Baroreflex buffering and susceptibility to vasoactive drugs.
BACKGROUND
The overall effect of vasoactive drugs on blood pressure is determined by a combination of the direct effect on vascular tone and an indirect baroreflex-mediated effect, a baroreflex buffering of blood pressure. Differences in baroreflex function affect the responsiveness to vasoactive medications, particularly baroreflex buffering of blood pressure; however, the magnitude is not known.


RESULTS
We characterized baroreflex function and responses to vasoactive drugs in patients with idiopathic orthostatic intolerance, patients with essential hypertension, patients with monogenic hypertension and brachydactyly, patients with multiple system atrophy, and control subjects. We used phenylephrine sensitivity during ganglionic blockade as a measure of baroreflex buffering. Phenylephrine (25 microg) increased systolic blood pressure 6+/-1.6 mm Hg in control subjects, 6+/-1.1 mm Hg in orthostatic intolerance patients, 18+/-3.9 mm Hg in patients with essential hypertension, 31+/-3.4 mm Hg in patients with monogenic hypertension, and 25+/-3.4 mm Hg in patients with multiple system atrophy. Similar differences in sensitivities between groups were observed with nitroprusside. The sensitivity to vasoactive drugs was highly correlated with baroreflex buffering function and to a lesser degree with baroreflex control of heart rate. In control subjects, sensitivities to nitroprusside and phenylephrine infusions were correlated with baroreflex heart rate control and sympathetic nerve traffic.


CONCLUSIONS
Our findings are consistent with an important effect of baroreflex blood pressure buffering on the sensitivity to vasoactive drugs. They suggest that even moderate changes in baroreflex function may have a substantial effect on the sensitivity to vasoactive medications.
Jordan
Jens
J
Franz-Volhard Clinical Research Center and Helios Klinikum, Medical Faculty of the Charité, Humboldt-University, Berlin, Germany. jordan@fvk-berlin.de
Tank
Jens
J
Shannon
John R
JR
Diedrich
Andre
A
Lipp
Axel
A
Schröder
Christoph
C
Arnold
Guy
G
Sharma
Arya M
AM
Biaggioni
Italo
I
Robertson
David
D
Luft
Friedrich C
FC
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000328:Adult; D017704:Baroreflex / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects; D004032:Diet; D004305:Dose-Response Relationship, Drug; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000503:physiopathology*; D007024:Hypotension, Orthostatic / Q000175:diagnosis / Q000503:physiopathology*; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000175:diagnosis / Q000503:physiopathology*; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011187:Posture; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000503:physiopathology; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology; D014666:Vasomotor System / Q000187:drug effects / Q000503:physiopathology
D000318:Adrenergic beta-Agonists; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine; D007545:Isoproterenol