This retrospective analysis in 73 patients compared consecutive platelet count on admission and during the total duration of the ECMO. It aimed to study the device-related platelet count disorders.
The most common technical complication of ECMO is clot formation.8 Clot formation in MOs can occur despite adequate anticoagulation that compromises gas transfer to the extent where MO exchange is necessary.9 Many studies and publications, both domestic and international, have detailed this phenomenon. Researchers hypothesize that it is the activation of platelets that subsequently may cause the deposition of fibrin, enhancing thrombus formation.
According to ELSO, thrombocytopenia is common in ECMO. This correlates with our findings. Circulating platelets adhere to plastic surfaces and undergo a release reaction that attracts other platelets.2
Removal of the MO resulted in a reduction of D-Dimer levels, delaying increases in fibrinogen concentration and platelet count over the next five days.7
Robinson et al. reported a mean decrease of 26% in the platelet count after the first 15 minutes of the initiation of ECMO, with an additional mean decrease of 16% by the end of one hour (p < 0.05). The resolution of platelet aggregation abnormalities and normalization of platelet count occurred 8 hours after the weaning of ECMO.10
This corresponds to our first result, regarding the significant mean decrease in the platelet count from the baseline platelet count found on day 2 after the initiation of ECMO (p<0.001), with an additional significant mean decrease on day 3 (p 0.001). Furthermore, we observed a significant decrease in average platelet count (p<0.001) between the first and second MO exchange in comparison with the baseline. Then a steady decrease in platelet count was witnessed after the third MO exchange. However, a resolution of platelet count occurred five days after the discontinuation of ECMO.
Using anticoagulation to avoid the formation of clots in the ECMO circuit is mandatory whereas it’s important to balance the patient’s risk of bleeding. Clots are very dark non-moving areas on the MO surfaces. Large clots on MO require the exchange to obtain the maximum benefit from this membrane. No intervention is necessary unless the white thrombi are greater than 5 mm or growing.2
Broi et al.7 resume the causes of system exchanges into acute (mechanical failure, acute clot formation) and elective system exchanges (progressive clot formation and worsening of gas transfer, suspected infection and device-related coagulation disorder).
This corroborates the findings of our study in which the incidence of MO exchange was due to the clot formation of MO, thrombocytopenia, transformation from VA-ECMO to VV-ECMO, failure of ECMO weaning, technical problems with the machine, and mechanical failure of the blood pump. No MOs were exchanged due to the suspicion of infection.
Dornia et al.,11 reported thrombotic clot formation in MO device after 8 days from the onset, and had an average duration of 5.9 ± 3.1 days.
In our experience, bleeding is the most common complication during ECMO because of systemic anticoagulation, thrombocytopenia, and thrombocytopathy. Furthermore, a platelet transfusion was ordered for a patient on ECMO if the platelet count falls below 100,000/µL to prevent generalized hemorrhage. Consequently, platelet transfusion carries risks as well as benefits. Infections due to bacteria or fungal are the most commonly reported complications of platelet transfusions.12
Blood products transfusion was routinely administered during ECMO. Particularly, MO exchange permitted a clear reduction in platelets and RBC transfusion, yet a less evident of FFP. We hypothesised that RBC and platelets are directly affected by the MO but the FFP need is dependent of the systemic inflammatory response induced by the pump itself.
Hemodynamic management can be particularly challenging. The management of bleeding begins with returning the coagulation status to normal as much as possible. Hemorrhagic complications can occur in up to 35% during ECMO by affecting the primary hemostasis.6
Adult ECMO patients with lower Hb require more daily RBC and FFP. According to Ang et al., on multivariate analysis, average daily transfusion of RBC increased with hemoglobin < 7·5 g/dl. An average daily platelet transfusion > 3 units was also associated with increased ECMO duration (p = 0·024).13
In our study, the average platelet count was 195.8 ± 84.3x109/L, with an average 0.5 ± 1.4 platelet transfusion associated with high mortality rate (p=0.02). Even with the average number of RBC transfusions at 3.4 ± 5.5, we found the same correlation (p=0.03).
Stallion et al. suggest maintaining a platelet count of greater than 200.000/µL while on ECMO, as it results in overall decreased bleeding complications without increasing morbidity or mortality.6
On the other hand, if the platelet count is less than 20,000 /µL spontaneous bleeding can occur. The usual practice is to transfuse platelets (adherence to the MO) to keep the count greater than 80,000 /µL. Even though the platelet count is over 80,000 /µL, platelet functions may be impaired.2
Future studies are needed to validate our results, particularly to investigate how ECMO survivors do in terms of cardio-pulmonary function, cognitive function, and quality of life.