Comparison of the effects of continuous and intermittent portal triad occlusion (PTO) in rats

It has previously been shown that prolonged ischemia of the liver had a mortal course and a method of intermittent occlusion of the hepatic pedicle was defined in order to minimize the damage to the liver. The present experimental study aimed to compare the effects of continuous and intermittent occlusion of the hepatic pedicle on the liver by measuring serum lactate, serum MDA malondialdehyde and glutathione levels and by evaluating the histologic changes in the liver tissue.

Thirty male Wistar albino rats weighing 300 +/- 50 g were divided into three groups of ten animals. Group 1 underwent a sham operation. Animals in group 2 underwent continuous portal triad occlusion (PTO group) for 30 minutes following laparotomy. The remaining ten animals in group 3 underwent intermittent occlusion consisting of 10 minutes of occlusion followed by 10 minutes of reperfusion for a total period of 30 minutes of ischemia. Blood samples were collected at the 1st and 6th postoperative hour for analytical evaluation. After sacrificing the animals, liver samples were obtained for histologic evaluation.

The serum lactate levels were significantly higher in both portal triad occlusion groups than in the control at the 1st hour. While lactate levels also increased at the 6th hour in the continuous PTO group, it decreased to the level of control values in the intermittent PTO group. The difference between continuous and intermittent groups was also significant. Despite the unchanged malondialdehyde levels in the control group, malondialdehyde levels were significantly increased at the first and sixth hour in both PTO groups and the levels were also significantly higher than control values. Malondialdehyde levels of intermittent PTO groups at the first and sixth hour were both significantly lower than continue PTO groups. Whole blood glutathione levels were not changed in control groups with time, levels increased significantly in both PTO groups. Glutathione levels were higher than control values in both PTO groups at the first hour. While it turned to its basal value in intermittent PTO groups at the 6th hour, it was still significantly higher in the continuous PTO group. When both PTO groups were compared, glutathione levels were found to be significantly higher in the continuous group both at the first and sixth hour than in the intermittent PTO group. Histopathologic evaluation also showed that there was less damage in the intermittent PTO group than in the continuous PTO group.

Our results show that continuous portal triad occlusion resulted in significant oxidative stress and cell damage as confirmed by increased serum lactate and blood malondialdehyde levels. The blood glutathione levels are increased due to a greater requirement in response to increased oxidative stress induced by portal triad occlusion. It is also confirmed that intermittent portal triad occlusion is safer as it causes less oxidative stress and cell damage so that its use is strongly suggested whenever portal triad occlusion is required.