Clinical cardiopulmonary bypass without systemic anticoagulation

Effects of albumin and synthetic polypeptide-coated oxygenators on IL-1, IL-2, IL-6, and IL-10 in open heart surgery

BACKGROUND

In this study, we have tried to demonstrate the effects of coating style used in oxygenators on various hematologic and clinical parameters.

MATERIALS AND METHODS

Twenty-seven patients were included in the study, who had undergone operations because of elective coronary artery disease. Albumin-coated oxygenator was used in Group I. In Group II, a synthetic polypeptide-coated oxygenator was used. C1-inhib (complement), C3c, C4, interleukins (IL-1β, IL2, IL-6, IL-10), and tumor necrosis factor alpha (TNF-α) levels were examined at four different time intervals. Hemoglobin, hematocrit, leukocyte and platelet counts, drainage, and transfused blood volumes were analyzed.

RESULTS

Albumin levels were significantly lower in Group I than those in Group II 5 minutes after the removal of the cross-clamp. Twenty-four hours after the surgery, Group I patients also had a significantly higher white blood cell count compared to Group II patients. TNF-α levels in Group I were always expressed in considerably higher amounts than those in Group II. IL-6 levels were significantly higher in Group I, but IL-10 levels were observed to be higher in Group II (p < 0.05).

CONCLUSION

Synthetic polypeptide-coated advanced technology, which employed oxygenators, had an important attenuator effect on acute phase reactants and also on the inflammatory response.

Duroflo II heparin bonding does not attenuate cytokine release or improve pulmonary function

BACKGROUND

Comparison of the cytokine generation and leukocyte activation properties of Duroflo II heparin bonded bypass circuit (Baxter Healthcare Corp, Compton, UK) and the conventional cardiopulmonary bypass circuit. Attempt to correlate these to pulmonary dysfunction postoperatively.

METHODS

Forty patients undergoing elective, isolated coronary artery bypass grafting were randomly allocated to have either plain extracorporeal circuits (group C) or heparin bonded extracorporeal circuits (group H). Full systemic heparinization was used in all patients. The inflammatory response was assessed by measuring plasma levels of interleukin-6, interleukin-8, interleukin-10, and polymorphonuclear elastase. Gas exchange was assessed by measuring the PaO2/FIO2 ratio.

RESULTS

Significant impairment of oxygenation was seen in both groups with the lowest values at the end of the operation before a gradual return to normal during the next 6 hours. There were no differences between the groups in gas exchange or times to extubation. There were significant elevations in all the cytokines, with interleukin-6 levels peaking at 4 hours in group H and 24 hours in group C, before starting to return to normal at 48 hours. The patterns of interleukin-8 and interleukin-10 rise were identical in the two groups. Polymorphonuclear elastase reached a peak at the end of the operation in group H and remained elevated up to 24 hours, whereas levels continued to rise in group C up to 4 hours. There were no significant differences in levels between groups at any time. There were no differences between the groups in blood loss or blood product usage.

CONCLUSIONS

Cardiopulmonary bypass induces a systemic inflammatory response with release of cytokines and activation of leukocytes. This correlates with the severe deterioration in pulmonary gas exchange from preoperative levels up to 6 hours postoperatively (p < 0.05). In the presence of systemic heparinization, Duroflo II heparin bondingtf the circuits has minor effects on the pattern of evolution of this inflammatory response.

Heparin-bonded circuits: clinical outcomes and costs

The aim of this study was to use meta-analysis to combine the results of numerous studies and examine the impact of heparin-bonded circuits on clinical outcomes and the resulting costs. Heparin-bonded circuits, both ionically and covalently bonded, are examined separately. The results of the study provide evidence that heparin-bonded circuits result in improved clinical outcomes when compared to the identical nonheparin-bonded circuits. These improved clinical outcomes result in subsequent lower costs per patient with their use. However, differences are apparent in the significance and magnitude of these outcomes between ionically and covalently bonded circuits. Covalently bonded circuits provide a greater magnitude and significance of improvement in clinical outcomes than ionically bonded circuits. Total cost savings can be expected to be three times greater with covalently bonded circuits ($3231 versus $1068). It was concluded that the choice regarding the use of a heparin-bonded circuits and the type of heparin-bonded circuit used has the potential to alter clinical outcomes and subsequent costs. Cost consideration cannot be ignored, but clinical benefits should be the main rationale for the choice of cardiopulmonary bypass circuit. This analysis provides evidence that clinical benefits and cost savings can both be derived from use of the same technology-covalently bonded circuits.

Inflammatory response to cardiopulmonary bypass: mechanisms involved and possible therapeutic strategies

BACKGROUND

Recent study of the inflammatory reactions occurring during and after cardiopulmonary bypass (CPB) has improved our understanding of the involvement of the inflammatory cascade in perioperative injury. However, the exact mechanisms of this complex response remain to be fully determined.

METHODS

Literature on the inflammatory response to CPB was reviewed to define current knowledge on the possible pathways and mediators involved, and to discuss recent developments of therapeutic interventions aimed at attenuating the inflammatory response to CPB.

RESULTS

CPB has been shown to induce complement activation, endotoxin release, leukocyte activation, the expression of adhesion molecules, and the release of many inflammatory mediators including oxygen-free radicals, arachidonic acid metabolites, cytokines, platelet-activating factor, nitric oxide, and endothelins. Therapies aimed at interfering with the inflammatory response include the administration of pharmacologic agents such as corticosteroids, aprotinin, and antioxidants, as well as modification of techniques and equipment by the use of heparin-coated CPB circuits, intraoperative leukocyte depletion, and ultrafiltration.

CONCLUSIONS

Improved understanding of the inflammatory reactions to CPB can lead to improved patient outcome by enabling the development of novel therapies aimed at limiting this response.

Cell activation and thrombin generation in heparin bonded cardiopulmonary bypass circuits using a novel in vitro model

OBJECTIVE

It is generally agreed that when the blood contact surfaces of a cardiopulmonary bypass circuit are treated with a layer of heparin molecules the activation of the humoral pathways is attenuated. However, there is still debate as to whether heparin-bonded circuits reduce thrombin generation. This study aims to examine the effects of immobilized heparin on cell activation and thrombin generation in a novel, well controlled model of cardiopulmonary bypass.

METHODS

The model used consisted of a heparin-bonded and a non-bonded cardiopulmonary bypass circuit perfused in tandem with the same unit of fresh heparinized (3.3 U/ml) human blood for a period of 6 h. Samples were taken for analysis from the bag just prior to perfusion and at 30, 60, 120 and 360 min of perfusion. Whole blood was used to analyse platelet and white blood cell count, haematocrit and activated coagulation time. Plasma samples were prepared for batch analysis of the cell activation markers p-selectin, elastase and interleukin-8, and the thrombin generation markers thrombin-antithrombin and prothrombin fragment F1 + 2. A sample of tubing was taken from each circuit at the end of the perfusion and prepared for visualization by scanning electron microscopy.

RESULTS

Platelet counts were significantly reduced in the non-bonded circuits compared with the heparin-bonded circuits at 30 (22 versus 200 x 10(9)/L P < 0.01), 60 (26 versus 193 x 10(9)/L P < 0.01) and 120 min (28 versus 193 x 10(9)/L P < 0.01) as were white blood cell counts at 30(1.5 versus 2.7 x 10(9)/L P < 0.01), 60 (0.9 versus 2.4 x 10(9)/L P < 0.01), 120 (0.9 versus 1.8 x 10(9)/L P < 0.01) and 360 min (0.4 versus 0.9 x 10(9)/L P < 0.05). The concentration of p-selectin was found to be significantly higher in the non-bonded circuits than in the heparin-bonded circuits at 30 (37 versus 29 ng/ml P < 0.01), 60 (37 versus 28 ng/ml P < 0.01). 120 (42 versus 27 ng/ml P < 0.01) and at 360 min (72 versus 46 ng/ml P < 0.01). Elastase was elevated in the non-bonded circuits at 30 (570 versus 145 micrograms/l P < 0.01), 60 (646 versus 278 micrograms/l P < 0.01) and 120 min (613 versus 403 micrograms/l P < 0.05) and interleukin-8 at 120 (705 versus 520 pg/ml P < 0.05) and 360 min (11326 versus 9910 pg/ml P < 0.05). A similar picture was found for the thrombin generation markers. Thrombin-antithrombin complexes were raised in the non-bonded circuits compared with heparin-bonded circuits at 60 (24 versus 13 micrograms/l P < 0.05) and 120 min (46 versus 17 micrograms/l P < 0.05) as was prothrombin fragment F1 + 2 at 30 (1.1 versus 0.7 nmol/l P < 0.01), 60 (1.3 versus 0.7 nmol/l P < 0.01), 120 (1.8 versus 0.9 nmol/l P < 0.01) and 360 min (15.0 versus 13.6 nmol/l P < 0.05). Scanning electron microscopy revealed a greater amount of adherent material on the non-bonded surface relative to the heparin-bonded surface.

CONCLUSIONS

In a cardiopulmonary bypass circuit perfused with human blood the activation of platelets and white blood cells has been seen to be significantly reduced in the presence of a heparin-bonded surface. Thrombin generation due to contact activation of the intrinsic coagulation pathway is also reduced.

Extracorporeal circulation, hemocompatibility, and biomaterials

BACKGROUND

Performance of a majority of cardiac surgical procedures requires the use of extracorporeal circulation. Contact of the patients' blood with the nonendothelial surface of the cardiopulmonary bypass circuit is responsible for several, potentially harmful systemic reactions.

METHODS

The patients' response to extracorporeal circulation is reviewed briefly. The interactions between patient and circuit are discussed not only as they relate to blood-material contact, but also from a mechanical and rheologic standpoint. The theoretic benefits of the newer, more hemocompatible materials are presented, along with a review of published clinical experience with heparinized cardiopulmonary bypass circuits.

RESULTS

The response to extracorporeal circulation extends far beyond a simple derangement of hemostasis. This inflammatory response is strongly influenced by the rheologic design of the circuit and by the physical and chemical properties of the surface. Heparinized circuits decrease inflammation, but the clinical benefits of this reduction remain unclear, except for extended cardiopulmonary support. The safe use of these circuits requires full heparinization and does not reduce allogeneic transfusions.

CONCLUSIONS

Clinicians are still in the search of the ideal material and the ideal extracorporeal circuit design. Newer, heparinized materials offer real but limited clinical benefits.

The effects of Carmeda Bioactive Surface on human blood components during simulated extracorporeal circulation

Postoperative morbidity after cardiopulmonary bypass most commonly manifests as bleeding diatheses or pulmonary dysfunction. The pathophysiology has been attributed to the activation of cellular and humoral components of blood after contact with an artificial surface. Development of a surface that would be nonthrombogenic and also would constitute a less potent inflammatory stimulus would therefore be beneficial. In the following experiments, we evaluated the heparin-bonded Carmeda Bioactive Surface (Medtronics Cardiopulmonary, Anaheim, Calif.) in an in vitro model of extracorporeal circulation at standard-dose heparin (5 U/ml), to examine the effects of the surface treatment on activation of blood elements, and at reduced-dose heparin (1 U/ml), to determine whether surface-bound heparin would serve as an effective anticoagulant. During the initial recirculation period, platelet counts in the Carmeda (n = 12) circuits were preserved at both doses of heparin and compared with control values (n = 12): At 5 U/ml, control 36% +/- 4% (mean +/- standard error of the mean) versus Carmeda 81% +/- 5%; at 1 U/ml, 43% +/- 3% versus 61% +/- 10%, expressed as a percent of baseline at 30 minutes, p < 0.05. Furthermore, plasma levels of platelet factor 4 and beta-thromboglobulin were significantly reduced in the Carmeda circuits throughout the experiment: At heparin 5 U/ml, 2500 +/- 340 ng/ml versus 604 +/- 191 ng/ml; at 1 U/ml, 2933 +/- 275 ng/ml versus 577 +/- 164 ng/ml of platelet factor 4 at 2 hours (p < 0.05). The pattern of beta-thromboglobulin release was similar, with effects more pronounced at the lower dose of heparin. Surface modification also reduced leukocyte depletion (p < 0.05) and release of elastase at both concentrations of heparin (5 U/ml, 0.72 +/- 0.29 ng/ml versus 0.33 +/- 0.23 ng/ml; 1 U/ml, 0.85 +/- 0.08 ng/ml versus 0.20 +/- 0.05 ng/ml, at 2 hours, p < 0.05). Moreover, as heparin concentration was reduced, Carmeda surface treatment significantly decreased generation of C3a des Arg (1 U/ml, 14,410 +/- 3558 ng/ml versus 3053 +/- 1039 ng/ml at 2 hours, p < 0.05). Although heparin bonding was originally intended to obviate the need for systemic heparinization, Carmeda treatment did not reduce fibrinopeptide A generation at the lower dose of heparin. In summary, Carmeda treatment failed to exhibit anticoagulant efficacy in this model; however, the data suggest that surface modification may have a role in ameliorating the typical inflammatory response initiated by blood contact with an artificial surface.

Extracorporeal membrane oxygenation for lung transplant recipients with primary severe donor lung dysfunction

Primary severe donor lung dysfunction (DLD) is a significant complication after lung transplantation (LTx), and a high mortality is reported with conventional therapy. The purpose of this report is to review the experience of the University of Pittsburgh with extracorporeal membrane oxygenation (ECMO) for primary severe DLD after LTx. From September 1991 to May 1995, 220 LTx were performed at our center. Eight patients (8/220 = 3.6%) with severe DLD after LTx required ECMO support. The age of LTx recipients was 44 +/- 5 years (mean +/- SD); seven patients were female and one was male. Indications for LTx were: chronic obstructive pulmonary disease in four patients, bronchiectasis in two, and pulmonary hypertension in two. There were three single LTx and five bilateral LTx. The interval from LTx to institution of ECMO was 5.6 +/- 3.2 h (range 0-10 h). Three patients were supported with veno-venous (v-v) ECMO and five had veno-arterial (v-a) ECMO. The duration of ECMO support was 7.3 +/- 4.8 days (range 3-15 days). activated glotting time (ACT) was maintained between 110 and 180 s with intermittent use of heparin. Seven patients (7/8 = 87%) were successfully weaned from ECMO and six patients (6/8 = 75%) were discharged home; they are currently alive after a follow-up of 17 +/- 10.1 months. One patient died on ECMO support for refractory DLD and another died 2 months after ECMO wean from multisystem organ failure. At 6 months follow-up, forced expiratory volume in 1 s (FEV1) is 2.35 +/- 0.91 (75% +/- 17.4% predicted) and mean forced vital capacity (FVC) is 2.53 +/- 0.81 (64% +/- 14% predicted). We conclude that ECMO can be lifesaving when instituted early after primary severe DLD. The v-v ECMO support is preferred when the patient is hemodynamically stable and adequate long-term function of the allograft is anticipated.

Surface-bound heparin fails to reduce thrombin formation during clinical cardiopulmonary bypass

The hypothesis that heparin-coated perfusion circuits reduce thrombin formation and activity; fibrinolysis; and platelet, complement, and neutrophil activation was tested in 20 consecutive, randomized adults who had cardiopulmonary bypass. Twenty identical perfusion systems were used; in 10, all blood-contacting surfaces were coated with partially degraded heparin (Carmeda process; Medtronic Cardiopulmonary, Anaheim, Calif.). All patients received a 300 U/kg dose of heparin. Activated clotting times were maintained longer than 400 seconds. Cardiopulmonary bypass lasted 36 to 244 minutes. Blood samples for platelet count, platelet response to adenosine diphosphate, plasma beta-thromboglobulin, inactivated complement 3b, neutrophil elastase, fibrinopeptide A, prothrombin fragment F1.2, thrombin-antithrombin complex, tissue plasminogen activator, plasminogen activator inhibitor-1, plasmin alpha 2-antiplasmin complex, and D-dimer were obtained at these times: after heparin was given, 5 and 30 minutes after cardiopulmonary bypass was started, within 5 minutes after bypass was stopped, and 15 minutes after protamine was given. After cardiopulmonary bypass, tubing segments were analyzed for surface-adsorbed anti-thrombin, fibrinogen, factor XII, and von Willebrand factor by radioimmunoassay. Heparin-coated circuits significantly (p < 0.001) reduced platelet adhesion and maintained platelet sensitivity to adenosine diphosphate (p = 0.015), but did not reduce release of beta-thromboglobulin. There were no significant differences between groups at any time for fibrinopeptide A, prothrombin fragment F1.2, or thrombin-antithrombin complex or in the markers for fibrinolysis: D-dimer, tissue plasminogen activator, plasminogen activator inhibitor-1, and alpha 2-antiplasmin complex. In both groups, concentrations of prothrombin fragment F1.2 and thrombin-antithrombin complex increased progressively and significantly during cardiopulmonary bypass and after protamine was given. Concentrations of D-dimer, alpha 2-antiplasmin complex, and plasminogen activator inhibitor-1 also increased significantly during bypass in both groups. Fibrinopeptide A levels did not increase during bypass but in both groups increased significantly after protamine was given. No significant differences were observed between groups for levels of inactivated complement 3b or neutrophil elastase. Radioimmunoassay showed a significant increase in surface-adsorbed antithrombin on coated circuits but no significant differences between groups for other proteins. We conclude that heparin-coated circuits used with standard doses of systemic heparin reduce platelet adhesion and improve platelet function but do not produce a meaningful anticoagulant effect during clinical cardiopulmonary bypass. The data do not support the practice of reducing systemic heparin doses during cardiac operations with heparin-coated extracorporeal perfusion circuitry.

Intracardiac thrombus: a risk of incomplete anticoagulation for cardiac operations

Mitral valve replacement was performed urgently in a patient with hemorrhagic brain lesions. To decrease the risk of intracranial hemorrhage, cardiopulmonary bypass was performed using a heparin-coated perfusion system and a reduced dose of heparin. The detection of an acute intracardiac thrombus by transesophageal echocardiography during cardiopulmonary bypass exposed a potential hazard of techniques employing reduced systemic anticoagulation for cardiac operations.

Risk and benefit of low systemic heparinization during open heart operations

Heparin surface-coated perfusion equipment with improved thromboresistance was evaluated in 104 consecutive patients undergoing open heart operation in a prospective, randomized trial with low versus full systemic heparinization. Surgical procedures included coronary artery revascularization in 47 of 54 (87%) for low versus 44 of 50 patients (88%; not significant [NS]) for full, valve repair/replacement in 8 of 54 (15%) for low versus 5 of 50 patients (10%; NS) for full, left ventricular aneurysm repair in 1 of 54 (2%) for low versus 2 of 50 patients (4%; NS) for full, and other in 3 of 54 (6%) for low versus 3 of 50 patients (6%; NS) for full. Cross-clamp time was 39.2 +/- 10.7 minutes for low versus 39.5 +/- 10.5 minutes for full (NS). Cardiopulmonary bypass time was 68.6 +/- 20.1 minutes for low versus 69.3 +/- 16.6 minutes for full (NS). Lowest activated coagulation time during perfusion was 255 +/- 75 seconds for low versus 537 +/- 205 seconds for full (p < 0.0005). In the low group, the target activated coagulation time of more than 180 seconds was not reached during perfusion in 4 of 54 patients (7%), the lowest value being 164 seconds. No oxygenator failure occurred. Hospital mortality was 0 of 54 (0%) for low versus 1 of 50 patients (2%) for full (NS). Bleeding required surgical revision in 0 of 54 (0%) for low versus 4 of 50 patients (8%) for full (p = 0.05). Drainage (24 hours) was 790 +/- 393 mL for low versus 1,039 +/- 732 mL for full (p < 0.025).(ABSTRACT TRUNCATED AT 250 WORDS)