HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): W. G. Williams Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Turner-Gomes, S. O. Articles by Andrew, M. Search for Related Content PubMed PubMed Citation Articles by Turner-Gomes, S. O. Articles by Andrew, M.

J Thorac Cardiovasc Surg 1994;107:562-0568
© 1994 Mosby, Inc.

Cardiopulmonary Bypass, Myocardial Management, and Support Techniques

Thrombin regulation in congenital heart disease after cardiopulmonary bypass operations

Hamilton and Toronto, Ontario, Canada

Supported by a grant from the Hospital for Sick Children Foundation No. XG91-003.

Received for publication Jan. 21, 1993. Accepted for publication July 7, 1993. Address for reprints: S. Turner-Gomes, MB, ChB, Department of Pediatrics, McMaster University Medical Centre, 1200 Main St. West, Hamilton, Ontario, Canada L8N 3Z5.

Abstract

Children with cyanotic congenital heart disease who undergo operation with cardiopulmonary bypass are at increased risk of thromboembolic or hemorrhagic complications, or both. Regulation of thrombin, a key enzyme in coagulation, is essential in preventing these complications. We therefore examined the in vitro capacity of plasma from 15 children with cyanotic congenital heart disease to generate thrombin and to inhibit ¹²⁵I-thrombin before and after cardiopulmonary bypass. We also assessed whether thrombin had been generated in vivo by assaying levels of fibrinogen, thrombin-antithrombin III complexes, and D-dimer. Plasma levels of the thrombin inhibitors, antithrombin III, -2-macroglobulin, and heparin cofactor II were also measured. Thrombin regulation was normal before operation. After cardiopulmonary bypass, the in vitro capacity to generate thrombin decreased by 50%, and this was primarily a result of hemodilution (31%). Similar postoperative decreases were noted in the levels of antithrombin III, heparin cofactor II, and -2-macroglobulin (26% to 45%). However, the total in vitro plasma thrombin inhibitory capacity decreased by only 13%. Levels of thrombin-antithrombin III and D-dimer increased after operation, indicating that thrombin had been generated and inhibited in vivo. Clinically, there were no thromboembolic complications although six patients required replacement therapy for excessive small-vessel bleeding. In conclusion, thrombin regulation is significantly altered after cardiopulmonary bypass. Although thrombin is generated in vivo, the total residual capacity to do so is impaired because of hemodilution. Despite a concomitant decrease in thrombin inhibitor levels, the total residual in vitro capacity of plasma to inhibit thrombin is relatively spared. This suggests that after cardiopulmonary bypass the risk of hemorrhagic complications after an additional hemostatic challenge is relatively greater than the risk of thrombotic complications. This might be reflected in the predominance of hemorrhagic complications in our patients. (J THORAC CARDIOVASC SURG 1994;107:562-8)

Children with congenital heart disease (CHD) who undergo corrective operations with cardiopulmonary bypass (CPB) are at increased risk of both thromboembolic ^1-4 and hemorrhagic ³ complications. There is relatively little information clarifying the predominant mechanisms by which these complications occur. Thrombin, a key enzyme in hemostasis with many functions, cleaves to fibrinogen so that a fibrin clot may form. ^{5, 6} Reduced capacity to generate thrombin for a variety of reasons can result in hemorrhagic complications. In contrast, an impaired ability to inhibit thrombin places patients at risk for thromboembolic complications. CPB can affect thrombin generation and inhibition by several mechanisms including dilution of components of hemostasis, activation by the extracorporeal membrane, ^7-9 and use of the anticoagulant heparin ^{5, 10} with subsequent neutralization by protamine. In this study, our aim was to assess the in vitro capacity of plasma from patients with cyanotic CHD to generate and inhibit thrombin, as well as to assess the evidence on ex vivo plasma samples for thrombin generation in vivo.

METHODS

Patient population
Using a protocol approved by the Human Subjects Committee at the Hospital For Sick Children, Toronto, Ontario, we obtained informed consent from parents of all patients before they were included in the study. Fifteen consecutive patients with cyanotic CHD aged 1 to 14 years (median 5 years) were enrolled in the study. The diagnoses included univentricular connection (n = 7), tricuspid atresia (n = 1), and tetralogy of Fallot (n = 7). CPB was done with use of a hollow-fiber membrane oxygenators (Dideco, Mirandola, Italy, and Capiox, Terumo, Tokyo, Japan). The calculated blood flows ranged from 1128 to 3312 ml/min. The extracorporeal circuit was primed with Ringer's lactate, 5% albumin in normal saline, mannitol, and heparin in a dose of 1 U/ml. After induction of anesthesia, a loading dose of heparin (300 U/kg) was administered. Additional heparin was given to maintain the activated clotting time (Hemochron, International Technidyne Corp., Edison, N.J.) greater than 450 seconds. After CPB, the effect of heparin was reversed with protamine in a 1.2:1 concentration. As per our current practice, at the end of the surgical procedure, the tendency to hemorrhage was assessed by the senior surgeon and additional fresh frozen plasma and cryoprecipitate were given if excess small-vessel bleeding was detected. Once the sternotomy was closed, mediastinal blood drainage was recorded hourly throughout the stay in the intensive care unit.

Collection of samples
After induction of anesthesia, preoperative blood samples were withdrawn from freshly inserted arterial lines. A postoperative sample was obtained 2 hours after the patient's return from the operating room. The samples were collected into 3.8% trisodium citrate and centrifuged at 1200 rpm at 4° C for 15 minutes. Multiple aliquots of plasma were frozen at -70° C until assayed. Control samples from healthy children were either from those previously established by our group ¹¹ or, if not available, established with pooled plasma from 15 healthy age-matched children before minor noncardiac operations. Similarly, pooled plasma from 20 healthy nonpregnant adult volunteers was also used as a control sample.

Hemodilution during CPB
To assess the degree to which plasma proteins were diluted by the CPB procedure, immunoglobulin G levels were assessed in preoperative and postoperative samples by rate nephelometry (Kallestad Diagnostics, Chaska, Minn.). As an additional measure of hemodilution, hematocrit values were measured in the preoperative and postoperative samples.

Thrombin regulation in vitro
Thrombin generation and prothrombin consumption
Thrombin generation was measured as previously described. ¹⁰ In brief, plasma samples were defibrinated with Arvin and then activated at 37° C with an activated partial thromboplastin reagent (Organon Tecknika, Scarborough, Ontario, Canada), followed by the addition of calcium chloride. The reaction was terminated by subsampling into ethylenediaminetetraacetic acid at 4° C. The quantity of enzymatically active thrombin present was measured by the amidolysis of the chromogenic substrate S-2238 (Kabi Pharmaci, Franklin, Ohio) at 405 nm.¹⁰ A biologic assay of prothrombin was performed on all samples. ¹²

Thrombin inhibition
Thrombin inhibition was measured with the method of Fernandez and associates. ¹³ Human--thrombin (a gift from Dr. John Fenton II, Albany, N.Y.) was iodinated by the lactoperoxidase method. ¹⁴ This resulted in a specific radioactivity of 3.7 to 4.3 x 10⁵ counts/min/unit with more than 85% of the radioactivity associated with -thrombin. Complex formation between ¹²⁵I--thrombin and plasma inhibitors was quantitated in polyacrylamide gels according to the method described by Tollefsen, Pestka, and Monafo. ¹⁵ Before assaying, plasma was defibrinated with Arvin as previously described. ^{10 125}I--thrombin in 0.05 mol/L Tris-HCl buffer, pH 7.4, containing 0.15 mol/L NaCl and 1% bovine serum albumin was prewarmed to 37° C. This was added to an equal volume of defibrinated plasma, also prewarmed to 37° C. The final concentration of thrombin was 2.5 National Institutes of Health units/ml (25 nmol/L). After incubation at 37° C for up to 3 minutes, one part of the reaction mixture was added to three parts of loading buffer (5% mercaptoethanol, 10% glycerol, 0.06 mol/L Tris-HCl, 0.01% bromophenol blue, pH 6.8). The samples were boiled for 2 minutes, cooled on ice and subjected to electrophoresis in 5% to 15% gradient polyacrylamide gels containing 0.1% sodium dodecyl sulfate. Approximately 7000 counts/min of ¹²⁵I-radioactivity were applied per channel. After autoradiography, the covalent complexes of ¹²⁵I--thrombin and its plasma inhibitors were identified and quantitated by scanning densitometry.

Thrombin regulation in vivo
Thrombin-antithrombin III complexes and D-dimer levels were assayed with use of enzyme-linked immunosorbent assay kits (Hoechst, Montreal, Quebec, Canada, ¹⁶ and Diagnostic Stago [Wellmark Diagnostics],Guelph, Ontario, Canada ¹⁷).

Additional coagulation assays
Plasma fibrinogen was measured by the Clauss ¹⁸ assay. Antithrombin III (ATIII) was measured functionally with a chromogenic substrate. ¹⁹ Heparin cofactor II (HCII) and -2-macroglobulin (₂M) were measured by radial immunodiffusion. ²⁰ Because the presence of heparin would affect the interpretation of the assays, all postoperative samples were analyzed for heparin by the antifactor Xa assay of Teien, Lie, and Abildgaard. ²¹ Specimens containing more than 0.05 units ofheparin per milliliter (n = 2) were not analyzed.

Statistical analysis
For most of the assays, comparisons between the preoperative and postoperative samples and between the preoperative and control samples were made by the Student's t test. For the thrombin-ATIII and D-dimer assays, the data were logged before analysis by the t test. In addition, a test of proportions was done on the D-dimer data. p Values less than 0.05 were considered significant.

RESULTS

Patient population
The median total time on CPB was 134 minutes (70 to 225 minutes). No macroscopic thrombi were noted in the circuit. Excessive small-vessel bleeding necessitating additional treatment with fresh frozen plasma and cryoprecipitate occurred in six patients. None of these patients needed further surgical intervention for prolonged bleeding. In one patient, large-vessel bleeding occurred necessitating a return to the operating room. In the first 2 hours after operation the median blood loss was 9 ml/kg (range 1.9 to 27 ml/kg).

Hemodilution during CPB
Plasma concentrations of immunoglobulin G decreased from preoperative values of 6.2 ± 0.4 gm/L to postoperative values of 4 ± 0.3 gm/L. Similarly hematocrit values decreased from preoperative values of 0.49 ± 0.01 to postoperative values of 0.34 ± 0.01. On the basis of these measurements, the degree of hemodilution occurring during CPB was 30% to 35%. To determine the contribution of hemodilution to changes in plasma concentrations of coagulation factors, mean preoperative/postoperative ratios of all coagulation factors were compared with the mean hematocrit preoperative/postoperative ratio by a Z test.

Thrombin regulation in vitro
Thrombin generation and prothrombin consumption (Fig 1)
The capacities of plasmas from adult control samples, pediatric control samples, and patients with CHD before operation to generate thrombin were similar (peak absorbance: adult control 0.62 ± 0.02 absorbance units at 405 nm; pediatric control 0.63 ± 0.03; patients with CHD 0.56 ± 0.04). After operation, the capacity of plasma from patients with CHD to generate thrombin decreased by 50% (peak absorbance 0.28 ± 0.02; p < 0.01) and could be accounted for by hemodilution (p = not significant).

View larger version (23K): [in this window] [in a new window]   Fig. 1. In vitro thrombin-generating ability of plasma assessed by amidolysis of chromogenic substrate S2238 at 405 nm. Before operation, there was no difference between results in patients with CHD compared with those for pediatric control pool. After operation, thrombin-generating ability of plasma was diminished by 50% (p < 0.01), but this was caused by dilutional factors.

Thrombin inhibition (Tables I and II, Fig. 2)
Before operation, average plasma concentrations of ATIII and HCII in patients with CHD were slightly decreased compared with pediatric control values, whereas average plasma concentrations of ₂M were within the normal range for children (Table I). After operation, average plasma concentrations of all three thrombin inhibitors decreased significantly by 26% (HCII), 33% (ATIII), and 45% (₂M) (p < 0.01; Fig. 2). However, this could be accounted for by hemodilution and the infusion of adult blood (p = not significant).

View larger version (80K): [in this window] [in a new window]   Fig. 2. Autoradiograph of 125I-thrombin complexes with its plasma inhibitors. Lane I, 125--thrombin; lane II, noncardiac, age-matched control sample; lane III, patient having Fontan procedure, preoperative sample; lane IV, postoperative sample of patient in lane III. Slight decreases in levels of all thrombin-inhibitor complexes are seen in postoperative sample.

Table II

In vivo thrombin generation
Before operation, plasma concentrations of fibrinogen, D-dimer, and thrombin-ATIII complexes in patients with CHD were within the pediatric range (Table III). After operation, plasma concentrations of D-dimer and thrombin-ATIII complexes significantly increased and could not be accounted for by hemodilution (p < 0.01). In contrast, plasma concentrations of fibrinogen decreased after operation and could be accounted for by hemodilution (p = not significant).

DISCUSSION

Pediatric patients with CHD requiring CPB are at risk for both hemorrhagic and thromboembolic complications. Regulation of thrombin is critical to the appropriate hemostatic response in these patients. In this study, thrombin regulation in vitro and in vivo was evaluated perioperatively in pediatric patients requiring CPB. We report that before operation, regulation of thrombin in vitro and in vivo was similar in pediatric patients with CHD compared with that in age-matched control subjects. During CPB, thrombin generation occurred as evidenced by increased plasma concentrations of markers of activation of coagulation. After operation, the in vitro capacity to inhibit thrombin was relatively spared (decreased by 13%) compared with the capacity to generate thrombin, which decreased by 50%. This suggests that children are at greater risk of bleeding after operation than of having thrombotic complications develop when faced with additional hemostatic stresses.

The hemostatic system of children with CHD has been assessed with a variety of coagulation assays in the past with variable results. ^{22, 23} The variability likely reflects the diverse clinical conditions and underlying structural defects in the patients with CHD. The overall effect of CHD on the generation and inhibition of thrombin by sensitive assays has not been reported previously. Although there were minor differences in preoperative plasma concentrations of the thrombin inhibitors, the overall capacity of plasma from patients with CHD to generate and to inhibit thrombin was preserved and was similar to that in healthy children. ₂M inhibited more thrombin in plasma from patients with CHD than in plasma from adults, reflecting increased plasma concentrations of ₂M throughout childhood. ^24-26 These results suggest that preoperative regulation of thrombin is intact in pediatric patients with CHD.

Immediately before CPB, patients at our institution receive heparin according to a standardized protocol that reflects current recommendations in the literature. ^27-29 Optimal administration of heparin therapy during CPB is important because excess heparin places patients at greater risk for bleeding complications ^30-33 and suboptimal heparinization may result in fibrin deposition in the microvasculature or catastrophic occlusion of cannulae. ^27-29 The overall success of our approach is reflected in a low mortality rate (7.8%) and low percentage of patients returning to the operating room because of postoperative bleeding (1.2%) (W. G. Williams, personal communication, 1991). In the past, measurement of fibrin monomer, the product of the action of thrombin on fibrinogen, has been used to assess the adequacy of anticoagulation during CPB. ²⁹ A previous study at our institution reported that fibrin monomer was not present during or after CPB in children treated with the same anticoagulant protocol used in the current study (unpublished data). Sensitive tests that reflect activation of coagulation with generation of thrombin were measured in our patients before and after CPB. Before operation, levels of thrombin complexed to its primary inhibitor ATIII (thrombin-ATIII) and of plasmin degradation of cross-linked fibrin (D-dimer) were similar to levels in age-matched control subjects but increased significantly at the completion of CPB. These results clearly document that thrombin is generated. However, the clinical significance of this remains to be elucidated. Elevated levels of D-dimer have also been reported in adult patients successfully undergoing CPB. ³⁴

After operation, plasma concentrations of fibrinogen, of prothrombin, and of the thrombin inhibitors ATIII, ₂M, and HCII decreased by 26% to 45%. The magnitude of the decrease was compatible with the degree of hemodilution determined by plasma concentrations of immunoglobulin G and by the hematocrit, both of which decreased by 30% to 35%. However, the total in vitro capacity to inhibit thrombin was reduced by 13% and could not be accounted for by hemodilution. This contrasted with the decrease in the in vitro capacity to generate thrombin (50%), which was likely a result of hemodilution.

Many investigators have reported the presence of hemostatic alterations after CPB. ^{7, 9, 22, 23} Experiments from our laboratory and others would support the conclusion that hemodilution is one of the most significant acquired coagulopathies. However, despite dilution of all the coagulation proteins during CPB, the coagulation cascade is not usually significantly altered. ³⁵ Our assessment of the role of thrombin in hemostasis after CPB suggests that the residual capacity of plasma to inhibit thrombin is relatively spared compared with its capacity to generate thrombin. This might place the postoperative patient at greater risk of hemorrhagic complications in the event of a subsequent hemostatic challenge.

Interestingly, 6 of the 15 patients studied had small-vessel bleeding as identified by the senior surgeon or by the intensive care unit staff. There were no features, however, to distinguish those patients whose postoperative course was complicated by small-vessel bleeding. The relationship between a decreased capacity to generate thrombin and bleeding complications needs to be studied further.

In summary, although many alterations are seen in the hemostatic factors after CPB, most are caused by dilution except for the increases in thrombin-ATIII complexes and D-dimer values, which indicates that activation of coagulation occurs during CPB despite adequate heparinization. Also, there is a relative imbalance in the capacity of plasma to regulate thrombin production in vitro with relative preservation of its thrombin-inhibitory capacity as compared with its thrombin-generating capacity. The role played by the thrombin inhibitors is intriguing, and it is likely that the development of hemostatic complications after CPB operation is multifactorial with the disruption of thrombin regulation, the activation of coagulation, and platelet dysfunction being some of the important factors.

We gratefully acknowledge the assistance of G. Norman, PhD, professor, The Department of Clinical Epidemiology and Biostatistics, consultant statistician, McMaster University, in the analysis of the data from this study. The assistance of the technologists at McMaster University Medical Centre was invaluable.

References

1. Dobell ARC, Trusler GA, Smallhorn JF, Williams WG. Atrial thrombi after the Fontan operation. Ann Thorac Surg 1986;42:664-7.[Abstract/Free Full Text]
   
2. Tamisier D, Vouhe PR, Vernant F, Leca F, Massot C, Neveux J-Y. Modified Blalock-Taussig shunts: results in infants less than 3 months of age. Ann Thorac Surg 1990;49:797-801.[Abstract/Free Full Text]
   
3. Coles JG, Kielmanowicz S, Freedom RM, et al. Surgical experience with the modified Fontan procedure. Circulation 1987;76(Suppl):III61-6.
   
4. Okita Y, Miki S, Kusuhara K, et al. Massive systemic venous thrombosis after Fontan operation: report of a case. Thorac Cardiovasc Surg 1988;36:234-6.[Medline]
   
5. Ofosu FA, Gray E. Mechanisms of action of heparin: applications to the development of derivatives of heparin and heparinoids with antithrombotic properties. Semin Thromb Hemost 1988;14:9-17.[Medline]
   
6. Fenton JW II. Regulation of thrombin generation and functions. Semin Thromb Hemost 1988;14:234-40.[Medline]
   
7. Addonizio VP Jr, Smith JB, Strauss JF III, Colman RW, Edmunds LH Jr. Thromboxane synthesis and platelet secretion during cardiopulmonary bypass with bubble oxygenator. J THORAC CARDIOVASC SURG 1980;79:91-6.[Medline]
   
8. Bick RL. Hemostatic defects associated with cardiac surgery, prosthetic devices, and other extracorporeal circuits. Semin Thromb Hemost 1985;11:249-80.[Medline]
   
9. Mammen EF, Koets MH, Washington BC, et al. Hemostasis changes during cardiopulmonary bypass surgery. Semin Thromb Hemost 1985;11:281-92.[Medline]
   
10. Ofosu FA, Cerskus AL, Hirsh J, Smith LM, Modi GJ, Blajchman MA. The inhibition of the anticoagulant activity of heparin by platelets, brain phospholipids, and tissue factor. Br J Haematol 1984;57:229-38.[Medline]
    
11. Andrew MA, Vegh P, Johnston M, Bowker J, Mitchell L. Maturation of the hemostatic system during childhood. Blood 1992;80:1998-2005.[Abstract/Free Full Text]
    
12. Denson KWE, Borrett R, Biggs R. The specific assay of prothrombin using the Taipan snake venom. Br J Haematol 1971;21:219-26.[Medline]
    
13. Fernandez F, Buchanan MR, Hirsh J, Kenton JW, Ofosu FA. Catalysis of thrombin inhibition provides an index for estimating the antithrombotic potential of glycosaminoglycans in rabbits. Thromb Haemost 1986;57:286-93.
    
14. Morrison M, Bayse GS. Catalysis of iodination by lactoperoxidase. Biochemistry 1970;9:2995-3001.[Medline]
    
15. Tollefsen DM, Pestka CA, Monafo WJ. Activation of heparin cofactor II by dermatan sulfate. J Biol Chem 1983;258:6713-6.[Abstract/Free Full Text]
    
16. Pelzer H, Schwarz A, Heimburger N. Determination of human thrombin-antithrombin III complex in plasma with an enzyme-linked immunosorbent assay. Thromb Haemost 1988;59:101-6.[Medline]
    
17. Rylatt DB, Blake AS, Cottis LE, et al. An immunoassay for human D dimer using monoclonal antibodies. Thromb Res 1983;31:767-78.[Medline]
    
18. Clauss A. Gerinnungsphysiologische Schnellmethode zur bestimmung des Fibrinogens. Acta Haematol 1957;17:237-46.[Medline]
    
19. Abildgaard U, Lie M, Odegard OR. Antithrombin (heparin cofactor) assay with "new" chromogenic substrates (S2238 and Chromozym TH). Thromb Res 1977;11:549-53.[Medline]
    
20. Mancini G, Carbonara O, Heremans JF. Immunochemical quantitation of antigens by single radial immunodiffusion. J Immunochem 1965;2:235-54.
    
21. Teien AN, Lie M, Abildgaard U. Assay of heparin in plasma using a chromogenic substrate for activated factor X. Thromb Res 1976;8:413-6.[Medline]
    
22. Turner-Gomes SO, Andrew M, Coles JG, Trusler GA, Williams WG, Rabinovitch M. Abnormalities in von Willebrand factor and antithrombin III after cardiopulmonary bypass operations for congenital heart disease. J THORAC CARDIOVASC SURG 1992;103:87-97.[Abstract]
    
23. Gill JC, Wilson AD, Endres-Brooks J, Montgomery RR. Loss of the largest von Willebrand factor multimers from the plasma of patients with congenital cardiac defects. Blood 1986;67:758-61.[Abstract/Free Full Text]
    
24. Schmidt B, Fernandez F, Modi G, Ofosu F, Andrew M. Alpha 2 macroglobulin and antithrombin III are equally important inhibitors of thrombin in neonatal plasma. [Abstract]. Pediatr Res 1987;21:411A.
    
25. Ganrot PO, Schersten B. Serum alpha-2-macroglobulin concentration and its variation with age and sex. Clin Chim Acta 1967;15:113-20.
    
26. Mitchell L, Piovella F, Ofosu F, Andrew M. Alpha-2-macroglobulin may provide protection from thromboembolic events in antithrombin III deficient children. Blood 1991;78:2299-304.[Abstract/Free Full Text]
    
27. Bull BS, Huse WM, Brauer FS, Korpman RA. Heparin therapy during extracorporeal circulation: II. The use of a dose-response curve to individualize heparin and protamine dosage. J THORAC CARDIOVASC SURG 1975;69:685-8.[Abstract]
    
28. Bull BS, Korpman RA, Huse WM, Briggs BD. Heparin therapy during extracorporeal circulation: I. Problems inherent in existing heparin protocols. J THORAC CARDIOVASC SURG 1975;69:674-84.[Abstract]
    
29. Young JA, Kisker CT, Doty DB. Adequate anticoagulation during cardiopulmonary bypass determined by activated clotting time and the appearance of fibrin monomer. Ann Thorac Surg 1978;26:231-40.[Abstract/Free Full Text]
    
30. Levine MN, Hirsh J. Hemorrhagic complications of anticoagulant therapy. Semin Thromb Hemost 1986;12:39-57.[Medline]
    
31. Jumean HG, Sudah F. Monitoring of anticoagulant therapy during open-heart surgery in children with congenital heart disease. Acta Haematol 1983;70:392-5.[Medline]
    
32. von Segesser L, Weiss B, Garcia E, Gallino A, Turina M. Reduced blood loss and transfusion requirements with low systemic heparinization: preliminary clinical results in coronary artery revascularization. Eur J Cardiothorac Surg 1990;4:639-43.[Abstract/Free Full Text]
    
33. Babka R, Colby C, El-Etr A, Pifarré R. Monitoring of intraoperative heparinization and blood loss following cardiopulmonary bypass surgery. J THORAC CARDIOVASC SURG 1977;73:780-2.[Abstract]
    
34. Giuliani R, Szwarcer E, Martinez Aquino E, Palumbo G. Fibrin-dependent fibrinolytic activity during extracorporeal circulation. Thromb Res 1991;61:369-73.[Medline]
    
35. Harker L, Malpass TW, Branson HE, Hessel II EA, Slichter SA. Mechanism of abnormal bleeding in patients undergoing cardiopulmonary bypass: acquired transient platelet dysfunction associated with selective release. Blood 1980;56:824-34.[Free Full Text]
    

This article has been cited by other articles:

				C. E. Gruenwald, C. Manlhiot, A. K. Chan, L. Crawford-Lean, C. Foreman, H. M. Holtby, G. S. Van Arsdell, R. Richards, H. Moriarty, and B. W. McCrindle Randomized, Controlled Trial of Individualized Heparin and Protamine Management in Infants Undergoing Cardiac Surgery With Cardiopulmonary Bypass J. Am. Coll. Cardiol., November 23, 2010; 56(22): 1794 - 1802. [Abstract] [Full Text] [PDF]

				M. Procelewska, J. Kolcz, K. Januszewska, T. Mroczek, and E. Malec Coagulation abnormalities and liver function after hemi-Fontan and Fontan procedures -- the importance of hemodynamics in the early postoperative period Eur J Cardiothorac Surg, May 1, 2007; 31(5): 866 - 872. [Abstract] [Full Text] [PDF]

				B. S. Donahue Factor V Leiden and Perioperative Risk Anesth. Analg., June 1, 2004; 98(6): 1623 - 1634. [Abstract] [Full Text] [PDF]

				A. H Stammers, E. D Rauch, L. D Willett, J. W Newberry, and K. F Duncan Pre-operative coagulopathy management of a neonate with complex congenital heart disease: a case study Perfusion, March 1, 2000; 15(2): 161 - 168. [Abstract] [PDF]

				S. O. Turner-Gomes, E. P. Nitschmann, G. R. Norman, M. E. Andrew, and W. G. Williams Effect of Heparin Loading During Congenital Heart Operation on Thrombin Generation and Blood Loss Ann. Thorac. Surg., February 1, 1997; 63(2): 482 - 488. [Abstract] [Full Text]

This Article Abstract Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): W. G. Williams Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Turner-Gomes, S. O. Articles by Andrew, M. Search for Related Content PubMed PubMed Citation Articles by Turner-Gomes, S. O. Articles by Andrew, M.