76 M. Bagherinasab et al.: J Extra Corpor Technol 2026, 58, 73--78
Table 3. Key variables observed during the initial 180 s following the initiation of CPB.
Time |
Fast( n = 30) |
Slow( n = 30) |
P-value |
|
Hematocrit |
|
|
T0 |
38.31 ± 4.93 |
37.55 ± 5.04 |
0.55 |
T1 |
24.12 ± 4.18 |
23.91 ± 3.39 |
0.82 |
T2 |
22.12 ± 5.37 |
23.81 ± 3.61 |
0.15 |
T3 |
23.15 ± 4.06 |
23.38 ± 3.34 |
0.81 |
T4 |
23.21 ± 3.92 |
23.69 ± 2.98 |
0.59 |
|
Partial arterial oxygen( mmHg) |
|
|
T0 |
190.66 ± 37.25 |
233.20 ± 69.52 |
0.00 |
T1 |
391.70 ± 46.91 |
419 ± 43.35 |
0.02 |
T2 |
379.83 ± 47.62 |
412.26 ± 39.73 |
0.00 |
T3 |
379.56 ± 46.87 |
409.00 ± 35.99 |
0.00 |
T4 |
376.20 ± 43.99 NIRS( Left side) |
402.83 ± 33.88 |
0.01 |
T0 |
70.56 ± 4.31 |
66.53 ± 5.97 |
0.00 |
T1 |
67.40 ± 4.44 |
66.43 ± 5.47 |
0.45 |
T2 |
67.10 ± 4.49 |
66.26 ± 5.20 |
0.50 |
T3 |
67.53 ± 4.32 |
66.96 ± 5.59 |
0.66 |
T4 |
67.83 ± 4.33 NIRS( Right side) |
66.80 ± 5.31 |
0.41 |
T0 |
70.26 ± 4.55 |
68.53 ± 4.31 |
0.13 |
T1 |
67.00 ± 5.11 |
67.66 ± 4.56 |
0.59 |
T2 |
66.10 ± 4.76 |
67.63 ± 4.42 |
0.20 |
T3 |
67.00 ± 4.98 |
68.30 ± 4.22 |
0.28 |
T4 |
67.50 ± 4.94 |
68.13 ± 4.51 |
0.60 |
T0 = Before anesthesia induction, T1 = 30 s after CPB commencement, T2 = 60 s after CPB commencement, T3 = 90 s after CPB commencement, T4 = 1800 s after CPB commencement. NIRS = Near infra-red spectrometry.
Table 4. Delirium occurs during the initial four days following surgery.
POD |
Fast( n = 30) |
Slow( n = 30) |
P-value |
First n(%) |
15( 50 %) |
9( 30 %) |
0.11 |
Second n(%) |
15( 50 %) |
8( 26.7 %) |
0.06 |
Third n(%) |
11( 36.7 %) |
5( 16.7 %) |
0.08 |
Fourth n(%) |
6( 20 %) |
3( 10 %) |
0.27 |
POD = Postoperative day.
PaO 2 in the fast group remained lower than that in the slow group, but the difference( ranging from 26.6 to 32.4 mmHg) was less than the baseline difference.
The occurrence of delirium within the study groups, assessed using the CAM-ICU, is detailed in Table 4. Patients in the slow group exhibited a not statistically significant trend for a lower incidence of delirium, particularly on the second and third days following surgery. However, these findings did not reach statistical significance( P = 0.06 and 0.08).
Discussion
Our research presents the first evidence of variations in regional brain tissue oxygenation associated with the gradual versus rapid initiation of CPB to achieve the desired target flow. While statistically significant PaO 2 differences(~ 30 mmHg) were observed between groups during CPB initiation, the clinical relevance of this finding requires careful interpretation: 1. Supraphysiological oxygen levels: Both groups maintained hyperoxic( PaO 2 > 375 mmHg) throughout initiation-- far exceeding physiological needs( normal PaO 2: 80--100 mmHg). At these levels, oxygen content plateaus due to maximal hemoglobin saturation, diminishing the clinical impact of a 30 mmHg difference [ 8 ]. 2. Potential hyperoxia risks Emerging evidence suggests hyperoxia during CPB may increase oxidative stress and neuronal injury [ 9 ], impair cerebral autoregulation [ 10 ], and correlate with worse neurocognitive outcomes [ 11 ]. Thus, the higher PaO 2 in the slow group( 400--420 mmHg) might paradoxically confer disadvantage. 3. Physiological context: The PaO 2 difference represents a < 1.5 % change in arterial oxygen content. This minimal change is unlikely to affect oxygen delivery( DO 2) atCPBflows > 2.4 L / min / m 2 [ 12 ].
Collectively, while the PaO 2 difference reached statistical significance, its physiological and clinical relevance appears limited in the hyperoxic context of routine CPB management.
The results of this study indicate that, despite the absence of asignificant difference in TOI and HCT between the study groups, patients classified in the slow group exhibited a clinically significant but not statistically significant lower incidence of delirium in comparison to those in the fast group.
Notwithstanding the variation in the rate of change, the absolute values concerning the impact on tissue oxygenation did not exhibit any differences at either the nadir or at 60 s after