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We investigated the effects of antithrombin on coagulation, fibrinolysis, and production of cytokines and adhesion molecules in abdominal aortic aneurysm repair surgery. Sixteen patients for Y-shaped graft replacement of abdominal aortic aneurysm were divided into an antithrombin group and a control group. In the antithrombin group, 3000 U antithrombin was infused over 30 min before heparin administration and 24 h later. White blood cell counts, platelet counts, prothrombin time ratio, and serum concentrations of antithrombin, polymorphonuclear leukocyte elastase, interleukin (IL)-1ß, IL-6, IL-8, tumor necrosis factor- , and adhesion molecules, and variables of coagulation and fibrinolysis were measured before surgery, at the end of surgery, and 1 and 2 days after surgery. The antithrombin concentration decreased in the control group, whereas it increased in the antithrombin group with significant differences between the groups. Prothrombin time ratio, concentrations of d-dimer, thrombin-antithrombin complex, and intercellular adhesion molecule-1 increased only in the control group and polymorphonuclear leukocyte elastase, IL-6, tumor necrosis factor- , and vascular cell adhesion molecule-1 increased in both groups. They were significantly less in the antithrombin group except for intercellular adhesion molecule-1. In conclusion, antithrombin could decrease hypercoagulation and inflammatory activation during abdominal aortic aneurysm surgery, which may decrease adverse events.
Patients with aortic aneurysm are in a chronic inflammatory state and a chronic hypercoagulable state. Preoperative thrombin-antithrombin complex (TAT), d-dimer, and cytokines are increased compared with normal values (1). In the late phase after dissecting aortic aneurysm repair, TAT and d-dimer are increased compared with healthy subjects, indicating a hypercoagulable state (2). The hypercoagulable state and inflammatory process activate macrophages and leukocytes to release cytokines. These cytokines further induce hypercoagulability and an inflammatory reaction (1,2). Thus, excessive activation of coagulation or severe inflammation can occur after aortic aneurysm surgery, which may be sometimes followed by organ failures. Antithrombin not only inhibits coagulation but also down-regulates anticoagulation and leukocyte activation (3). In addition, antithrombin has antiinflammatory actions that are independent of its effects on coagulation (4). In the present study, to evaluate the effects of antithrombin on hypercoagulability and inflammation, we investigated the changes of coagulation and fibrinolysis variables and serum concentration of cytokines and adhesion molecules in patients with or without antithrombin during abdominal aortic aneurysm surgery.
After approval from the research committee and informed consent from patients, 16 adult patients scheduled for Y-shaped graft replacement of an abdominal aortic aneurysm were randomly divided into 2 groups, the control group (n = 8) and the antithrombin group (n = 8), by an envelope method. Patients with liver, renal, cardiac, or respiratory disease or taking anticoagulant drugs were excluded from the study. After premedication with IM midazolam (23 mg) 30 min before entering the operating room, an epidural catheter was placed at the T10-11 level. Anesthesia was induced with thiopental (35 mg/kg), midazolam (0.050.1 mg/kg), and fentanyl (23 µg/kg). Orotracheal intubation was facilitated with vecuronium (0.15 mg/kg). The radial artery was cannulated for arterial blood pressure measurement and arterial blood sampling. Anesthesia was maintained with sevoflurane (0.5%1.5%) and nitrous oxide (67%) in oxygen and epidural block with intermittent 1% mepivacaine (46 mL). Vecuronium was used as a muscle relaxant. The abdominal aortic aneurysm was replaced with a Y-shaped graft. Heparin (2000 U) was administered before aortic clamping to keep activated clotting time between 150 s and 200 s. In the antithrombin group, antithrombin (3000 U, Neuart TM; Mitsubishi Pharma CO Ltd., Tokyo, Japan) was infused over 30 min, before heparin administration, and 24 h later. No other drugs affecting coagulation, fibrinolysis, cytokine release, or hepatic blood flow were administered. Concentrated red blood cells (Japan Red Cross, Tokyo, Japan) were used for blood transfusion.
Arterial blood (8 mL) was drawn before surgery, at the end of surgery, and 1 and 2 days after surgery. White blood cell counts, platelet counts, prothrombin time ratio, and serum concentrations of antithrombin, fibrinogen, plasminogen, fibrin and fibrinogen degradation product (FDP), d-dimer, TAT, plasmin-plasmin inhibitor complex (PIC), polymorphonuclear leukocyte elastase (PMNE), interleukin (IL)-1ß, IL-6, IL-8, tumor necrosis factor (TNF)-
Data are shown as mean and standard deviation. Statistical analysis was performed with the 2 test for gender, one-way factorial analysis of variance for the other demographic data, two-way repeated measures analysis of variance followed by the Contrasts, a multiple-comparisons correction as a post hoc test for the measured variables. A P value <0.05 was considered to be statistically significant. Post hoc power analysis was performed for the sample size with the G Power TM version 2.1.2 (Trieter University, Trieter, Germany).
The power of the study was 0.504. Demographic as well as general surgical information were similar between the two groups (Table 3). The antithrombin concentration decreased significantly in the control group, whereas it increased in the antithrombin group; it was significantly increased in the antithrombin group. Prothrombin time ratio, concentrations of d-dimer, TAT, and ICAM-1 increased only in the control group and PMNE, IL-6, TNF- , and VCAM-1 increased in both groups. They were significantly lower in the antithrombin group except for ICAM-1 (Tables 1 and 2). WBC increased but no difference was found between groups. Platelet counts, fibrinogen, plasminogen, FDP, PIC, IL-1ß, IL-8, and ELAM-1 did not change in both groups and no differences were observed between groups (Tables 1 and 2). No patients suffered from complications requiring treatment after surgery such as disseminated intravascular coagulation (DIC), bleeding, infection, renal failure, or liver failure.
The present results suggest that antithrombin could inhibit the activation of coagulation, leukocyte-endothelial interaction, and cytokine release in graft replacement of an abdominal aortic aneurysm. The variables measured in the present study might have reached peak levels with different time courses. Therefore, we might not have been able to detect their peak concentrations with the sampling intervals and the number of sampling points used. In addition, the number of patients was too small to yield a definite conclusion (considered from the power of 0.504). However, it was difficult to gather many patients by these criteria in our hospital and to increase the measurement points because of limited resources to obtain the measurements. Even with the small number of patients, significant differences between the groups could be identified in the effects of antithrombin. In addition, the purpose was to inhibit continuous overproduction of the mediators. Therefore, missing the peak concentrations was not important in the present study. In the present study, TAT, and d-dimer were increased above normal values before surgery, which indicate a hypercoagulable state as reported by Nomura et al. (1). On 2 days after surgery in the present study, the hypercoagulable state persisted. However, this hypercoagulable state was inhibited by antithrombin. PMNE is produced from activated leukocytes according to the inflammatory reaction (6) and has some relations with coagulation and fibrinolysis (5). Antithrombin decreased PMNE in the present study. This might also contribute to the inhibition of hypercoagulability.
TNF-
The increased variables in coagulation, cytokines, and adhesion molecules were inhibited by antithrombin in the present study. Antithrombin attenuates leukocyteendothelial cell interaction shown by the smaller increase in ICAM-1, TNF- In the present study, IL-1ß, IL-8, and ELAM-1 concentrations were not different between the two groups. These concentrations did not increase even in the control group. Therefore, antithrombin might inhibit only excess production of cytokines and adhesion molecules without any effects on their normal production. In DIC, antithrombin 1500 U per day for 2 to 3 days could decrease d-dimer, fibrin monomer, and DIC score (15). These effects were proven in the present study where TAT and d-dimer were lower in the antithrombin group.
Antithrombin did not influence plasminogen, In patients with sepsis, antithrombin is consumed by thrombin generation, shortened half-life, enhanced degradation by elastases produced by activated neutrophils, and decreased hepatic synthesis (17). Low antithrombin plasma activities correlate with frequent mortality (18). Dickneite (19) recommended that antithrombin plasma levels be adjusted to approximately 200%, i.e., doubling the normal value, to treat inflammation. Approximately 200% to 250% of normal levels of antithrombin would be necessary to derive maximum benefits in the severely septic population (20). The antithrombin concentration increased to about 150% of the control value in the present study. Therefore, if more antithrombin is administered, those observed effects will likely be more significant. Heparin 2000 U was administered before clamping the aorta to keep activated clotting time between 150 to 200 seconds in the present study. Heparin inhibits the effects of antithrombin (21). However, 2000 U of heparin might be too small to prevent the effects of administered antithrombin, while there is still the possibility of decreasinge the effects of antithrombin. In conclusion, antithrombin could decrease hypercoagulation and inflammatory activation during abdominal aortic aneurysm surgery. Therefore, it may prevent some adverse events after abdominal aortic aneurysm surgery.
Department funding was used for this study. Accepted for publication December 6, 2005.
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