| PrefaceAspiration is one of the most serious causes of death during clini-cal anesthesia and the resuscitation of seriously ill patients. So, it has been one of the popular focuses of research in anesthetic field.The mortality after aspiration of gastric content is 3% - 70%. Recent data shows 5% . The lung damage differs according to the aspi-ration of different gastric content. It is very difficult to determine the morbidity after aspiration. In clinic, it includes a series of complex complications, for example; bronchiole spasm, mild hypoxia, pneu-monia and lung abscess. Among these complications, ARDS belongs to one of the most severe complications.In the past, scientists has been using animal model to observe di-rect effect on lung injury by injecting hydrochloric acid ( HC1) to whole lung of animals, but very few studies were found to study on ad-vance lung injury. In order to study advance lung injury, scientist used animal by injecting HC1 to one lung and observe the advance in-jury of contralateral lung, but no report has been found using single lung injection of Pepsin to observe contralateral advanced lung injury.This study has been designed to compare the contralateral lung injury by injecting HC1 and Pepsin to single lung of rabbits, and the patho-genesis was investigated by examining the changes in inflammatory mediators TXB2, 6K - PGF1a, in order to provide theoretical evidence for its treatment.Materials and Methods16 rabbits, weight between 3.0 - 4. 0 kg, were randomly divid-ed into two groups: Pepsin group ( n = 8 ) and HC1 group (n = 8 ).The preparing of aspiration model: The animals were anesthetized with intravenous ketamine and fixed on a table at supine position. A cuffed endotracheal tube I. I). 3.0 mm was intubated to the trachea and connected to ventilator for mechanical ventilation with respiratory frequency of 40 times/min, tidal volume (Vt) of 8ml/kg. The anes-thesia was maintained by inhaling Isoflurane, paralyzed by intravenous administering vecuronium 0. 4mg/kg. The right femoral artery was cannulated with 22 G arterial catheter and connected to a pressure me-ter to measure the arterial pressure and draw arterial blood sample. Then the endotracheal tube was inserted to right bronchi and the cuff was inflated for preventing air leakage. Through the endotracheal tube, an epidural catheter was inserted into right bronchi and pepsin 1. 5ml/kg or HC1 1. 5ml/kg, was instilled to right lung. During aspi-ration , the left lung of rabbit was ventilated with a high frequency jet ventilator (work pressure: 0.5 MPa, respiratory ratio: 1;1, frequen-cy 60 times/min). In both groups, before aspiration, one hour after aspiration and two hours after aspiration, the respiratory mechanic pa-rameters of right lung were measured and arterial blood 1 ml wasdrawn for blood gas analysis, next 3 ml for cytokine examination.Two hours after aspiration, animals were killed. The thoracic cavities were immediately opened and small pieces of lung tissue were extracted from each lobe to observe lung pathology changes.Result1. In both groups, the values of pH, Pa02 and PaC02 are in nor-mal range. In Pepsin group one rabbit died ten minutes after aspira-tion. In HC1 group, one rabbit died during tracheotomy due to hemor-rhage.2. Arterial blood gas: in both group, Pa02 and pH of animals significantly decreased, whereas PaC02 of animals significantly in-creased , but no significant difference was found between groups.3. Respiratory mechanic parameters; In two groups, airway pres-sure ( Ppeak) , airway pause pressure ( Ppause) increased significant-ly ( P < 0. 05 ) , Thoracic - Lungs compliance decreased significantly ( P < 0.05 ) . No significant difference was found between groups.4. Changes of TXB2 and 6 - K - PGFla: In both groups, TXB2 and 6 - K - PGF1a increased significantly and the TXB2 of pepsin group was significantly higher than HC1 group after aspiration.5. Pathologic observation; In both groups, healthy lungs are af-fected in dif...
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