Whole blood heparin concentration measurements by automated protamine titration agree with plasma anti-Xa measurements

Accurate protamine:heparin matching (not just smaller protamine doses) decreases postoperative bleeding in cardiac surgery; results from a high-volume academic medical center

BACKGROUND

A multidisciplinary Quality Assurance/Performance Improvement study to identify the incidence of "heparin rebound" in our adult cardiac surgical population instead detected a thromboelastometry pattern suggestive of initial protamine overdose in 34% despite Hepcon-guided anticoagulation management. Analysis of our practice led to an intervention that made an additional lower-range Hepcon cartridge available to the perfusionists.

METHODS

One year later, an IRB-approved retrospective study was conducted in >500 patients to analyze the effects of the intervention, specifically focusing on the impact of the initial protamine dose accuracy and 18-h mediastinal chest tube drainage (MCTd).

RESULTS

No differences were observed between group demographics, surgical procedures, duration of CPB or perioperative blood product transfusion. Both groups were managed using the same perfusion and anesthesia equipment, strategies, and protocols. The median initial protamine dose decreased by 19% (p < .001) in the intervention group (170 [IQR 140-220] mg; n = 295) versus the control group (210 [180-250] mg; n = 257). Mean 18-h MCTd decreased by 13% (p < .001) in the intervention group (405.15 ± 231.54 mL; n = 295) versus the control group (466.13 ± 286.73 mL; n = 257). Covariate-adjusted mixed effects model showed a significant reduction of MCTd in the intervention group, starting from hour 11 after surgery (group by time interaction p = .002).

CONCLUSION

Though previous investigators have associated lower protamine doses with less MCTd, this study demonstrates that more accurately matching the initial protamine dose to the remaining circulating heparin concentration reduces postoperative bleeding.

Heparin Rebound: An In-Depth Review

The common conception of "heparin rebound" invokes heparin returning to circulation in the postoperative period after apparently adequate intraoperative reversal with protamine. This is believed to portend increased postoperative bleeding and provides the rationale for administering additional empiric doses of protamine in response to prolonged coagulation tests and/or bleeding. However, the relevant literature of the last 60+ years provides only a weak level of evidence that "rebounded" heparin itself is a significant etiology of postoperative bleeding after cardiac surgery with cardiopulmonary bypass. Notably, many of the most frequently cited heparin rebound investigators ultimately concluded that although exceedingly low levels of heparin activity could be detected by anti-Xa assay in some (but not all) patients postoperatively, there was no correlation with actual bleeding. An understanding of the literature requires a careful reading of the details because the investigators lacked standardized definitions for "heparin rebound" and "adequate reversal" while studying the phenomenon with significantly different experimental methodologies and laboratory tests. This review was undertaken to provide a modern understanding of the "heparin rebound" phenomenon to encourage an evidence-based approach to postoperative bleeding. Literature searches were conducted via PubMed using the following MeSH terms: heparin rebound, heparin reversal, protamine, platelet factor 4, and polybrene. Relevant English language articles were reviewed, with subsequent references obtained from the internal citations. Perspective is provided for both those who use HepCon-guided management and those who do not, as are practical recommendations for the modern era based on the published data and conclusions of the various investigators.

Intraoperative Monitoring of Heparin: Comparison of Activated Coagulation Time and Whole Blood Heparin Measurements by Different Point-of-Care Devices with Heparin Concentration by Laboratory-Performed Plasma Anti-Xa Assay

BACKGROUND

Cardiac surgical interventions, extracorporeal membrane oxygenation, transcutaneous coronary-artery angioplasty, and stenting are carried out while patients are being treated with the anticoagulation drug heparin. Monitoring the level and reversal of heparinization during and at the conclusion of medical and surgical procedures is a critical issue in patient care.

METHODS

We performed parallel testing of the ACCRIVA Hemochron Signature Elite ACT+ and Hemochron Response analyzer, iSTAT platform, and 2 Hepcon Hemostasis Management System (HMS) Plus analyzers for monitoring intraoperative heparin treatment. Laboratory anti-Xa assay was used as the criterion standard for heparin measurement.

RESULTS

Poor correlation between the 2 Hemochron analyzers was identified at 0.78. Correlation between the analyzers on the i-STAT platform was 0.97. Regression analysis revealed that i-STAT values were generally lower, by 43 seconds, than Hemochron values. The correlation between Hepcon and i-STAT activated clotting time (ACT) results was 0.94. The i-STAT ACT results were generally 23 seconds lower than the Hepcon ACT values. Correlation coefficients on comparing Hepcon ACT and i-STAT ACT using laboratory anti-Xa assay were 0.83 and 0.87, respectively. The correlation between Hepcon heparin concentration and anti-Xa results was 0.85.

CONCLUSIONS

ACT monitoring with iSTAT offers good correlation between instruments and with the Hepcon ACT. Hepcon occupies a specific niche in cardiac operating departments because of its ability to provide additional information regarding heparin concentration; however, lack of suitable proficiency testing may impair its use. The iSTAT is a more reliable platform for broader, hospital-wide application.

Identifying optimal heparin management during cardiopulmonary bypass in obese patients: A prospective observational comparative study

BACKGROUND

The heparin regimen providing anticoagulation during cardiopulmonary bypass (CPB) is usually adapted to total body weight (TBW), but may be inaccurate in obese patients in whom TBW exceeds their ideal body weight.

OBJECTIVES

The objective is to compare the effects of heparin injection based on TBW on haemostatic parameters between obese and nonobese patients during cardiac surgery and to calculate the optimal heparin regimen.

DESIGN

Prospective comparative study.

SETTING

University hospital.

PATIENTS

Two groups of 50 patients (BMI≥ or <30 kg m) were included in the study over a 9-month period in 2013. The study started on 27 February 2013.

INTERVENTIONS

An unfractionated heparin (UFH) bolus of 300 IU kg TBW was injected before initiation of CPB followed by additional doses (50 to 100 IU kg) to maintain a target activated coagulation time (ACT) of at least 400 s.

MAIN OUTCOME MEASURES

ACT and plasma heparin concentration were measured at different time points after initiation of, and weaning from CPB.

RESULTS

Obese patients received higher initial and total doses of heparin (P < 0.0001). Plasma heparin concentrations were significantly higher in obese patients at each time point (P < 0.001) and reached very high values after the initial bolus (5.90 vs. 4.48 IU ml, P < 0.0001). The relationship between plasma heparin concentration and ACT after the initial bolus was not linear and followed an asymptotic regression curve. Haemoglobin concentration decreased intraoperatively to a greater extent in the obese group (P < 0.001). No significant differences in postoperative bleeding or global transfusion requirements were observed.

CONCLUSION

The standard heparin regimen based on TBW in obese patients during CPB results in excessive plasma heparin concentrations and a significant intraoperative decrease in haemoglobin concentration. ACT monitoring was not accurate in identifying this excess dosage. An initial bolus of 340 IU kg ideal body weight would achieve a heparin concentration of 4.5 IU ml, similar to that observed in nonobese patients. Further investigations are warranted to confirm this heparin regimen.

Changes in heparin dose response slope during cardiac surgery: possible result in inaccuracy in predicting heparin bolus dose requirement to achieve target ACT

Introduction:

The substantial interpatient variability in heparin requirement has led to the use of a heparin dose response (HDR) technique. The accuracy of Hepcon-based heparin administration in achieving a target activated clotting time (ACT) using an HDR slope remains controversial.

Methods:

We prospectively studied 86 adult patients scheduled for cardiac surgery requiring cardiopulmonary bypass. The total dose of calculated heparin required for patient and pump priming was administered simultaneously to achieve a target ACT of 450 s for HDR on the Hepcon HMS system. Blood samples were obtained after the induction of anesthesia, at 3 min after heparin administration and after the initiation of CPB to measure kaolin ACT, HDR slope, whole-blood heparin concentration based on the HDR slope and anti-Xa heparin concentration, antithrombin and complete blood count.

Results:

The target ACT of 450 s was not achieved in 68.6% of patients. Compared with patients who achieved the target ACT, those who failed to achieve their target ACT had a significantly higher platelet count at baseline. Correlation between the HDR slope and heparin sensitivity was poor. Projected heparin concentration and anti-Xa heparin concentration are not interchangeable based on the Bland–Altman analysis.

Conclusion:

It can be hypothesized that the wide discrepancy in HDR slope versus heparin sensitivity may be explained by an inaccurate prediction of the plasma heparin level and/or the change in HDR of individual patients, depending on in vivo factors such as extravascular sequestration of heparin, decreased intrinsic antithrombin activity level and platelet count and/or activity.

Implementing a Statistical Model for Protamine Titration: Effects on Coagulation in Cardiac Surgical Patients

OBJECTIVES

To implement a statistical model for protamine titration.

DESIGN

Prospective randomized trial.

SETTING

University hospital.

PARTICIPANTS

Sixty (n = 30+30) patients scheduled for elective coronary artery bypass surgery were randomly assigned to 2 groups.

INTERVENTIONS

Protamine dose calculated according to an algorithm established from a statistical model or to a fixed protamine-heparin dose ratio (1:1).

MEASUREMENTS AND MAIN RESULTS

Both groups demonstrated comparable patient demographics and intraoperative data. Coagulation effects were evaluated using rotational thromboelastometry. Using the statistical model reduced (p<0.01) the protamine dose from 426±43 mg to 251±66 mg, followed by significantly (p<0.01) shorter intrinsic clotting time (208±29 seconds versus 244±52 seconds) and stronger clot firmness (p = 0.01), and effects on indices of extrinsic or fibrinogen coagulation pathways were insignificant. Test of residual heparin was negative in all patients after protamine administration, aligned with insignificant (p = 0.27) intergroup heparinase-verified clotting time differences.

CONCLUSIONS

The statistical model for protamine titration is clinically feasible and protects the patient from exposure to excessive doses of protamine, with advantageous effects on coagulation as measured using rotational thromboelastometry. Significance regarding clinical outcome is yet to be defined.

Heparin monitoring during cardiac surgery. Part 1: validation of whole-blood heparin concentration and activated clotting time

There is limited published data on the agreement between techniques for monitoring heparin levels. The aim of this study was to validate the Hepcon/HMS, with particular focus on the agreement with laboratory anti-Xa assay. The performances of two ACT instruments - Hemochron and HemoTec - were also evaluated, including an assessment for interchangeability. Blood samples from 42 adult cardiopulmonary bypass (CPB) patients were analysed for activated clotting time (ACT), whole-blood heparin concentration (Hepcon/HMS) and anti-factor Xa (anti-Xa) plasma heparin concentration. Agreement between measures was determined using the method of Bland and Altman. Simple analysis of agreement between the Hepcon and anti-Xa heparin revealed the Hepcon has a mean bias of -0.46 U/mL, with the limits of agreement ±1.12 U/mL. The comparison between ACT instruments indicated a mean difference of -96 seconds for the HemoTec, with limits of ±265 seconds. The Hepcon/HMS instrument displayed satisfactory agreement with anti-Xa plasma heparin concentration, as the expected variation would not be expected to cause problems in the clinical setting. Agreement between the two measurements of ACT may be satisfactory, provided each is assigned a different target value.

Bivalirudin as an adjunctive anticoagulant to heparin in the treatment of heparin resistance during cardiopulmonary bypass-assisted cardiac surgery

Heparin resistance (unresponsiveness to heparin) is characterized by the inability to reach acceptable activated clotting time values following a calculated dose of heparin. Up to 20% of the patients undergoing cardiothoracic surgery with cardiopulmonary bypass using unfractionated heparin (UFH) for anticoagulation experience heparin resistance. Although UFH has been the "gold standard" for anticoagulation, it is not without its limitations. It is contraindicated in patients with confirmed heparin-induced thrombocytopenia (HIT) and heparin or protamine allergy. The safety and efficacy of the use of the direct thrombin inhibitor bivalirudin for anticoagulation during cardiac surgery has been reported. However, there have been no reports on the treatment of heparin resistance with bivalirudin during CPB. In this review, we report the favorable outcome of our single-center experience with the alternative use of bivalirudin in the management of anticoagulation of heparin unresponsive patients undergoing coronary artery bypass graft surgery.

Anticoagulation management associated with extracorporeal circulation

The use of extracorporeal circulation requires anticoagulation to maintain blood fluidity throughout the circuit, and to prevent thrombotic complications. Additionally, adequate suppression of hemostatic activation avoids the unnecessary consumption of coagulation factors caused by the contact of blood with foreign surfaces. Cardiopulmonary bypass represents the greatest challenge in this regard, necessitating profound levels of anticoagulation during its conduct, but also quick, efficient reversal of this state once the surgical procedure is completed. Although extracorporeal circulation has been around for more than half a century, many questions remain regarding how to best achieve anticoagulation for it. Although unfractionated heparin is the predominant agent used for cardiopulmonary bypass, the amount required and how best to monitor its effects are still unresolved. This review discusses the use of heparin, novel anticoagulants, and the monitoring of anticoagulation during the conduct of cardiopulmonary bypass.

Reversal of heparin after cardiac surgery: protamine titration using a statistical model

OBJECTIVE

To establish a statistical model for determination of protamine dose in conjunction with cardiopulmonary bypass.

DESIGN

Prospective.

SETTING

University hospital.

PARTICIPANTS

Ninety consecutive cardiac surgical patients.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A series of clinically oriented variables were introduced into a statistical model for projection of the protamine dose after cardiopulmonary bypass. The following significant predictors were identified using multivariable regression analysis: The patient's body surface area, the administered dose of heparin, heparin clearance, and the preoperative platelet count. The statistical model projected the protamine dose within 3±23 mg of the point-of-care test used as reference.

CONCLUSION

Protamine dosing based on statistical modeling represents an alternative to point-of-care tests.

The coagulopathy of cardiopulmonary bypass

There have been numerous publications on the coagulopathy of cardiopulmonary bypass (CPB). This review provides an introduction to the history and main components of current CPB circuits and summarizes the current knowledge of pathogenesis, prevention, and treatment of the CPB coagulopathy. It encompasses an overview of intra- and postoperative monitoring of coagulation with special emphasis on the near-patient testing, its main complications, and the transfusion support, while taking into account the major changes in the technology used and supportive care provided since its inception.

Point-of-care testing in haemostasis

Point-of-care testing (POCT) in haematology has seen a significant increase in both the spectrum of tests available and the number of tests performed annually. POCT is frequently undertaken with the belief that this will reduce the turnaround time for results and so improve patient care. The most obvious example of POCT in haemostasis is the out-of-hospital monitoring of the International Normalized Ratio in patients receiving a vitamin K antagonist, such as warfarin. Other areas include the use of the Activated Clotting Time to monitor anticoagulation for patients on cardio-pulmonary bypass, platelet function testing to identify patients with apparent aspirin or clopidogrel resistance and thrombelastography to guide blood product replacement during cardiac and hepatic surgery. In contrast to laboratory testing, POCT is frequently undertaken by untrained or semi-trained individuals and in many cases is not subject to the same strict quality control programmes that exist in the central laboratory. Although external quality assessment programmes do exist for some POCT assays these are still relatively few. The use of POCT in haematology, particularly in the field of haemostasis, is likely to expand and it is important that systems are in place to ensure that the generated results are accurate and precise.

Antithrombotic therapy in cardiac surgery

PURPOSE

To review the perioperative management of antithrombotic therapy in cardiac surgery, including the management of cardiopulmonary bypass (CPB) and off-pump surgery.

METHODS

A review of the relevant English literature over the period 1975-2005 was undertaken, in addition to a review of international practices in antithrombotic therapy in cardiac surgery.

PRINCIPAL FINDINGS

Cardiopulmonary bypass is required in most procedures and makes anticoagulation mandatory. Anticoagulation is, usually, achieved with unfractionnated heparin (UFH). Unfractionated heparin is monitored by point-of-care (POC) testing, such as the activated clotting time or the determination of heparin concentration. The target values of both tests remain empirical, with no clearly validated thresholds. The target value needs to be adjusted according to the POC test, given significant variations between devices and activators. After CABG, the need for antiplatelet therapy is well demonstrated, in order to limit the risk of postoperative death or ischemic events, and improve venous graft patency. Immediately after valvular surgery, antithrombotic therapy should take into account the specific risk carried by each patient and by each prosthetic device. The risk of venous thromboembolism, though poorly defined, is also present in the postoperative period and may require additional attention. Given the frequent exposure to UFH, occurrence of heparin-induced thrombocytopenia is not infrequent in these patients and requires careful individual management.

CONCLUSIONS

Antithrombotic therapy is an essential component of cardiac surgery. Yet, with the exception of antiplatelet agents in CABG patients, antithrombotic therapy is often based on the clinical experience of medical teams more than on an evidence-based assessment of the literature.

Surveillance de l'anticoagulation des circulations extracorporelles par l'héparine non fractionnée : quels sont les problèmes non résolus ?

Cardiac surgery with extracorporeal circulation induces major alterations of haemostasis and requires high level of anticoagulation, usually achieved by unfractionated heparin infusion. Optimization of anticoagulant regimen, through adapted biological monitoring, can probably improve postoperative course, at least for postoperative haemostatic status. Despite increasing knowledge on extracorporeal circulation-induced haemostatic abnormalities and the development of new biological devices for heparin monitoring, the optimal level of anticoagulation remains matter of debate, as well as the monitoring procedures. This critical review presents the current available data on heparin anticoagulation and monitoring in this specific context, and underlines the pending issues about anticoagulation management during extracorporeal bypass.

Comparison of structured use of routine laboratory tests or near-patient assessment with clinical judgement in the management of bleeding after cardiac surgery

BACKGROUND

Using algorithms based on point of care coagulation tests can decrease blood loss and blood component transfusion after cardiac surgery. We wished to test the hypothesis that a management algorithm based on near-patient tests would reduce blood loss and blood component use after routine coronary artery surgery with cardiopulmonary bypass when compared with an algorithm based on routine laboratory assays or with clinical judgement.

METHODS

Patients (n=102) undergoing elective coronary artery surgery with cardiac bypass were randomized into two groups. In the point of care group, the management algorithm was based on information provided by three devices, the Hepcon, thromboelastography and the PFA-100 platelet function analyser. Management in the laboratory test group depended on rapidly available laboratory clotting tests and transfusion of haemostatic blood components only if specific criteria were met. Blood loss and transfusion was compared between these two groups and with a retrospective case-control group (n=108), in which management of bleeding had been according to the clinician's discretion.

RESULTS

All three groups had similar median blood losses. The transfusion of packed red blood cells (PRBCs) and blood components was greater in the clinician discretion group (P<0.05) but there was no difference in the transfusion of PRBCs and blood components between the two algorithm-guided groups.

CONCLUSION

Following algorithms based on point of care tests or on structured clinical practice with standard laboratory tests does not decrease blood loss, but reduces the transfusion of PRBCs and blood components after routine cardiac surgery, when compared with clinician discretion. Cardiac surgery services should use transfusion guidelines based on laboratory-guided algorithms, and the possible benefits of point of care testing should be tested against this standard.

Devices for Monitoring Heparin and Protamine in the Operating Room

Ongoing monitoring of heparin anticoagulation is an essential component of many cardiothoracic and vascular surgical procedures in order to prevent significant thrombotic and hemorrhagic complications. The classic test to assess high-dose (>1 unitlmL) heparin anticoagulation is the activated clotting time. Although simple to perform, the activated clotting time has many variations and can be affected by a number of nonanalytical and patient-related factors. Correlation with the heparin concentration may be poor. Alternatively, other test systems assess the individual patient's responsiveness to heparin in order to customize the heparin administration and subsequent protamine neutralization. The choice of test and system depends on the clinical application and the desired outcome. Regulatory and accreditation standards govern this type of testing; modern instrumentation can facilitate compliance with these standards. Understanding of the nature of the test and its performance under a variety of conditions is critical for proper interpretation.

The plasma supplemented modified activated clotting time for monitoring of heparinization during cardiopulmonary bypass: a pilot investigation

The standard celite or kaolin activated clotting time (ACT) correlates poorly with heparin levels during cardiopulmonary bypass (CPB). We compared a modified kaolin ACT, in which plasma was supplemented, to a standard undiluted kaolin ACT for monitoring heparin levels during CPB. Fifteen patients undergoing normothermic CPB were enrolled in this prospective study. Heparin management was performed according to the Hepcon HMS results (Medtronic, Minneapolis, MN). The ACTs were performed with the ACT II device (Medtronic). Hepcon HMS calculations, standard kaolin ACTs, and plasma supplemented modified ACTs (mACTs), prepared by diluting blood samples 1:1 with human plasma (Behring, Marburg, Germany), were measured every 30 min during CPB. The data obtained were correlated to the plasma chromogenic anti-Xa activity as a reference assay for heparin levels. A total of 64 samples were evaluated. The chromogenic anti-Xa activity ranged from 0.2 to 5.5 IU/mL. The Hepcon HMS calculations ranged from 2.7-8.2 IU/mL of heparin, the standard ACT ranged from 424 to >999 s, and the mACT ranged from 210 to 801 s. The correlation to the chromogenic anti-Xa method was r = 0.43 for the standard kaolin ACT and r = 0.69 for the plasma mACT. The plasma mACT provided an improved correlation to chromogenically measured levels of anti-Xa activity during CPB. The improved correlation most likely results from a correction of the effects of the impairment of the coagulation system caused by hemodilution and consumption of procoagulants on extracorporeal surfaces.

IMPLICATIONS

During cardiopulmonary bypass, the plasma modified kaolin activated clotting time (ACT) provides a better correlation with heparin levels than the standard kaolin ACT.

Individualized heparin and protamine management in infants and children undergoing cardiac operations

BACKGROUND

Measurements of activated coagulation time do not correlate with plasma concentration of heparin. This study investigated the effects of a patient-specific method to manage anticoagulation and its reversal in pediatric patients undergoing cardiopulmonary bypass.

METHODS

Infants and children were randomly assigned to receive either a standard dose of heparin (300 IU/kg; group C, n = 13) or an individualized dose, calculated by an in vitro heparin dose-response test (group HC, n = 13). Protamine dose was based on a 1 mg/l mg ratio of total administered heparin for patients in group C and of the residual heparin concentration in group HC.

RESULTS

Administered heparin was significantly higher and total protamine dose was significantly reduced in the HC group (both p < or = 0.001). There was less thrombin generation (p = 0.02) and fibrinolysis (p = 0.05) in group HC. Blood loss and requirement for transfusion of blood and fresh frozen plasma were also lower in group HC (all p < or =0.05).

CONCLUSIONS

An individualized management of anticoagulation and its reversal results in less activation of the coagulation cascade, less fibrinolysis, and reduced blood loss and need for transfusions. Further studies are warranted to better define the clinical impact of these findings.

A quick anti-Xa-activity-based whole blood coagulation assay for monitoring unfractionated heparin during cardiopulmonary bypass: a pilot investigation

We developed a quick and easy method to perform anti-Xa-activity-based whole blood assay and assessed its reliability for online monitoring of unfractionated heparins (UFHs) during cardiopulmonary bypass. Seventy-five microliters of a mixture of 1:3 large- and small-range Heptest reagent were transferred into blank cartridges of the ACT II device. The plastic flags for clot detection and stirring the sample and reagent were inserted and overlaid with 75 microL of Recalmix for recalcification. One-hundred fifty microliters of citrated whole blood were added and measurements performed. In vitro, the linearity of the test over a range of 1-8 IU/mL UFH, as well as the influence of variations in hematocrit (60%, 30%, and 20%), plasma coagulation factors (50%, 30%, and 20%) and platelets (100, 50, and 20 x 10(3)/microL) on the test results were assessed. In vivo measurements performed during cardiopulmonary bypass were compared with the chromogenic assay. The test revealed linearity to concentrations of 6 IU/mL of UFH and was not significantly influenced by the variations in the in vitro set-up despite a prolongation in samples with a hematocrit of 60%. In vivo, the correlation to the chromogenic test was R: = 0.90. The ACT II anti-Xa-UFH assay performed in whole blood was reliable when used over a wide range of conditions that could be encountered clinically. Although the test is useful for point-of-care monitoring, the necessity of individual calibrations and pipetting in the operation room requires further automation before its use in clinical practice.

IMPLICATIONS

The ACT II anti-Xa-unfractionated heparin assay allows for reliable monitoring of large concentrations of UFH over a wide range of hematocrit, platelet, and coagulation factor levels. Further evaluation of this point-of-care device is indicated.

Clinical role of blood heparin level monitoring during open heart surgery

Protamine has been used for neutralizing heparin and its dosage is decided by the initial fixed dose of heparin. Adequate protamine neutralization is very important to reduce complications. To attenuate excess reactions, in particular, whole blood heparin concentration during and after cardiopulmonary bypass was measured using Hepcon, and the efficacy of optimal protamine dose in open heart surgery was evaluated. Twenty patients were randomly divided into two comparable groups, P and C. In the C group, heparin was neutralized with an initial fixed dose of protamine, 1.67 mg protamine per milligram total heparin (n = 8). In the P group, protamine dose was determined for residual heparin concentration (n = 12). In the P group, blood heparin concentrations at 60 minutes after the establishment of cardiopulmonary bypass, just after cardiopulmonary bypass and first protamine administration were 2.35 +/- 0.14, 2.31 +/- 0.17 and 0.13 +/- 0.08 U/ml, respectively. Concentrations reached zero with the second protamine administration. The requirement of transfusion (659 +/- 224 vs. 1559 +/- 323 ml, p = 0.0314), pulmonary vascular resistance index just after the protamine administration (190 +/- 22 vs. 286 +/- 18 dyne.s.cm-5.m2, p = 0.0137) and the IL-8 levels (just after protamine: 26.9 +/- 5.1 vs. 43.5 +/- 5.9 pg/ml, p = 0.0499, 12 hours after cardiopulmonary bypass: 37.1 +/- 12.1 vs. 86.8 +/- 20.0, p = 0.0435) in the P group were significantly lower than those in the C group. These data suggested that heparin level monitoring in whole blood may be useful to determine the optimal dose of protamine resulting in the decrease of a requirement of blood components in open heart surgery and attenuating in transient pulmonary hypertension and excess protamine-induced inflammatory reactions.