Cold stimulation of the oral cavity redistributes blood towards the brain in healthy volunteers

Abstract

Background: The aim of this study was to analyze cold stimulation-induced changes in cerebral and cardiac hemodynamics.

Methods: Upon ingestion of an ice cube, the changes in resistance index, mean flow velocity and flow index of the middle cerebral arteries (MCA) were assessed using transcranial Doppler sonography. Extracranial duplex sonography was used to measure the mean flow velocity and resistance index of the right internal carotid artery (ICA). The change in mean arterial pressure, heart rate, root mean square of successive differences (RMSSD) and end-tidal carbon dioxide pressure were analyzed additionally. These changes were compared to sham stimulation.

Results: Compared with sham stimulation, cooling of the oral cavity resulted in significant changes in cerebral and cardiac hemodynamics. The cold stimulation decreased the resistance index in the MCA (-4.5% ± 5.4%, p < 0.0001) and right ICA (-6.3% ± 15.6%, p = 0.001). This was accompanied by an increase in mean flow velocity (4.1% ± 8.0%, p < 0.0001) and flow index (10.1% ± 43.6%, p = 0.008) in the MCA. The cardiac effects caused an increase in mean arterial pressure (1.8% ± 11.2%, p = 0.017) and RMSSD (55% ± 112%, p = 0.048), while simultaneously decreasing the heart rate (-4.3% ± 9.6%, p = 0.0001).

Conclusion: Cooling of the oral cavity resulted in substantial changes in cerebral and cardiac hemodynamics resulting in a blood flow diversion to the brain.

Keywords: Doppler; autonomic nervous system; cardiovascular physiology; cerebral blood flow; physical stimulation.

FIGURE 1

(a) A self‐constructed, probe‐holding device (“Hallesche Halterung”) was used, to which two transcranial Doppler probes and an extracranial duplex probe were attached. (b) Study protocol: the volunteers pressed their tongue softly to their palate for 90 s (sham stimulation). After a 5‐min break, the volunteers put an ice cube on their tongue and softly pressed it to their palate for 90 s (cold stimulation). *Measurements of peak systolic velocity (PSV) and end diastolic velocity (EDV) in both middle cerebral arteries and the right internal carotid artery, Doppler spectra of both middle cerebral arteries, mean arterial pressure at the left arm, and end‐tidal pCO₂ concentration in exhaled air.