Does heparin pretreatment affect the haemostatic system during and after cardiopulmonary bypass?

Preoperative Low-Molecular-Weight Heparin Prophylaxis Associated with Increased Heparin Resistance Frequency in On-Pump Coronary Artery Bypass Graft Surgery

Background

Unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) are being used for preoperative management of critical coronary artery disease. However, preoperative UFH therapy may cause a reduction in antithrombin concentrations, leading to various degrees of heparin resistance (HR). The main purpose of this study is to investigate the effects of preoperative LMWH on HR during cardiopulmonary bypass (CPB).

Methods

Data were retrospectively reviewed from adult patients that underwent on-pump coronary artery bypass graft (CABG) surgery. Four hundred fifty-seven patients underwent CABG, and 139 of them, who had isolated on-pump CABG, were included in the study. The heparin sensitivity index was calculated if activated clotting time levels were discovered below 400 seconds. Values less than 1.3 were accepted as HR.

Results

Of 139 patients who underwent on-pump CABG, preoperative LMWH was administered in 59 patients (56.8%). Intraoperative HR occurred in 29 patients (20.9%). Patients who received preoperative LMWH had an increased risk of developing HR compared with patients who did not receive LMWH (odds ratio 4.8 and 95% confidence interval 1.7–13.5). CPB duration and aortic clamp duration were significantly longer in patients who developed intraoperative HR when compared to those in patients who did not develop HR.

Conclusion

Preoperative treatment with LMWH may cause intraoperative HR. Corrective and preventive arrangements with close follow-up should be performed in this group of patients.

The effects of intermittent prebypass heparin dosing in patients undergoing coronary artery bypass grafting

In this study, 10 patients (Group B) were given three consecutive prebypass doses of heparin (100 IU/kg) with a 4 min interval prior to cardiopulmonary bypass (CPB) institution. They were compared with 10 patients (Group A) receiving the standard single prebypass heparin dose (300 IU/kg). The haemostatic response and anticoagulant monitoring during the perioperative period were investigated by point-of-care and several coagulation tests. Results of both groups were also correlated to blood loss. Three patients in Group B required additional heparin during bypass as compared with six patients in Group A. This suggests that intermittent prebypass heparin dosing is more effective in maintaining adequate levels of anticoagulation during CPB. Group B had a lower mean decrease in factor VIII (13.9% versus 43.2%), fibrinogen (38.5% versus 46.6%), antithrombin III (34.7% versus 40.1%) and platelet count (23.2% versus 28.9%) during bypass while only one unit of red cell concentrate was required postoperatively as compared with four units in Group A. In one patient, high fibrinolytic assays were associated with a haemorrhagic pericardial effusion occurring beyond 24 hours postsurgery.

Influence of aspirin or heparin on platelet function and postoperative blood loss after coronary artery bypass surgery

The aim of the study was to assess the effect of aspirin or heparin pretreatment on platelet function and bleeding in the early postoperative period after coronary artery bypass grafting (CABG) surgery.

Seventy-five male patients with coronary artery disease who underwent CABG with cardiopulmonary bypass (CPB) were studied. The patients were divided into three groups: Group 1 ( n = 25) included patients receiving aspirin pretreatment, Group 2 ( n = 22) received heparin pretreatment, and Group 3 ( n = 28) included patients who received no antiplatelet or anticoagulant pretreatment. Twenty-four hours after surgery, all patients were administered aspirin therapy that was continued throughout their hospitalization period. We assessed the following preoperative blood coagulation indices: activated partial thromboplastin time (aPTT), international normalized ratio (INR), and fibrinogen. We compared platelet count and platelet aggregation induced by adenosinediphosphate (ADP) before surgery, 1 h after surgery, 20 h after surgery and on the seventh postoperative day. We assessed drained blood loss within 20 postoperative hours.

Preoperative blood coagulation indices did not differ among the groups. Platelet count was also similar. One hour after surgery, platelet count significantly decreased in all groups ( p <0.001), after 20 postoperative hours it did not undergo any marked changes, and on the seventh postoperative day, it significantly increased in all groups ( p <0.001). Before surgery, the lowest index of ADP-induced platelet aggregation was found in Group 1 ( p <0.05). One hour after surgery, platelet aggregation significantly decreased in all groups, most markedly in Group 3 ( p <0.001), yet after 20 h, its restitution tendency and a significant increase in all groups was noted. On the seventh day, a further increase in the statistical mean platelet aggregation value was noted in Groups 2 and 3. Comparison of platelet aggregation after 20 postoperative hours and on the seventh day after surgery revealed a significantly higher than 10% increase of the index in 32% of patients in Group 1 ( p <0.05), 27.3% of patients in Group 2 ( p <0.05) and in 35.7% of patients in Group 3 ( p <0.001). The lowest statistically significant value of postoperative blood loss was noted in Group 2 ( p <0.01).

Our study has shown that aspirin or heparin pretreatment had no impact on the dynamics of platelet function in the early postoperative period after CABG. The lowest postoperative blood loss was noted in patients pretreated with heparin.

Prothrombotic SERPINC1 Gene Polymorphism may Affect Heparin Sensitivity Among Different Ethnicities of Chinese Patients Receiving Heart Surgery

The purpose of this study was to investigate a possible correlation between single-nucleotide polymorphisms (SNPs) of the antithrombin (gene, SERPINC1, and perioperative sensitivity to heparin in patients receiving heart surgery. The SERPINC1 genotype and allele frequency, coagulation parameters 24 hours before and after surgery, and clinical findings were compared among 3 ethnic groups, Han, Uighur, and Kazakh, patientswho received heart surgery. In Han patients, longer coagulation time as well as higher heparin and protamine dosage was observed. SERPINC1 gene sequencing identified 2 mutations in exon 5, g.981A>G (rs5877) and g.1011A>G (rs5878). The minor allele frequency of allele (A>G) for rs5877 and rs5878 was higher in the Han patients and was significantly different among the ethnic groups ( P = .004 and P = .006, respectively). The increased SERPINC1 SNP frequency among Han patients receiving heart surgery might contribute to the differences in their perioperative sensitivity to heparin.

Identification of a new SERPINC1 mutation in a Kazak family that alters the heparin binding capacity of antithrombin

INTRODUCTION

Given its central role in mediating heparin-induced anti-coagulation, antithrombin (AT) gene mutations may result in heparin resistance. This study investigates the relationship between familial AT gene mutations and tolerance to heparin.

METHODS

The medical history of a male patient with heparin resistance who received heart surgery and six of his family members was reviewed. Activated partial thromboplastin time (APTT), prothrombin time (PT), fibrinogen (Fib), D-dimer (D=D), and platelet count were determined to assess coagulation function. AT activity and the AT gene were also analyzed. For the newly identified gene mutations, polymorphisms were excluded in 120 healthy Kazak controls.

RESULTS

Two mutations were identified in exon 7 of the AT gene, SERPINC1: g.1267G>A (p.A391T) found in five participants, including the index patient, and g.1334G>A, a silent mutation, in two family members. The g.1267G>A mutation may alter focal AT protein conformation. Neither of these mutations was observed in the healthy Kazak controls. Although all coagulation parameters and AT activity were within the normal ranges for the index patient and his family members, the platelet levels were significantly lower than that observed for the healthy Kazak controls (p=0.001). There was no significant difference in AT antigen levels between the groups; however, participants with the g.1267G>A mutation had a 44.25% reduction in heparin binding compared to the control group (p<0.001).

CONCLUSION

We identified a novel hereditary mutation, g.1267G>A (p.A391T), in the AT gene, which reduces its heparin binding capacity and might be associated with resistance to heparin.

The influence of heparin resistance on postoperative complications in patients undergoing coronary surgery

Background

Heparin resistance is relatively frequent in patients undergoing coronary surgery. We aimed to assess the impact of heparin resistance on the outcome of patients undergoing coronary surgery with cardiopulmonary bypass (CABG). Three definitions of heparin resistance were adopted.

Material/Methods

We performed a retrospective review of 756 consecutive patients undergoing isolated CABG. All anaesthesia records were reviewed manually. Heparin resistance was recognized if: ACT was less than 400 seconds after 300 U/kg heparin (local criteria), ACT was less than 480 seconds after 400 U/kg or more heparin (stringent criteria), or if heparin sensitivity index was lower than 1.3. Postoperative assessment included perioperative morbidity and mortality. A multiple logistic regression model was used to investigate the influence of all demographic, preoperative and surgical variables, as well as heparin resistance (variably defined) on hospital mortality and postoperative complications.

Results

Heparin sensitivity index, local criteria and stringent criteria identified 64.8%, 12.0% and 4.3% heparin resistant patients, respectively. Heparin-resistant patients more frequently had preoperative heparin administration, unstable course of coronary artery disease, and higher coronary symptoms scoring. Severe form of heparin resistance (expressed by the ACT less than 480 seconds after 400 U/kg heparin) was an independent predictor of death (OR 4.92; CI 1.11–21.89).

Conclusions

Mild forms of heparin resistance are relatively frequent and are not associated with increased morbidity and mortality. The isolation of severe heparin resistance as an independent predictor of death in our large cohort of coronary patients suggests that this phenomenon should be given more attention in future studies.

Preoperative low molecular weight heparin reduces heparin responsiveness during cardiac surgery

PURPOSE

Cardiac surgery with cardiopulmonary bypass requires systemic anticoagulation, defined by an activated clotting time (ACT) of 400-480 sec. Patients with altered heparin responsiveness require disproportionately higher doses of heparin to achieve this target ACT. A common risk factor for heparin resistance is preoperative heparin therapy. Recently, therapy with low molecular weight heparin (LMWH) has become an acceptable substitute for prolonged heparin therapy. The current study examines the effect of preoperative LMWH therapy on subsequent heparin responsiveness during cardiac surgery.

METHODS

Records of patients undergoing cardiac surgery with cardiopulmonary bypass over a period of four months were reviewed. We identified patients who, during the week preceding surgery, had received prolonged (>24 hr) therapy with either sc LMWH (LMWH group) or continuous iv unfractionated heparin (Heparin group). A Control group consisted of patients who received neither heparin nor LMWH preoperatively. The heparin sensitivity index (calculated as the first change in ACT from baseline divided by the first intraoperative heparin dose, normalized to body weight), was compared among groups using ANOVA.

RESULTS

One hundred and thirty-nine patients were included in the analysis. The heparin sensitivity index was 33-45% higher in the Control group (1.6+/-0.7 sec.IU-1.kg-1; P<0.0001) compared to the LMWH (1.2+/-0.4 sec.IU-1.kg-1) and Heparin (1.1+/-0.5 sec.IU-1.kg-1) groups. In a multivariable model, the use of preoperative LMWH remained a significant predictor of reduced intraoperative heparin responsiveness (P=0.002).

CONCLUSION

Prolonged preoperative LMWH therapy, similar to the known effect of prolonged unfractionated heparin infusion, reduces subsequent intraoperative response to heparin.

Decreased concentration of antithrombin after preoperative therapeutic heparin does not cause heparin resistance during cardiopulmonary bypass

OBJECTIVE

To determine if preoperative heparin therapy causes an increase in the incidence of intraoperative heparin resistance by reducing the concentration of antithrombin in plasma.

DESIGN

Prospective laboratory investigation of clinical samples.

SETTING

Public tertiary care hospital and public pathology service.

PARTICIPANTS

Forty-six patients undergoing cardiac surgery involving cardiopulmonary bypass.

INTERVENTIONS

Fourteen patients received preoperative heparin therapy (POHI group) and 32 patients were controls (CONT group).

MEASUREMENTS AND MAIN RESULTS

The concentration of antithrombin, activated coagulation time (ACT), and clinical parameters were measured at intervals. More POHI patients had on-bypass heparin resistance than CONT (43% and 3%, respectively, p < 0.01). The POHI group had a lower concentration of antithrombin than the CONT group before (80.9% and 92.6%, respectively, p < 0.01) and while on cardiopulmonary bypass (51.6% and 57.5%, respectively, p = 0.04). Comparison of heparin-resistant and heparin-responsive POHI patients showed that the concentration of antithrombin did not differ before bypass (82.4% and 79.8%, respectively, p = 0.53) or during bypass (51.8% and 51.4%, respectively, p = 0.91). In fact, antithrombin concentrations were slightly higher in the heparin-resistant POHI patients (not significant). POHI patients received more heparin than CONT patients (medians 787 U/kg and 600 U/kg, respectively, p = 0.01) and were transfused with more fresh frozen plasma on bypass (p = 0.03).

CONCLUSIONS

Preoperative heparin causes an increased incidence of heparin resistance and reduced antithrombin concentrations. However, heparin resistance was not causally related to reduced antithrombin because antithrombin concentrations were not different between heparin-resistant and heparin-responsive patients in the POHI group.