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CPB, the arterial line must be clamped while the pump still rotates.
These are the product usage instructions that the manufacturers of such pumps have defined to prevent retrograde blood flow in the arterial line. These instructions mandate the establishment and maintenance of a minimum rotation speed exceeding the patient’ s resistance, with the arterial line clamped before halting the pump’ s rotation [ 8 ]. This method imposes mechanical stress on the blood, that may be harmful [ 9 ]. The perfusionist undertakes to initiate or cease blood flow at rotation levels higher than necessary, potentially increasing trauma to blood cells and contributing to increase hemolysis in CPB.
Hemolysis is defined as the rupture of red blood cells, leading to the release of its contents, such as hemoglobin and lactate dehydrogenase, into the plasma. The hemoglobin released in plasma, or plasma free hemoglobin, subsequently binds to the circulating haptoglobins, which are then metabolized in the liver. However, when hemoglobin release exceeds the plasma haptoglobin concentration, plasma free hemoglobin will exert its deleterious effects causing complications such as acute kidney injury [ 10 ].
AmSECT, the American Society of ExtraCorporeal Technology, as well as the Society of Clinical Perfusion Scientists, the Society for Cardiothoracic Surgery, the Association for Cardiothoracic Anaesthesia and Critical Care of Great Britain & Ireland, and Brazilian Society for Extracorporeal Circulation, together with Brazilian Society of Cardiovascular Surgery, recommend that at least one method be used to prevent retrograde blood flow during CPB in circuits using centrifugal pumps [ 11, 12 ]. This document recommends that at least one method of preventing backflow when using a centrifugal pump should be used during CPB procedures, such as one-way flow valves; hard-stop check controls to prevent accidental reduction in pump speed; electronically activated arterial line clamps; or a low-speed visual and audible alarm [ 11 ].
In Brazil, addressing this issue constitutes a significant aspect of a perfusionist’ s daily responsibilities, given the absence of available devices to meet this requirement. The Safe- CEC Ò valve is constructed of silicone and affixed to polycarbonate inlet and outlet connectors with a 3 / 8 00 diameter. It is positioned in the arterial line of the CPB circuit, specifically in the segment after the centrifugal pump outlet. This valve’ s primary feature is its capability to permit flow in a unique direction. It was designed in the form of a cartwheel [ 13, 14 ], with a central plug fixed to the center by slender rods attached to the outer rim. As flow initiates and pressure builds at the valve inlet, the valve plug moves away from the inlet port, allowing flow towards the valve outlet. By ceasing flow at the inlet, the valve closes, preventing backflow from occurring( Fig. 1).
The SafeCEC Ò valve is constructed of silicone and affixed to polycarbonate inlet and outlet connectors. Positioned within the blood pump outlet line of the CPB circuit, this valve’ sprimary feature is the ability to permit flow in a singular direction. It was designed in the form of a cartwheel, that is, a central plug fixed to the center by slender rods attached to the outer rim. As flow initiates and pressure builds at the valve inlet, the valve plug moves away from the inlet port, allowing flow towards the valve outlet. By ceasing flow at the inlet, the valve closes, preventing backflow from occurring.
To clinically evaluate SafeCEC Ò, weproposeapilotrandomized comparative study to assess its safety and efficacy in cardiopulmonary bypass. Our objective includes verifying whether the use of SafeCEC Ò increases patient risk, comparing the degree of blood trauma produced in CPB procedures with and without the use of SafeCEC Ò.
Materials and methods
After approval by the Ethics Committee of Hospital Pedro Ernesto – Universidade do Estado do Rio de Janeiro( Rio de Janeiro, Brazil), 31 patients who underwent CPB with a centrifugal pump were included. Patients were randomly assigned using the random function in Microsoft Excel, without blinding, and divided into two groups: group A, in which SafeCEC Ò was incorporated into the arterial line, and group B, where the conventional circuit was used. Inclusion criteria of patients over 18 years of age, with indication for elective cardiac surgery with CPB, who agreed to participate in this study.
Hemolysis was evaluated using the following protocol: blood samples were collected from each participant for analysis of plasma free hemoglobin, before CPB, after CPB, and 24 h after weaning of CPB. Plasma free hemoglobin analysis was performed by collecting samples and subjecting them to centrifugation for 10 min at 1500 rpm. Subsequently, 1 mL of plasma was collected, centrifuged again at 1500 rpm and analyzed by HemoCue Ò Plasma / Low Hb system as per its instructions for use.
Other parameters analyzed were arterial blood flow, CPB time, diagnosis, type of surgery performed, hematocrit levels, and descriptive data. Exploratory data analysis comprised the calculation of descriptive statistics, including measures of central tendency( mean), dispersion( standard deviation), percentiles, and the minimum and maximum values for numerical variables, alongside frequencies and proportions for categorical variables. To evaluate the distributional properties of continuous variables, the Shapiro-Wilk test was employed to assess adherence to the assumption of normality [ 15 ].
For comparisons of continuous variables between two independent groups, parametric data were analyzed using the Student’ s t-test. In instances where the assumption of homogeneity of variances was violated, Welch’ s correction was applied to ensure the robustness of the inference. Effect sizes were quantified using Cohen’ s d, a widely recognized measure of effect magnitude, interpreted as follows: 0.2 representing a small effect, 0.5 a medium effect, and 0.8 or higher a large effect [ 16 ].
For non-parametric data, the Mann-Whitney U-test was utilized to compare scale scores across independent variables. In these analyses, the effect size was reported as the point-biserial correlation coefficient( r), which expresses the strength of association between a dichotomous and a continuous variable. Interpretation of r followed the thresholds proposed by Cohen [ 17 ], with 0.10 – 0.29 representing a small effect, 0.30 – 0.49 a medium effect, and values above 0.50 indicating a large effect.
Associations between categorical variables were examined using the chi-square test of independence. Effect sizes for these associations were calculated using the Phi coefficient, which