Objectives To characterize an experimental model of pulmonary embolism by studying hemodynamics, lung mechanics and histopathologic derangements caused by pulmonary microembolism in pigs. To identify lung alterations after embolism that may be similar to those evidenced in pulmonary inflammatory conditions. Materials and methods Ten Large White pigs (weight 35-42 kg) were instrumented with arterial and pulmonary catheters, and pulmonary embolism was induced in five pigs by injection of polystyrene microspheres (diameter ~300 µM), in order to obtain a pulmonary mean arterial pressure of twice the baseline value. Five other animals injected with saline served as controls. Hemodynamic and respiratory data were collected and pressure x volume curves of the respiratory system were performed by a quasi-static low flow method. Animals were followed for 12 hours, and after death lung fragments were dissected and sent to pathology. Results Pulmonary embolism induced a significant reduction in stroke volume (71 ± 18 ml/min/bpm pre vs 36 ± 9 ml/min/bpm post, P < 0.05), an increase in pulmonary mean arterial pressure (27 ± 4 mmHg pre vs 39 ± 6 mmHg post, P < 0.05) and pulmonary vascular resistance (193 ± 122 mmHg/l/min pre vs 451 ± 149 mmHg/l/min post, P < 0.05). Respiratory dysfunction was evidenced by significant reductions in the PaO 2 /FiO 2 ratio (480 ± 50 pre vs 159 ± 55 post, P < 0.05), the dynamic lung compliance (27 ± 6 ml/cmH 2 O pre vs 19 ± 5 ml/cmH 2 O post, P < 0.05), the increase in dead space ventilation (20 ± 4 pre vs 47 ± 20 post, P < 0.05) and, the shift of pressure x volume curves to the right, with reduction in pulmonary hysteresis. Pathology depicted inflammatory neutrophil infiltrates, alveolar edema, collapse and hemorrhagic infarctions. Conclusion This model of embolism is associated with cardiovascular dysfunction, as well as respiratory injury characterized by a decrease in oxygenation, lung compliance and hysteresis. Pathology findings were similar to those verified in inflammatory pulmonary injury conditions. This model may be useful to study pathophysiology, as well as pharmacologic and ventilatory interventions useful to treat pulmonary embolism. P6 Hemodynamic and metabolic features of a porcine systemic low flow state model

Background The presence of hepatic portal venous gas (HPVG) has been associated with intestinal necrosis and is an indication for surgical intervention. But some cases can be treated conservatively. This study aimed to examine the factors associated with the need for surgical intervention and the development of intestinal necrosis in patients with HPVG.Methods This was a retrospective, multicenter and observational cohort study consisting of 166 patients who were diagnosed as having HPVG based on CT findings between April 2013 and March 2019. The patients were divided into two groups: surgery Required Group and Non-surgery Required Group. We reviewed medical records for clinical backgrounds, vital signs, laboratory data, CT findings, and compared the two groups using the Chi-square test and Student’s t-test with p-values < 0.05 indicating statistical significance.Results There were 72 patients in the Surgery Required Group and 94 in the Non-surgery Required Group. There were no statistically significant differences in age and sex between the two groups. Pulse rate (PR) ( p = 0.004), C-reactive protein (CRP) ( p = 0.012), lactate dehydrogenase (LDH) ( p = 0.006) and abnormality of the white blood cell count (WBC) ( p = 0.012) in the Surgery Required Group were significantly higher than those in the Non-surgery Required Group. The diameter of the superior mesenteric artery (SMA) and vein (SMV), and ratio of SMV/SMA were measured but no statistically significant difference was observed. Band-like pneumatosis ( p < 0.001) and ring like pneumatosis( p < 0.001) were observed with a significantly higher frequency in the Surgery Required Group, but no significant difference was observed in bubble-like pneumatosis. Intrahepatic HPVG was significantly more frequent in the Non-surgery Required Group than surgery Required Group ( p < 0.001), and extrahepatic HPVG ( p < 0.001) was the opposite result. There was no significant difference of HPVG distribution in lobes.Conclusions PR, CRP, LDH, abnormality of WBC, band-like pneumatosis, ring-like pneumatosis, and extrahepatic HPVG are the factors associated with an indication for surgery indication and intestinal necrosis in patients with HPVG.