Journal: J Anesth 21(3):297-303, 2007. 31 References
Reprint: Div of Cardiothoracic Anesthesia, Dept of Anesthesiology, Emory University School of Medicine, 1364 Clifton Road, NE, Atlanta, Georgia 30322 (KA Tanaka, MD)
Faculty Disclosure: Abstracted by L. Easley, who has nothing to disclose.
Conventional on-pump coronary artery bypass graft (CABG) routinely uses anticoagulation with high-dose heparin (≥ 300 U/kg) whereas the heparin protocol in off-pump coronary artery bypass (OPCAB) varies among surgeons. The authors analyzed coagulation status from their recent randomized prospective OPCAB or conventional on-pump CABG surgery to make it useful for practicing physicians who manage anticoagulation during CABG surgery.
In this study, 200 patients were randomized to OPCAB or conventional on-pump CABG. Cardiopulmonary bypass (CPB) was performed according to the routine protocol, with a roller pump, non-heparin coated circuit, and moderate hypothermia in the on-pump CABG group. Preoperative laboratory coagulation data were recorded, including hematocrit, platelet count, fibrinogen level, and international normalized ratio (INR) of prothrombin time.
Anticoagulation for OPCAB was performed with an initial dose of heparin, 180 U/kg, followed by a 3000-U bolus every 30 min, to maintain the activated clotting time (ACT) at 350 sec or more. In the CABG patients, anticoagulation was obtained with an initial dose of heparin, 400 U/kg, to maintain an ACT greater than 400 sec. Heparin reversal was achieved with protamine 200-250 mg to achieve a normal ACT.
Postoperatively, the platelet count was higher in the OPCAB group compared to the CABG group. The percentage of patients who had a platelet count < 100 x 103 per microliter was less in the OPCAB group than in the CABG group. Postoperatively, international normalized ratio (INR) was lower in the OPCAB group, and partial thromboplastin time (PTT) was higher in the OPCAB group. In the CABG group, the postoperative angle and maximum amplitude values were significantly smaller and K time was longer than the preoperative values, and the postoperative native thromboelastography (TEG) index indicated that fewer patients were considered hypercoagulable in the CABG group than in the OPCAB group. Total heparin and protamine doses were lower in the OPCAB group.
This study showed that the current anticoagulation regimen in the OPCAB patients achieved a peak ACT of 445 ± 73 sec, and it preserved platelet counts and fibrinogen levels. Maintaining high levels of anticoagulation with heparin titration or supplemental antithrombin has been shown to reduce the activation of coagulation. The percentage of patients who were at high risk for platelet transfusion was 4.1% in the OPCAB group and 22.2% in the CABG group, whereas the incidence of a low fibrinogen level (<150 mg/dL) was similar in the two groups.
The rate of bleeding complications requiring re-exploration was similar in the OPCAB and CABG groups. OPCAB patients may present a hyper-coagulable state because of the better-preserved coagulation factors, platelets, and fibrinogen. In contrast to CABG patients who develop platelet dysfunction during CPB, pharmacological platelet inhibition with aspirin, 650 mg, was used routinely in the OPCAB group.
In conclusion, this study showed that a heparin anticoagulation regimen of 180 U/kg plus 3000 U every 30 min, with intraoperative aspirin, 650 mg, in OPCAB patients does not lead to a hypercoagulable state. Total doses of heparin and protamine were smaller in the OPCAB group compared with the CABG group and there was a residual heparin effect on TEG and PTT in the early postoperative period in the OPCAB group. A further study is required to evaluate the postoperative coagulation status in OPCAB patients, and the necessity for antithrombotic or anti-platelet therapy. |
