The Journal of ExtraCorporeal Technology No 57-3 | Page 15

S. Diop et al.: J Extra Corpor Technol 2025, 57, 123--128 125

Table 1. Patient’ s characteristics and perioperative bypass data.

The following data were recorded in an anonymized file: demographic data, medical history, and preoperative cardiac evaluation. The duration of CPB, aortic clamping, and circulatory arrest times were recorded. The volume of blood contained in the cardiotomy reservoir, the sweep gas inflow, the arterial shunt line flow, and the F m O 2, were recorded during the period of DHCA. The values of arterial blood gas, corrected and uncorrected to the temperature, performed at the beginning and the end of the DHCA were recorded. The strong ion difference( SID) was also reported and calculated as follows:

Statistical analysis

SID ¼ðNa þ þ K þ Þ�Cl �:

Qualitative data are expressed as numbers and percentages, and quantitative data as means and standard deviations. Continuous variables were compared using the Mann-Whitney test. All tests were two-sided, and p values < 0.05 were considered significant. The search for correlation was achieved through the calculation of the Spearman coefficient. The analyses were performed using the R statistical program, version 4.1.0( R Foundation for Statistical Computing, Vienna, Austria). Results are expressed in mean(± SD) and number(%). Volume of the cardiotomy reservoir corresponds to the volume of blood contained in the reservoir during the circulatory arrest.

Management of the CPB during circulatory arrest

At the time of the circulatory arrest, the revolutions per minute( RPM) of the spinning pump was decreased to 1500 RPM. The arterial cannula was then clamped. The blood was passively drained into the cardiotomy reservoir via the venous lines. The blood continued to circulate through the oxygenators via the arterial shunt line, at a flow ranging from 0.4 to 0.8 L / min. The sweep gas inflow was determined by the perfusionist in charge during cooling. It was kept constant throughout the first DHCA. The F m O 2 ranged from 80 % to 100 % according to our local protocol. At the end of circulatory arrest, the arterial cannula was unclamped, and the pump RPM progressively increased to its initial level to restore a cardiac index of at least 1.8 L / min / m 2.

Blood samples during circulatory arrest

The first blood gas was sampled on the arterial shunt line at 18 ° C just before the beginning of the DHCA. A second one was sampled on the same site at the end of the DHCA, just before resuming CPB. The blood volume in the cardiotomy container, the sweep gas inflow, and the F m O 2 were systematically recorded. Measurements were done only on the first circulatory arrest. All blood gases were immediately analyzed according to the alpha stat and the pH-stat strategies, with the ABL90 FLEX PLUS Ó Radiometer( Copenhagen, Denmark) as the blood gas analyzer.

Data collection

Results Patient’ s and CPB characteristics

Twenty five consecutive patients were included during the four-month inclusion period, 13 of them were( 52 %) males, with a mean age of 59.2(± 15.7) years. The preoperative mean pulmonary arterial pressure( mPAP) was 39.3(± 11.5) mmHg. The mean duration of CPB, aortic cross clamp time, and DHCA were 244.9(± 28.8), 58.3(± 11.6), and 15.2(± 4.1) min, respectively. During the DHCA, the mean sweep gas inflow was 1.4(± 0.8) L / min( Table 1).

Blood gas parameters

In the alpha-stat analysis, initial pH and PaCO 2 were 7.31(± 0.09) and 43.2(± 9.9) mmHg, respectively, and final pH and PaCO 2 were 7.51(± 0.14); p < 0.001, and 23.4(± 11.9) mmHg; p < 0.001. In the pH-stat analysis, the mean final pH was 7.79(± 0.16), and the mean PaCO 2 was 11.3(± 5.8) mmHg. The PaO 2 was significantly lower at the end of the DHCA. Sodium and calcium ion concentrations were significantly lower at the end of the DHCA( 139(±) vs. 137(±) mmol / L; p < 0.05 and 1.15(± 0.04) vs. 1.13(± 0.07) mmol / L; p = 0.03, respectively). The strong ion difference was significantly lower at the end of the DHCA( 31.6(± 4.4) vs. 28.7(± 4.3) mmol / L; p = 0.01)( Table 2).

Correlation analysis

There was a significant correlation between the gas sweep flow on the one hand, and the post-DHCA pH and PaCO 2 on the other hand( r = 0.797; p < 0.0001 and r = �0.792; p < 0.0001, respectively; Figure 1). There were no correlations between the duration of DHCA and the post-DHCA pH, nor between the arterial shunt line flow and the post-DHCA pH( r = 0.002; p = 0.99andr = �0.254; p = 0.21, respectively; Figure 2).