Pre-op thrombin generation predicts excessive post-CPB blood loss
MedWire News: Study findings published in the journal Anesthesia and Analgesia may help identify patients at high risk for postoperative blood loss following cardiopulmonary bypass (CBP) surgery.
The results show greater post-CPB blood loss in patients who had a reduced pre-operative thrombin generation rate, and increased post-CPB consumption and dilution of clotting factors than those without these characteristics.
Keyvan Karkouti (Toronto General Hospital, Ontario, Canada) and co-workers studied 101 patients, who lost a median of 952 ml of blood between heparin reversal after CPB and 24 hours after admission to intensive care.
Blood samples were taken immediately before induction of anesthesia and after heparin reversal. Platelet count and levels of prothrombin fragments F1 and 2 were the only pre-operative coagulation variables that predicted blood loss, with lower values associated with more blood loss.
CPB caused about a third reduction in levels of patients’ hemoglobin, antithrombin, and all clotting factors except factor VIII, as well as about halving patients’ platelet counts. All of these reductions were significantly associated with post-CPB blood loss, as was the activation of the coagulation cascade indicated by increased F1 and 2 and soluble fibrin monomer complex (FM) levels.
Fibrinolysis also increased during CPB, but was not associated with postoperative blood loss.
When the researchers accounted for confounders, reduced pre-operative F1 and 2 levels remained associated with increased postoperative blood loss, as did reduced postoperative platelet count, increased FM level, and larger percent decrease in fibrinogen concentration.
In addition, patients with previous sternotomies lost more blood than those without.
The amount of blood patients lost correlated positively with their risk for serious adverse events, particularly infection.
Karkouti et al conclude that their findings “provide important insight into how coagulation is altered during complex cardiac surgery and what impact these alterations have on postoperative blood loss.”
“This information can be used to construct accurate prediction rules aimed at improving our ability to identify patients at high risk for excessive blood loss, and to design interventional studies aimed at preventing or treating postcardiac surgery coagulopathy and excessive blood loss.”
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By Eleanor McDermid