• Wendy C Ziai, Dhaval Shah, Fabrizio R Assis, Harikrishna Tandri, and Romergryko G Geocadin.
• Department of Neurology, Division of Neurocritical Care, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Phipps 455, Baltimore, MD, 21287, USA. weziai@jhmi.edu.
• Neurocrit Care. 2019 Oct 1; 31 (2): 280-287.

BackgroundFever is an important determinant of prognosis following acute brain injury. Current non-pharmacologic techniques to reduce fever are limited and induce a shivering response. We investigated the safety and efficacy of a novel transnasal unidirectional high flow air device in reducing core body temperature in the neurocritical care unit (NCCU) setting.MethodsThis pilot study included seven consecutive patients in the NCCU who were febrile (> 37.5 °C) for > 24 h despite standard non-pharmacologic and first-line antipyretic agents. Medical grade high flow air was delivered transnasally using a standard continuous positive airway pressure machine with a positive pressure of 20 cmH2O for 2 h. Core esophageal and tympanic temperature were continuously monitored.ResultsMean age was 40 ± 14 yo, and 72% (5/7 patients) were men. Five patients had intracerebral or intraventricular hemorrhage, one subject had transverse myelitis, and the remaining patient had anoxic brain injury due to a cardiac arrest. After 2 h of cooling, core temperature was significantly lower than the baseline pre-cooling temperature (37.3 ± 0.5 °C vs. 38.4 ± 0.6 °C; p < 0.002). Mean transnasal airflow rate was 57.5 ± 6.5 liters per minute. Five of the seven subjects were normothermic at the end of the 2-h period. One subject with severe hyperthermia (39.7 °C) and the other with multiple interruptions to therapy due to technical reasons did not cool. The core temperature within 30 min of cessation of airflow increased and was similar to the pre-cooling baseline temperature (38.3 ± 0.4 °C vs. 38.4 ± 0.6 °C, p = NS). Rate of core cooling was 0.6 ± 0.15 °C per hour at this flow rate. No shivering response was observed. No protocol-related adverse events occurred.ConclusionsHigh flow transnasal air in a unidirectional fashion lowers core body temperature in febrile patients in the NCCU setting. No adverse events were seen, and the process showed no signs of shivering or any other serious side effects during short-term exposure. This pilot study should inform further investigation.

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