W. van Oeveren

Leukocyte depletion results in improved lung function and reduced inflammatory response after cardiac surgery

Leukocyte depletion during cardiopulmonary bypass has been demonstrated in animal experiments to improve pulmonary function. Conflicting results have been reported, however, with clinical depletion by arterial line filter of leukocytes at the beginning of cardiopulmonary bypass. In this study, we examined whether leukocyte depletion from the residual heart-lung machine blood at the end of cardiopulmonary bypass would improve lung function and reduce the postoperative inflammatory response. Thirty patients undergoing elective heart operations were randomly allocated to a leukocyte-depletion group or a control group. In the leukocyte-depletion group (n = 20), all residual blood (1.2 to 2.1 L) was filtered by leukocyte-removal filters and reinfused after cardiopulmonary bypass, whereas in the control group an identical amount of residual blood after cardiopulmonary bypass was reinfused without filtration (n = 10). Leukocyte depletion removed more than 97% of leukocytes from the retransfused blood (p < 0.01) and significantly reduced circulating leukocytes (p < 0.05) and granulocytes (p < 0.05) compared with the control group. Levels of the inflammatory mediator thromboxane B2 determined at the end of operation (p < 0.05) were significantly lower in the depletion group than in the control group, whereas no statistical differences in interleukin-6 levels were found between the two groups. After operation, pulmonary gas exchange function (arterial oxygen tension at a fraction of inspired oxygen of 0.4) was significantly higher in the leukocyte-depletion group 1 hour after arrival to the intensive care unit (p < 0.05) and after extubation (p < 0.05). There were no statistical differences between the two groups with respect to postoperative circulating platelet levels and blood loss, and no infections were observed during the whole period of hospitalization. These results suggest that leukocyte depletion of the residual heart-lung machine blood improves postoperative lung gas exchange function and is safe for patients who are expected to have a severe inflammatory response after heart operations.

A novel hydroxyethyl starch (Voluven) for effective perioperative plasma volume substitution in cardiac surgery.

Purpose: To compare the new hydroxyethyl starch HES 130/0.4 (Voluven®) and the standard HES 200/0.5 (pentastarch) regarding effectiveness for plasma volume substitution and safety of large volumes in heart surgery.Methods: Fifty-nine patients scheduled for coronary artery bypass grafting were enrolled in a prospective, randomised, double-blind, parallel-group, multicentre, clinical, phase III study. Hydroxyethyl starch was used as the exclusive artificial colloid for acute normovolemic hemodilution, priming of the heart lung machine, and for intra- and postoperative plasma volume substitution from induction of anesthesia until 16 hr after the end of surgery. Efficacy was evaluated by comparing the amount of colloid infused, hemodynamics, and colloid osmotic pressure (COP). Safety endpoints were blood loss, the use of allogeneic blood products, coagulation variables, and adverse events.Results: Effectiveness, as assessed by the total amount of infused HES volumes within the treatment period, was similar between HES 130/0.4 and HES 200/0.5 (2550 mL±560 mL vs 2466 mL ±516 mL). Also, no differences were found for the use of other colloids (pasteurised plasma), hemodynamics, and COP. In HES 130/0.4 patients, the postoperative increase of von-Willebrand factor (vWF) was higher (P<0.01), blood loss was lower, and less packed red blood cells were transfused.Conclusion: Hydroxyethyl starch 130/0.4 is an effective plasma volume expander in heart surgery and may be used as the sole artificial colloid to cover the perioperative period. We found a reduced influence of HES 130/0.4 on the physiologic postoperative increase of vWF.RésuméObjectif: Comparer le nouvel hydroxyéthylamidon HEA 130/0,4 (Voluven®) et l’HEA standard 200/0,5 (pentamidon) au plan de l’efficacité, quand on l’utilise comme substitution du volume plasmatique, et au plan sécuritaire de l’emploi de volumes importants en cardiochirurgie.Méthode: Cinquante-neuf patients qui devaient subir un pontage aorto-coronarien ont participé à une étude clinique multicentrique, prospective, randomisée, à double insu et en groupes parallèles, de phase Ill. L’hydroxyéthylamidon a été utilisé comme colloïde artificiel exclusif pour l’hémodilution normovolémique pratiquée d’emblée, pour amorcer l’utilisation du coeur-poumon artificiel et pour le remplacement du volume plasmatique peropératoire et postopératoire depuis l’induction de l’anesthésie jusqu’à 16 h après la fin de l’opération. L’efficacité a été évaluée en comparant la quantité de colloïde perfusé, l’hémodynamie et la pression osmotique du colloïde (POC). Les paramètres mesurés ont été: la perte sanguine, l’utilisation de produits sanguins allogéniques, les variables de coagulation et les inconvénients.Résultats: L’efficacité, évaluée selon la quantité totale d’HEA perfusé pendant le traitement, a été similaire pour l’HEA 130/0,4 et l’HEA 200/0,5 (2550 mL±561 mL vs 2466 mL±516 mL). De plus, il n’y a eu aucune différence quant à l’utilisation d’autres colloïdes (plasma pasteurisé), à l’hémodynamie et à la POC. Chez les patients qui ont reçu l’HEA 130/0,4, l’augmentation postopératoire du facteur de von Willebrand (vWF) a été plus élevée (P<0,01), la perte sanguine plus faible et la transfusion de globules rouges concentrés moins importante.Conclusion: L’hydroxyéthylamidon 130/0,4 représente un substitut du plasma sanguin efficace en cardiochirurgie et peut être utilisé comme colloïde artificiel unique pendant la période périopératoire complète. Nous avons constaté une action réduite de l’HEA 130/0,4 sur l’augmentation physiologique postopératoire du vWF.

The impact of heparin-coated cardiopulmonary bypass circuits on pulmonary function and the release of inflammatory mediators

Reduction of the inflammatory reaction with the use of heparin coating has been found during and after cardiopulmonary bypass (CPB). The question remains whether this reduced reaction also decreases the magnitude of CPB-induced pulmonary dysfunction. We therefore evaluated the effects of a heparin-coated circuit versus a similar uncoated circuit on pulmonary indices as well as on inflammatory markers of complement activation (C3b/c), elastase-&agr;1-antitrypsin complex, and secretory phospholipase A2 (sPLA2) during and after CPB. Fifty-one patients were randomly assigned into two groups undergoing coronary artery bypass grafting with either a heparin-coated (Group 1) or an uncoated (Group 2) circuit. During CPB, a continuous positive airway pressure of 5 cm H2O and a fraction of inspired oxygen (FIO2) of 0.21 were maintained. Differences in favor of the coated circuit were found in pulmonary shunt fraction (P < 0.05), pulmonary vascular resistance index (P < 0.05), and PaO2/FIO2 ratio (P < 0.05) after CPB and in the intensive care unit. During and after CPB, the coated group demonstrated lower levels of sPLA2. After CPB, C3b/c and the elastase-&agr;1-antitrypsin complex were significantly less in the coated group (P < 0.001). The coated circuit was associated with a reduced inflammatory response, decreased pulmonary vascular resistance index and pulmonary shunt fraction, and increased PaO2/FIO2 ratio, suggesting that the coated circuit may have beneficial effects on pulmonary function. The correlation with sPLA2, leukocyte activation, and postoperative leukocyte count suggests reduced activation of pulmonary capillary endothelial cells.

Superhydrophobic modification fails to improve the performance of small diameter expanded polytetrafluoroethylene vascular grafts

To determine whether superhydrophobic modification of small diameter expanded polytetrafluoroethylene (ePTFE) vascular grafts improves the performance of these grafts, we assessed neointima formation and platelet deposition in standard and superhydrophobic modified ePTFE grafts. Standard and superhydrophobic vascular grafts were implanted in the carotid arteries of two rabbits and two pigs. Furthermore, standard and superhydrophobic vascular patches were implanted in the carotid arteries of seven pigs. After 4 weeks of implantation all patches were removed and histomorphometric data were analyzed. The early thrombotic effect of superhydrophobic modification was examined by quantifying platelet glycoprotein receptor IIIa deposition onto each type of vascular graft after 15 min of in vitro circulation with human blood. All superhydrophobic and standard ePTFE vascular grafts occluded 15 min to 1 h after implantation in both rabbit and pig carotid arteries. All implanted patches remained patent and were completely covered by endothelium. Superhydrophobic modification of ePTFE vascular grafts did not lead to less neointima formation and resulted in significantly more platelet deposition than did standard ePTFE vascular grafts. Thus, superhydrophobic modification does not improve the performance of small diameter ePTFE vascular grafts.

Effect of biologically active coating on biocompatibility of Nitinol devices designed for the closure of intra-atrial communications

Anti-thrombogenicity and rapid endothelialisation are prerequisites for the use of closure devices of intra-atrial communications in order to reduce the risk of cerebral embolism. The purpose of this study was therefore to assess the effect of bioactive coatings on biocompatibility of Nitinol coils designed for the closure of intra-atrial communications. Nitinol coils (n = 10, each) and flat Nitinol bands (n = 3, each) were treated by basic coating with poly(amino-p-xylylene-co-p-xylylene) and then coated with either heparin, r-hirudin or fibronectin. Anti-thrombogenicity was studied in vitro in a dynamic model with whole blood by partial thromboplastin time (PTT), platelet binding and thrombin generation, respectively, and cytotoxicity by hemolysis. Endothelialisation was studied on Nitinol bands with human umbilical venous endothelial cells (HUVEC) by 3-(4,5-dimethylthiazole-2yl)-2,5-triphenyl tetrazolium (MTT) assay and immnuofluorescence analysis of Ki67, vinculin, fibronectin and von Willebrand Factor. Uncoated or coated devices did not influence hemolysis and PTT. r-Hirudin (but not heparin) and fibronectin coating showed lower platelet binding than uncoated Nitinol (p < 0.005, respectively). Heparin and r-hirudin coating reduced thrombin formation (p < 0.05 versus Nitinol, respectively). HUVEC adhesion, proliferation, and matrix formation decreased in the order: fibronectin coating > uncoated Nitinol > r-hirudin coating > heparin coating > basic coating. MTT assay corroborated these findings. In conclusion, r-hirudin and fibronectin coating, by causing no acute cytotoxicity, decreasing thrombogenicity and increasing endothelialisation improve in vitro biocompatibility of Nitinol devices designed for the closure of intra-atrial communications.

Alternative perioperative anticoagulation monitoring during cardiopulmonary bypass in aprotinin-treated patients.

Monitoring of anticoagulation during cardiopulmonary bypass by means of the activated coagulation time (ACT) has become questionable due to the prolongation in the clotting time of patients receiving aprotinin. Because the celite-based ACT only indicates intrinsic coagulation, and sufficient anticoagulation is needed to also prevent extrinsic coagulation, the ACT may not be reliable. Three different clotting times, the celite-based ACT, the kaolin-based activated coagulation time (AKT) and the high-dose thrombin time (HITT), were compared in a prospective, double-blind, placebo-controlled study of 20 patients who were to undergo cardiopulmonary bypass. As expected, neither the kaolin-based assay nor the high-dose thrombin time was influenced by aprotinin, whereas the celite-based ACT was significantly prolonged in aprotinin-treated patients as compared to control patients (P < 0.05). This study confirms that both kaolin-based and thrombin-based tests provide a reliable means of determining the degree of heparinization in the presence of aprotinin during cardiopulmonary bypass.

Clotting and fibrinolytic disturbance during lung transplantation: Effect of low-dose aprotinin

UNLABELLED Patients undergoing lung transplantation are often confronted with a bleeding problem that may be due in part to the use of cardiopulmonary bypass and its activation of blood clotting and fibrinolysis. OBJECTIVE We performed a prospective study to determine whether and to what extent the clotting and fibrinolytic systems are being activated and whether low-dose aprotinin is effective in inhibiting blood activation during lung transplantation. METHODS Thirty lung transplantations performed on 29 patients were divided into a group with cardiopulmonary bypass alone (n = 12), a group with cardiopulmonary bypass and 2 x 10(6) KIU aprotinin administered at the beginning of bypass in the pump prime (n = 12), and a group without cardiopulmonary bypass (n = 6). Serial blood samples were taken from the recipient before anesthesia, seven times during the operation, and 4 and 24 hours thereafter. RESULTS Results show that in the group having cardiopulmonary bypass alone, the concentration of the clotting marker thrombin/antithrombin III complex increased significantly during the early phase of the operation (p < 0.01) and remained high until the end of the operation. Levels of tissue-type plasminogen activator, a trigger of fibrinolysis released by injured endothelium, also increased sharply in the early phase of the operation in the cardiopulmonary bypass group (p < 0.01), followed by a significant increase in fibrin degradation products (p < 0.01). In the aprotinin group, a significant reduction of thrombin/antithrombin III complex (p < 0.05), tissue-type plasminogen activator (p < 0.05), and fibrin degradation products (p < 0.05) was observed in the early phase of the operation compared with levels in the bypass group, but these markers increased late during bypass associated with a significant drop (p < 0.05) of plasma aprotinin level monitored by plasmin inhibiting capacity. In the nonbypass group, concentrations of thrombin/antithrombin III complex and tissue-type plasminogen activator also rose significantly (p < 0.05) in the early phase of the operation, but the levels were significantly lower than those of the bypass group (p < 0.05). Blood loss during the operation was 2521 +/- 550 ml in the bypass group, 1991 +/- 408 ml in the aprotinin/bypass group, and 875 +/- 248 ml in the nonbypass group. CONCLUSION These results suggest that clotting and fibrinolysis are activated during lung transplantation, especially in patients undergoing cardiopulmonary bypass. Aprotinin in a low dose significantly reduced activation of clotting and fibrinolysis in the early phase of the operation but not during the late phase of lung transplantation.

Activation of plasma components by leukocyte removal filters.

The technique of leukocyte filtration has been introduced into cardiac surgery to reduce leukocyte mediated reperfusion injury. When autologous whole blood (WB) is used as filtrate, it is more likely to be activated by the filter material than are banked red blood cell concentrates (RCC), because of its richness in plasma components. This study was designed to compare the activation of plasma components during leukocyte filtration from WB (n = 10) taken from the heart-lung machine, with RCC (n = 10) obtained from the blood bank. Leukocyte filters made from either cellulose acetate or polyester were used. Blood samples were taken simultaneously from the inlet and outlet of the filter after filtration of either 700 ml of WB or 350 ml of RCC. Results indicated that the complement cascade was activated, as reflected by the increase of C3a and C5a during filtration of WB by filters made from cellulose acetate. In contrast, there was no significant increase of C3a and C5a during filtration of RCC. The clotting system, indicated by fibrinopeptide A, and the fibrinolytic system, indicated by fibrinogen degradation products, were not activated during leukocyte filtration. These data suggest that it is the WB taken from the heart-lung machine rather than the RCC from the blood bank that is being activated during leukocyte filtration. Thus, careful selection of filter material is important for leukocyte filtration of autologous whole blood during cardiac surgery.

Comparison of three commercially available hollow fiber oxygenators : Gas transfer performance and biocompatibility

The new generation of oxygenators have improved blood flow pathways that enable reduction in priming volume and, thus, hemodilution during cardiopulmonary bypass (CPB). We evaluated three oxygenators and two sizes of venous reservoirs in relation to priming volume, gas transfer, and blood activation. To compare priming volume, gas transfer, and biocompatibility of three hollow fiber oxygenators and two different size venous reservoirs, 60 patients were randomly allocated in groups to undergo cardiopulmonary bypass. In each group, an oxygenator with a different surface area and priming volume was used: 1.8 m2 and 220 ml (group 1, n = 23), 2.2 m2 and 290 ml (group 2, n = 20), and 2.5 m2 and 270 ml (group 3, n = 17). In groups 1 and 3, a large soft shell (1900 ml) venous reservoir was used, whereas in group 2, a smaller soft shell (600 ml) venous reservoir was used. Gas transfer was assessed by calculating the oxygen transfer rate for each group and per square meter for each oxygenator group. Partial arterial oxygen pressure (paO2) and partial arterial carbon dioxide pressure (paCO2) between the groups were assessed with forward stepwise regression analysis. Biocompatibility was evaluated through measurement of platelet numbers, complement activation products (C3b/c), coagulation (thrombin anti-thrombin III complex), and fibrinolysis (plasmin anti-plasmin complex). No differences were found in oxygen transfer rate per group. However, when correcting the oxygen transfer rate for surface area, group 1 demonstrated a higher oxygen transfer rate compared with group 2 (p < 0.05) at an FiO2 of 40 and 60% and compared with group 3 at an FiO2 of 60 and 70%. The regression analysis showed that the average arterial pO2 was the highest in group 3, i.e., 79.2 mm Hg higher than in group 1 (p < 0.001) and 73.5 mm Hg higher than in group 2 (p < 0.001). Group 3 also had the lowest average arterial pCO2, 0.57 mm Hg lower than in group 1 (p = 0.004) and 0.81 mm Hg lower than in group 2 (p < 0.001). During CPB, platelet numbers decreased significantly in all groups (p < 0.001), without differences between the groups. C3b/c levels increased in all groups during CPB. At cessation of CPB the C3b/c level in group 2 (398 nmol/L−1) was significantly higher compared to group 1(251 nmol/L−1;p < 0.05) and group 3 (303 nmol/L−1;p < 0.05). Thrombin anti-thrombin III complexes and plasmin anti-plasmin complex complexes increased during CPB to significantly high levels at cessation of CPB, but there were no differences between the groups. The oxygenator with the smallest surface area and lowest priming volume (group 1) had the highest oxygen transfer rate per square meter and showed the least blood damage, as depicted by complement activation. The oxygenator with the largest blood contact surface area and improved geometric configuration (group 3) showed the lowest oxygen transfer rate per square meter. However, this oxygenator elevated oxygen partial pressure the most and reduced carbon dioxide partial pressure the most. In group 2, where a smaller venous reservoir was used, the highest blood activation was observed.

ACTIVATION OF PLASMA SYSTEMS AND BLOOD-CELLS BY ENDOTOXIN IN RABBITS

Endotoxin plays an important role in the pathogenesis of septicaemia by activation of cellular and plasmatic systems. This study was performed to investigate the effects of infusion of endotoxin in rabbits by measuring the activation of cellular and plasma systems. Endotoxin was infused at a rate of 1 mg/kg body wt for 10 min, which caused death of all rabbits within 72 h. Endotoxin induced early leukopenia and thrombopenia, increased plasma levels ofβ-glucuronidase and leukotriene B4 (LTB4), and decreased complement total hemolytic activity (CH50) and tissue plasminogen activator (t-PA) activity. These observations correlate with the cellular and plasma changes that have been documented in severely ill endotoxemic patients. Therefore, we conclude that this endotoxin model in rabbits is a valuable tool for investigation of pathophysiology and treatment of endotoxic shock.