Effects of afferent neural stimulation on critical oxygen delivery:
a hemodynamic explanation.
Kirkman, E., H. Zhang, H. Spapen, R. A. Little & J. L. Vincent.
Depertment of Intensive Care, Erasme University Hospital, Free
University of Brussels, Belgium, and North Western Injury Research
Centre, University of Manchester, Manchester, UK
APStracts 2:0186R, 1995.
Injury and activation of somatic afferent nerve fibers may alter
critical oxygen delivery (DO2C); the point at which oxygen
consumption becomes dependent upon delivery, and hence reduce
tolerance to hypovolaemia. The present study investigated the
mechanism of this. Anaesthetized mongrel dogs were divided into two
groups; CONTROL (n=6), and BNS (n=5) which were subject to brachial
nerve stimulation. Whole body oxygen delivery (DO2I) and consumption
were initially similar in both groups. DO2I was reduced by cardiac
tamponade to determine DO2C. DO2C was significantly higher in BNS
compared to CONTROL (11.5: 11.0-16.7 vs 7.5: 6.9-9.5 ml.min-1.kg-1,
median:Q1-Q3), while critical oxygen extraction ratios were lower
(54.8: 39.7-61.2 vs 78.3: 53.5-92.4%). At approximately DO2C
normalized femoral blood flow was lower than renal flow in CONTROL
(renal-femoral difference 17.4:8.7-40.0%), but not in BNS (-7.8:-14.8
to +11.8%). These results indicate that activation of somatic
afferent nerve fibres elevates DO2C. This could be due to an
impairment in peripheral oxygen extraction as a consequence of a
redistribution of blood flow away from metabolically active vital
organs towards relatively inactive skeletal muscle.
Received 7 December 1994; accepted in final form 29 June 1995.
APS Manuscript Number R695-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.