Preoperative platelet function predicts perioperative bleeding complications in ticagrelor-treated cardiac surgery patients: a prospective observational study

BACKGROUND

Treatment with P2Y12 receptor antagonists increases the risk for perioperative bleeding, but there is individual variation in the antiplatelet effect and time to offset of this effect. We investigated whether preoperative platelet function predicts the risk of bleeding complications in ticagrelor-treated cardiac surgery patients.

METHODS

Ninety patients with ticagrelor treatment within <5 days of surgery were included in a prospective observational study. Preoperative platelet aggregation was assessed with impedance aggregometry using adenosine diphosphate (ADP), arachidonic acid (AA), and thrombin receptor-activating peptide (TRAP) as initiators. Severe bleeding complications were registered using a new universal definition of perioperative bleeding. The accuracy of aggregability tests for predicting severe bleeding was assessed using receiver operating characteristic (ROC) curves, which also identified optimal cut-off values with respect to sensitivity and specificity, based on Youden's index.

RESULTS

The median time from the last ticagrelor dose to surgery was 35 (range 4-108) h. The accuracy of platelet function tests to predict severe bleeding was highest for ADP [area under the ROC curve 0.73 (95% confidence interval 0.63-0.84, P<0.001); TRAP 0.61 (0.49-0.74); AA 0.53 (0.40-0.66)]. The optimal cut-off for ADP-induced aggregation was 22 U. In subjects with ADP-induced aggregation below the cut-off value, 24/38 (61%) developed severe bleeding compared with 8/52 (14%) when aggregation was at or above the cut-off value (P<0.001). The positive and negative predictive values for this cut-off value were 63 and 85%, respectively.

CONCLUSIONS

Preoperative ADP-induced platelet aggregability predicts the risk for severe bleeding complications in ticagrelor-treated cardiac surgery patients.

Cell saver processing mitigates the negative effects of wound blood on platelet function

BACKGROUND

Wound blood is highly activated and has poor haemostatic properties. Recent data suggest that retransfusion of unwashed wound blood may impair haemostasis. We hypothesized that cell saver processing of wound blood before retransfusion reduces the negative effects.

METHODS

Wound blood was collected from 16 cardiac surgery patients during cardiopulmonary bypass. One portion of the wound blood was processed in a cell saver and one portion left unprocessed. Increasing amounts of unprocessed blood (10% and 20% of the systemic blood volume) or corresponding volumes of processed blood were added ex vivo to whole blood samples from the same patient. Clot formation was assessed by modified thromboelastometry (ROTEM(®) ) and platelet function with impedance aggregometry (Multiplate(®) ).

RESULTS

Addition of unprocessed wound blood significantly impaired clot formation and platelet aggregability. Cell saver processing before addition did not influence clot formation but abolished completely the negative effects of wound blood on platelet aggregability tested with all agonists. Median adenosine diphosphate-induced platelet aggregation was 51 (25th and 75th percentiles 42-69) when 20% processed cardiotomy suction blood was added vs. 34 (24-52) U when 20% unprocessed blood was added, P < 0.001. The corresponding figures for arachidonic acid-, thrombin receptor activating peptide- and collagen-induced aggregation was 21 (17-51) vs. 13 (10-25) U, 112 (87-128) vs. 78 (65-103) U and 58 (50-73) vs. 33 (28-44) U, respectively, all P < 0.001).

CONCLUSION

The results suggest that cell saver processing before retransfusion mitigates the negative effects of wound blood on platelet function despite that cell saver processing reduces platelet count.

Effects of ex vivo platelet supplementation on platelet aggregability in blood samples from patients treated with acetylsalicylic acid, clopidogrel, or ticagrelor

BACKGROUND

Transfusion of platelet concentrate is often used to treat bleeding in patients on platelet inhibitors, but little is known about its efficacy between different inhibitors. We assessed the effect of ex vivo platelet supplementation on platelet aggregability in blood samples from patients treated with acetylsalicylic acid (ASA), clopidogrel, or ticagrelor.

METHODS

Platelet aggregability was investigated with multiple electrode aggregometry with adenosine diphosphate (ADP), arachidonic acid (to assess ASA-dependent aggregability), and thrombin receptor activating peptide-6 (TRAP) as activators in whole-blood samples from patients treated with ASA (n=10), ASA+clopidogrel (n=15), or ASA+ticagrelor (n=15), and from healthy controls (n=10). Aggregability was measured before and after supplementation of AB0-compatible fresh apheresis platelets (+46, +92, and +138×10(9) litre(-1)).

RESULTS

Both ASA-dependent and ADP-dependent aggregability improved in a dose-dependent fashion after platelet supplementation. ASA-dependent aggregability was completely restored in all patient groups, but there was only a small improvement in ADP-dependent aggregability in patients on dual antiplatelet therapy. There was less effect of platelet supplementation on ADP- and ASA-dependent aggregability in ticagrelor-treated patients than in clopidogrel-treated patients [3.9 (95% confidence interval 1.6-6.3) vs 9.0 (5.2-12.8) AU×min (P=0.021) and 48 (36-59) vs 69 (60-78) AU×min (P=0.004), respectively, at the highest platelet dose].

CONCLUSIONS

Platelet supplementation improved platelet aggregability independently of antiplatelet therapy. The effect on ADP-dependent platelet inhibition was limited however. Reduced effect of platelet transfusion is more likely within 2 h of drug intake in patients treated with ASA+ticagrelor compared with ASA+clopidogrel.