Intraoperative laser flowmetry reflects levels of cerebral blood flow during neurosurgical procedures

Changes in cerebral blood flow (CBF) during craniotomies (mean 62.2 years, n = 31) were studied using a laser flowmeter (LFM) to evaluate the utility in CBF monitoring. A small flat probe was applied to the brain surface near the surgical field. The output voltage from LFM was recorded as CBF changes. The percent change in CBF was calculated using the formula [intrasurgical-CBF-control-CBF]/control-CBF x 100. Post-operative neurologic status was evaluated. Control-CBF values were similar among the groups representing different pathologies. The mean CBF decrease ranged from -7.3% following phenytoin injection (n = 9) to -32.7% during induced intrathoracic pressure (n = 10). The mean CBF increase was 41.4% following vascular anastomosis. A decrease > 50% for more than 15 min was associated with a severe permanent neurologic deficit. The CBF monitoring using an LFM during craniotomy may be useful in detecting critical CBF levels for reducing post-operative neurological deficits.