Hypocapnia attenuates mesenteric ischemia-reperfusion injury in a rat model.
OBJECTIVE
Hypocapnia, a recognized complication of high frequency oscillation ventilation, has multiple adverse effects on lung and brain physiology in vivo, including potentiation of free radical injury. We hypothesized that hypocapnia would potentiate the effects of mesenteric ischemia-reperfusion on bowel, liver and lung injury.


METHODS
Anesthetized male Sprague-Dawley rats were ventilated with high frequency oscillation and were randomized to one of four groups, exposed to either mesenteric ischemia-reperfusion or sham surgery, and to either hypocapnia or normocapnia.


RESULTS
All animals survived the protocol. Ischemia-reperfusion caused significant histologic bowel injury. Bowel 8-isoprostane generation was greater in ischemia-reperfusion vs sham, but was attenuated by hypocapnia. Laser-Doppler flow studies of bowel perfusion confirmed that hypocapnia attenuated reperfusion following ischemia. Plasma alanine transaminase, reflecting overall hepatocellular injury, was not increased by ischemia-reperfusion but was increased by hypocapnia; however, hepatic isoprostane generation was increased by ischemia-reperfusion, and not by hypocapnia. Oxygenation was comparable in all groups, and compliance was impaired by ischemia-reperfusion but not by hypocapnia.


CONCLUSIONS
Hypocapnia, although directly injurious to the liver, attenuates ischemia-reperfusion induced lipid peroxidation in the bowel, possibly through attenuation of blood flow during reperfusion.
Duggan
Michelle
M
Lung Biology Program, The Research Institute and the Department of Critical Care Medicine, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada.
Engelberts
Doreen
D
Jankov
Robert P
RP
Worrall
Jordan M A
JM
Qu
Rong
R
Hare
Gregory M T
GM
Tanswell
A Keith
AK
Mullen
J Brendan
JB
Kavanagh
Brian P
BP
D000818:Animals; D016857:Hypocapnia / Q000503:physiopathology*; D007422:Intestines / Q000098:blood supply / Q000473:pathology; D008099:Liver / Q000473:pathology; D008297:Male; D017538:Mesenteric Artery, Superior / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000517:prevention & control*