Laboratory tests
Results of laboratory tests are shown in Fig. 1(A). Local capillary lactate was significantly higher in the severe group (14.2 ± 8.6 mmol/L) than in the mild group and the sham group (4.1 ± 3.1 and 1.0 ± 0.1 mmol/L, P = .01 and .002, respectively). There was no significant difference between the mild group and the sham group (P = .58). Systemic lactate was significantly higher in the severe group and in the mild group (0.6 ± 0.1 and 0.7 ± 0.2 mmol/L) than in the sham group (0.4 ± 0.1 mmol/L, P = .03, 001, respectively), but there was no significant difference between the severe group and the mild group (P = .27). LDH (severe, 431.3 ± 131.0; mild, 188.7 ± 34.9; sham, 139.7 ± 18.5 U/L; respectively) and CK (severe, 406.2 ± 144.5; mild, 143.3 ± 11.8; sham, 125.8 ± 23.1 U/L; respectively) were significantly higher in the severe group than in the others (all P < .001, for details, see Fig. 1(A)), but there was no significant difference between the mild and the sham groups (P = .54 and .93). AST did not show a significant difference between any two groups (severe, 73.5 ± 20.5; mild, 64.3 ± 8.9; sham, 63.0 ± 5.9 U/L; respectively. P = .36).
Time course of oxygenation in AMI
Before clamping, average oxygenation was greater than 70%. All rats showed a rapid decrease of oxygenation after clamping, and then reached a plateau (< 30%) within five minutes. The time course of the oxygenation after clamping is shown in Fig. 1(B).
The appearance of ischemic intestine was dark, and it tended to be darker in the severe group, but it was not always distinguishable between the two ischemic groups (Fig. 2).
Figure 3(A), Fig. 3(B), and Table 1 show the time course of oxygenation in two groups after reperfusion. Before removing the vascular clamps, there was no significant difference between the two groups. Once the vascular clamps were removed, oxygenation recovered to the baseline level (about 65–75%) immediately in the mild group. On the other hand, oxygenation recovered slightly but remained lower in the severe group. At 1, 5, 10, 30, and 60 minutes after the removal of vascular clamps, oxygenation was significantly lower in the severe group than in the mild group.
Table 1
Oxygenation after reperfusion in the mild group and the severe group
Time (min) | Oxygenation in the mild group | Oxygenation in the severe group | P value |
0 | 17.6 (2.2) | 24.9 (2.6) | .30 |
1 | 65.3 (3.2) | 34.2 (5.3) | .006 |
5 | 68.8 (1.9) | 33.8 (5.8) | .007 |
10 | 69.6 (3.0) | 29.4 (4.3) | < .001 |
30 | 65.7 (1.6) | 33.5 (4.3) | .002 |
60 | 66.8 (3.1) | 33.8 (4.6) | .001 |
Note – After reperfusion, the time course of oxygenation was clearly different between the mild group and the severe group. Oxygenation was significantly higher in the mild group than in the severe group at 1, 5, 10, 30, and 60 min. All values are shown as means (standard error).
Pathological findings
In the severe group, all tissue samples showed irreversible damage, and the average score was 7.2 ± 0.4, significantly higher than in the other groups (both P < .001). In the mild group, the average score was 1.2 ± 1.8, and in the sham group, the average score was 0.
Correlation analysis between oxygenation and the pathological score
Correlation analysis between oxygenation and the pathological score was performed (Fig. 3(C), Table 2). Table 2 shows Spearman’s correlation coefficient (rs-value) along with the corresponding P-values for the correlation between oxygenation and the pathological score, showing a significant strong negative correlation at each time point after reperfusion. Correlation analysis between local capillary lactate and the pathological score was also performed, but it did not show a significant correlation (P = 0.06).
Table 2
Correlation between oxygenation and the pathological score
Time (min) | P value | rs value |
0 | .065 | .554 |
1 | .007 | -0.754 |
5 | .014 | -0.706 |
10 | .016 | -0.695 |
30 | .008 | -0.747 |
60 | .003 | -0.806 |
Note – The P value and rs value between oxygenation and the pathological score are shown. There was a significant, strong negative correlation between oxygenation and the pathological score at 1, 5, 10, 30, and 60 min.