Conjunctival Microcirculation Is Associated with Cerebral Cortex Microcirculation in Post‐Resuscitation Mild Hypothermia: A Rat Model

OBJECTIVE: This study aimed to compare the changes in sublingual and conjunctival microcirculation occurring with cerebral cortex microcirculation changes during mild hypothermia in a rat model of cardiac arrest. METHODS: Twenty-four rats were randomized into mild hypothermia (M) or normothermia (C) groups. Ventricular fibrillation was electrically induced and left untreated for 8 minutes, followed by 8 minutes of cardiopulmonary resuscitation. The core temperature in group M reduced to 33 +/- 0.5 degrees C at 13 minutes after restoration of spontaneous circulation and was maintained for 8 hours. In group C, the core temperature was maintained at 37 +/- 0.2 degrees C. The hemodynamics and microcirculation in the sublingual region, bulbar conjunctiva, and cerebral cortex were measured at baseline and 1, 2, 3, 4, 6, and 8 hours after restoration of spontaneous circulation. RESULTS: The M group showed significantly worse sublingual microcirculation at 6 hours post-resuscitation. However, microcirculation in the conjunctiva and cerebral cortex at 3 hours post-resuscitation were better in the M group. In the M group, microcirculation in the cerebral cortex was significantly correlated with that in the conjunctiva but not the sublingual microcirculation. CONCLUSIONS: Changes in conjunctival microcirculation are closely related to cerebral cortex microcirculation during mild hypothermia, indicating that cerebral cortex microcirculation could be monitored by measuring conjunctival microcirculation.