anti-Xa Heparin Research Articles

High antithrombin III levels attenuate hemostatic activation and leukocyte activation during cardiopulmonary bypass

Despite heparinization, cardiac surgery involving cardiopulmonary bypass (CPB) induces a powerful activation of the coagulation and inflammation system. This is caused by the contact of the blood with the large non-endothelial surfaces of CPB, the release and reinfusion of tissue factor-enriched blood from the operation field, the surgical trauma, and the reperfusion of ischemic tissue. As a result, the plasma coagulation factors and platelets are progressively consumed, the complement system and leukocytes are activated, and the proteases and cytokines are released. Clinical consequences of this sequel are hemorrhage, transfusions, and organ damage. Particularly in the myocardium, this systemic activation of the inflammatory system may further trigger regional reperfusion injury and thereby contribute to myocardial stunning, impaired contractility, and low cardiac output. Thrombin plays a pivotal role in the modulation of leukocyte activation: It increases neutrophil recruitment, neutrophil rolling by the expression of endothelial P- and E-selectin, neutrophil adhesion by the expression of intracellular adhesion molecule 1, and the production of endothelial platelet-activating factor. 1 The current investigation assesses the impact of enhanced antithrombin (AT) activity, induced by a high dose of ATIII before the initiation of CPB, on key biochemical markers of hemostatic and leukocyte activation. Methods Patients and anticoagulation protocol. After approval by the local ethics committee and informed consent were obtained, 80 patients undergoing elective coronary artery bypass grafting were enrolled in this prospective, randomized, controlled investigation. No patient received warfarin (Coumadin, Bristol-Myers Squibb, New York, NY) or antiplatelet therapy within 10 days before surgery. Two groups with 40 patients each were formed. In group one (H), in accordance with the departmental standard, anticoagulation was performed according to the results of the Hepcon HMS Plus (Medtronic, Minneapolis, Minn). In group two (HATIII), an additional bolus of 50 IU/kg ATIII (Grifols, Langen, Germany) was given with the initial bolus of heparin before CPB. Blood samples were collected 10 minutes after the administration of the heparin bolus before CPB and after termination of CPB before protamine infusion. Anesthesia was performed using a total intravenous technique with propofol, sufentanil, midazolam, and pancuronium bromide. Normothermic CPB was accomplished with nonheparin-coated systems, membrane oxygenators, and roller pumps. None of the patients received antifibrinolytic agents or the kallikrein inhibitor aprotinin. Laboratory analysis. Heparin anti-Xa activity was determined using the STA-Rotachrom Heparin (Roche, Mannheim, Germany). ATIII was determined using the Coamatic LR Antithrombin Chromogenix assay (Hemochron Diagnostica, Essen, Germany). Prothrombin 1 and 2 fragments (PTF12) were assessed using the Enzygnost F1-2 micro assay (Dade Behring, Marburg, Germany). Soluble fibrin was measured using the COATEST Soluble Fibrin assay (Chromogenix, Milano, Italy). Interleukin (IL)-6 was measured using the IL-6 enzyme-linked immunosorbent assay (DPC Biermann, Nauheim, Germany). Polymorphonuclear leukocyte (PMNL) elastase was determined with the use of a luminescence immunoassay (Auto-CliniLumat LB 952, Bertold, Wildbad, Germany).

Rinsing Dialyzers without Heparin in Hemodialysis (HD) with Low-Molecular Weight Heparin (LMWH)

Saline plus unfractionated heparin (UFH) is routinely used for priming dializers before HD start. The aim of this study is to assess if heparin is necessary in pre-rinsing procedure of extracorporeal systems, anticoagulated with LMWH. We carried-out a prospective study in 14 stable HD patients, aged 58.5 ± 3.6 years old. All patients were treated by standard bicarbonate HD, 3 sessions × week, HD time 220 ± 12 min, Qb 276 ± 21 ml/min, low-flux dialyzers (polisulfone 5, cellulose diacetate 9). Clotting was prevented with a single bemiparin (LMWH) bolus 2900 ± 140 IU. Three rinsing protocols were applied in three consecutive weeks: 1st week- Saline 1000 ml + LMWH 2500 IU. 2d week- Saline 1000 ml + UFH 5000 IU. 3th week- Saline 1000 ml. Anti-Xa activity (IU/ml) was measured at each HD (at 10 min/end). Clotting events and post-HD AVF hemostasis were recorded in a semiquantitative scale. No significant statistical differences (Anova) were found in anti-Xa heparin activity (IU/ml) among the three rinsing protocols tested: 10 min (NS) End (NS) 1st week 0.81 ± 0.16 0.55 ± 0.43 2nd week 0.76 ± 0.21 0.58 ± 0.16 3th week 0.86 ± 0.14 0.64 ± 0.16 No differences were observed in drip chamber or dialyzer appearance after HD. Massive clotting was not recorded. No important bleeding was observed at stick needle sites. In conclusion, HD performed with LMWH no needs heparin in rinsing solution. The procedure is effective and safe.

Anticoagulant Effect at the Time of Epidural Catheter Removal in Patients Receiving Twice-daily or Once-daily Low-molecular-weight Heparin and Continuous Epidural Analgesia after Orthopedic Surgery

In patients who receive co-administered low-molecular-weight heparin (LMWH) and continuous epidural analgesia (CEA) after orthopedic surgery, there is concern about an increased risk of a spinal epidural hematoma. The practice of twice-daily LMWH dosing in North America might, in part, account for the greater number of epidural hematomas reports compared to Europe where once-daily LMWH is used. We performed a prospective cohort study in patients who had orthopedic surgery and received co-administered LMWH and CEA. We investigated the trough anticoagulant effect, as measured by an anti-Xa heparin level, at the time of epidural catheter removal in patients who received twice-daily or once-daily LMWH. Twenty-five patients who received enoxaparin, 30 mg twice-daily, and 25 patients who received dalteparin, 5,000 IU once-daily, had anti-Xa heparin levels measured on the second or third post-operative day at the time of epidural catheter removal. In patients who received twice-daily enoxaparin, or once-daily dalteparin, the anti-Xa heparin level was measured, on average, 10.4 h and 21.8 h, respectively, after the preceding LWMH dose. All 25 patients who received once-daily LMWH had an anti-Xa heparin level < 0.10 U/ml at the time of catheter removal. Of 25 patients who received twice-daily LMWH, the anti-Xa heparin level at the time of catheter removal was > or = 0.20 U/ml in 5 patients (P = 0.050), and > or = 0.10 U/ml in 7 patients (P = 0.009). We conclude that in patients who are receiving co-administered LMWH and CEA after orthopedic surgery, twice-daily but not once-daily LMWH administration is more likely to be associated with a clinically important anticoagulant effect at the time of epidural catheter removal.

Apparent heparin resistance from elevated factor VIII during pregnancy

Background: Heparin resistance is the need for more than 35,000 units of heparin per 24 hours to achieve therapeutic activated partial thromboplastin time (APTT) values. Elevated factor VIII can cause apparent heparin resistance by suppressing the APTT result without inhibiting the antithrombotic effect of heparin. Case: A 41-year-old gravida 2 para 0 presented at 25 weeks of a twin gestation with a deep venous thrombosis that required unusually high doses of heparin, resulting in hematuria. Apparent heparin resistance caused by elevated factor VIII was diagnosed, and the heparin dose was appropriately decreased with anti-Xa heparin monitoring. The deep venous thrombosis and hematuria resolved. Conclusion: Factor VIII rises significantly during pregnancy, and can cause apparent heparin resistance. When this occurs, anti-Xa heparin levels are superior to APTT for monitoring heparin therapy.

Pharmacokinetic Profile of a Low-Molecular Weight Heparin (Reviparin) in Pregnant Patients: A Prospective Cohort Study

Anticoagulant therapy during pregnancy is problematic. Patients are frequently treated with long-term low-molecular weight heparin despite a lack of evidence for its effectiveness, and in the absence of validated dosing recommendations. The objectives of this investigation were to characterize the safety and pharmacokinetic behavior of a low-molecular weight heparin (reviparin) administered throughout pregnancy. Forty-two patients followed in a tertiary-care rheumatology clinic who received prophylactic doses of reviparin (4900 anti-Xa units subcutaneously once daily) were enrolled in this investigation. Anti-Xa heparin levels, weights, and gestational ages of the patients were obtained on up to four occasions distributed throughout their pregnancy. The achieved anti-Xa heparin levels were highly correlated with the patient's weight, irrespective of the gestational age. No toxicity other than injection site hematomas was observed. The achieved intensity of anticoagulation with reviparin varies during pregnancy in direct proportion to the patient's weight. This variability may mandate dose adjustment in response to changes in a patient's weight during pregnancy, particularly if low-molecular weight heparin is administered at therapeutic doses.

Efficacy and Safety of Weight-Adapted Nadroparin Calcium vs. Heparin Sodium in Prevention of Clinically Evident Thromboembolic Complications in 1,190 General Surgical Patients

Aims: In a prospective, randomized, single, general surgery center trial, comparison of the safety and efficacy of two low molecular weight heparin (LMWH; anti-Xa heparin sodium and weight-adapted nadroparin calcium) regimens was made. Patients and Methods: Eleven hundred and ninety patients undergoing various elective and emergency operations were randomized to receive daily either a fixed dose of 3,000 IU anti-Xa heparin sodium or a variable body weight-dependent dose of nadroparin calcium (weight <50 kg, 2,050 IU anti-Xa (WHO); 51–80 kg, 3,075 UI; 81–100 kg, 4,100 UI, and >100 kg, 6,150 UI) once until discharge. The first injection was administered 2.5–6 h before elective and emergency operations, respectively. Patients with clinical suspicion of deep venous thrombosis (DVT) underwent phlebography. Patients with signs of pulmonary embolism (PE) were further investigated by a ventilation-perfusion scan. Results: Statistically, there were no significant differences in the incidence of clinically evident DVT, PE or LMWH-related complications between both prophylactic regimens. Only 4 of the total of 15 hemorrhagic complications (4 wound hematomas in the nadroparin calcium group) were not classified as clearly surgically related, Two DVTs were confirmed by phlebography (both in the nadroparin calcium group). PE was confirmed by ventilation-perfusion scans (1 fatal, 1 on autopsy) in 1 patient with heparin sodium and in 6 patients with nadroparin calcium. Conclusions: Both regimens were equally safe and the risk of clinically evident DVT and PE was similar.

Improved protamine-sensitive membrane electrode for monitoring heparin concentrations in whole blood via protamine titration§

An improved protamine-sensitive electrode based on a polymeric membrane doped with the charged ion exchanger dinonylnaphthalenesulfonate (DNNS) is used for monitoring heparin concentrations in whole blood. The electrode exhibits significant nonequilibrium potentiometric response to polycationic protamine over the concentration range of 0.5-20 mg/L in undiluted whole-blood samples. The sensor can serve as a simple end point detector for the determination of heparin via potentiometric titrations with protamine. Whole-blood heparin concentrations determined by the electrode method (n > or = 157) correlate well with other protamine titration-based methods, including the commercial Hepcon HMS assay (r = 0.934) and a previously reported potentiometric heparin sensor-based method (r = 0.973). Reasonable correlation was also found with a commercial chromogenic anti-Xa heparin assay (r = 0.891) with corresponding plasma samples and appropriate correction for whole-blood hematocrit levels. Whereas a significant positive bias (0.62 kU/L; P < 0.001) is observed between the anti-Xa assay and the protamine sensor methods, insignificant bias is observed between the protamine sensor and the Hepcon HMS tests (0.08 kU/L; P = 0.02). The possibility of fully automating these titrations offers a potentially simple, inexpensive, and accurate method for monitoring heparin concentrations in whole blood.

Acquired inhibitors to factors V and X after exposure to topical thrombin: Interference with monitoring of low molecular weight heparin and warfarin

Repeated surgical exposure to topical bovine thrombin is known to be associated with the development of antibodies to bovine and human thrombin and factor V. This is demonstrated by abnormalities of in vitro coagulation assays and, rarely, postoperative bleeding. We describe a 4-year-old child in whom an antibody to bovine factor X developed after cardiac surgery; this antibody interfered with the heparin anti-Xa assay, thereby complicating the monitoring of heparin therapy.

Recurrent thrombosis of biventricular-support devices associated with accelerated intravascular coagulation and increased heparin requirements

Recurrent thrombosis of biventricular-support devices associated with accelerated intravascular coagulation and increased heparin requirements

More Effective Suppression of Hemostatic System Activation in Patients Undergoing Cardiac Surgery by Heparin Dosing Based on Heparin Blood Concentrations rather than ACT

This study was designed to determine whether the maintenance of higher than usual patient-specific heparin concentrations during cardiopulmonary bypass (CPB) was associated with more effective suppression of hemostasis system activation. Thirty-one patients scheduled for repeat cardiac surgery or combined procedures (i.e., coronary revascularization + valve repair/replacement) were consented and enrolled in this study. All patients received porcine heparin and protamine and were randomly assigned to monitoring of anticoagulation by either celite ACT alone (Control, n = 16) or by kaolin ACT combined with on-site measurements of whole blood heparin concentration (Intervention, n = 15). Blood specimens collected before administration of heparin, before weaning from CPB and after administration of protamine were analyzed with a battery of coagulation assays. Patients in the intervention cohort received appreciably greater heparin doses than control patients, resulting in higher anti-Xa heparin levels at the end of CPB. Fibrinopeptide A and D-dimer levels were higher in the control group before discontinuation of CPB. Percent decrease during CPB were greater in the control group for factors V and VIII, fibrinogen and antithrombin III. Percent decrease in complement 3 was greater in the control group after protamine and bleeding times measured in the Intensive Care Unit were significantly more prolonged in this group. Maintenance of higher patient-specific heparin concentrations during CPB more effectively suppresses excessive hemostatic system activation than do standard heparin doses chosen based on measurement of ACT. These findings may explain, at least in part, the significant reduction in perioperative blood loss and blood product use when higher heparin concentrations are maintained.

Effect of aprotinin on activated clotting time whole blood and plasma heparin measurements

Twenty cardiac surgical patients requiring cardiopulmonary bypass were enrolled in this study designed to evaluate the effect of aprotinin on activated clotting time (kaolin and celite), whole blood, and laboratory-based plasma (anti-Xa) heparin measurements. Whole blood heparin measurements were not different (p = 0.98) between aprotinin-treated (3.2 +/- 2.8 U/mL) and control (3.2 +/- 3.0 U/mL) specimens. Plasma anti-Xa heparin measurements were also not different (p = 0.95) between aprotinin-treated (2.7 +/- 2.5 U/mL) and control (2.8 +/- 2.5 U/mL) specimens. The relationship between whole blood (plasma equivalent) and plasma heparin measurements was similar (p = 0.1) in the presence (slope, 1.04; r2 = 0.89) or absence (slope, 1.11; r2 = 0.89) of aprotinin. In contrast to weak correlations between celite (r = 0.50) or kaolin (r = 0.53) activated clotting time values, whole blood heparin measurements correlated well (r = 0.93) with plasma heparin measurements during cardiopulmonary bypass in the presence of aprotinin. These findings indicate that whole blood heparin measurements are unaffected by aprotinin and correlate well with plasma anti-Xa heparin measurements even in the presence of aprotinin. Therefore, the automated protamine titration assay can be used to monitor accurately heparin concentrations in patients receiving aprotinin.

Comparison of activated coagulation time and whole blood heparin measurements with laboratory plasma anti-Xa heparin concentration in patients having cardiac operations

Previous reports suggest that activated clotting times do not correlate with heparin concentration during cardiopulmonary bypass. This study was designed to compare whole blood heparin concentration and activated clotting time measurements with laboratory-based plasma heparin concentration. Sixty-two patients having cardiac operations requiring cardiopulmonary bypass were enrolled in this study. The study was conducted in two phases. In phase I of this trial, blood specimens were obtained from 30 patients before heparin administration and after each of three heparin doses (20, 80, and 150 U/kg). In phase II, blood specimens were obtained from 32 patients before heparin administration and 10 minutes after each of the following: heparin administration (250 or 300 U/kg), initiation of cardiopulmonary bypass, achievement of hypothermia, initiation of rewarming, and immediately before discontinuation of bypass. Blood specimens were used to measure activated clotting time (kaolin and celite), whole blood heparin concentration, and anti-factor Xa plasma heparin concentration. In phase I, activated clotting time (celite: r = 0.91; kaolin: r = 0.93) and whole blood heparin concentration (r = 0.98) measurements correlated well with plasma heparin concentration. After initiation of cardiopulmonary bypass (phase II), weak correlations for activated clotting time measurements (celite: r = 0.34; kaolin: r = 0.59) and a strong correlation for whole blood heparin concentration (r = 0.95) were evident when compared with plasma heparin concentration. During bypass, activated clotting time measurements also inversely correlated with temperature (celite: r = -0.21; kaolin: r = -0.19) and hematocrit (celite: r = -0.26; kaolin: r = -0.21). A weak correlation between activated clotting time measurements and plasma heparin concentration is evident during the cardiopulmonary bypass period, probably because of the influence of both reduced hematocrit and temperature on the activated clotting time assay. In contrast, whole blood heparin measurements correlate well with plasma heparin concentration before and during bypass. Further studies are needed to determine whether maintaining heparin levels during cardiopulmonary bypass by monitoring heparin concentration is more effective in preventing consumptive activation of the hemostatic system, reducing bleeding, and minimizing the use of blood products after cardiopulmonary bypass when compared with a protocol based on activated clotting time.

Comparison of ACT and Whole Blood Heparin Measurements to Laboratory Plasma Anti-XA Heparin Concentration in Cardiac Surgery PatientsG

Comparison of ACT and Whole Blood Heparin Measurements to Laboratory Plasma Anti-XA Heparin Concentration in Cardiac Surgery PatientsG

Efficacy and toxicity of differently charged polycationic protamine-like peptides for heparin anticoagulation reversal.

The role of total cationic charge of synthetic protamine-like peptides in heparin anticoagulation reversal and accompanying adverse hemodynamic effects was studied. Five protamine variants having specific total charges of [+8], [+16], [+18], [+20], and [+21] were synthesized by fluorenylmethoxycarbonyl procedures. Each of these lysine-containing peptides plus arginine-containing control salmine native protamine (n-protamine, [+21] charge) was studied in five dogs who received heparin 150 IU/kg intravenously followed by 1.5 mg/kg (intravenously during a 10-second period) of the synthesized peptide or control n-protamine. Anticoagulation reversal as assessed by a number of coagulation tests was more effective with peptides of greater cationic charge. In this regard, activated clotting time reversal 3 minutes after peptide administration was 7%, [+8]; 54%, [+16]; 81%, [+18]; 92%, [+20]; 81%, [+21]; and greater than 100% [n-protamine]. Reversal of heparin anticoagulation at 3 and 30 minutes, respectively, correlated significantly (*p < or = 0.05, p < or = 0.01 [see corresponding symbols within abstract]) with total cationic charge as assessed by activated clotting time (r = 0.97, 0.99 ), prothrombin time (r = 0.98, 0.87*), activated partial thromboplastin time (r = 0.99, 0.78), thrombin clotting time (r = 0.84,* 0.85*), heparin anti-Xa activity (r = 0.87,* 0.85*), and heparin anti-IIa activity (r = 0.79 at 3 minutes, p = 0.06). Maximum declines in systemic mean arterial pressure (MAP) were greater with more positively charged peptides: -1 mm Hg, [+8]; -3 mm Hg, [+16]; -31 mm Hg; [+18]; -31 mm Hg, [+20]; -35 mm Hg, [+21]; and -34 mm Hg [n-protamine]. Maximum decreases in MAP, cardiac output, and systemic oxygen consumption were highly correlated (p < or = 0.05) with total cationic charge: MAP, r = 0.87; cardiac output, r = 0.87; and systemic oxygen consumption, r = 0.86. A total toxicity score, reflecting adverse hemodynamic effects, was greater with increasing charge: -1.9 +/- 1.1, [+8]; -2.7 +/- 0.8, [+16]; -6.6 +/- 3.3, [+18]; -6.1 +/- 3.5, [+20]; -6.9 +/- 3.8, [+21]; and -7.0 +/- 5.2 [n-protamine]. The correlation of mean peptide total toxicity score to total cationic charge was significant (r = 0.89, p < 0.05). These data suggest for the first time that effective alternatives to salmine protamine for reversal of heparin anticoagulation can be synthesized. Furthermore, total cationic charge appears to be an important determinant for both anticoagulation reversal and toxicity of protamine-like peptides.

Partial reversal of low molecular weight heparin (PK 10169) anti-Xa activity by protamine sulfate: in vitro and in vivo study during cardiac surgery with extracorporeal circulation.

Neutralization of a low molecular weight (LMW) heparin fraction by protamine sulfate was evaluated in vitro and in vivo. Anti-Xa and anti-IIa activities were measured by amidolytic and coagulation methods (activated partial thromboplastin time, APTT). Fifteen patients (4 males and 11 females) underwent surgery with extracorporeal circulation. In vitro, anti-Xa and anti-IIa activities and APTT of unfractionated heparin were neutralized with a protamine/heparin (P/H) gravimetric ratio of 1.6, 1.33 and about 2, respectively. Anti-IIa activity and APTT induced by PK 10169 were completely corrected at a P/H ratio of 1 and 2, respectively, while anti-Xa activity was incompletely neutralized at a ratio of 5. In vivo, in 9 patients who did not receive intravenous protamine sulfate, a good correlation was found between doses of PK 10169 infused, anti-IIa plasma level and blood loss. In 3 patients who were treated prophylactically with protamine, bleeding was normal or only slightly increased. In 3 patients who received protamine because of hemorrhage, mean anti-Xa and anti-IIa were 2.3 and 0.54 U before and 1.32-0.06 U after neutralization. Bleeding was stopped by a second dose of protamine in 1 patient, but blood loss was abnormal in the other patients. However, a correlation between bleeding and anti-Xa or anti-IIa activities was not clearly evident.

Pharmacokinetic studies of standard heparin and low molecular weight heparin in patients with chronic renal failure.

The disappearance of the anticoagulant activities of a standard commercial heparin and of a low molecular weight (LMW) heparin (PK 10169), administered as single intravenous injections, was studied in patients with chronic renal failure. Heparin and LMW heparin anticoagulant activities were determined by activated partial thromboplastin time (APTT) and chromogenic assays of anti-Xa and anti-IIa activities. Following heparin injection, a fast initial decay of anticoagulant activities preceded a slow convex disappearance curve, in semilogarithmic plots. These experimental data are in agreement with a model based on a predominant saturable mechanism of elimination of heparin in patients with renal failure. The disappearance of LMW heparin anti-Xa activity was obviously different, with linear or concave elimination curves, and longer apparent half-life. Taken together, our kinetic data and those previously reported in normal subjects strongly suggest that the mechanism of elimination of the LMW heparin studied is not saturable (at least for the tested dosages), and that the kidneys play a minimal role in the elimination.

Heparin-like activity in uterine fluid.

Uterine fluid was collected from a group of normal patients and a group of patients with menorrhagia. Heparin-like activity was detected in 34 out of 38 samples using an anti-Xa heparin assay. The heparin-like activity in uterine fluid was inhibited by adding the heparin antagonist hexadimethrine bromide to the assay. Concentrations of fibrinogen-fibrin degradation products (FDPs) were measured in five samples of uterine fluid. FDPs in the concentration detected had no effect on the anti-Xa assay. Heparin-like activity was higher in the group with menorrhagia, although the differences were not significant. Heparin-like activity increased throughout the menstrual cycle and decreased during menstruation, suggesting a possible cyclical variation in activity. There was no correlation between mast cell numbers in the endometrium and myometrium and heparin-like activity in uterine fluid and no correlation between the numbers and the stage in the menstrual cycle. In a few patients with intrauterine contraceptive devices (IUCDs) heparin-like activity was increased.