Effects of sildenafil in experimental model of endotoxemia in pigs

INTRODUCTION: Despite all efforts, mortality rates in septic shock are still high, and among the various complications pulmonary hypertension is considered a poor prognostic factor. Sildenafil is a drug with pulmonary arterial vasodilator effect, acts through inhibition of phosphodiesterase V that increases GMPc promoting the vasodilator effect. OBJECTIVE: Evaluate if sildenafil attenuates hemodynamic changes caused by septic shock, as well as ventilation and oxygenation parameters in an experimental model of endotoxemia in pigs. METHODS: Twenty pigs in which endotoxemia was induced through intravenous LPS infusion (4µg/kg/h) were randomly assigned to Control group (CTL, n = 10) – which received saline solution previous the endotoxemia; or to Sildenafil group (SIL, n = 10) – which received sildenafil orally (100 mg) previous the endotoxemia. Hemodynamic, ventilation and oxygenation were evaluated from at baseline up to 180 minutes of LPS infusion. The inflammatory and myocardial damage effects were also evaluated. Lung tissue was collected for histological analysis. Parametric data were compared using two-way repeated measures ANOVA, followed by Tukey test when necessary, while for non-parametric data the Mann-Whitney test was used. RESULTS: Endotoxemia induced pulmonary hypertension with an increase in pulmonary arterial pressure and pulmonary vascular resistance index and also a decrease in PaO2/FiO2. Pulmonary and systemic arterial pressures were significantly lower in the Sildenafil group, wherein the PAPM maximum values observed at 30 minutes of LPS infusion were 35 and 52 mmHg in the sildenafil and control groups, respectively. Sildenafil maintained oxygenation with superior PaO2/FiO2 and higher SvO2, but had no effect on intrapulmonary shunt. All cytokines and troponin increased after LPS infusion and there was no significant intergroup difference. Sildenafil did not attenuate the histologic alterations from endotoxemic shock. CONCLUSION: Sildenafil attenuated pulmonary hypertension induced by endotoxemia, but decreased systemic blood pressure. Sildenafil maintained oxygenation without effecting shunt fractioning. There was no effect in lung injuries, cytokines and troponin.