Colloidal volume expansion during acute cerebral ischaemia: assessed by local cerebral blood flow and computerized power ratio index

Colloidal volume expansion during acute cerebral ischaemia was assessed by local cerebral blood flow (CBF) and the power ratio index (PRI) in 8 anaesthetized Macaque monkeys. Focal cerebral ischaemia was produced by right middle cerebral artery occlusion. The animals were then volume expanded (to maximum cardiac output) with 6% hetastarch and then exsanguinated to baseline cardiac output. During volume expansion, local CBF in the ischaemic hemisphere increased from 25 +/- 12 to 39 +/- 23 cc/100 g/min (p less than 0.01) and during exsanguination decreased to 32 +/- 18 cc/100 g/min. Local CBF did not change significantly in the nonischaemic hemisphere. EEG power data, as assessed by PRI [(delta + theta power/alpha + beta power) x 100] changed significantly during blood volume manipulation. The mean PRI value in the right hemisphere deteriorated by increasing from 65 +/- 22 to 94 +/- 25 (p less than 0.01) following vessel occlusion but improved by decreasing to 81 +/- 23 (p less than 0.05) following volume expansion. Following exsanguination, the PRI value increased to 87 +/- 21. These data demonstrate the benefits of volume expansion during acute cerebral ischaemia. Changes in local CBF were consistently associated with changes in the PRI maps and values.