Unclamping the inferior vena cava during retrograde cerebral perfusion increases the safe range of retrograde perfusion pressures and improves brain perfusion.

We investigated the effect of different methods of management of the inferior vena cava (IVC) during retrograde cerebral perfusion (RCP) on the relationships between RCP pressure, regional cerebral blood flow, tissue oxygenation, and intracranial pressure (ICP). Fourteen pigs were subjected to hypothermic (15 degrees C) RCP at RCP pressures varying from 10 to 110 mmHg with clamping (closed group, n=7) or without clamping of the IVC (open group, n=7). Intracranial pressures increased more slowly in the open group than in the closed group and were significantly lower at any level of RCP pressure in the open group than in the closed group. In the closed group, RCP pressures of 20-30 mmHg resulted in an ICP of 25 mmHg. In contrast, in the open group, when RCP pressures were maintained below 70 mmHg, ICP never reached 25 mmHg. Brain tissue blood flow and CO2 production were relatively higher in the open group than in the closed group. The maximum brain tissue blood flow was achieved at an RCP pressure of 40 mmHg in the open group. We conclude that the maximum safe RCP pressure differs according to the type of management of the IVC. Opening the IVC during RCP not only improves brain tissue perfusion, but also significantly increases the safety margin of RCP pressures. In the pig model, when the IVC is not clamped, the optimal RCP pressure appears to be 40 mmHg.