Internal Medicine Resident University of Houston/ HCA Houston Clear Lake League City, Texas, United States
Disclosure(s):
Yves Najm Mrad, MD, MPH, MSAI: No financial relationships to disclose
Background: Hemolysis is a frequent and clinically significant complication of temporary mechanical circulatory support (MCS), associated with acute kidney injury, transfusion requirements, and mortality. While hemolysis is commonly reported, the hemodynamic determinants remain poorly defined. We performed a systematic review and meta-analysis to identify hemodynamic predictors of hemolysis during temporary MCS.
Methods: We systematically searched PubMed, Embase, Web of Science, and the Cochrane Library from inception through December 2025 for studies evaluating hemolysis in adult patients supported with temporary MCS, including Impella devices, venoarterial extracorporeal membrane oxygenation (VA-ECMO), and TandemHeart. Eligible studies reported quantitative associations between hemodynamic variables (pump flow, device size, pressure gradients, or shear surrogates) and laboratory-defined or clinically significant hemolysis. Random-effects models were used to pool odds ratios (ORs) with 95% confidence intervals (CIs). Heterogeneity was assessed using the I² statistic, and sensitivity analyses were performed.
Outcome: Eleven studies encompassing 1,392 patients were included. Higher pump flow rates were significantly associated with hemolysis, with flows ≥3.5–4.0 L/min conferring increased risk (pooled OR 2.48, 95% CI 1.40–4.38; p=0.002). Each 1 L/min increase in flow was associated with a 30% increase in hemolysis risk (OR 1.30 per L/min, 95% CI 1.10–1.53). Smaller device or cannula size was a strong predictor of hemolysis; use of smaller microaxial pumps compared with larger devices was associated with substantially higher hemolysis risk (OR 5.90, 95% CI 2.20–15.80; p< 0.001). Elevated circuit pressure gradients and suction events were also associated with increased hemolysis (OR 2.01, 95% CI 1.01–3.99). Mean arterial pressure was not independently associated with hemolysis after adjustment for flow and device characteristics. Between-study heterogeneity was moderate (I²=55%), but effect direction was consistent across MCS platforms.
Conclusion: Across temporary MCS devices, hemolysis is driven by hemodynamic conditions, including elevated pump flow and smaller device or cannula size. These findings support a physiology-based approach to hemolysis prevention, optimizing flow targets and device selection. Integration of hemodynamic thresholds into MCS management protocols may reduce hemolysis-related complications and improve outcomes.
