[Effect of carbon dioxide (hypocapnia and hypercapnia) on regional myocardial tissue oxygen tension in dogs with coronary stenosis].
Carbon dioxide (CO2) has been well documented to act as a potent vasodilator of coronary vessels under normal conditions. But there is little data available on the effect of CO2 on the collateral perfusion of patients with coronary insufficiency. We studied the effects of CO2 on the myocardial tissue PO2 in anesthetized dogs with critical coronary stenosis. Twelve mongrel dogs were anesthetized with pentobarbital and ventilated with 100% O2 to maintain normocapnia. Electromagnetic blood flow (BF) probe was applied on the left anterior descending artery (LAD). Regional myocardial PO2 was measured at two different sites using two pairs of monopolar polarographic needle electrodes; one inserted in the epicardial (EPI) layer, and the other in the endocardial (ENDO) layer. These were placed in the regions supplied by LAD and circumflex. Following the baseline recording, critical stenosis of LAD was produced by adjusting a copper-wire clamp occluder until LADBF was reduced by 50%. After a stable normocapnic ventilation, hypocapnia was produced by hyperventilation. To induce hypercapnia, exogenous CO2 was added to the inspired gas stepwise until end-tidal CO2 fraction reached 10%. Hypocapnia resulted in a significant reduction in myocardial PO2 in both EPI and ENDO non-stenotic areas, while hypercapnia increased these PO2 values dose-dependently. After coronary stenosis, hypocapnia resulted in a small but significant reduction of PO2 in endocardial ischemic area. Hypercapnia did not induce any sign of reduced regional myocardial PO2 or evidence of regional or intramural "steal" phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)
Okazaki
K
K
Department of Anesthesiology, Yokohama City University School of Medicine.
Hashimoto
K
K
Okutsu
Y
Y
Okumura
F
F
D000818:Animals; D003251:Constriction, Pathologic; D003327:Coronary Disease / Q000503:physiopathology*; D004285:Dogs; D006935:Hypercapnia / Q000503:physiopathology*; D016857:Hypocapnia / Q000503:physiopathology*; D009206:Myocardium / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*
D010100:Oxygen