Introduction: Monitoring brain tissue oxygenation could be of great value in the evaluation of cerebrovascular angioplasty procedures. Quantitative (frequency domain) near infrared spectroscopy (Q-NIRS) allows quantitative, continuous, non-invasive measurements of tissue Oxy- (HbO2), Deoxy- (HHb), total (tHb) hemoglobin concentrations and brain tissue oxygen saturation (SO2). Q-NIRS offers three major advantages:1) absolute values of tissue oxygenation 2) real-time measurement and 3) measurements independent from scalp tissue oxygenation (ref.1,2,3,4). This technology provides immediate feedback about changes in cerebral oxygenation related to the procedure; currently there is no other portable monitoring instrument able of providing this information.

Methods: We used Q-NIRS to monitor six patients undergoing cerebrovascular angioplasty: three internal carotid artery and three middle cerebral artery angioplasties. Q-NIRS sensors were applied to the scalp of patients bilaterally to monitor the affected and the contralateral hemispheres. Monitoring was performed before, during and after the procedure, and absolute changes in cerebral oxygenation parameters were analyzed. In addition, the difference in tHb between the two hemispheres (tHb polarization) was calculated.

Results: At baseline, the patients had lower tHb on the affected hemisphere as compared to the contralateral hemisphere (P = 0.04) (fig-1). During the angioplasty procedure, Q-NIRS demonstrated an increase in HbO2, tHb and SO2 as well as a decrease in HHb on the treated hemisphere (P < 0.003) (fig-2). In contrast, there were no significant changes in cerebral oxygenation in the non treated hemisphere. Additionally, follow up measurements done 24 hours after the procedure showed that tHb had significantly increased on the affected hemisphere as compared to baseline (P = 0.001). The largest increase in tHb (135% from baseline) was found in a patient who developed reperfusion injury after middle cerebral artery angioplasty.

Conclusions: Q-NIRS provides a noninvasive technique to evaluate patients undergoing cerebrovascular angioplasty, and may provide a method for evaluating the success of the procedure and predicting the risk for reperfusion/hyperperfusion injury.