Spontaneous blood pressure fluctuations and renal blood flow
dynamics.
Cupples, William A., Peter Novak, Vera Novak, and Fred C. Salevsky.
Departments of Medicine and Neurological Sciences, Sir Mortimer B.
Davis-Jewish General Hospital, and Department of Anesthesiology,
Montreal Neurological Hospital and Institute
APStracts 2:0120F, 1995.
Two mechanisms operating at 0.03-0.05 and 0.1-0.2 Hz are involved in
autoregulation of renal blood flow. To examine the behavior of the
faster system, the response of renal blood flow to spontaneous
fluctuations of arterial pressure was assessed in Sprague-Dawley rats
anesthetized by isoflurane or halothane. During halothane anesthesia,
autonomous oscillation of total renal blood flow was observed at
0.10-0.15 Hz and normalized admittance gain became negative at 0.11
+/- 0.01 Hz. During isoflurane anesthesia there was autonomous power
in blood flow in a broad peak between 0.15 and 0.25 Hz and gain
became negative at 0.15 +/- 0.01 Hz. Increasing inspired [isoflurane]
from 1.4 +/- 0.1% to 2.2 +/- 0.1% reduced pressure by 22 +/- 2 mmHg
but did not alter blood flow or the transfer function, indicating
that the operating frequency was not changed. In another experiment,
changing from isoflurane to halothane increased peak power in the
autonomous blood flow oscillation five-fold and reduced its frequency
from 0.18 +/- 0.01 to 0.14 +/- 0.01 Hz. Gain became negative at a
higher frequency, 0.16 +/- 0.01 Hz, during isoflurane than halothane
anesthesia, 0.12 +/- 0.01 Hz. The results show that the 0.1-0.2 Hz
system is reliably detected under unforced conditions and provides
modest attenuation of pressure fluctuations at
Received 13 March 1995; accepted in final form 7 July 1995.
APS Manuscript Number F85-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.