ENHANCED CEREBRAL BLOOD-FLOW IN ACUTE MOUNTAIN-SICKNESS

Mean blood flow velocity (v) of both middle cerebral arteries (MCA) wa s assessed by transcranial Doppler sonography (TCD) in 23 subjects at an altitude of 490 m, as well as after a rapid ascent to a high altitu de research laboratory at 4559 m, and daily during a continued 72-h st ay at this altitude. Relative changes of mean blood flow velocities (v ) of both MCA at high altitude were expressed as percentages of low al titude values and correlated with the development of signs and symptom s of acute mountain sickness (AMS) and changes of arterial Po2, Pco2, and hemoglobin. After ascent to 4559 m, overall MCA-v (mean of all mea surements obtained in each subject at high altitude) increased signifi cantly to 148 +/- 16% of baseline values in the subjects with AMS (AMS +) and to 127 +/- 24% in the subjects without AMS (AMS-) (mean +/- SD) . This v increase was higher in subjects with AMS and reached statisti cal significance on day 1 (+50 +/- 19%) and on day 2 (+48 +/- 23%) as compared to the healthy subjects (+27 +/- 24% and +21 +/- 26% an days 1 and 2, respectively). The rise of MCA-v correlated inversely with ar terial Po2 on days 2 (r = -0.62, p < 0.005), 3 (r = -0.67, p < 0.025) and 4 (r = -0.69, p < 0.025) and from days 1 to 4 (r = -0.51, p < 0.00 1). MCA-v did not correlate with blood pressure, arterial Pco2 or hemo globin. Our results suggest that subjects with AMS have a higher MCA-\ v increase due to a lower arterial Po2 than healthy subjects.