Background and objective: Pulmonary aspiration of gastric acid is a serious complication during anaesthesia and may cause aspiration pneumonitis and adult respiratory distress syndrome. The development of pulmonary hypertension may aggravate the initial course of the aspiration pneumonitis. The authors hypothesized that acid aspiration induces an acute increase in right ventricular pressure in the rat heart. Additionally, it was hypothesized as a secondary study that endothelin levels would be increased in this rat model.
Methods: Male Sprague Dawley rats, anaesthetized with sevoflurane, underwent tracheostomy, and catheters were inserted into the carotid and right ventricle. Lung injury was induced by instillation of 0.4 ml kg(-1) 0.1 mol l(-1) HCl; a control group received the same volume of 0.9% NaCl. Rats were then ventilated for 6 hours. p(a)O2, mean arterial blood pressures and right ventricular systolic pressures were documented every 30 minutes, and arterial blood gases were measured at baseline, 30, 90, 180, 270 and 360 min. Wet/dry ratio was performed and additionally endothelin-1 levels were examined before and 180 and 360 min after aspiration.
Results: p(a)O2 values were lower, whereas right ventricular systolic pressures were significantly higher in the HCl group. Mortality rate was 50% after HCl aspiration, whereas 100% of the rats survived NaCl aspiration. Wet/dry ratio and endothelin-1 levels showed a significant increase after 180 and 360 min of HCl aspiration.
Conclusion: Acid aspiration induces a significant increase in right ventricular systolic pressure and endothelin levels, and causes metabolic acidosis in this animal model.