Monitoring the Brain-Stem State Through the Assessment of the Baroreceptor-Heart Rate Reflex in Critically Brain-Injured Patients
CENTRO DI BIOINGEGNERIA MILAN (ITALY)
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Aim of this study was to evaluate whether the analysis of cardiovascular dynamics and the assessment of the baroreceptor-heart rate reflex can be used to derive information on the functionality of the cardiomotor brain-stein centers and whether this information may facilitate the diagnosis of brain death. We estimated during impending brain death in 11 comatose patients hospitalized in ICU 1 spontaneous variability of systolic and diastolic blood pressure SBP and DBP and pulse interval PI, the reciprocal of heart-rate by spectral analysis and 2 spontaneous baroreflex sensitivity BRS and baroreflex effectiveness index BEI by the sequence technique. Brain death was associated with significant spectral changes, including a generalized reduction in PI spectra and a decrease of the 0,1 Hz power in SBP and DBP spectra, BRS and BEI, close to normal values just before brain death, dropped to 0 after the brain death event. These changes -likely to reflect the cessation of activity of the cardiovascular brainstem centers- suggest that techniques for blood pressure and heart rate spectral analysis and for the dynamic estimation of spontaneous baroreflex control of the heart can be used for monitoring the brain-stem state in ICU and may complement the traditional assessment of brain-stem death.
- Anatomy and Physiology