Hemorheological optimization via isovolemic hemodilution in COVID-19 ARDS under chronic environmental hypoxia: A...

Chronic environmental hypoxia induces compensatory secondary erythrocytosis and elevated whole-blood viscosity, which may aggravate microvascular thromboinflammation in severe COVID-19 acute respiratory distress syndrome (ARDS). We evaluated the feasibility, safety, and exploratory outcomes of isovolemic hemodilution (IVHD) in high-altitude COVID-19 ARDS.

Retrospective cohort study of 30 consecutive adult lifelong high-altitude residents (elevation 3,640 m) admitted to the ICU with severe COVID-19 ARDS on invasive mechanical ventilation. Seven patients underwent clinician-selected IVHD (controlled phlebotomy of 0.5-2.0 L with isovolemic crystalloid replacement over 6-12 hours), while 23 received conventional ICU management.

Baseline illness severity scores (APACHE II, PaO₂) were comparable. Admission hematocrit was 59% (55-66) in the IVHD group versus 52% (36-68) in conventional controls (p=0.065). IVHD achieved rapid hemorheological decompression at 72 hours, reducing hematocrit to 38% (32-46, p=0.015) and hemoglobin to 11 g/dL (10-15, p=0.015). ICU survival was 71.4% (5/7) in the IVHD cohort versus 8.7% (2/23) in conventional controls (Fisher's exact p=0.003; crude odds ratio 26.25, 95% CI 2.9-234.3). No procedural adverse events occurred.

Rapid hemorheological optimization via IVHD was feasible, safe, and associated with an exploratory survival signal in high-altitude COVID-19 ARDS, providing a physiological rationale for prospective randomized trials.