Cerebral circulation estimated by laser speckle flowgraphy in retrograde femoral arterial perfusion during minimally invasive cardiac surgery

OBJECTIVES: Laser speckle flowgraphy (LSFG) is a novel modality to assess blood flow of the optic nerve head (ONH), which is reported to be a surrogate marker of cerebral microcirculation. We conducted LSFG measurements during minimally invasive cardiac surgery with retrograde femoral arterial perfusion and evaluated its feasibility and usability as a neuromonitor. METHODS: We prospectively enrolled 7 patients who underwent mitral valve repair through a right minithoracotomy with retrograde femoral arterial perfusion. LSFG was used to analyse the ONH blood flow based on examinations of the mean blur rate (MBR). The MBR was measured after the induction of anaesthesia (time 1); after the initiation of cardiopulmonary bypass (time 2); during cardiac arrest (time 3) and after the termination of cardiopulmonary bypass (time 4). RESULTS: All procedures were performed successfully, and there were no neurovascular complications or deaths. LSFG measurements were easily and uneventfully conducted without any related complications. The MBR was 11.2 +/- 2.3 at time 1, 11.1 +/- 1.8 at time 2, 11.3 +/- 1.7 at time 3 and 13.6 +/- 3.5 at time 4. Statistically, the MBR at time 4 was significantly higher than those at all other times (P < 0.05). CONCLUSIONS: LSFG measurements were safely conducted during minimally invasive cardiac surgery and assessed ONH blood flow quantitatively. We consider this modality to be easy to manipulate and less operator dependent, resulting in good reproducibility. The results are well visualized and compared quantitatively. Our result suggests that LSFG might be an accurate neuromonitor.