Sildenafil in endotoxin-induced pulmonary hypertension: an experimental study

Abstract Background Sepsis and septic shock still represent great challenges in critical care medicine. Sildenafil has been largely used in the treatment of pulmonary arterial hypertension, but its effects in sepsis are unknown. The aim of this study was to investigate the hypothesis that sildenafil can attenuate endotoxin-induced pulmonary hypertension in a porcine model of endotoxemia. Methods Twenty pigs were randomly assigned to Control group (n = 10), which received saline solution; or to Sildenafil group (n = 10), which received sildenafil orally (100 mg). After 30 minutes, both groups were submitted to endotoxemia with intravenous bacterial lipopolysaccharide endotoxin (LPS) infusion (4 µg.kg-1.h-1) for 180 minutes. We evaluated hemodynamic and oxygenation functions, and also lung histology and plasma cytokine (TNFα, IL-1β, IL6, and IL10) and troponin I response. Results Significant hemodynamic alterations were observed after 30 minutes of LPS continuous infusion, mainly in pulmonary arterial pressure (from Baseline 19 ± 2 mmHg to LPS30 52 ± 4 mmHg, p< 0.05). There was also a significant decrease in PaO2/FiO2 (from Baseline 411 ± 29 to LPS180 334 ± 49, p< 0.05). Pulmonary arterial pressure was significantly lower in the Sildenafil group (35 ± 4 mmHg at LPS30, p< 0.05). The Sildenafil group also presented lower values of systemic arterial pressure. Sildenafil maintained oxygenation with higher PaO2/FiO2 and lower oxygen extraction rate than Control group but had no effect on intrapulmonary shunt. All cytokines and troponin increased after LPS infusion in both groups similarly. Conclusion Sildenafil attenuated endotoxin-induced pulmonary hypertension preserving the correct heart function without improving lung lesions or inflammation.

Nebulization of Vancomycin Provides Higher Lung Tissue Concentrations than Intravenous Administration in Ventilated Female Piglets with Healthy Lungs.

BACKGROUND: Intravenous vancomycin is used to treat ventilator-associated pneumonia caused by methicillin-resistant Staphylococcus aureus, but achieves high rates of failure. Vancomycin nebulization may be efficient to provide high vancomycin lung tissue concentrations. The aim of this study was to compare lung tissue and serum concentrations of vancomycin administered intravenously and by aerosol in mechanically ventilated and anesthetized healthy piglets. METHODS: Twelve female piglets received a single intravenous dose of vancomycin (15 mg/kg) and were killed 1 (n = 6) or 12 h (n = 6) after the end of administration. Twelve piglets received a single nebulized dose of vancomycin (37.5 mg/kg) and were killed 1 (n = 6) or 12 h (n = 6) after the end of the aerosol administration. In each group, vancomycin lung tissue concentrations were assessed on postmortem lung specimens using high-performance liquid chromatography. Blood samples were collected for serum vancomycin concentration measurement 30 min and 1, 2, 4, 6, 8, and 12 h after the end of vancomycin administration. Pharmacokinetics was analyzed by nonlinear mixed effect modeling. RESULTS: One hour after vancomycin administration, lung tissue concentrations in the aerosol group were 13 times the concentrations in the intravenous group (median and interquartile range: 161 [71, 301] µg/g versus 12 [4, 42] µg/g; P < 0.0001). Twelve hours after vancomycin administration, lung tissue concentrations in the aerosol group were 63 (23, 119) µg/g and 0 (0, 19) µg/g in the intravenous group (P < 0.0001). A two-compartment weight-scaled allometric model with first-order absorption and elimination best fit serum pharmacokinetics after both routes of administration. Area under the time-concentration curve from 0 to 12 h was lower in the aerosol group in comparison to the intravenous group (56 [8, 70] mg · h · l vs. 121 [103, 149] mg · h · l, P = 0.002). Using a population model, vancomycin bioavailability was 13% (95% CI, 6 to 69; coefficient of variation = 85%) and absorption rate was slow (absorption half life = 0.3 h). CONCLUSIONS: Administration of vancomycin by nebulization resulted in higher lung tissue concentrations than the intravenous route.