Power spectral analysis of heart rate and arterial blood pressure oscillation in brain-dead patients.
To clarify the mechanism of the slow arterial blood pressure oscillation seen in brain-dead patients, we investigated the frequency of fluctuations in arterial blood pressure and heart rate using power spectral analysis. The electrocardiogram, arterial blood pressure and respiration were recorded simultaneously from 9 brain-dead patients and 8 vegetative patients. Power spectral analysis of these data revealed a very slow fluctuation (0.002-0.01 Hz) in arterial blood pressure in brain-dead patients, the frequency of which was equal to that of the low-frequency spectrum of heart rate, indicating vasomotor sympathetic activity. Neuropathological examinations of the medulla and spinal cords of 4 autopsied brain-dead patients revealed that the spinal cord, ventral and dorsal nerve roots, and the nucleus intermediolateralis of the lateral horn below the level of C3/4 were virtually intact. These findings suggest strongly that the slow oscillation of arterial blood pressure in brain-dead patients originates from the vasomotor tone controlled by spinal sympathetic nerves.
Kita
Y
Y
Section of Emergency Medicine, Kanazawa University, Japan.
Ishise
J
J
Yoshita
Y
Y
Aizawa
Y
Y
Yoshio
H
H
Minagawa
F
F
Shimizu
M
M
Takeda
R
R
D000293:Adolescent; D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D001926:Brain Death / Q000175:diagnosis; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008526:Medulla Oblongata / Q000473:pathology; D008875:Middle Aged; D012119:Respiration / Q000502:physiology; D013116:Spinal Cord / Q000473:pathology; D013564:Sympathetic Nervous System / Q000502:physiology