1.2% Hydrogen gas inhalation protects the endothelial glycocalyx during hemorrhagic shock: a prospective laboratory study in rats

Purpose: Hydrogen gas (H2) inhalation improved the survival rate of hemorrhagic shock. However, its mechanisms are unknown. We hypothesized that H2 protected the endothelial glycocalyx during hemorrhagic shock and prolonged survival time.Methods: 83 Sprague–Dawley rats were anesthetized with isoflurane. The animals were randomly assigned to 5 groups: room air with no shock, 1.2% H2 with no shock, room air with shock (Control-S), 1.2% H2 with shock (H2 1.2%-S), and 3.0% H2 with shock (H2 3.0%-S). Shock groups were bled to a mean arterial pressure of 30 to 35 mmHg and held for 60 min, then resuscitated with normal saline at 4-fold the amount of the shed blood volume.Results: The syndecan-1 level was significantly lower in the H2 1.2%-S [8.3 ± 6.6 ng/ml; P=0.01; 95% confidence interval (CI), 3.2–35.8] than in the Control-S (27.9 ± 17.0 ng/ml). The endothelial glycocalyx was significantly thicker in the H2 1.2%-S (0.15 ± 0.02 μm; P=0.007; 95% CI, 0.02–0.2) than in the Control-S (0.06 ± 0.02 μm). The survival time was longer in the H2 1.2%-S (327 ± 67 min, P=0.0160) than in the Control-S (246 ± 69 min). The hemoglobin level was significantly lower in the H2 1.2%-S (9.4 ± 0.5 g/dl; P=0.0034; 95% CI, 0.6–2.9) than in the Control-S (11.1 ± 0.8 g/dl). However, the H2 3.0%-S was not significant.Conclusions: Inhalation of 1.2% H2 gas protected the endothelial glycocalyx and prolonged survival time during hemorrhagic shock. Therapeutic efficacy might vary depending on the concentration.