EFFECTS OF INTERMITTENT REPERFUSION ON BRAIN PH(I), RCBF, AND NADH DURING RABBIT FOCAL CEREBRAL-ISCHEMIA

Background and Purpose The use of intermittent reperfusion versus stra ight occlusion during neurovascular procedures is controversial. This experiment studied the effects of intermittent reperfusion and single occlusion on intracellular brain pH (pH(i)), regional cerebral or cort ical blood flow, and nicotinamide adenine dinucleotide (NADH) fluoresc ence during temporary focal ischemia. Methods Twenty fasted rabbits un der 1.0% halothane anesthesia were divided into four groups: (1) nonis chemic controls, (2) 60 minutes of uninterrupted focal ischemia, (3) 2 x 30-minute periods of focal ischemia separated by a 5-minute reperfu sion, and (4) 4 x 15-minute periods of focal ischemia separated by thr ee 5-minute reperfusion periods. Focal ischemia was produced by occlus ion of both the middle cerebral and ipsilateral anterior cerebral arte ries, After the final occlusion, there was a 3-hour reperfusion period in all groups. Regional cerebral and cortical blood flow, brain pH(i) , and NADH fluorescence were measured with in vivo panoramic fluoresce nce imaging. Results During occlusion, regional cerebral and cortical blood flows and NADH fluorescence values were not different among the groups. Brain pH, was significantly lower in the 4 x 15-minute group c ompared with the 1 x 60-minute group (6.57 +/- 0.02 versus 6.73 +/- 0. 06; P <,03) but not significant when compared with the 2 x 30-minute g roup. During the short reperfusion periods, all parameters returned to normal except for NADH fluorescence levels, which remained elevated. During the postischemic final reperfusion period, there was a mild bra in alkalosis of approximately 7.1 in all groups, There were no signifi cant differences in NADH fluorescence among groups during the final re perfusion. Regional cerebral and cortical blood flow returned to near normal values in all groups. Conclusions This study demonstrates that intermittent reperfusion during temporary focal ischemia has different effects on the intracytoplasmic and the intramitochondrial compartmen ts: worsening of brain cytoplasmic pH(i) but no significant difference s in the oxidation/reduction level of mitochondrial NADH.