The influence of intermittent versus continuous brain retractor pressure on regional cerebral blood flow and neuropathology in the rat.

To evaluate the possible advantage of intermittent versus continuous brain retractor pressure (BRP) both regional cerebral blood flow (rCBF) measurements and neuromorphological studies have been conducted in the rat. In the same rat model as used in this study it has previously been demonstrated that BRP of 30-40 mm Hg for 15 minutes or more caused severe decrease of rCBF and produced brain damage. In this study a BRP of 40 mm Hg intermittent for 5 and 7 minutes with intervals of 1 minute without BRP for a total of 29 and 31 minutes respectively did not produce brain damage. After BRP for 10 minutes brain damage has been observed. Concerning the rCBF it was demonstrated that a sufficient recirculation after BRP of 30 mm Hg was re-established within 1 minute (70-90 ml/100 g/min) and no significant changes of rCBF were observed in the first 10 minutes after discontinuation of the BRP. Judging from these results intermittent BRP has to be preferred to continuous BRP and the time threshold of the BRP is approximately 7 minutes. Sufficient rCBF is re-established quickly after ischaemia so only short intervals between BRP application periods are necessary.