ABSTRACT
On-pump cardiac surgery is accompanied by complex alterations of hemostasis. The excessive
postoperative bleeding has been attributed to acquired platelet dysfunction, impaired
plasmatic coagulation, and increased fibrinolysis. The characterization of the hemostatic
defects responsible for bleeding is crucial for specific treatment and optimal clinical
management of the patient. For rapid determination of platelet-dependent primary hemostatic
capacity (PHC), the Platelet Function Analyzer PFA-100® system is available. To evaluate
the PFA performance in perioperative monitoring, a study was performed in 49 patients
selected for low bleeding risk undergoing selective primary coronary artery bypass
grafting (CABG). We compared PHC with Simplate™ bleeding time (BT) and platelet aggregometry. Furthermore, we analyzed global hemostasis
by thromboelastography (TEG) and plasmatic coagulation by standard clotting tests
prothrombin time (PT, Quick), activated partial thromboplastin time (aPTT), thrombin
time (TT) and clotting factors and fibrinolysis by batroxobin (reptilase) time (RT).
In all patients BT was postoperatively increased by 1.5- to 2-fold irrespective of
perioperative complications and decreased to mildly prolonged values on the first
postoperative day (1st day). In patients without complications, PHC in both collagen-adenosine
diphosphate closure time (CADP-CT: 83 seconds preop, 78 seconds postop, and 74 seconds
1st day) and collagen-epinephrine closure time (CEPI-CT: 98 seconds preop, 95 seconds
postop, 85 seconds 1st day) remained nearly stable. Apart from a patient with postoperative
moderate thrombocytopenia, in bleeding patients no other significant defect of postoperative
platelet hemostatic capacity was observed. However, on 1st day, the PHC of those patients
was significantly reduced compared with nonbleeding patients.
In patients with postoperative myocardial ischemia, increased PHC was identified by
significantly shorter postoperative CADP-CT (66 seconds vs. 83 seconds) than in uncomplicated
patients. By aggregometry, partial platelet dysfunction was observed in some patients
without correlation to bleeding complications.
In seven of 9 patients the postoperative bleeding complication was attributed to prolonged
heparin anticoagulation and/or mildly enhanced fibrinogenolysis/fibrinolysis by TEG
and standard plasmatic coagulation tests (TEG: k time 18 minutes vs. 8 minutes; aPTT:
47 seconds vs. 32 seconds; TT: 18.0 seconds vs. 12.3 seconds) and (RT: 19.5 seconds
vs. 17.7 seconds).
The impairment of PHC, platelet aggregation, and clotting factors observed on the
1st day in bleeding and in intra-aortic balloon pump (IABP) patients are most likely
secondary effects, for example, loss of active platelets and clotting factors, to
the primary postoperative bleeding or implantation of the IABP.
In conclusion, our data indicate that in standard CABG procedures highly variable
alterations of the hemostatic system occur after cardiopulmonary bypass (CPB) even
in patients with assumed low operative risks.
For identification of post-CPB bleeding complications, thromboelastography, aPTT,
and TT and heparin and batroxobin (reptilase) time as fibrinolysis-sensitive assays
are useful. Platelet function appears to be rapidly restored in uncomplicated CABG.
PHC determination by PFA-100 demonstrates a high specificity for adequate platelet
function and, therefore, could be beneficial in improved transfusion of platelet concentrates.
PHC testing by PFA-100 may help identify postoperative platelet hyper-reactivity associated
with myocardial lesion.
KEYWORDS
Coronary bypass surgery - hemostasis - primary hemostasis - PFA-100 - fibrinolysis
- bleeding
