Abstract: Ten trials including 657 patients compared different methods of vascular occlusion. All trials were of high risk of bias. Only one or two trials were included under each comparison. There was no statistically significant differences in mortality, liver failure, or other morbidity between any of the comparisons. Hepatic vascular occlusion does not decrease the blood transfusion requirements. It decreases the cardiac output and increases the systemic vascular resistance. In the comparison between continuous portal triad clamping and intermittent portal triad clamping, four of the five liver failures occurred in patients with chronic liver diseases undergoing the liver resections using continuous portal triad clamping. In the comparison between selective inflow occlusion and portal triad clamping, all four patients with liver failure occurred in the selective inflow occlusion group. There was no difference in any of the other important outcomes in any of the comparisons. In elective liver resection, hepatic vascular occlusion cannot be recommended over portal triad clamping. Intermittent portal triad clamping seems to be better than continuous portal triad clamping at least in patients with chronic liver disease. There is no evidence to support selective inflow occlusion over portal triad clamping. The optimal method of intermittent portal triad clamping is not clear. There is no evidence for any difference between the ischaemic preconditioning followed by vascular occlusion and intermittent vascular occlusion for liver resection in patients with non-cirrhotic livers. Further randomised trials of low risk of bias are needed to determine the optimal technique of vascular occlusion.

Plain-language summary: Ten trials including 657 patients were included in this review. All were of high risk of bias (systematic error) and play of chance (random error). Only one or two trials were included under each comparison. There was no difference in mortality, liver failure, or post-operative complications between any of the comparisons. Hepatic vascular occlusion does not decrease the blood transfusion requirements. It decreases the cardiac output (amount of blood pumped by the heart in one second) and increases the systemic vascular resistance (resistance to the flow of blood in the vessels), which may have potential problems in patients with heart disorders. Although there was no statistically significant difference in the incidence of liver failure between continuous portal triad clamping and intermittent portal triad clamping (5/60; 8.5% versus 0/61), most of them occurred in patients with chronic liver diseases undergoing the liver resections using continuous portal triad clamping. There was no benefit in selective inflow occlusion compared to portal triad clamping. There was no statistically significant difference in the incidence of liver failure between the two groups (4/41; 9.8% versus 0/39), but all patients with liver failure occurred in the selective inflow occlusion group. There were no significant differences in any of the important outcomes between the different methods of intermittent portal triad clamping or between ischaemic preconditioning followed by continuous vascular occlusion and intermittent vascular occlusion in non-cirrhotic patients undergoing liver resections. Further randomised trials of low risk of bias are needed to determine the optimal technique of vascular occlusion.