Hypertension, Vol 5, 79-85, Copyright © 1983 by American Heart Association
AM Shepherd, MS Lin, JL McNay, GE Musgrave and TK Keeton
Baroreflex activity is a determinant of the homeostatic response to
alteration in blood pressure. We examined the factors that determine the
magnitude of the vasodepressor response to sequential incremental
intravenous infusions of sodium nitroprusside (NP), 0.05 to 6.4
micrograms/kg/min, in eight male patients with essential hypertension. Each
infusion level was of 10 minutes' duration. Change from control values of
mean arterial pressure (delta MAP), heart rate (delta HR) and plasma
norepinephrine (delta NE) were obtained at the end of each infusion level.
Significant correlations were found between delta MAP vs log dose NP, delta
HR vs delta MAP and delta NE vs delta MAP for each patient (p less than
0.05). However, the slopes of these relationships varied widely between
subjects and were significantly correlated with the control blood pressure
of each patient. In addition, the sympathetic responsiveness, as measured
by delta NE vs delta MAP, was inversely correlated with the degree of
vasodepressor response seen. Thus, the magnitude of the vasodepressor
response was determined by two major factors: 1) the predrug blood
pressure, possibly reflecting altered vascular geometry with hypertension;
2) the degree of sympathetic response, which probably acts by mediating the
degree of reflex alpha-adrenergic-mediated arteriolar vasoconstriction.
ARTICLES
Baroreflex sensitivity modulates vasodepressor response to nitroprusside
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