Effects of hypertonic saline on a pig model of acute lung injury induced by hydrochloric acid instillation

Introduction

Controversy exists over the possible beneficial effects of hypertonic saline (HS) in pulmonary inflammatory response, particularly in neutrophil immunomodulation [1, 2]. This study was designed to investigate possible benefits of HS in the treatment of pigs submitted to experimental acute lung injury.

Methods

Twelve anesthetized, tracheotomized pigs (25 to 30 kg) were mechanically ventilated by pressure, adjusted to 8 ml/kg tidal volume, with FiO₂ 50%, and submitted to intratracheal instillation of 4 ml/kg hydrochloric acid (HCl) 0.1 N. They were then randomized to ALI group (n = 7) or ALI + HS group (n = 5), where animals of the latter group received 4 ml/kg intravenous hypertonic saline, 15 minutes after injury. Hemodynamic parameters, pulmonary compliance (C_stat), peak pressure (P_peak), plateau pressure (P_plat) and tidal volume (V_t) were analyzed at baseline (TBL), 15 minutes after HCl instillation (TALI) and hourly thereafter for 4 hours (T0 to T3). Bronchoalveolar lavage was performed at the end of the observation period for flow cytometry analysis of neutrophil burst activity. Postmortem histopathology of the right diaphragmatic lung was also performed in all animals.

Results

After TALI, animals of both groups presented significant increases in P_peak and P_plat, and a decrease in C_stat, at all time points, when compared with TBL. V_t was preserved in both groups over time. There were significant differences between groups ALI and ALI + HS, respectively, in: central venous pressure (T0, T1 and T2), pulmonary artery occlusion pressure (T1 and T2) and pulmonary vascular resistance index (TALI). In the ALI group, significant differences related to TBL were found in mean arterial pressure (T1), mean pulmonary artery pressure (TALI, T0, T1, T2 and T3) and pulmonary vascular resistance index (TALI, T0, T3). In the ALI + HS group, there were significant differences related to TBL in mean arterial pressure (T0, T1, T2), mean pulmonary artery pressure (TALI, T0, T1, T2, T3), cardiac index (T0, T1, T2) and pulmonary vascular resistance index (T1, T2, T3). No differences were found between groups regarding histopathology and flow cytometry analyses.

Conclusions

HS produced no significant benefit in the studied parameters regarding the lungs, in the proposed model of ALI.