Systemic leukocyte filtration during cardiopulmonary bypass

Abstract

Cardiopulmonary bypass (CPB) induces a whole body inflammatory response leading to postoperative lung dysfunction. Activated leukocytes may play a role in the pathogenesis of pulmonary dysfunction. We evaluated postoperative lung function after the use of leukocyte-depleting filters incorporated in the extracorporeal circuit during CPB. From November 1997 to March 2000, 40 patients underwent isolated coronary artery bypass grafting. Patients were randomly allocated to the leukocyte-depletion group (group F, 20 patients) or to the control group (group C, 20 patients). There was no significant difference between the two groups with respect to age, sex, weight, height, body surface area, haemoglobin and haematocrit levels, preoperative left ventricular ejection fraction, cooling temperature, aortic crossclamping and CBP duration. Blood samples were drawn preoperatively, at aortic declamping, 60 min after CPB, after arriving at the intensive care unit (ICU) and 24 h after the operation. We analysed blood cell count, elastase, interleukin-8 (IL-8) and tumour necrosis factor (TNF-alpha) levels and continuous monitoring of arterial blood gases in the intensive care unit (ICU). The analysis of total circulating white blood cells (WBCs) showed a significant reduction of WBCs in both groups soon after aortic declamping [from the right atrium: 6.4 x 10(9)/l +/- 1.4 x 10(9)/l in group F vs 10.3 +/- 1.8 x 10(9)/l in group C (p<0.05); from the left atrium: 5.8 +/- 1.3 x 10(9)/l in group F vs 8.4 +/- 1.9 x 10(9)/l in group C (p<0.05)] and after 60 min of CPB [7.1 +/- 2.2 x 10(9)/l in group F vs 10.4 +/- 1.8 x 10(9)/l in group C (p<0.05)]. The analysis of circulating neutrophils showed similar findings in both groups. Elastase levels increased during CPB in both groups with a peak at the end of CPB without significant difference between the two groups (group C: 260 +/- 148 microg/l vs group F: 371 +/- 68 microg/l). The decrease of plasmatic elestase levels was observed, for both groups, in the 24 h after CPB. There was no difference in intubation time between the two groups (16.4 h for group C vs 11.2 h for group F). Pulmonary function tested by pulmonary respiratory index [RI = partial pressure of oxygen/fraction of inspired oxygen (PaO2/FiO2 x 100)] did not show significant difference between the two groups, either arriving in the ICU (group C RI 265 vs group F RI 322), or after 3 h (group RI 304 vs group F RI 305) or after 6 h (group C RI 292 vs group F RI 319). Leukocyte-depleting filters reduce with blood cells count during CPB, but, in this study, WBC depletion did not significantly improve clinical conditions or laboratory finding.

The effects of various leukocyte filtration strategies in cardiac surgery

“…This was supported by Johnson et al, who measured PaO 2 and intra-pulmonary shunt (Qs/Qt) and found both to be worse in controls, although only in the first 4 h post CPB [55]. Subsequent studies report no impact on pulmonary function post-operatively, using a variety of indices [9,26,43,44,46]. More recent studies, however, describe beneficial effects of leukofiltration.…”

“…Whereas some studies showed similar elastase levels in the filtered and control patients [9,10,46], others have unexpectedly showed higher elastase levels following leukocyte filtration [35,43,44] and suggested this reflects increased elastase release by neutrophils trapped within the filter, rather than a higher activation of neutrophils within the tissues. Chen et al demonstrated a reduction in MDA [52] following leukocyte filtration, as did Allen et al in cyanotic infants [59].…”

“…Only eight studies within this section of the review did not record pre-and post-operative WCC. Of the 26 that did, 15 found no significant difference between filtered patients and controls at any point in the patients admission [9,22,23,27,[39][40][41][42][43][44][45][46][47][48][49][50]. The remaining 11 papers found reduced WCCs in the filtered group mainly during CPB, although these differences tended to disappear after CPB [10,26,35,[51][52][53].…”

“…IL-1, IL-6, IL-8 and TNF) during or after cardiac surgery [22,23,39,46,50,55]. The only study to show a significant effect utilized a venous line leukodepleting filter [10] and observed a significant decrease in IL-8 compared to controls.…”

“…One of the concerns regarding systemic leukodepletion is that simultaneous removal of platelets might adversely influence post-operative haemostasis [12]. However, a multitude of studies have shown leukocyte filtration to have no significant adverse impact on the degree of post-operative blood loss or the requirements for blood transfusion [9,23,46,49,53,56]. Contrary to this large body of evidence, Sahlman et al found chest drainage in the first 24 h to be significantly higher in the filtered group ( p < 0.05) [45], however this was not accompanied by an increased need for blood transfusion.…”