous tone in congestive heart failure (CHF) has been recently questioned, the venous volume of the elevated calf at a venous pressure of 30 mm Hg (VV[30]) was determined in 18 normal volunteers (N) and 10 CHF patients with a mercury-in-rubber strain gauge plethysmograph. CHF patients had a significantly lower VV[30] at rest and after intra-arterial phentolamine (2 mg) than normal subjects, suggesting that in these patients a state of peripheral venoconstriction existed (rest-N: 4.63+/-0.17, CHF: 1.7+/-0.23 ml/100 ml, P < 0.01; pre- and postphentolamine-N: 4.85+/-0.21 to 4.95+/-0.31, CHF: 2.26+/-0.29 to 2.68+/-0.38 ml/100 ml, P < 0.01). Of note is that alpha adrenergic blockade failed to increase VV[30] significantly in N, but did increase it in CHF (P < 0.05), suggesting that part of the decreased VV[30] in CHF in due to an augmented sympathoadrenal discharge. When sodium nitrite (30 mg) was given as a single intra-arterial injection before or after phentolamine or when given in four successive doses at 3-min intervals, the VV[30] of CHF patients was never increased to more than 3.62+/-0.42 ml/100 ml and was always less than N (P < 0.01). Importantly, VV[30] in CHF after these interventions was even significantly less than that of N before intervention (P < 0.05), suggesting that factors other than local active smooth muscle venoconstriction were operative in CHF to lower VV[30]. It is suggested that perhaps clinically undetectable edema and an elevated tissue pressure may account for these differences.