The role of gastric small particles in the pathogentsis of aspiration lung injury

Objective The purpose of this study was to determine the role of aspiration of HCI and/ or gastric small particles in the pathogenesis of aspiration lung injury. Methods Thirty-two New Zealand male rabbits weighting 2.0-2.5kg were anesthetized with diazepam and ketamine. The animals were randomly divided into four groups of 8 each: in group A normal saline ( NS, pH = 5.3) was instilled into the lungs; in group B HCI (pH= 1.25); in group C gastric small particles in NS was instilled into the lungs and in group D gastric small particles in HCI was instilled. Gastric small particles were prepared according to the methods of Davidson BA , et al. The volume of fluid instilled into the lungs was 1.2ml· kg-1 in the four groups. Blood samples were taken at 0,1,2,3,4,5 and 6 h after aspiration for determination of plasma IL-8 level. PaO2 was measured before and 1, 3, 6, h after aspiration. The animals were killed 6 h after aspiration. The wet/dry weight ratio of left upper lobe and the levels of total protein and IL-8 and polymorphonuclear(PMN) counts of bronchoalveolar lavage fluid (BALF) from right lung were measured. Results 1. PaO2 decreased dramatically in group B, C and D at 1 h after aspiration, especially in group B and D. PaO2 returned to normal level at 6h after aspiration in group C, but remained low in group B and D. 2. PMN counts and levels of total protein and IL-8 of BALF and W/D ratio were significantly higher in group B, C and D than those in group A especially in group C and D. 3. There was no significant change in plasma IL-8 level after aspiration in group A and B. Plasma IL-8 level began to increase significantly at 3 h after aspiration in group C and at 4 h in group D (P 0.05) . Conclusion Aspiration of gastric small particles can cause lung injury different from that caused by HCI and IL-8 may play a role in that difference.