The time limit of inflow occlusion for the purpose of direct-vision cardiac surgery has been studied in both euthermic1-3 and hypothermic4-8 dogs. Although some investigators have felt that anoxia of the heart is the most important factor in limiting the available time, it is now widely believed that the brain is more susceptible than the myocardium to anoxia.
During inflow occlusion, the brain is subjected not only to anoxia but also to a high venous pressure. In an attempt to determine whether the elevated venous pressure was responsible for augmenting the damaging effects of anoxia, the following studies were performed. The first compared the effect of simple decompression of the cerebral venous system during inflow occlusion with a control series without decompression. The second group of experiments studied the effect of pumping the cerebral venous blood into the arterial system during the period of inflow occlusion.
SMITH JW, CONNOLLY JE. Methods of Lengthening the Safe Time Interval of Inflow Occlusion Under HypothermiaExperimental Studies. Arch Surg. 1960;81(3):510-513. doi:10.1001/archsurg.1960.01300030170022