Hypothermic brain protection has been linked to how rapidly cooling is initiated and how quickly and uniformly the therapeutic hypothermic zone (THZ) is reached. The nasopharyngeal (NP) approach is uniquely suited for preferential brain cooling due to anatomic proximity to the cerebral circulation, cavernous sinus, and carotid arteries. This study explores a novel NP cooling approach employing evaporative characteristics of aerosolized perfluorochemical (PFC).Methods
Anesthetized, normotensive sheep (n = 30) were instrumented with temperature probes and vascular catheters, then randomized to NP approach (NP-PFC: PFC spray device; n = 24) or whole body surface (WBS: n = 6) cooling. Regional temperatures, vital signs, and blood chemistries were assessed serially. Two animals were exposed to double PFC flow rates and PFC was measured in blood during NP-PFC cooling to assess PFC uptake and elimination. Cooling rates were evaluated (ANOVA) as a function of method (NP-PFC versus WBS) and time to reach the brain THZ (i.e., ≤−3.5°C below baseline).Results
Independent of region, brain cooling was faster during NP-PFC versus WBS (P < 0.001). During NP-PFC, brain > vascular > rectal cooling rates (P < 0.001), brain to systemic temperature gradients were maintained, the brain THZ was reached within 15 min, and the NP epithelial surface appeared histologically intact. During WBS, brain versus systemic cooling rates were not significantly different and the brain THZ could not be reached within 2 h.Conclusions
The NP-PFC procedure more rapidly induced preferential brain cooling as compared to WBC without adverse effects.