Neuroprotection provided by hypothermia initiated with high transnasal flow with ambient air in a model of pediatric cardiac arrest

Clinical trials of hypothermia after pediatric cardiac arrest have not seen robust improvement in functional outcome, possibly because of the long delay in achieving target temperature. Previous work in infant piglets showed that high nasal airflow, which induces evaporative cooling in the nasal mucosa, reduced regional brain temperature uniformly in half the time needed to reduce body temperature. The mouth is kept open to allow the high nasal airflow to easily exit. Here, we evaluated whether initiation of hypothermia with high transnasal airflow (32 L/min) provides neuroprotection without adverse effects in the setting of asphyxic cardiac arrest. Anesthetized, mechanically ventilated piglets (approximately 2-weeks-old) underwent sham-operated procedures (Group 1) or asphyxic cardiac arrest (Groups 2-6). The asphyxic insult consisted of reducing the inspired oxygen from 30% to 9.5-10% for 45 minutes (hypoxia period), then briefly increasing the inspired oxygen to 21% for 5 min (to imp...,
Body temperature was measured with a rectal thermometer.
Arterial pressure was measured with a pressure transducer connected to a fluid-filled catheter in the femoral artery.
Heart rate was derived from the frequency of the arterial pressure pulses.

Blood samples were periodically drawn from the femoral artery and analyzed for pH, PCO2, PO2, oxyhemoglobin saturation, and hemoglobin concentration on a Radiometer ABL800 Flex blood gas analyzer, with values corrected for body temperature.
For histopathology, deeply anesthetized piglets underwent transcardial perfusion with cold phosphate-buffered saline, followed by ice-cold 4% paraformaldehyde. The brains were post-fixed overnight, then carefully removed from the skull. Each brain was bisected along the mid-sagittal plane and sectioned into a 20-mm coronal slab, ranging from -2 to +18 mm from the bregma. This process ensured the inclusion of key areas: the basal ganglia, sensorimotor cortex, and thalamus. The slab was further divided in..., , # Neuroprotection provided by hypothermia initiated with high transnasal flow with ambient air in a model of pediatric cardiac arrest

This study examined whether two techniques for inducing therapeutic hypothermia (standard body surface cooling and a novel technique in which high airflow through the nostrils to produce evaporative cooling of blood draining the nasal mucosa) after resuscitation from hypoxic-asphyxic cardiac arrest improves the survival of neurons in four brain regions (putamen, sensorimotor cortex, thalamus, and prefrontal cortex) in an infant swine model. For each cooling technique, separate groups were studied in which cooling commenced at either 10 or 120 minutes after resuscitation. The trial had 6 arms:
Group 1 = Sham surgery and anesthesia
Group 2 = Cardiac arrest + normothermia recovery
Group 3 = Cardiac arrest + surface cooling from 10 minutes through 20 hours
Group 4 = Cardiac arrest + transnasal cooling from 10 minutes through 120 minutes followed by surface c...