MODELS TO STUDY THE RELATION BETWEEN OXYGEN CONSUMPTION AND OXYGEN DELIVERY DURING AN ACUTE REDUCTION IN BLOOD FLOWcolon; COMPARISON OF BALLOON FILLING IN THE INFERIOR VENA CAVA, TAMPONADE, AND HEMORRHAGE

摘要

ABSTRACTDifferent animal models have been used to study the relationship between oxygen consumption (VO2) and oxygen delivery (DO2) and each of them has its own specificity. The present study compared the models of balloon inflation in the inferior vena cava (BALL), tamponade (TAMP), and hemorrhage (HEM) to acutely reduce blood flow in pentobarbital-anesthetized dogs. The order of the procedures was randomized first, but HEM was irreversible so that HEM was applied as the third procedure (n equals; 10) or as a unique procedure (n equals; 4). Critical DO2(DO2 crit) was determined as the intercept of two best fitted lines of regression of VO2against DO2, but similar results were obtained when it was calculated from blood lactate or from arterio-venous differences in pH (AVpH) or Pco2(VAPco2). At DO2 crit, VO2was 6.6 plusmn; .7 mL/minmiddot;kg in BALL, 6.2 plusmn; .6 mL/minmiddot;kg in TAMP and 6.0 plusmn; .7 mL/minmiddot;kg in HEM (p .05 vs. BALL). DO2 critwas significantly greater with BALL (14.3 plusmn; 2.3 mL/minmiddot;kg) than with TAMP (10.2 plusmn; 1.7 mL/minmiddot;kg,p .01 vs. BALL) or HEM (9.1 plusmn; 1.4 mL/minmiddot;kg,p .01 vs. BALL). Also, critical oxygen extraction (EO2 crit) was significantly lower with BALL (46.5 plusmn; 4.8percnt;) than with TAMP (62.1 plusmn; 11.5percnt;,p .01 vs. BALL) or HEM (66.8 plusmn; 11.4percnt;,p .01 vs. BALL,p .05 vs. TAMP). The earlier onset of tissue hypoxia with BALL was probably related to the blood flow redistribution induced by this model. Study of the pressure/flow relationship revealed that the vascular responsiveness was significantly decreased in HEM compared to TAMP. The lack of reversibility of HEM could account, at least in part, for the decreased vascular reactivity when blood volume is reduced.