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Significance of D-dimer concentrations during and after cardiopulmonary bypass
M E Comunale1, J M Carr, R M Moorman
1Department of Anesthesia and Critical Care, Beth Israel Hospital, Boston, MA 02215, USA.
Insights
D-dimer levels typically do not rise during cardiopulmonary bypass (CPB). Postoperative D-dimer increases may reflect clot remodeling, not necessarily coagulopathy or predict blood loss.
Area of Science:
- Cardiovascular Surgery
- Hematology
- Biochemistry
Background:
- Cardiopulmonary bypass (CPB) is a critical procedure in cardiac surgery.
- Understanding hemostatic changes during and after CPB is vital for patient outcomes.
- D-dimer fragments are markers of fibrinolysis and clot breakdown.
Purpose of the Study:
- To investigate D-dimer fragment levels during CPB.
- To determine if D-dimer increases correlate with postoperative blood loss.
- To assess if D-dimer elevation predicts postoperative coagulopathy.
Main Methods:
- Prospective observational study of 65 patients undergoing first-time CABG or valve replacement.
- Blood samples collected preoperatively, during CPB, after heparin neutralization, and postoperatively.
- D-dimer, fibrinogen, and coagulation parameters (ACT, PT, PTT) were measured.
Main Results:
- D-dimer levels generally did not increase during CPB.
- A few patients showed modest D-dimer increases post-heparin neutralization (<2.0 ug/mL).
- Significant D-dimer elevations (>2.0 ug/mL) occurred postoperatively, correlating with higher blood loss.
Conclusions:
- D-dimer is usually not elevated during CPB with adequate anticoagulation (ACT monitoring).
- Postoperative D-dimer increases, particularly without fibrinogen decrease, do not indicate coagulopathy.
- Elevated postoperative D-dimer may reflect clot remodeling rather than active bleeding or coagulopathy.
Objective:
To determine whether D-dimer fragments predictably increase during cardiopulmonary bypass (CPB), and if so, whether increases correlate with postoperative blood loss or predict postoperative coagulopathy.
Design:
Prospective observational study of 65 consecutive patients undergoing first-time coronary artery bypass graft (CABG) or first-time valve replacement.
Setting:
Single center University teaching hospital.
Participants:
Male and female patients between the ages of 30 and 90 years undergoing first-time CABG or valve replacement surgery using CPB. Patients were excluded from study for prolonged preoperative bleeding time, preoperative warfarin therapy, perioperative intra-aortic balloon pump support, thrombolytic therapy in the week preceding operation, reoperation, and emergency operation.
Interventions:
None.
Measurements And Main Results:
Blood sampling for platelet count, prothrombin time, partial thromboplastin time, thrombin time, fibrinogen, activated coagulation time (ACT) and D-dimer concentrations was obtained at four times during each case; (1) preoperatively, after insertion of the internal jugular introducer, before insertion of pulmonary artery catheter; (2) during CPB at 28 degrees C, immediately before rewarming; (3) after heparin neutralization (20 minutes after initial protamine dose); (4) 12 to 24 hours postoperatively. Blood loss in the intensive care unit was calculated by measuring total mediastinal drainage output at 1 and 4 hours after arrival from the operating room. An initial decrease in fibrinogen was noted during bypass, but no increase in D-dimer was identified. A few patients developed a modest increase in D-dimer after heparin neutralization, but none greater than 2.0 ug/mL. Postoperatively, fibrinogen concentration increased toward baseline levels. However, this is when six patients developed significant (> 2.0 ug/mL) D-dimer formation. Results suggest appropriate physiologic response-normalization of fibrinogen with new synthesis and remodeling of clot in the operative site causing D-dimer formation. Patients with highest D-dimer levels at 12 to 24 hours postoperatively had the highest blood loss at 4 hours postoperatively, suggesting that early postoperative excess bleeding predisposed to increased clot formation and subsequent clot remodeling causing elevated D-dimer concentrations.
Conclusions:
D-dimer concentration is not usually elevated in patients undergoing CPB when adequately anticoagulated as monitored using the ACT. When mild elevation of D-dimer occurs, it is most often after heparin neutralization and/or in the postoperative period and is not predictive of increased postoperative blood loss. Elevations of D-dimer concentrations in the postoperative period without corresponding decreases in fibrinogen concentrations may occur and do not signify coagulopathy.