[Experimental study on liver injury induced by intraperitoneal hypertension under mechanical ventilation]

To investigate the effects of mechanical ventilation on liver cytological and enzymatic indexes in abdominal compartment syndrome (ACS) by establishing a porcine model of abdominal hypertension.

Six healthy adult pigs were selected. After general anesthesia, they were intubated and given ventilator assisted breathing. The breathing mode was volume controlled ventilation (VCV), tidal volume (VT) 10 mL/kg, respiratory rate (RR) 16 time/min, fraction of inspiration oxygen (FiO₂) 0.40, positive end expiratory pressure (PEEP) 5 cmH₂O (1 cmH₂O = 0.098 kPa). Intraperitoneal pressure was simulated by injecting normal saline into the pressurized water sac, and the pressure was measured once every 50 mL of normal saline. 5 mL of blood was collected from ear vein every 1 hour before and 4 hours after operation for liver enzyme examination. 4 hours after operation, the animals were sacrificed and the liver was collected to observe pathological changes under light microscope.

Six pigs were successfully modeled. The RR and heart rate (HR) of the animals remained stable. No one suffered from barotrauma or death during the experiment. There was a positive correlation between abdominal pressure and abdominal volume increase (r² = 0.839 6, P = 0.003 7). There were no significant differences in the levels of alanine aminotransferase (ALT), alkaline phosphatase (ALP) and cholinesterase (ChE) preoperative and 1, 2, 3, 4 hours after operation. As time went on, aspartate aminotransferase (AST) increased first and then decreased, and increased significantly at 1 hour after operation (U/L: 46.84±8.57 vs. 23.35±5.14, P < 0.05), and decreased significantly 2, 3, 4 hours after operation (U/L: 16.33±3.58, 14.54±3.35, 15.44±3.21 vs. 23.35±5.14, all P < 0.05). The level of γ-glutamyltranspeptidase (GGT) increased and then decreased, but there was significant difference only at 1 hour after operation, compared with baseline (U/L: 101.20±17.79 vs. 51.34±9.13, P < 0.05). Under the light microscope, there were dilation and congestion of interlobular vein, dilation of interlobular bile duct, hyperplasia of small bile duct, hyperplasia of connective tissue in portal area, infiltration of a large number of acute and chronic inflammatory cells, swelling of hepatocytes, light staining of cytoplasm, balloon like transformation of some cells, and punctate necrosis.

Abdominal hypertension under mechanical ventilation can cause obvious enzyme changes and cytological damage of liver.