Effect of recurrent endotoxemia on hemodynamics, lung function and neutrophil activation in sheep

The aim of the study was to find out in which way lung permeability and polymorphonuclear leukocyte (PMNL) functions are modulated under recurrent endotoxin challenge, as it might occur in clinical septic patients. In a sheep model with chronic lung lymph fistula, performing bronchoalveolar lavage (BAL), we investigated the relationship between PMNL function and endothelial as well as epithelial damage in the lung in a sepsis syndrome, using a protocol of recurrent endotoxemia induced by 1 microgram/kg body weight Escherichia coli endotoxin treatment every 12 h over a 5-day period. Pulmonary response showed constantly increased pulmonary arterial pressure at mean values of 24-30 mm Hg. Also, lymph flow did not return to baseline, but remained on a level of 6-9 ml/30 min, after an increase to 12-15 ml/30 min following each endotoxin injection. In contrast, a lower increase in protein clearance was noted upon subsequent endotoxin administration. After initial values of 7-8 ml/30 min following the first endotoxin injection, almost baseline values were measured on the 5th day (3-4 ml/30 min). In systemic hemodynamics, we noted a decrease in cardiac output to 3.0 l/min after the first endotoxin injection, followed by a significant increase to 7 l/min under subsequent endotoxin administration. In PMNL function, we observed an attenuation of the acute response of the decrease in PMNL count, in vitro chemiluminescence response and plasma beta-N-acetylglucosaminidase level. The plasma urea concentration revealed a transient reduction in kidney function. In the epithelial lining fluid (ELF) of the alveoli, total cell count did not change significantly, but the fraction of PMNL increased from 2 to 20% during the 5 days. The ELF/plasma ratios of albumin and total protein did not change significantly. In conclusion, recurrent endotoxemia in a sheep model can produce a hyperdynamic state like in a sepsis syndrome which is further characterized by an initial leakage of the endothelial barrier, only minor affection of the epithelial barrier and by an exhaustion of PMNL function.