[Left ventricular function during hypoxia. 1: Effect of blood glucose level].

We investigated the effects of blood glucose levels and myocardial glucose uptake on cardiac function during hypoxia in mongrel dogs (N = 50). During hypoxia (PaO2 = 20 mmHg) caused by inhalation of low concentration of oxygen for 2 hours, left ventricular (LV) function including LV pressure, maximum rate of rise of LV pressure, and cardiac index decreased significantly following initial enhancement. There were significant correlations between these hemodynamic parameters and blood glucose levels. The blood glucose levels correlated significantly with myocardial glucose uptake and blood lactic acid levels (r = 0.660: P = 0.000, r = 0.380: P = 0.000, respectively). Eight of nine dogs which died within 90 minutes during hypoxia showed low blood glucose levels and high lactic acid levels. During hypoxia, myocardial glucose uptake increased to more than five times of control value. On the other hand myocardial lactic acid uptake decreased and turned to production. At the same degree of blood lactic acid levels, LV function was maintained better with high blood glucose levels than with low levels. With low blood glucose levels, myocardial lactic acid uptake and production tended to cease. The pronounced change in LV function during hypoxia could be partially explained by decreased production of ATP due to decrease in myocardial glucose uptake and high lactic acid levels. It seems that high blood glucose levels are preferable to maintain cardiac performance under such a condition.