Heart rate variability during artificial ventilation and apnea in
brain damaged rabbits.
Kawamoto, Masashi, Kotaro Kaneko, Hardian, and Osafumi Yuge.
Department of Anesthesiology and Critical Care, Hiroshima
University School of Medicine, Kasumi 1-2-3, Minami-ku, Hiroshima
734, Japan
APStracts 2:0431H, 1995.
The effect of artificial ventilation, apnea and norepinephrine
administration on heart rate variability was determined in brain
damaged rabbits. Electrocardiographic R-R intervals and circulatory
variables were measured for 5 min at 3 different ventilatory
frequencies including apnea under isoflurane general anesthesia. The
same measurements were repeated after brain damage had been inflicted
by inflating an intracranial balloon. In control rabbits (n=8) and in
those receiving norepinephrine (n=8), power spectral analysis of R-R
intervals were repeated, and spectral components of very low (Vl:
0.04-0.09 Hz), mid (Mi: 0.09-0.15 Hz) and high (Hi: 0.15-0.40 Hz)
frequency band areas were assessed. Vl+Mi (p<0.05) increased
during apnea, while Hi did not change under general anesthesia.
However, after brain damage, in both groups, Vl+Mi did not change
while Hi was depressed (p<0.05). There was no intergroup
difference in decreases of Hi/(Vl+Mi) (p<0.05) during apnea
under either condition. Norepinephrine increased heart rate and
arterial pressure (p<0.05), but did not produce any intergroup
difference in the spectral components. We suggest that sympathovagal
balance is apt to be sympathotonic during apnea under general
anesthesia while it is vagolytic with brain damage.
Received 20 March 1995; accepted in final form 13 September 1995.
APS Manuscript Number H266-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 31 October 95