Hemolysis and Nonhemorrhagic Stroke During Venoarterial Extracorporeal Membrane Oxygenation

Background: Hemolysis, even at low levels, activates platelets to create a prothrombotic state and is common during mechanical circulatory support. We examined the association of low-level hemolysis (LLH) and nonhemorrhagic stroke during venoarterial extracorporeal membrane oxygenation (VA ECMO) support. Methods: A single-center retrospective review of all adult patients placed on VA ECMO from January 2012 to September 2017 was conducted. To determine the association between LLH and nonhemorrhagic stroke, patients were categorized as those with and without LLH. LLH was defined by 48-hour plasma free hemoglobin (PFHb) of 11 to 50 mg/dL after VA ECMO implantation. Results: Of 201 patients who underwent VA ECMO placement, 150 (75%) met inclusion criteria and comprised the study population. They were 55 ± 14 years of age and 50 (33%) were women. Sixty-two (41%) patients had LLH. Patients with LLH had a higher likelihood of incident nonhemorrhagic stroke during VA ECMO support (20 [32%] versus 4 [5%]; adjusted hazard ratio [HR], 7.6; 95% confidence interval [CI], 2.2 to 25.9; p = 0.001). The severity of LLH was associated with an incrementally higher likelihood of a nonhemorrhagic stroke (PFHb 26 to 50 mg/dL: HR, 11.3; 95% CI, 3.6 to 35.1; p = 0.001; PFHb 11 to 25 mg/dL: HR, 4.4; 95% CI, 1.36 to 14.85; p = 0.014) in comparison with no LLH. Those with LLH had a 2-fold greater increase in mean platelet volume after VA ECMO placement (0.98 ± 1.1 fL versus 0.49 ± 0.96 fL; p = 0.03). Patients with a nonhemorrhagic stroke had a higher operative mortality (20 [83%] versus 57 [45%]; adjusted HR, 3.1; 95% CI, 1.8 to 5.3; p < 0.001). Conclusions: Hemolysis at low levels during VA ECMO support is associated with subsequent nonhemorrhagic stroke.