Background

We hypothesized that improvements in cellular immune function after hypertonic saline (HTS) resuscitation will alter the outcome of sepsis after hemorrhage.

Methods

To test this hypothesis, a two-hit model was used. Hemorrhage was induced in BALB/c mice by catheterizing the femoral artery and bleeding until a mean arterial pressure= 35 mm Hg was reached and maintained for 1 hour. Resuscitation was performed with HTS (NaCl 7.5%, 4 mL/kg) or lactated Ringer's (LR, twice the shed blood volume), plus the shed blood. Cecal ligation and puncture (CLP) was performed 24 hours after hemorrhage. Mortality was assessed for 72 hours, comparing HTS (n= 14) and LR (n= 13) resuscitation. Another set of animals (n= 10) in each group at each time point) were killed at 2 and 24 hours after blood collection. Liver and blood were cultured for the presence of bacteria, and lung and liver samples were scored on a scale from 0 (normal) to 4 (most severe) in a blind fashion by a pathologist.

Results

Mortality 72 hours after CLP was 14.3% in HTS and 76.9% in LR treated animals (p< 0.002). At 24 hours after CLP, 44% of HTS, but 77% of LR treated animals had> 1,000 colony forming units/mL of blood. Positive liver cultures (> 100,000 colony forming units/g) also showed the same trend (HTS= 30%, LR= 60%). Autopsies revealed a better containment of the infection (abscess formation) in the HTS group. At 2 hours, lung scores were 1.2+/-0.25 and 2.6+/-0.31 for HTS and LR, respectively (p< 0.002). At 24 hours, HTS treated animals showed marked improvement of lung injury, while the scores in the LR group remained high. A significant difference was also observed regarding liver injury. At 2 hours, scores were 0.4+/-0.22 and 2.3+/-0.16 for HTS and LR, respectively (p< 0.002). At 24 hours, HTS treated animals showed normal hepatic architecture, although mild injury was still observed in the LR group.

Conclusion

HTS resuscitation leads to increased survival after hemorrhage and CLP. Marked improvements were observed in lung and liver injury compared with isotonic resuscitation. The better containment of the infection observed with HTS resuscitation corresponds to a marked decreased in bacteremia. HTS resuscitation stands as an alternative resuscitation regimen with immunomodulatory potential.