Neuroprotective Effects of Nasopharyngeal Perfluorochemical Cooling in a Rat Model of Subarachnoid Hemorrhage

Abstract

Subarachnoid hemorrhage (SAH) frequently results in severe morbidity, even mortality. Hypothermia is known to have a neuroprotective effect in ischemic injuries. The aim of this study was to determine whether nasopharyngeal (NP) perfluorochemical (PFC) cooling could be used in a rat model of SAH model for neuroprotection. SAH was induced in 16 male Sprague-Dawley rats by cisterna magna injection of 0.3 mL autologous blood. Vital signs, temperatures, cerebral blood flow (CBF), and brain histology were assessed. Brain cooling was performed on the treatment group using the NP-PFC method starting from 20 minutes after SAH. No SAH-related deaths were observed in either group. SAH caused an immediate decrease in mean arterial pressure (17.0% ± 4.90% below baseline values). SAH induction caused a significant and rapid decrease in CBF frombaseline (approximately-65%, ranging from -32% to-85%) in both hemispheres. In the left hemisphere, cooling facilitated the return of CBF to baseline values within 20 minutes of treatment with further increase in CBF that stabilized by the 2 hours after injury time point. Quantitative immunohistochemistry showed that there were significantly more NeuN-positive cells in the cortex and significantly fewer IBA-1-positive microglia and glial fibrillary acidic protein-positive astrocytes cells in both cortex and hippocampus in the animals that received NP-PFC cooling compared with no treatment, reflecting preserved neuronal integrity and reduced inflammation. The data from this study indicate that local hypothermia by NP-PFC cooling supports return of CBF and neuronal integrity and suppresses the inflammatory response in SAH, suggestive of a promising neuroprotective approach in management of SAH.