Cold Blooded: Evaluating Brain Temperature by MRI During Surface Cooling of Human Subjects

Abstract

Background: Targeted temperature management (TTM) confers neurological and survival benefits for post-cardiac arrest patients with return of spontaneous circulation (ROSC) who remain comatose. Specialized equipment for induction of hypothermia is not available in the prehospital setting, and there are no reliable methods for emergency medical services personnel to initiate TTM. We hypothesized that the application of surface cooling elements to the neck will decrease brain temperature and act as initiators of TTM.

Methods: Magnetic resonance (MR) spectroscopy was used to evaluate the effect of a carotid surface cooling element on brain temperature in healthy adults.

Results: Six individuals completed this study. We measured a temperature drop of 0.69 ± 0.38 °C (95% CI) in the cortex of the brain following the application of the cooling element. Application of a room temperature element also caused a measurable decrease in brain temperature of 0.66 ± 0.41 °C (95% CI) which may be attributable to baroreceptor activation.

Conclusion: The application of surface cooling elements to the neck decreased brain temperature and may serve as a method to initiate TTM in the prehospital setting.

Keywords: Cardiac arrest; Cooling collar; Magnetic resonance spectroscopy; Surface cooling; Targeted temperature management; Therapeutic hypothermia.

Conflict of interest statement

Conflict of interest The authors declare that they have no conflict of interest.

Figures

Fig. 1

Representation of magnetic resonance (MR) spectroscopy data. Brain temperature was calculated using: Temp. °C = 296.1–97.1 (Δwater–N-acetylaspartate). The chemical shift of N-acetylaspartate (NAA) is independent of temperature

Fig. 2

MR spectroscopy voxel placement in the fronto-parietal white matter of the human brain

Fig. 3

Verification of magnetic resonance imaging (MRI) measurements using phantom solution. MRI temperature recordings of a precooled water and N-acetylaspartate (NAA) phantom solution as it reached room temperature

Fig. 4

Comparing cold and room temperature elements in human subjects before and during application of elements. Comparison of magnetic resonance (MR) brain temperature measurements before and during the application of a cold elements and b room temperature elements. Multiple measurements for individual subjects were compiled; figure shows the combined results for all subjects (n = 6)

Fig. 5

Comparing cold and room temperature elements in individual human subjects before and during application of elements. Comparison of average magnetic resonance (MR) brain temperature measurements before and during the application of a cold elements and b room temperature elements. Each line represents a single subject (n = 6)