The clinical significance of continuous monitoring of mixed venous blood oxygen saturation during acute phase of myocardial infarction relationship of blood oxygen saturation to cardiac pump function
Journal of the Iwate Medical Association 40(3): 373-384
The clinical significance of continuous monitoring of mixed venous oxygen saturation (S.hivin.vO2) was evaluated in 45 patients with acute myocardial infarction. S.hivin.vO2 correlated well with the clinical course of patients and hemodynamic condition. In those patients with no clinical evidence of congestive heart failure (CHF-), the mean S.hivin.VO2 was 69.8 .+-. 5.6%. When congestive heart failure (CHF+) was present, the mean S.hivin.VO2 was less than 60% patients showed some evidence of heart failure and their mortality rate was proved to be very high. Patients with acute myocardial infarction were classified to 4 groups according to Forrester's hemodynamic classification. The values mean S.hivin.VO2 for each group were 70.7 .+-. 4.1% for H-I group, 54.7 .+-. 6.9% for H-II group, 55.8 .+-. 9.8% for H-III group, 47.0 .+-. 8.0% for H-IV group. The values of S.hivin.VO2 measured from H-I and H-II group were found to be significantly lower than that of the H-I group (p < 0.01). The mean S.hivin.VO2 of 14 cases whose cardiac indices (CI) were less than 2.2 1/min/m2 was 53.3 .+-. 9.6%, whereas the mean S.hivin.VO2 of 31 cases whose cardiac indices were more than 2.2 l/min/m2 was 6.66 .+-. 8.6%. The former was significantly lower than the latter (p < 0.01). The mean S.hivin.VO2 of 12 cases whose pulmonary capillary wedge pressures (PCW) were higher than 18 mmHg was 52.2 .+-. 7.9%, whereas the mean S.hivin.vO2 of 33 cases whose PCWs were lower than 18 mmHg was 66.2 .+-. 9.2%, the former S.hivin.VO2 being significantly lower than the latter (p < 0.01). The relationships of S.hivin.vO2 (y) to CI (x1) stroke volume index (SVI) (x2), left ventricular stroke work index (LVSWI) (x3) were represented as next regression equations such as y = 53.8 log x1 + 42.7, y = 47.7 log x2 + 6.6, y = 36.2 log x3 = 9.8, respectively. The correlation between PCW and S.hivin.vO2 was represented by a regression equation y = -o.8x + 73.8, with a negative correlation coefficient (p < 0.01). Changes in S.hivin.VO2 values also correlated with hemodynamic changes. There were highly significant positive correlation between the S.hivin.VO2 change greater than 5% and corresponding change in cardiac index (p < 0.001). This study suggested that continuous monitoring of S.hivin.vO2 in the observation of instantaneous changes in hemodynamic state and helpful for the management of critical patients with acute myocardial infraction. The S.hivin.vO2 should be maintained above 60% for stabilization of hemodynamic state, because decrease in S.hivin.vO2 more than 5% is an indication of a significant decrease in the cardiac index.