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Ann Thorac Surg 1999;67:1268-1273
© 1999 The Society of Thoracic Surgeons
a Department of Thoracic & Cardiovascular Surgery, The Cleveland Clinic Foundation, Cleveland, Ohio, USA
b Department of Cardiothoracic Anesthesia, The Cleveland Clinic Foundation, Cleveland, Ohio, USA
c Department of Perfusion Services, The Cleveland Clinic Foundation, Cleveland, Ohio, USA
Accepted for publication September 22, 1998.
Address reprint requests to Dr McCarthy, The Cleveland Clinic Foundation, 9500 Euclid Ave, F-25, Cleveland, OH 44195
e-mail: mccartp{at}cesmtp.ccf.org
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Abstract |
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 TopFootnotes Abstract IntroductionMaterial and methodsResultsCommentReferences |
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Methods. Three hundred fifty patients who had reoperation with CABG only (58%), or with valve operations (42%) were randomly assigned to receive either a heparin-coated (Duraflo II; study group) or uncoated (control group) circuit. Clinical outcomes were compared and the variables were analyzed using the following three groups: entire populations of study group and control group, subgroup of patients who had CABG reoperation only, and a subgroup who had valve reoperation or combined valve and CABG reoperation.
Results. Preoperative variables were the same in both groups. No difference in clinical outcomes could be demonstrated except that the percentage of patients with major bleeding episodes was significantly lower in the study group (1.2% versus 5.4%, p = 0.035). In the subgroup analysis of patients who had valve reoperations, lower blood transfusion requirements in the intensive care unit (p = 0.013) were found in the study group. When the subgroup of patients who had CABG reoperations was analyzed separately, there was a trend toward less reoperation for bleeding in the study group (0% versus 4.0%, p = 0.058).
Conclusions. We conclude that the use of heparin-coated circuits was safe and imparted protection from reoperations for bleeding and major bleeding episodes. Material-independent blood activation (eg, blood-air interface and cardiotomy suction) blunted the total effect of the heparin-coated surface.
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Introduction |
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Heparin-coated CPB circuits have been shown to reduce inflammatory responses, including decreased complement activation [7–10], leukocyte activation [11, 12], and cytokine release [13, 14]. Reduced blood loss and transfusion requirements, along with improved outcome have also been reported when a heparin-coated circuit was used in conjunction with reduced systemic heparin [15–17]. However, most prior studies involving full systemic heparin only included patients who had low-risk coronary artery bypass operations. Clinical results from these studies have been mixed, but generally have shown small improvements in clinical outcomes for patients who had a heparin-coated circuit versus those treated with an uncoated circuit [8, 18]. A recent European multicenter clinical study involving 805 patients who had elective coronary artery operations in 11 centers showed little overall difference in blood usage, morbidity, and mortality with the use of heparin-coated circuits [19]. However, in subgroups of female patients and patients requiring prolonged cross-clamp times, some improvements were observed in patients perfused with heparin-coated circuits. The lack of significant improvement in overall study outcome was attributed to differences in patient characteristics, perfusion techniques, blood handling procedures, and postoperative care among participating centers.
We hypothesized that a large patient population undergoing more complex cardiac operations would be more likely to demonstrate clinically beneficial effects of the heparin-coated circuit because CPB time and morbidity are higher in this population. The objective of the present prospective, randomized study was to determine whether the use of heparin-coated circuits improved the clinical outcome of patients who had cardiac reoperations for coronary artery bypass grafting (CABG), valve operation, or both CABG and valve operation.
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Material and methods |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentReferences |
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Inclusion criteria were elective cardiac reoperation surgery, age 18 to 80 years, and signed consent to participate. Exclusion criteria were (1) emergency cardiac operation; (2) anticipated operation other than revascularization or valve (eg, aortic aneurysm, cardiac endarterectomy); (3) known preoperative coagulopathy or liver disease, bilirubin higher than 2 mg/dL, prothrombin time longer than 15 seconds, partial thromboplastin time longer than 45 seconds (if not secondary to heparin), or platelet count less than 75,000/mm3; (4) active endocarditis; (5) preoperative intraaortic balloon pump or assist devices; (6) aprotinin usage; (7) preoperative steroid replacement; (8) short- or long-term dialysis; and (9) inability to obtain signed consent.
The experimental protocol was reviewed and approved by the Cleveland Clinic Institutional Review Board. All components of the perfusion circuit, both heparin-coated and uncoated, were approved by the Food and Drug Administration and were commercially available. Informed consent was obtained during the preoperative visit by physician assistants. After entry into the study the patients were randomly assigned into two the study group (heparin-coated circuits) or control group (uncoated circuits). Randomization took place on arrival to the operating room and was carried out by the perfusionist, who used a randomization schedule. Coded envelopes were used for each patient that qualified for the study. Only the perfusionist was aware of which circuit was used, the remainder of the surgical and postoperative team were blinded to group assignment.
The Higgins score [20] was determined preoperatively for each patient and was used to compare the clinical severity and comorbidities of the patient case load in each group. The Higgins score, preoperative data, intraoperative data, and postoperative data were collected prospectively by a study nurse.
Anesthesia and extracorporeal circulation
Anesthesia and extracorporeal circulation were standardized throughout the study. Anesthesia was induced and maintained with a combination of fentanyl and midazolam, supplemented with isofluorane. A roller pump (Cobe, Lakewood, CO) was used for both study and control groups. Unless otherwise indicated, all study and control circuit components were from Bentley Division, Baxter Healthcare Corp (Irvine, California). The coated system consisted of AF 1025 GOLD arterial filter, HSR-4000 GOLD venous reservoir with cardiotomy autotransfusion filter, Univox GOLD membrane oxygenator, HE-30 GOLD cardioplegia heat exchange system, venous and arterial GOLD cannulas (Research Medical Inc, Salt Lake City, UT), and custom tubing pacs GOLD. All GOLD devices were coated with Duraflo II heparin as described previously [20]. The control circuit was the same only without heparin coating, except that the administration set for blood cardioplegia and the arterial filter were available only in heparin-coated versions. The uncoated circuit consisted of AF-1025 GOLD arterial filter, HSR-4000 venous reservoir with cardiotomy autotransfusion filter, Univox membrane oxygenator, HE-30 GOLD cardioplegia heat exchange system, BCR-3500 cardiotomy (only for high-volume cases), venous and arterial cannulas (Research Medical Inc, Salt Lake City, UT), and custom tubing pacs.
The extracorporeal circuit was primed with Plasmalyte-A (Baxter Healthcare-IV Systems, Deerfield, IL), heparin (2,500 U/L), sodium bicarbonate 25 mEq/L, and 50 g of mannitol. Heparin (300 USP units/kg) was administered before aortic cannulation. Anticoagulation was maintained during cardiopulmonary bypass by measurement of activated clotting time (Hemochron 801, International Technidyne, Edison, NJ). Incremental doses of heparin were given during bypass to maintain the activated clotting time at greater than 480 seconds. During CPB, a cardiotomy suction device was used to return the shed pericardial blood to systemic circulation. Standardized surgical strategy, myocardial preservation techniques, transfusion thresholds and protocol, and extubation protocol, as previously described by Muehrcke and associates [21], were applied uniformly to all patients. After the operation, the residual content of the CPB circuit was returned to patients without further treatment.
Statistical analysis
The study data were gathered on case record forms, after which SAS software (SAS Inc, Cary, NC) was used for storage and a preliminary analysis. Secondary analyses used the SPSS software package (SPSS for Windows, SPSS Inc, Chicago, IL). The following clinical variables were analyzed:
The variables were analyzed in the following three groups: (1) entire population of study group versus control group, (2) subgroup of patients who had reoperation coronary bypass only (study vs. control groups), and (3) patients who had valve reoperation and combined valve and coronary bypass (study group versus control group). Continuous variables were expressed as mean ± standard deviation, and categoric variables were expressed as percents with n (case counts) included. Univariate analysis was performed using t-test and Wilcoxon tests, 
2 and Fisher exact tests as appropriate. A two-sided p of 0.05 or less was considered to be statistically significant.
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Results |
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Comment |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentReferences |
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In the present study, we used an integrated open venous-cardiotomy reservoir in the cardiopulmonary bypass circuit rather than the closed venous reservoir that has was used in all other clinical studies involving heparin-coated circuits. The heparin-coated integrated reservoir became available only recently. Although the open reservoir involves additional blood-air interaction and might be considered less biocompatible [22], the open system is used more commonly and is believed to have better air handling capability.
In the present study, there were no adverse effects related to the use of heparin-coated circuits. The use of heparin-coated circuits was strongly associated with decreased administration of blood products in the intensive care unit in patients who had valve reoperations and combined valve and CABG and with a decrease in the percentage of patients requiring massive blood transfusion (16 units or more). We also found a trend in favor of the heparin-coated circuits in the reduction of extreme cases of bleeding. In addition, in the subgroup of patients who had coronary bypass reoperation only, a more uniform patient group than the patient population that included valve operation or combined valve and coronary bypass, there were no reoperations for bleeding in the group that had a heparin-coated circuit.
Our findings are similar to those of previously reported studies. The use of a heparin-coated circuit with full systemic heparin in patients who had CABG had been most frequently associated with reduced complement activation, reduced leukocyte activation, and reduced generation of other inflammatory mediators [23]. Other studies demonstrated improved postoperative recovery [8] and improved pulmonary function [18] when patients were perfused with heparin-coated circuits. None of the studies, however, found statistically significant reduction in blood loss and blood transfusion requirements [10, 19, 24–26]. A possible reason for the lack of improvement in bleeding complications is the design of those studies, in particular the inclusion of relatively low-risk patients who had coronary artery bypass operations. The lack of overall clinical improvements shown in a recent European multicenter study was attributed to differences in patient characteristics, perfusion techniques, blood handling procedures, and other factors among the participating centers [19]. Those weaknesses led to the present study design in which a large number of high-risk patients were included at the Cleveland Clinic. Although the blood loss and blood transfusion requirements between the study group and control group in the entire population were similar, statistically significantly fewer massive blood transfusions were done in patients perfused with heparin-coated circuits in the present study. This observation along with the findings that no reoperations for bleeding in the CABG subgroup that had heparin-coated circuits and reduced blood transfusion requirements in patients who had valve reoperations and combined valve and CABG procedures suggests that heparin coating might offer protective benefits.
It has been reported recently that postoperative rhythm disturbances were the most frequent complications in patients who had CABG. The use of heparin-coated circuits has been shown to significantly reduce the incidence of arrhythmias [26, 27]. The reason for these improvements is not known and could be related to the beneficial effects of heparin-coated surfaces on the inflammatory response to cardiopulmonary bypass. In the present study, however, there were no differences in postoperative arrhythmias between the study and control groups.
Our previous study [21] showed that the biochemical markers, such as thrombin-antithrombin complex levels in plasma, increased significantly with time throughout the operation. Other studies in which closed reservoirs and minimal suctions were used [28] found reduced levels of thrombin-antithrombin complex increase (about an order of magnitude lower) during the intraoperative period. It has been shown that blood in the pericardial cavity is highly activated by tissue factor and tissue-type plasminogen activator [29] as well as by the use of the open-style reservoir [22]. The major differences in perfusion techniques between the current study and those of Aldea and associates [17] and Pradam and associates [25] are that, in this study, suctioned blood was returned continuously to systemic circulation throughout the intraoperative period and that we used an open system. We therefore believe that the material-independent blood activation had an effect in the outcome of the present study.
The morbidity and coagulopathy associated with CPB remains a formidable problem in cardiac operations. The complexity of the inflammatory responses to CPB makes an effective anti-inflammatory strategy a difficult challenge. We think that the heparin-coated circuit can ameliorate some of these untoward events, as it is designed to prevent the early activation of inflammatory cascades and blood activation caused by the CPB circuits. Other studies using simulated extracorporeal circuits have shown that heparin coating can significantly reduce blood trauma during extracorporeal circulation [23, 30]. Our findings from the subgroup analyses, ie, less major bleeding episodes and reduced blood transfusion requirements, might reflect the lower levels of material-dependent blood activation with the coated circuits. Further strategies to eliminate these untoward events might include the addition of aprotinin to the heparin-coated circuit [31] or the use of heparin-coated circuits with greatly reduced levels of systemic heparin [16]. The administration of heparin, independent of CPB, causes platelet dysfunction and fibrinolysis [32]; therefore, these adverse effects of heparin might be dose related. Heparin-protamine complex is also known to activate complement via the classic pathway [33], and reduced complement and leukocyte activation has been related to lower systemic heparin requirements and the use of heparin-coated circuits [34, 35]. The use of extracorporeal blood purification devices, such as hemofilters, leukocyte depleting and cell-saving devices, could help to control and remove activated blood components resulting from both material-dependent and -independent sources [36]. A randomized study involving patients who had CABG and using heparin-coated circuits with reduced systemic heparin along with an integrated blood conservation strategy [17] showed that outcome-related factors were substantially improved in patients receiving heparin-coated circuits compared with those in the control group. The cost savings was estimated at more than $1,655 per case. Comparable clinical outcome was recently reported [28] in patients receiving full-dose systemic heparin with the use of heparin-coated circuits. Although the impact on cost in the present study was not quantified, it is estimated that the difference in cost between this heparin-coated circuit (Duraflo II) compared with an uncoated circuit is less than $50. This marginal cost increase of the coated circuit is offset by the potential for less major bleeding and blood transfusion requirements.
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References |
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TopFootnotesAbstractIntroductionMaterial and methodsResultsCommentReferences |
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during cardiopulmonary bypass. Acta Anaesthesiol Scand 1996;40:311-317.[Medline]
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