Heparin-coated equipment reduces the risk of oxygenator failure

Risk factors and treatment of oxygenator high-pressure excursions during cardiopulmonary bypass

INTRODUCTION

A high-pressure excursion (HPE) is a sudden increase in oxygenator inlet pressure during cardiopulmonary bypass (CPB). The aims of this study were to identify factors associated with HPE, to describe a treatment protocol utilizing epoprostenol in severe cases, and to assess early outcome in HPE patients.

METHODS

Patients who underwent cardiac surgery with cardiopulmonary bypass at Sahlgrenska University Hospital 2016-2018 were included in a retrospective observational study. Pre- and post-operative data collected from electronic health records, local databases, and registries were compared between HPE and non-HPE patients. Factors associated with HPE were identified with logistic regression models.

RESULTS

In total, 2024 patients were analyzed, and 37 (1.8%) developed HPE. Large body surface area (adjusted Odds Ratio (aOR): 1.43 per 0.1 m²; 95% confidence interval (CI): 1.16-1.76, p < 0.001), higher hematocrit during CPB (aOR: 1.20 per 1%; (1.09-1.33), p < 0.001), acute surgery (aOR: 2.98; (1.26-6.62), p = 0.018), and previous stroke (aOR: 2.93; (1.03-7.20), p = 0.027) were independently associated with HPE. HPE was treated with hemodilution (n = 29, 78.4%), and/or extra heparin (n = 23, 62.2%), and/or epoprostenol (n = 12, 32.4%). No oxygenator change-out was necessary. While there was no significant difference in 30-day mortality (2.7% vs 3.2%, p = 1.0), HPE was associated with a higher perioperative stroke rate (8.1% vs 1.8%, aOR 5.09 (1.17-15.57), p = 0.011).

CONCLUSIONS

Large body surface area, high hematocrit during CPB, previous stroke and acute surgery were independently associated with HPE. A treatment protocol including epoprostenol appears to be a safe option. Perioperative stroke rate was increased in HPE patients.

Leukocyte-derived extracellular DNA contributes to abnormal pressure elevation in the extracorporeal circulation circuit

An abnormal elevation in pressure is a serious complication involving the extracorporeal circulation circuit. Clot formation might be associated with this complication, but the precise mechanism of an abnormal elevation in pressure has not been identified. We investigated sufficient conditions for in-circuit elevation in pressure using an ex vivo re-circulation circuit with porcine blood. Specifically, we investigated the effect of blood conditions, the type of anticoagulation, and pro-inflammatory stimulation on in-circuit pressure. We also examined the cause of an abnormal elevation of in-circuit pressure by specifically degrading DNA, RNA, or protein components of an obstructed filter and by using immunofluorescent techniques. Neither a change in temperature nor change in pH in the blood increased in-circuit pressure. In contrast, long-term storage of blood, pro-inflammatory stimulation by phorbol myristate acetate, and heparin administration significantly increased in-circuit pressure. Abnormal in-circuit elevation in pressure was associated with deposition of extracellular DNA on the outlet surface of the filter. Administration of DNase resulted in a rapid decline of in-circuit pressure. In an ex vivo re-circulation circuit system, extracellular DNA deposition on the filter is responsible for an abnormal in-circuit elevation in pressure. Senescent leukocytes, stimulated leukocytes, and heparin exposure are associated with extracellular DNA deposition.

Current Understanding of How Extracorporeal Membrane Oxygenators Activate Haemostasis and Other Blood Components

Extracorporeal membrane oxygenators are used in critical care for the management of severe respiratory and cardiac failure. Activation of the coagulation system is initiated by the exposure of blood to synthetic surfaces and the shear stresses of the circuit, especially from device pumps. Initial fibrinogen deposition and subsequent activation of coagulation factors and complement allow platelets and leucocytes to adhere to oxygenator surfaces and enhance thrombin generation. These changes and others contribute to higher rates of thrombosis seen in these patients. In addition, bleeding rates are also high. Primary haemostasis is impaired by platelet dysfunction and loss of their key adhesive molecules and shear stress causes an acquired von Willebrand defect. In addition, there is also altered fibrinolysis and lastly, administration of systemic anticoagulation is required to maintain circuit patency. Further research is required to fulyl establish the complexities of the haemostatic changes with these devices, and to elucidate the mechanistic changes that are mainly responsible so that plans can be made to reduce their complications and improve management.

Detection of Echinocyte during Perfusion with Oxygenator Based on Continuous Blood Viscosity Monitoring

We applied our proposed continuous blood viscosity monitoring system for cardiopulmonary bypass to an experimental model that introduced echinocytes, and we confirm the viscosity change detection due to red blood cell (RBC) deformability decline. For the in vitro experiment, a test circuit including an oxygenator and a controlled bovine blood sample with excessive alkalemia to induce the echinocyte were prepared, and a perfusion experiment was performed. During the experiment, the anticoagulated bovine blood sample maintained a hematocrit of approximately 22%, temperature of 37°C, and more than 800 s of the activated clotting time. The estimated viscosity obtained from the proposed system was 2.10 mPas at the beginning of the experiment and 3.58 mPas at the end of the experiment, and it increased 1.48 mPas during the experiment. According to the scanning electron micrographs of blood samples, the echinocytes with multiple spicules at the beginning of the experiment and distorted spherical RBCs including the echinocytes with multiple spicules at the end of experiment were observed. We conclude that the system may be helpful for clinical perfusion management, because it detected the presence of echinocytes as the blood viscosity in an oxygenator flow pass increased.

Surface and Hemocompatibility Studies of Bi-Soft Segment Polyurethane Membranes

Cross-linked urethane/urea membranes with two soft segments were prepared by extending a poly(propylene oxide) based tri-isocyanate-terminated prepolymer (PUR) with polybutadiene diol (PBDO). The ratio of prepolymer and polybutadiene diol was varied to yield cross-linked membranes with different compositions, exhibiting different degrees of phase-separation of the PBDO segments in the bulk and of surface enrichment in PUR. In this work, surface energy and hemocompatibility aspects (hemolysis and thrombosis) of the PUR/PBDO membranes were evaluated. The results showed that the membrane surface energy increased with the PBDO content until 25% of PBDO, and decreased thereafter. The introduction of the second, more hydrophobic, soft segment (PBDO) in the PUR membranes turned hemolytic into non-hemolytic membranes and, for a blood-material contact time of 10 minutes, decreased the thrombogenicity significantly. The 10% PBDO membrane was the least thrombogenic and was also non-hemolytic. The hemolysis degree did not vary significantly with the PBDO content while, for blood-material contact times of 10 minutes, the thrombogenicity increased with an increase in PBDO content above 10%. Membrane thrombogenicity varied with the blood-material contact time. For blood contact times of 10 minutes, all membranes tested were less thrombogenic than glass.

A new oxygenator change-out system and procedure

Official reports relate that, in the US, one patient/month dies as a result of the emergency oxygenator change-out procedure, and the permanent injury of some patients is the result of current oxygenator change-out procedures or oxygenator failures, both in extracorporeal circulation (ECC) and extracorporeal membrane oxygenation (ECMO).

The aim of this article is to evaluate a new system and procedure, dedicated to oxygenator change-out, represented by two three-way stopcocks inserted in the ECC line in use. A dedicated back-up oxygenator and circuit can be easily primed and connected to the dedicated connector on the stopcocks, then blood flow is diverted to the new oxygenator without interruption of the ECC.

Tests performed showed that oxygenator change-out can be completed by perfusionists in 62.139+11.12 sec. Results obtained show that the new system and procedure allows fast, safe and reproducible oxygenator change-out without interruption of the ECC.

Miniaturization in cardiopulmonary bypass

Cardiopulmonary bypass (CPB) remains the key technology for more complex cardiac operations. The perfusion equipment used nowadays has seen tremendous progress since its introduction into clinical practice 50 years ago. However, overall, CPB is still far from perfect. Major haemodilution is not only a problem for red cell-dependent gas transport, but also for the platelet and humeral factor-dependent coagulation, the protein-dependent intravascular oncotic pressure and so forth. Reduction of the priming volume through further miniaturization of CPB equipment is, therefore, the most obvious next step. A systematic approach needs to optimize all CPB components, including pumps, oxygenator/heat exchanger structures, filters, reservoirs, cardiotomy suction, tubings and cannulas. This report provides an update of already commercially available low prime perfusion devices (e.g., the CORx integrated pump-oxygenator) as well as promising prototypes like the smart suction system and the smartcanula.™

Blood compatible materials: state of the art

Devices that function in contact with blood are ubiquitous in clinical medicine and biotechnology. These devices include vascular grafts, coronary stents, heart valves, catheters, hemodialysers, heart-lung bypass systems and many others. Blood contact generally leads to thrombosis (among other adverse outcomes), and no material has yet been developed which remains thrombus-free indefinitely and in all situations: extracorporeally, in the venous circulation and in the arterial circulation. In this article knowledge on blood-material interactions and "thromboresistant" materials is reviewed. Current approaches to the development of thromboresistant materials are discussed including surface passivation; incorporation and/or release of anticoagulants, antiplatelet agents and thrombolytic agents; and mimicry of the vascular endothelium.

An ex vivo evaluation of blood coagulation and thromboresistance of two extracorporeal circuit coatings with reduced and full heparin dose

OBJECTIVES

Bioactive Carmeda® heparin-coated extracorporeal circuits (ECCs) have been shown to reduce contact phase and coagulation activation during cardiopulmonary bypass (CPB). Heparin coating is therefore effective in safely reducing coagulation during routine CPB. Balance® Biosurface is a new, recently developed biopassive coating containing negatively charged sulphonated polymers. This study sought to compare the clotting activation and thromboresistance of the Balance® (B) circuit with that of the Carmeda® (C) with full-dose systemic heparin (FDH) and reduced-dose systemic heparin (RDH).

METHODS

This ex vivo study set-up comprising 40 experiments consisted of simplified ECC and circulation of freshly donated human blood. RDH and FDH regimens were obtained with 0.5 IU/ml and 1 IU/ml heparin administered to reach target activated clotting times (ACTs) of 250 and 500 s, respectively. The study design comprised four groups: FDH-C, FDH-B, RDH-C and RDH-B (all n = 10). Blood was sampled prior to and during the 2-h CPB. Coagulation activation was assessed (FXIIa, F1.2) and electron microscope scan imaging of oxygenators enabled determination of adhesion scores.

RESULTS

With a biopassive compared with bioactive surface, mean ACT was lower, regardless of the heparin regimen applied (P < 0.001), whereas the total heparin dose required to maintain ACT was above target level (P < 0.001). However, FXIIa and F1.2 values were similar in all groups throughout, as were pressure gradients among oxygenators. All groups demonstrated similar adhesion scores following ultrastructural oxygenator assessment.

CONCLUSIONS

In the absence of surgical-related haemostatic disturbances and based on target ACT levels under reduced- or full-dose heparin, the clotting process was similar to heparin-coated and new sulphonated polymer-coated ECC, both demonstrating similar thromboresistance.

[Oxygenator thrombosis without heparin resistance in polycythemia vera]

A 55-year-old male with a history of positive HIV serology and polycythemia vera underwent coronary artery bypass graft surgery with normothermic extracorporeal circulation. Following heparin administration the activated clotting time (ACT) was 633 seconds (Hemocron with kaolin). Lower than expected arterial and venous oxygen partial pressures together with high pressure (350 mmHg) in the arterial line upstream of the oxygenator were observed. Because of these signs the oxygenator was changed during the procedure. The outcome was uneventful. Electronic microscopic examination of the oxygenator membrane and thermic exchanger revealed fibrin and platelet deposits. Similar cases are described in the literature during polycythemia vera. Therefore the prevention might be a preoperative treatment with antiplatelet therapy in polycytemia vera.

Sub-micron tailoring of bi-soft segment asymmetric polyurethane membrane surfaces with enhanced hemocompatibility properties

Enhancement of membrane hemocompatibility is achieved through the control of the surface morphology. Bi-soft segment integrally skinned poly(ester urethane urea) (PEUU) membranes containing polycaprolactone (PCL) as a second soft segment are synthesized with PCL-diol ranging from 0% to 15% (w/w). Scanning electron microscopy and atomic force microscopy characterized membrane asymmetry and sub-micron roughnesses, R(a), of top dense surfaces as major assets to the development of platelet/membrane surface interactions. Here we show that the top dense surfaces of asymmetric PEUU membranes can be tailored with different morphologies when the ratio of the two soft segments PPO/PCL varies. A strong correlation between the top surface roughnesses, R(a) and platelet deposition is identified. The membrane with 15% (w/w) of PCL-diol, PEUU 85, shows the smoothest top dense layer with a R(a) as low as 1 nm which is 5 times below the characteristic value of the PEUU membrane with a single soft segment. The PEUU 85 asymmetric membrane displayed minimal platelet deposition and inhibition of extreme stages of platelet activation.

Outcomes comparison of 5 coated cardiopulmonary bypass circuits versus an uncoated control group of patients undergoing cardiac surgery

Attenuated inflammatory response and decreased platelet activation have been claimed repeatedly when biocompatible circuits are used for cardiopulmonary bypass. We evaluated five Health Canada approved biocompatible circuit coatings (BCC) against an un-coated control group to determine their effectiveness in improving post-operative outcomes.

Patients were assigned to the Control group or one of the 5 coated circuit groups: 40 Control; 33 Trillium; 32 Phisio; 34 Bioline; 33 X; and 11 GBS. Measured outcomes included: ventilator time; ICU time; post-operative chest tube drainage and transfusion volume; high sensitivity C-reactive protein (hsCRP); tau protein; and pre- and 72-hour post-operative anti-saccadic eye movement test comparisons.

Results: 183 patients were enlisted into the study. One arm of the study (GBS) was abandoned after 11 patients on account of inconsistent pressure excursions within the oxygenator and the excessive consumption of platelets necessitating transfusion. Patients in the X-coated group had significantly longer ventilator and intensive care unit (ICU) time compared to the three remaining coated circuit study groups. Though not significant, patients in the X group also demonstrated the highest post-operative chest tube losses, the most platelet transfusions, the highest tau protein levels and the lowest post-operative anti-saccadic eye movement test (ASEMT) results compared to the three remaining coated groups. The patients in the Trillium, Bioline and Phisio groups showed an improvement in ventilator and ICU time relative to the Control group. The diabetic patients in the Trillium, Bioline and Phisio groups showed an improvement in bleeding relative to the diabetic patients in the Control group.

Conclusion: We compared all 5 coated circuits approved for clinical use in Canada against an uncoated control circuit. Three of the 5 coated circuits (Trillium, Phisio and Bioline BCC) were found to improve ventilator and ICU time compared to Control. Further studies are indicated to validate these results and their impact upon approval criteria, purchasing choices and safe clinical practice, especially as applied to higher risk diabetic patients.

An Update on Interventional Lung Assist Devices and Their Role in Acute Respiratory Distress Syndrome

In recent years, pumpless arteriovenous systems for extracorporeal gas exchange have become a new therapeutic option for the treatment of patients suffering from acute respiratory failure. Experiences with the pumpless extracorporeal membrane lung in animal experiments and in patients with adult respiratory distress syndrome published in the current literature are reviewed. In addition this article presents a case of varicella pneumonia with persistent hypoxemia and hypercapnia under mechanical ventilation that showed a significant improvement with treatment with a pumpless extracorporeal lung assist using an arteriovenous shunt for eight days. The patient made a complete recovery. This is the first report of a patient with a life-threatening varicella pneumonia successfully treated with pumpless extracorporeal lung assist device. This review provides an update on interventional lung assist devices and a critical discussion of their advantages and limitations.

[Oxygenator thrombosis without heparin resistance]

A 55-year-old male with a history of positive HIV serology and Polycytemia vera underwent coronary artery bypass graft surgery with normothermic extracorporeal circulation. Following heparin administration the activated clotting time (ACT) was 633 seconds (Hemocron) with kaolin). Lower than expected arterial and venous oxygen partial pressures together with high pressure (350 mmHg) in the arterial line upstream of the oxygenator were observed. Because of these signs the oxygenator was changed during the procedure. The outcome was uneventful. Electronic microscopic examination of the oxygenator membrane and thermic exchanger revealed fibrin and platelet deposits.

Normal and abnormal trans-oxygenator pressure gradients during cardiopulmonary bypass

A prospective study was conducted with the aims of 1) determining the normal trans-oxygenator pressure gradient characteristics for a range of oxygenators and 2) determining the characteristics, incidence and outcome of abnormally raised gradients. The trans-oxygenator pressure gradient was monitored in 3684 patients undergoing open-heart surgery in eight different hospitals. When the normal pressure gradient was measured during cardiopulmonary bypass in mmHg/L blood flow, a constant figure was obtained which was specific for each oxygenator. This gradient was abnormally raised in 16 cases (one in every 230 cases) and was raised to such an extent in three of these cases that an emergency oxygenator changeout was required (one in every 1228 cases). Among the 16 reported incidents, three different patterns of gradient changes occurred, suggesting the possibility that there were three different aetiologies. In nine of these incidents, the pressure gradient was normal immediately upon going on bypass, but rose rapidly to a plateau value, which then returned to the normal value within 40 minutes. In three cases, the pressure gradient was raised immediately upon going on bypass and then rapidly returned to the baseline. In one case, the pressure gradient was raised immediately upon going on bypass and stayed raised throughout the operation.

Heparin-coated cardiopulmonary bypass circuits: current status

Heparin-coated circuits have been subjected to vigorous testing, both experimentally and clinically, for the past decade. When the functions of heparin are preserved on the surface, the heparinized surface plays multiple roles in attenuating the systemic inflammatory response. These include the ability to attenuate contact activation, coagulation activation, complement activation and, directly or indirectly, platelet and leukocyte activation. The heparinized surface also renders the cardiopulmonary bypass (CPB) circuits hydrophilic and protein resistant and augments lipoprotein binding. The multifunctional nature of the heparinized surface contributes to the overall biocompatibility of the surface. Clinically, heparin-coated circuits become most effective in reducing systemic inflammatory response and in improving morbidity, mortality, and other patient outcome related parameters when material-independent blood activation is controlled or minimized through a global biocompatibility strategy. Techniques involved in the global biocompatibility strategy are readily available and are being effectively and safely practiced at several centers. With the global biocompatibility strategy, outstanding and reproducible results have been routinely achieved with conventional CPB techniques. Alternative revascularization procedures should equal or surpass conventional CPB, using best clinically proven strategies with respect to patient outcome and long-term graft patency.

Oxygenator thrombosis: worst case after development of an abnormal pressure gradient--incidence and pathway

The development of an abnormally high pressure gradient (APG) before the membrane oxygenator (MO) is a complication that occurs during some extracorporeal circulation (ECC) procedures. The present study deals with the incidence of an APG and discusses a probable causative pathway by comparing surface-coated and uncoated oxygenation systems. Five thousand six hundred and seventeen adult ECCs were carried out (2,581 without and 3,036 with surface coatings). The incidence of an APG, therefore, amounted to 0.03% in the group with coated systems and 4.3% in the uncoated group. In addition, an in vitro study demonstrated significantly reduced adhesion and activation of platelets and leucocytes when the surfaces of the MOs were coated with heparin or polypeptides. The advantages of coating surfaces of ECC devices possibly depend on the selective adsorption of particular plasma proteins. These will presumably form a biocompatible membrane on the surface, and minimize pathological deposit of fibrin, platelets and other blood cells, and, therefore, implicate the prevention of an oxygenator failure.

A retrospective study on perfusion incidents and safety devices

Despite the acceptance of extracorporeal circulation as an effective modality to facilitate cardiac surgery, patient outcomes can be negatively influenced by the occurrence of perfusion incidents. A perfusion survey was conducted to identify safety techniques and incidents related to cardiopulmonary bypass (CPB). An 80-question survey was mailed to chief perfusionists of all 1030 USA cardiac surgical centers using CPB. The survey was designed to examine practices and incidents that occurred during a 2-year period (July 1996 to July 1998). Five-hundred-and-fifty-two (54% response rate) surveys were returned, which accounted for 797 hospitals (79% of all cardiac centers) and 653,621 surgical procedures. Of the 27 identified CPB safety devices, the highest utilization was arterial line filters (98.5%) and the lowest arterial line bubble traps (3.4%). Of the reported cases, a CPB incident occurred once every 138 cases. The most common occurring incidents were protamine reactions (1:783), coagulation problems (1:771), and heater/cooler failures 11:1809). The rate of occurrence of an incident resulting in a serious injury or death was one for every 1453 procedures. Although techniques and safety devices create a relatively secure environment for CPB, lower incident rates may be achieved with further improvements in coagulation monitoring and incident reporting.

Oxygenator thrombosis: an international phenomenon

Oxygenator thrombosis, despite adequate anticoagulation, has become a recent concern amongst perfusionists worldwide. The phenomenon is characterized by a transient increase in oxygenator inlet pressure of up to 900 mmHg about 10-15 min after the institution of cardiopulmonary bypass (CPB). Depending on the size and location of the thrombus, shunting may occur that compromises gas transfer to the extent where oxygenator change-out is necessary. This article presents various case reports and publications, both domestic and international, detailing this phenomenon. Research hypothesizes that it is the activation of platelets that subsequently may cause the deposition of fibrin, yielding thrombus formation; however, the primary etiology of this phenomenon remains unknown. Possible catalysts include bypass techniques, equipment selection, pharmacological agents, prime and the patient. This paper will review all of the above with an emphasis on the often overlooked factor--the patient, as there are certain variables in patient hematology that provoke a hypercoagulable state leading to thrombosis, including blood type, genetics, age, disease state, gender and heparin.

Coating-techniques to improve the hemocompatibility of artificial devices used for extracorporeal circulation

OBJECTIVE

Extracorporeal circulation procedures have been shown to induce complement and leukocyte activation, release of endotoxin and inflammatory mediators, including cytokines, nitric oxide, oxygen free radicals, and platelet activating factors. The contact between the blood and the various artificial surfaces of the extracorporeal system results in an unspecific post-perfusion syndrome. For diminishing these negative side effects several coating-techniques have been developed to create devices with improved hemocompatibility.

METHODS

This review deals with the current knowledge of heparin-coated and otherwise surface-modified perfusion systems. The pathway how heparin-coated surfaces work is discussed and techniques for surface-coatings, both clinically introduced as well as newly developed are presented.

RESULTS

Numerous clinical studies compared heparin-coated versus non-coated circuits. Heparin-bonded devices showed lessened humoral and cellular activation, in particular a reduced complement activation with a reduced inflammatory post-perfusion syndrome. Also platelet protection and more favorable post-operative lung function are of particular note. Recent clinical trials demonstrated shortened hospital stays, less drainage bleeding, and reduced cerebral complications using heparin-coated oxygenation systems. The diminished expression of the leukocyte adhesion molecules CD 11b/c in CBAS devices points to a decreased activation of neutrophils. In addition, one research group found a reduced production of oxygen radicals. Heparin-bonding minimizes oxygenator failure by a significant reduced pressure gradient across the oxygenator, probably caused by decreased fibrin and platelet deposition at the hollow fiber surfaces. A meta analysis examined the impact of heparin-bonded systems on clinical outcomes and resulting costs. Using heparin-bonded circuits led to total cost savings from US $1000 to 3000. Several authors demonstrated reduced blood loss and better clinical outcome by reduction of systemic heparinization and the employment of heparin-coated devices.

CONCLUSION

Above and beyond the long-term applications, routine heart operations have also markedly begun to utilize heparin-coated devices. This trend will assuredly continue in the coming years and is an important step toward higher hemocompatibility of blood-contacting surfaces in the ECC device. Heparin-coatings are merely the beginning of improved hemocompatibility for all materials that come into contact with human blood or tissues. Intelligent materials with almost completely physiological surfaces will be at the surgeon's disposal within the next few years.

Synthetic protein treated versus heparin coated cardiopulmonary bypass surfaces: similar clinical results and minor biochemical differences

OBJECTIVE

Complications associated with cardiopulmonary bypass (CPB) have gained more attention due to increased interest in coronary artery bypass grafting without CPB. The impact of heparin coating of CPB circuits has been discussed controversially. The present study examines if the treatment of the oxygenator surface with a synthetic protein may serve as an alternative to a completely heparin coated circuit.

METHODS

Fifty-eight patients undergoing coronary artery bypass grafting with CPB were randomly assigned to completely heparin coated circuits or synthetic protein treated oxygenators in a double blind protocol, focussing on the inflammatory reaction resulting in membrane damage, coagulation changes and markers of cerebral injury or dysfunction. Treatment groups did not differ as to preoperative demographics, and intraoperative clinical data. Patients with any neurologic disease or risk factors for cerebral dysfunction were not included in the study.

RESULTS

Postoperative clinical data did not differ between groups. Both surface treatments resulted in similar coagulation activation, hyperfibrinolysis and disseminated intravascular coagulation. Platelet count displayed a difference in favour of the heparin coated group (P = 0.029). Increased leukocyte activation reflected by rising myeloperoxidase concentrations on CPB was present in both synthetic protein and heparin coating groups. Interleukins 6 and 8 reacted similarly, but interleukin 8 increased significantly more (P = 0.0061) at the end of surgery in patients treated with protein treated oxygenators. The same pattern was observed for complement activation as determined by total complement complex (P = 0.006). Both surface changes resulted in moderately increased S-100B protein and neuron specific enolase, without difference between groups. Both markers did not reach concentrations associated with clinical manifestation of cerebral injury.

CONCLUSIONS

These results in routine patients with short bypass time, imply that protein treated oxygenators are associated with a limited increase of biochemical markers similar to heparin coating. However, significantly lower interleukin 8 release and complement activation can be achieved by heparin coating. The protein treatment is a standard feature of the oxygenator examined in both groups. It is not associated with additional cost and therefore appropriate for use in routine patients.