Different anticoagulation protocols needed for two ECMO profiles

Venoarterial and venovenous extracorporeal membrane oxygenation (ECMO) are different beasts requiring different anticoagulation strategies, according to new Australian research.

The HECTIC study, published in Scientific Reports, compared haemostatic and coagulation profiles of 17 VA ECMO and 22 VV ECMO patients at the Royal Prince Alfred Hospital, Sydney,  between 2017 and 2019.

The study described a pattern of consumptive coagulopathy in VA patients characterised by elevated D-dimers, bilirubin and lactate and prolonged prothrombin time and lower fibrinogen and platelet levels, decreased clot strength and platelet dysfunction.

Among the differences between VA and VV ECMO, VA patients received significantly lower daily heparin doses (8500 IU v 28,800 IU; p < 0.001) and fewer hours on heparin (14 hr v 24 hr; p < 0.001).

“There was no significant difference in the overall mean daily aPTT, however VA patients had significantly lower mean daily anti-FXa levels (0.06 IU/mL v 0.27 IU/mL; p < 0.017),” the study authors said.

“Median platelet count was lower in the VA group 97 mm3/L (IQR 71–146) versus 192 mm3/L (IQR 134–241); p < 0.001 and platelet counts declined throughout ECMO run.”

VA patients also had significantly lower indices of clot strength on Thromboelastography (TEG) Platelet Mapping compared to VV patients when measured by TEG and multiplate multi-platelet aggregometry.

There was no significant difference in days on any antiplatelets; (22% v 12%; p=0.069), nor number of patients who had any antiplatelet VV (13.6% v 23.5%; p = 0.677) but VA patients had significantly more days on dual antiplatelet therapy VA 14 (18% v 5%; p = 0.002).

Bleeding also occurred earlier in VA patients (0.30 v 4.30 days, p = 0.001).

“There was no difference in amount of blood product supplementation between VA and VV cohorts.”

The study authors said the substantial differences between VA and VV coagulation profiles was likely explained by different baseline patient characteristics and underlying pathologies requiring support.

For example: “VA patients with inherent cardiac dysfunction and periods of poor end-organ perfusion and liver dysfunction prior to, and during implementation of extracorporeal support may exhibit decreased coagulation factor production.”

“Substantial differences in the coagulation and haemostatic profile of VA and VV patients exist and the monitoring using traditional anticoagulation tests, in particular aPTT, is highly variable and the heparin required to suppress thrombin generation varied between ECMO modality,” they said.

They concluded that tailored anticoagulation protocols for and monitoring of VA and VV ECMO patients may be of benefit and called for RCTs of different protocols.

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