Effect of low-dose endotoxin on pulmonary vascular permeability following acute hemorrhagic shock

The purpose of the current study was to determine the effect of low-dose Escherichia coli lipopolysaccharide (LPS) on pulmonary vascular permeability when administered after hemorrhagic shock (40% of baseline cardiac output) followed by resuscitation. Animals were monitored for 3-4 h after LPS infusion. Thirty minutes prior to termination of the experiment, 3 mCi of 125I-human serum albumin was injected intravenously to calculate a permeability index from the left lung lavage and plasma 125I ratios. The two control groups were (1) shock only (no LPS, n = 4), and (2) LPS only (no shock, n = 8). The permeability index for the shock-only group was 0.0015 +/- 0.0007 (mean +/- SE) and that for the LPS-only group was 0.0035 +/- 0.0014. The permeability index for the experimental group (shock followed by LPS, n = 10) was 0.0071 +/- 0.0030 (p > 0.05). Similarly, there was no difference in the wet-to-dry ratios between the three groups. The shock+LPS group required more intravenous fluids to maintain mean arterial blood pressure at control values than the LPS-only group (p < 0.003). We conclude that hemorrhagic shock and resuscitation do not lead to an acute increased permeability of the lung when it is subsequently challenged by a low dose of bacterial LPS.