Influences Of Hypothermia On The Cortical Blood Supply By Laser Speckle Imaging

Clinical induced hypothermia has been applied in intensive care unit and demonstrated with neuroprotective effects in patients with traumatic brain injury, stroke and various other disorders. It is meaningful to investigate the influences of temperature change on the cerebral blood flow (CBF).In the present study, temporal laser speckle image contrast analysis (tLASCA) was implemented to investigate the relative CBF change in artery, vein and capillary level under mild (35℃) and moderate (32℃) hypothermia. Twelve male rats were anesthetized with sodium pentobarbital and randomly assigned to mild and moderate hypothermia groups (n=6 each). Laser speckle imaging trials were acquired during baseline (37℃), hypothermia (35℃or 32℃) and post-rewarming (37℃) phases. By segmentation methods packaged in Insight Toolkit (ITK) software, the cortical vessels were segmented to map the CBF. In the mild group, mean CBF in different vessels all increased throughout the hypothermia and post-rewarming phases. On the contrast, mean CBF was reduced by 10% to 20% at 32℃and could return to ~90% of the baseline level during post-rewarming in the moderate group. Moreover, artery showed higher thermal sensitivity than vein and capillary under hypothermia, particularly in the mild group.In conclusion, we demonstrated LSI as a promising, quantitative, and real-time method to achieve high spatiotemporal resolution CBF change with minimal invasion. We would suggest that moderate hypothermia be more applicable for clinical purpose in the aspect of CBF recovery level after the rewarming. The physiological foundation of CBF change in vascular level under hypothermia still need further study.