Selective Brain Cooling with Transnasal Flow of Ambient Air for Pediatric Resuscitation

Abstract

Discharge rates and neurologic outcome from out‐of‐hospital pediatric cardiac arrest remains poor. The recent THAPCA trial for out‐of‐hospital pediatric cardiac arrest reported only a small, non‐significant favorable outcome with hypothermic treatment. A major limitation of this study was the median 5.9‐hour delay in inducing hypothermia, as studies in animals show loss of efficacy with this delay in initiation of hypothermia. To minimize this delay, we developed a simple yet innovative technique of transnasal cooling. Air at ambient temperature is passed through standard nasal cannula and out of the mouth to produce evaporative cooling of the nasal passages and a countercurrent heat exchange with cephalic arterial blood. We determined whether an age‐dependent effect exists in the ability to cool the brain because of potential differences in air humidification capacity during development. We studied piglets at 2–5 days of age (1.8 kg; 40 g brain weight), 2 weeks of age (4 kg; 45 g brain weight) and 6 weeks of age (16 kg; 75 g brain weight; adult brain = 110 g). The corresponding nasal turbinate surface area was estimated to be 3176±243, 4847±417, and 8651±1234 mm2. In anesthetized 1.8‐kg piglets with mechanical ventilation and an open mouth to permit airflow exit, institution of nasal airflow of 4 L/min through nasal cannula decreased brain temperature from 38.0±0.4°C to 36.4±0.9, 35.6±1.2, and 34.4±1.7°C at 30, 60, and 120 min, respectively. In 4‐kg piglets, nasal airflow of 32 L/min decreased brain temperature from 38.3±0.3°C to 35.0±0.6, 33.8±0.6, and 31.9±0.6°C at 30, 60, and 120 min, respectively. In 16‐kg piglets, nasal airflow of 32 L/min decreased brain temperature from 38.5±0.4°C to 35.1±1.6, 34.1±1.8, and 32.9±1.6°C at 30, 60, and 120 min, respectively. No further benefit was seen by increasing airflow to 48 L/min. No substantial spatial temperature gradients were seen among the sensory cortex, putamen, thalamus, cerebellum and olfactory bulb in any age group, suggesting that heat transfer is via blood convection rather than direct conduction from the airway wall. Decreases in rectal temperature lagged brain temperature by 30–60 min at all three ages. The rapid and selective brain cooling indicates that a high humidifying capacity of the nasal turbinates is present early in life. Because of its simplicity, portability, and low cost, transnasal cooling potentially could be deployed in the field by emergency medical technicians, in both community hospital emergency rooms, and in low resource areas for early initiation of brain cooling prior to maintenance with standard surface cooling after pediatric cardiac arrest.Support or Funding InformationSupported by NIH NS095036This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.