On the number of measurement sites required to assess regional cerebral blood flow by laser-Doppler scanning during cerebral ischemia and reperfusion

The aim of this study was to determine whether the number of measurement si tes affected the precision of regional cerebral blood flow (CBF) assessment by Laser-Doppler (LD). A simulation study was applied based on data obtain ed by scanning the cortex in 25 rats during baseline conditions, 15 min glo bal cerebral ischemia and reperfusion. Random samples were repeatedly colle cted from 1 to 100 locations and deviations from the median of the entire C BF data pool (800 locations) were determined. Single location CBF measureme nts missed the true median by 24.8 +/- 2.2 LD-units (baseline conditions, n = 100 simulations, mean +/- SEM), 2.7 +/- 0.6 LD-units (ischemia), and 31. 9 +/- 21.4 LD-units (30th min reperfusion), which can be reduced to 10.9 +/ - 1.0 LD-units (baseline), 0.9 +/- 0.1 LD-units (ischemia), and 15.5 +/- 1. 3 LD-units (30th min reperfusion) by scanning ten locations. Reliability is further improved by scanning 30 sites with deviations of 6.1 +/- 0.6 LD-un its (baseline), 0.4 +/- 0.0 LD-units (ischemia), and 8.9 +/- 0.7 LD-units ( 30th min reperfusion). Single location CBF assessment was sufficient during global ischernia only. In order to keep the deviation from the true flow b elow 10 LD-units, at least 15 locations are recommended during baseline con ditions and 25 during reperfusion. Laser-Doppler scanning improves the reli ability and reduces the variability of CBF measurements. (C) 2001 Elsevier Science B,V. All rights reserved.