Unilateral acid aspiration augments the effects of ventilator lung injury in the contralateral lung.

BACKGROUND: Mechanical ventilation is necessary during acute respiratory distress syndrome, but it promotes lung injury because of the excessive stretch applied to the aerated parenchyma. The authors' hypothesis was that after a regional lung injury, the noxious effect of mechanical ventilation on the remaining aerated parenchyma would be more pronounced. METHODS: Mice, instilled with hydrochloric acid (HCl) in the right lung, was assigned to one of the following groups: mechanical ventilation with tidal volumes (VT) 25 ml/kg (HCl-VILI25, n = 12), or VT 15 ml/kg (HCl-VILI15, n = 9), or spontaneous breathing (HCl-SB, n = 14). Healthy mice were ventilated with VT 25 ml/kg (VILI25, n = 11). Arterial oxygenation, lung compliance, bronchoalveolar lavage inflammatory cells, albumin, and cytokines concentration were measured. RESULTS: After 7 h, oxygenation and lung compliance resulted lower in HCl-VILI25 than in VILI25 (P < 0.05, 210 ± 54 vs. 479 ± 83 mmHg, and 32 ± 3.5 vs. 45 ± 4.1 µl/cm H2O, mean ± SD, respectively). After right lung injury, the left lung of HCl-VILI25 group received a greater fraction of the VT than the VILI25 group, despite an identical global VT. The number of total and polymorphonuclear cells in bronchoalveolar lavage resulted significantly higher in HCl-VILI25, compared with the other groups, in not only the right lung, but also in the left lung. The albumin content in the left lung resulted higher in HCl-VILI25 than in VILI25 (224 ± 85 vs. 33 ± 6 µg/ml; P < 0.05). Cytokines levels did not differ between groups. CONCLUSION: Aggressive mechanical ventilation aggravates the preexisting lung injury, which is noxious for the contralateral, not previously injured lung, possibly because of a regional redistribution of VT.

Prevalence of endotoxemia after surgery and its association with ICU length of stay.

INTRODUCTION: The aim of this observational study was to investigate the prevalence of endotoxemia after surgery and its association with ICU length of stay. METHODS: 102 patients admitted to a university ICU after surgery were recruited. Within four hours of admission, functional data were collected and APACHE II severity score calculated. Arterial blood samples were taken and endotoxemia was measured by chemiluminescence (Endotoxin Activity (EA)). Patients were stratified according to their endotoxin levels (low, intermediate and high) and according to their surgical procedures. Differences between endotoxin levels were assessed by ANOVA, accepting P < 0.05 as significant. Data are expressed as mean +/- SD. RESULTS: EA levels were low in 68 (66%) patients, intermediate in 17 (17%) and high in 17 (17%). Age (61 +/- 17 years) and APACHE II score 8.3 +/- 3.7 (P = 0.542) were not significantly different in the three EA groups. Functional parameters on admission were similar between EA groups: white blood cells 11093 +/- 4605 cells/mm3 (P = 0.385), heart rate 76 +/- 16 bpm (P = 0.898), mean arterial pressure 88.8 +/- 13.6 mmHg (P = 0.576), lactate 1.18 +/- 0.77 mmol/L (P = 0.370), PaO2/FiO2 383 +/- 109 mmHg (P = 0.474). Patients with high levels of EA were characterized by longer length of stay in the ICU: 1.9 +/- 3.0 days in the low EA group, 1.8 +/- 1.4 days in intermediate and 5.2 +/- 7.8 days in high group (P = 0.038). CONCLUSIONS: 17% of our patients were characterized by high levels of endotoxemia as assessed by EA assay, despite their low level of complexity on admission. High levels of endotoxin were associated with a longer ICU length of stay.