Why is it so important to diagnose platelet dysfunction?
MP: I would rather say that it is important to quantify platelet function, which may be considered as a continuous spectrum from severe platelet dysfunction to high platelet reactivity. Both ends of this spectrum are not desirable as may theoretically lead to bleeding complications in cases of severe platelet dysfunction and to thrombotic complications in cases of hyper-reactive platelets. The contemporary management of cardiac surgery patients requires a personalised approach. In that regard, the use of platelet function testing certainly helps to guide antiplatelet therapy management and assumable optimise patient outcomes by adjusting antiplatelet therapy management according to platelet function test results. The same holds for perioperative hemostatic management where we may direct our hemostatic approach according to the platelet function testing results.
Since when have you been using the ROTEM® platelet? What are your experiences until now?
MP: We introduced ROTEM® platelet at UHC Zagreb – Department of Cardiac Surgery in September 2014. So far, we have a good experience. Our POC lab staff is experienced in performing POC testing of hemostasis and the implementation of ROTEM® platelet was smooth with short time needed to learn how to use it. We found it to be user friendly. Results are available within minutes and are easy to interpret. At Department of Cardiac Surgery we usually perform both rotational thromboelastometry and impedance aggregometry at the same time. Since the ROTEM® platelet module is attached to the ROTEM® delta, we may run both thromboelastometry and impedance aggregometry at the same time and have a comprehensive insight into hemostatic properties available on the single screen within a short amount of time.
In which clinical settings is the ROTEM® platelet particularly used in your hospital?
MP: We use ROTEM® platelet module in two clinical settings:
Firstly, we use ROTEM® platelet for perioperative hemostatic management. Here we have, at our Department, some valuable research experience that yielded valuable results published in highly a competitive peer review Journal (Anaesthesia 2016, 71, 636–647). By using ROTEM® platelet, we defined cut-off values that delineate excessive bleeding tendency. These cut-off values were associated with a high negative predictive value which is very important for our practice. For instance, if ROTEM® platelet quantifies platelet function to be above the predefined cut-off value, we have very high negative predictive values (chances that patient will not bleed excessively due to platelet dysfunction). This is very important to us as we may direct our hemostatic management towards surgical measures in cases where we have diffuse bleeding but the platelet function seems to be sufficient (above the cut-off value).
Secondly, we use ROTEM® platelet to tailor post-operative antiplatelet therapy type and dose. Herein, we have a very limited experience since this approach is in early beginning. However, considering our previous research based on impedance aggregometry, we may say that it might be very important to identify patients who have high residual platelet reactivity while taking antiplatelet drugs. By identifying such patients, we may be able to adjust the drug dosage and even add some other antiplatelet drugs to overcome platelet hyper-reactivity, which may occur in early post-operative period. Such a personalised approach could optimise patient outcomes; however further research is needed to evaluate this hypothesis.
What are the advantages of platelet function testing in the POC area with ROTEM® platelet compared to laboratory tests?
There are numerous advantages of using ROTEM® platelet relative to, let’s say, conventional laboratory tests. ROTEM® platelet assesses platelet function in whole blood, therefore in a physiologic environment. Secondly, the turnaround time, time from sampling blood to obtaining results is significantly shorter in POC setting relative to conventional laboratory testing. This may be considered as the most important advantage, in particular in cardiac surgery patients where dynamic circumstances prompt timely reactions. It is very important to get the platelet function results timely so we may adjust our hemostatic management accordingly.
Why is the ARATEM test an important addition to the first ROTEM® platelet tests ADPTEM and TRAPTEM?
The ARATEM test is a very important assay in addition to ADPTEM and TRAPTEM assays. From my clinical and research experience, I think that the role of Aspirin® is sometimes underestimated in the process of bleeding risk assessment. Our recent results (Anaesthesia 2016, 71, 636–647) have shown that numbers of assays below the cut-off value reflect the amount of packed red blood cells transfused as well as the frequency of both fresh frozen plasma and platelets concentrate transfusions. Based on these results, I would definitively suggest the use of all three ROTEM® platelet assays. In our recent study, by using ROTEM® platelet assays we defined the cut-off values that delineate bleeding tendency. The measurements were performed before surgery and during the surgery (after aortic declamping and after protamine administration). ARATEM test results above the cut-off were found to have high negative predictive values (94% and 95%). This is very important as may rule out platelet dysfunction as a cause of bleeding. Notably, pre-operative testing revealed a negative predictive value of 94%. Thus, ARATEM test is definitively a useful assay and theoretically could help in tailoring aspirin dosage and pre-operative discontinuation management. The same could be true for post-operative platelet function testing and we may assume that identification of Aspirin® resistant patients in early post-operative period could be useful, as could direct antiplatelet type and dose management. However, we need a large cohort studies to evaluate this approach in post-operative period.
When and in which combination with the other ROTEM® platelet tests would you use ara-tem®?
It sounds reasonable to use ARATEM test for patients that were exposed to Aspirin®. Since all CABG patients at our department are exposed to Aspirin® pre-operatively up to the day of surgery, I would prefer to use ARATEM test for every CABG patient and every other patient exposed to Aspirin®. When considering bleeding risk assessment, it makes sense to use all three assays. Our results indicate that number of assays below the cut-off actually reflects transfusion requirements, so I would definitively suggest to use all three ROTEM® platelet assays.
For post-operative antiplatelet therapy effecting quantification, I would suggest the same. It makes sense to use drug specific assays to quantify the antiplatelet therapy effects. In absence of antiplatelet therapy, trap-tem® may represent natural platelet reactivity and even use of both ARATEM and ADPTEM tests may be useful as may provide baseline values relative to, which we would be able to compare the test results after antiplatelet drug initiation and to quantify platelet inhibitory response.