AJP - Regulatory, Integrative and Comparative Physiology, Vol 235, Issue 5 279-R285, Copyright © 1978 by American Physiological Society
Unstable state of the arterial pressure control system after a mild hemorrhage
H. Hosomi
The stability of the arterial pressure control system after a mild
hemorrhage (5 ml/kg body wt) was studied in 10 anesthetized cats by
analyzing the responses of arterial pressure and of heart rate and the dead
time (L) of heart rate response to a minute, rapid test hemorrhage (1 ml/kg
body wt). The overall open-loop gain (H) of the arterial pressure control
system was estimated from the ratio of arterial pressure fall immediately
after the quick hemorrhage over the steady-state fall. Increases in H and L
were correlated with the tendency of the arterial pressure control system
to be unstable and oscillate. Oscillation in arterial pressure was always
accompanied by a marked increase in heart rate (deltaHR), which represents
an enhanced activity of the sympathetic nervous system and serves to
restore arterial pressure toward the prehemorrhage level. The present study
indicates that the magnitude of deltaHR also serves as a good predictor of
arterial pressure oscillation.
