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Processing cardiotomy blood decreases pulmonary, systemic resistance and improves cardiac performance, prospective study shows

Thursday, October 16 2008 | Comments

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What's This? Processing shed mediastinal blood during cardiac surgery with cardiopulmonary bypass (CPB) decreases systemic and pulmonary vascular resistance and improves cardiac performance perioperatively, according to the results of a prospective study.

To evaluate the effects of processing shed mediastinal cardiotomy blood on cardiovascular and pulmonary functioning following cardiac surgery, researchers at the Heart Institute of the University of Ottawa in Canada conducted a randomized, double-blind study of patients undergoing isolated, nonemergent coronary artery bypass (CABG) or aortic valve surgery, or both. A total of 154 patients were randomized to receive shed mediastinal cardiotomy blood that had been processed to filter out fat, particulate matter, and vasoactive mediators, or unprocessed cardiotomy blood (n=77 in each group). Pulmonary function, arterial and venous blood gases, and hemodynamics were measured before, immediately after, and 2 hours after cessation of CPB.

The groups had similar patient demographics, and there was no difference in indexes of pulmonary mechanical functioning at any of the measured time points. There were also no significant differences between groups in CPB or cardiac ischemia time, number of distal anastomoses, or types of bypass conduits used. The volume of collected cardiotomy blood was 704 mL in the control group and 830 mL in the treatment group (P=.21).

There were no differences at any of the 3 measured time points in the indexes of mechanical pulmonary function, which included tidal volume, peak inspiratory pressure, and positive end-expiratory pressure. When compared with baseline values, impaired oxygen exchange was seen immediately after CPB in both groups.  There were significant reductions in arterial PO2 and oxygen delivery as well as increased alveolar-arterial oxygen gradient, pulmonary shunt, and oxygen extraction ratio  (P=.01 for all). Each of these indexes of pulmonary gas exchange improved 2 hours following cessation of CPB, and there were no significant differences between groups at this time point.

Pulmonary and systemic vascular resistance decreased in the treated arm both immediately and 2 hours after CPB. In addition, the postoperative cardiac index also demonstrated significant improvement in the treated versus untreated arms (P=.004).

Multivariate analysis of 17 preoperative and intraoperative variables indicated that the only significant independent predictors of improved cardiac index were decreased cardiac ischemia time (P=.02), higher levels of hemoglobin (P=.003), and randomization to the treatment arm of the study.

There was a dose-dependent relationship between postoperative hemodynamics and cardiotomy blood volume. Higher volumes of collected cardiotomy blood resulted in an increase in the magnitude of reduced systemic vascular resistance (P=.04) and in the amount of pheynlephrine used (P<.001). There was also a stronger relationship between groups in systemic vascular resistance and volume of cardiotomy blood in the treatment group (P=.02) and in the volume of cardiotomy blood and pulmonary vascular resistance (P=.08).

There were no significant differences between groups in postoperative mortality. In the control group, 4 patients (5.2%) were diagnosed with perioperative myocardial infarction as compared with no patients in the treatment arm (P=.12).

The control patients had significantly higher postoperative creatine kinase levels (P=.003), but postoperative troponin levels were similar between groups. Finally, there was a trend toward decreased ventilation time in the treated patients, but it did not reach statistical significance (P=.12).

Although the study researchers indicated that management of shed cardiotomy blood during CPB remains a controversial issue, they found processing this blood by centrifugation, washing, and filtration reduces systemic and pulmonary vascular resistance and improved cardiac performance perioperatively. They recommended that management of cardiotomy blood should be tailored to the patient to maximize the benefit of the procedure. (Boodhwani M, et al. Ann Thorac Surg 2008;86:1167-1174.)

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