| Objective: To establish an animal model of intra-abdominal hypertension(IAH) in rats to evaluate the effects of different levels of intra-abdominalpressure (IAP) and different duration on liver, to make preparations for furtherstudying the relationship between IAH and multiple organ dysfunction andprovide experimental evidence for clinical IAP monitoring.Methods: IAH was induced in rats by intraperitoneal injection of gaseousnitrogen. A disposable Venous Infusion Needle was inserted into the abdominalcavity through a lower left quadrant of the abdomen puncture for nitrogen gasinsufflation. The Disposable Venous Infusion Needle was connected to adisposable infusion catheter. This catheter was connected to a nitrogen gas bagand a50ml injector and a hematomanometer for continuous IAP monitoringthrough two three-way stop cocks. Forty–five male Sprague–Dawley rats wererandomly divided into control group (15rats) and model groups (30rats). Modelgroups rats were randomly divided into two groups (15rats in each group)according to different levels of IAP (IAP10mmHg and IAP20mmHg). The lasttwo groups were further randomly divided into three groups (5rats in eachgroup) according to different duration of time (1h，2h and4h), respectively. The control group rats were only anesthetized with a Disposable Venous InfusionNeedle inserted into the abdominal cavity for1h,2h and4h, without pressureapplication. The model groups volume of nitrogen gas changes were recordedand analyzed when the desired pressure was initially reached and unchanged for30seconds. Arterial blood samples were obtained via aortaventralis at the end ofthe experiments. Additionally, tissue specimens of right lobe of liver were takenfor histopathologic examinations.Results: The rat model is simple in design method, low-cost, steady,reliable and fewer side effects. And it overcomes shortcomings of previousexperimental animal model. In the model groups, the body weight of the animalsdid not differ between the two groups at baseline (IAP10mmHg group:311.73±35.18g vs. IAP20mmHg group:295.67±19.99g, t=1.538, P＞0.05). TheIAP20mmHg group nitrogen gas volume was significantly increased comparedwith the IAP10mmHg group (146.87±14.25ml vs.127.73±12.00ml, t=3.978,P＜0.001). Both the serum AST and ALT values were significantly higher in theIAP10mmHg4h group compared with the IAP10mmHg1h group (297.40±48.42U/L vs.169.40±47.69U/L, P<0.01;173.60±73.67U/L vs.74.00±22.57U/L, P<0.01) and the IAP10mmHg2h group (297.40±48.42U/L vs.223.40±61.78U/L, P<0.05;173.60±73.67U/L vs.103.60±40.44U/L, P＜0.05). But there were no significantly difference in the serum AST and ALTvalues between the IAP10mmHg1h group and the IAP10mmHg2h group.Both the IAP20mmHg4h group serum AST and ALT values were significantlyhigher compared with the IAP20mmHg1h group (398.80±83.35U/L vs.199.60±33.95U/L, P<0.01;237.20±74.40U/L vs.81.40±30.53U/L, P<0.01)as well as the IAP20mmHg2h group (398.80±83.35U/L vs.306.40±72.40U/L, P<0.05;237.20±74.40U/L vs.154.20±42.03U/L, P＜0.05). Both the IAP20mmHg2h group serum AST and ALT values were also higher than theIAP20mmHg1h group (P＜0.05). There were no significantly difference in theserum AST and ALT results among the IAP10mmHg1h group and the IAP20mmHg1h group and the control group with a Disposable Venous InfusionNeedle inserted into the abdominal cavity for1h. Both the IAP20mmHg2hgroup serum AST and ALT values were higher than the control group with aDisposable Venous Infusion Needle inserted into the abdominal cavity for2h(306.40±72.40U/L vs.158.00±33.92U/L, P＜0.01;154.20±42.03U/L vs.77.60±7.16U/L, P＜0.01) and the IAP10mmHg2h group (306.40±72.40U/Lvs.223.40±61.78U/L, P＜0.05;154.20±42.03U/L vs.103.60±40.44U/L, P＜0.05). Both the IAP20mmHg4h group serum AST and ALT values werehigher than the control group with a Disposable Venous Infusion Needle insertedinto the abdominal cavity for4h (398.80±83.35U/L vs.160.80±21.30U/L, P＜0.01;237.20±74.40U/L vs.75.20±18.43U/L, P＜0.01). The IAP20mmHg4h group serum AST value was significantly higher compared with the IAP10mmHg4h group (398.80±83.35U/L vs.297.40±48.42U/L, P＜0.05).However, there was no significantly difference in the serum ALT results amongthe IAP20mmHg4h group and the IAP10mmHg4h group (237.20±74.40U/Lvs.173.60±73.67U/L, P＞0.05). And both the IAP10mmHg4h group serumAST and ALT values were significantly higher compared with the control groupwith a Disposable Venous Infusion Needle inserted into the abdominal cavity for4h (297.40±48.42U/L vs.160.80±21.30U/L, P＜0.01;173.60±73.67U/L vs.75.20±18.43U/L, P＜0.05). Liver histopathological examination: Thehistopathologic study revealed parenchymal injury in liver. Histopathologicstudy of morphologic changes of the liver in the IAP10mmHg4h groupdemonstrated hepatocyte surrounding central vein slight swelling, occasional vacuolization, nucleus slight swelling, slight hepatic sinusoidal hyperemia anddilatation surrounding central vein. The IAP20mmHg1h group showed clear ofliver lobule, and hepatocyte slight swelling surrounding central vein, hepatocytedisorder, slight hepatic sinusoidal hyperemia. And it increased thereafter alongwith the prolongation of IAP. Occasional parenchymal spotty necrosis andinflammatory cells were observed in the hepatic sinusoid as well as the presenceof red blood cells in the IAP20mmHg4h group. And HE staining showeddisorganized hepatic lobules.Conclusion: This animal model of IAH in rats was established successfully.It is simple in design method and operation, low-cost, easily reproducible andfeasible. A big change in IAP will be aroused by a little bit change in theabdominal cavity volume, when the IAP reach to a certain degree. Elevated IAPcan induce marked liver injury in rats. And the liver injury may be positivecorrelated with the level of IAP and the duration of time. Hepatocytesurrounding central vein slight swelling was observed in the IAP10mmHg4hgroup. There may be slight liver injury with IAP of20mmHg for1hour. Andoccasional parenchymal spotty necrosis and inflammatory cells were observedin the hepatic sinusoid in the IAP20mmHg4h group. |
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