# Investigating Roles of Cerebral Blood Flow to Maintain Thermal Stability of Neonatal Brain Against Cold Stress Using Non-Invasive Probes for Brain Perfusion and Temperature Gradient

## TL;DR

This study shows how cerebral blood flow helps regulate neonatal brain temperature during cold stress using non-invasive sensors.

## Contribution

Non-invasive probes reveal cerebral blood flow's role in maintaining brain thermal stability during cold stress in infants.

## Key findings

- Cerebral blood flow shifts from heat dissipation to heat delivery during cold stress.
- Superficial brain temperatures returned to baseline after 2 hours of cap use.
- Non-invasive sensors effectively monitored brain temperature and perfusion relationships.

## Abstract

Background: Brain temperature is an important determinant of neurological outcomes in ill infants, yet contributions of environmental temperature and cerebral blood flow remain uncovered because of the lack of non-invasive probes. Methods: Using non-invasive cot-side probes, we examined how cerebral blood flow influences brain temperature during mild cold stress induced by incubator-to-cot transfer. We studied 43 clinically stable infants in a tertiary neonatal intensive care unit. After cot transfer, infants were routinely fitted with knit caps and wrapped in cotton blankets. Scalp and superficial and deep brain temperatures were measured using infrared and zero-heat-flux thermometers, and superior vena cava (SVC) flow—a proxy for cerebral blood flow—was assessed using Doppler velocimetry before, immediately after, and 2 h after transfer, adjusting for rectal temperature. Results: Ambient temperature decreased from 29.7 (SD 0.8) °C to 26.8 (SD 0.9) °C, while rectal temperature remained stable. Scalp and brain temperatures declined after transfer but superficial and deep brain temperatures returned to baseline after 2 h of cap use. The regression coefficient between SVC flow and superficial brain temperature shifted from −0.176 (95% CI, −0.386 to 0.035) to 0.239 (−0.280 to 0.759) after transfer (difference: 0.415 [0.106 to 0.724]; p = 0.009), and then returned to baseline after 2 h (−0.079 [−0.528 to 0.372]). Conclusions: Relationships between brain temperature and perfusion were successfully monitored using non-invasive cot-side biosensors; cerebral blood flow appears to shift from facilitating heat dissipation in warm conditions to supporting heat delivery during cold stress. These findings underscore the physiological role of cerebral blood flow in maintaining brain temperature.