Treatment with 24 h-delayed normo- and hyperbaric oxygenation in severe sepsis induced by cecal ligation and puncture in rats

Abstract

Background: Septic shock remains a leading cause of death worldwide. Hyperbaric oxygen treatment (HBO₂) has been shown to alter the inflammatory response during sepsis and to reduce mortality. A therapeutic window of HBO₂ treatment has been demonstrated experimentally, but optimal timing remains uncertain. We investigated the effects of 24 h delayed normobaric oxygen (NBO₂) and HBO₂ treatment on the endogenous production of the inflammatory markers interleukin (IL)-6, tumor necrosis factor (TNF)-α and IL-10, and on mortality in rats with cecal ligation and puncture (CLP) induced sepsis.

Method: Fifty-five male Sprague-Dawley rats underwent CLP and were randomized to the following groups: 1) HBO₂ 2.5 bar absolute pressure (p_abs); 2) NBO₂ 1.0 bar p_abs; 3) Control (no-treatment), and they were individually monitored for 72 h with intermittent blood sampling.

Results: IL-6, TNF-α, and IL-10 were increased 24 h after the procedure, and IL-6 was significantly higher in non-survivors than in survivors. The level of IL-10 was significantly higher at hour 48 in the HBO₂ group compared to control (p = 0.01), but this was not the case at other time points. No other significant differences in cytokine levels were found for any group comparisons. Delayed NBO₂ and HBO₂ treatment failed to change the mortality in the animals.

Conclusion: High levels of IL-6 in non-surviving animals with sepsis suggest that IL-6 is a potential biomarker. We found a significantly higher concentration of IL-10 in the HBO₂ group at hour 48 vs. control animals. However, 24 h-delayed treatment with HBO₂ did not change the levels of pro-inflammatory cytokines and survival, suggesting that earlier intervention may be required to obtain an anti-inflammatory effect.

Keywords: CLP; Cytokines; HBO2; Inflammation; Mortality; Sepsis.

Fig. 1

Experimental protocol showing interventions on a timeline. Intervention being either hyperbaric oxygen treatment, normobaric oxygen treatment or no intervention (control). CLP, cecal ligation and puncture. Blood = 1 ml of full blood withdrawn for analysis and substituted by 1 ml 0.9% NaCl

Fig. 2

Kaplan-Meier curves showing the percentage survival in HBO₂, NBO₂ and control group during 72 h. HBO₂, hyperbaric oxygen treatment; NBO₂, normobaric oxygen treatment. HBO₂ group compared to NBO₂ group p = 0.59. HBO₂ group compared to the control group p = 0.24. NBO₂ group compared to the control group p = 0.59. Groups are compared using log-rank test