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Biomedical subjects

B Kayser

Publications and source records attributed to B Kayser.

63 records · Page 4Linked to original sources
PubMed1988

[Photoplethysmography and laser Doppler velocimetry in the study of cutaneous vasomotility at high altitudes].

During the second French scientific medical expedition to the Himalaya (ARPE, Annapurna IV, 1985), modifications of cutaneous circulation in hypoxia were studied. Two techniques were used for the first time to evaluate cutaneous vasoactivity under such conditions: laser Doppler velocimetry and photoplethysmography. Measurements were performed on the pulp of the third and fourth fingers of the right hand in 6 subjects native of sea-level countries: first at sea level, then in hypoxia after 15 days at 4,800 m before and after ingestion of a vasodilator drug (nicardipine 20 mg). Cutaneous circulation was explored under three thermal conditions: baseline (ambient temperature); after vasodilation obtained by immersion of the hand in hot water (40 degrees C), and after immersion of the hand in cold water (12 degrees C). In prolonged hypoxia a reduction in vasoconstriction at 12 degrees C was observed with both techniques. No significant change was observed at 40 degrees C. After dosing with nicardipine, the results differed according to the exploratory technique: a slight increase of the laser Doppler signal (NS) and a decrease of the photoplethysmographic signal were recorded. Acclimatization to cold and to hypoxia may concur to determine this response of cutaneous circulation. The action of vasodilating agents on cutaneous microcirculation in prolonged hypoxia is not clear and deserves further investigation. These drugs must be used with caution in the prevention and treatment of frostbite.

Adult↗
PubMed1987

[Aneurysm of the ampulla of Galen. Nosologic reflections and endovascular therapy].

Nosologic concepts distinguish three types of aneurysm of Galen's ampulla: true aneurysms, related aneurysms, false aneurysms, whatever the type the majority of these malformations can be treated by the endovascular approach, frequently the most effective alternative therapy. Experience acquired during treatment of intracerebral arteriovenous angioma allows perfect control of direct, high output arteriovenous fistula by injection of pure isobutyl cyanoacrylate. Occlusion of shunts should be combined with prevention of consequences, that is to say extensive venous thrombosis. Two cases are reported that demonstrate the value of post-embolization heparin therapy.

Adult↗
PubMed1983

Autoregulation in vasa recta of the rat kidney.

Vasa recta blood flow autoregulation was studied by measuring flow velocity in individual vessels on the papilla surface with a video adaptation of the dual-slit erythrocyte velocity method. Vessel diameter did not vary with arterial pressure in the range of 60-150 mmHg, allowing the calculation of the ratio of flows in a single vessel at two pressures from the ratio of velocities. Flow velocity in single vasa recta increased with arterial pressure to 75 mmHg, remained constant in the range of 75-125 mmHg, and increased with higher pressures. In a second series of animals, whole kidney blood flow auto-regulated above 90 mmHg. Vasa recta and whole kidney flow patterns were not changed by extracellular fluid volume expansion. Volume expansion caused a greater increase in ascending than in descending vasa recta flow, reflecting the volume load from enhanced collecting duct reabsorption in diuresis. In a final series, Na excretion varied with arterial pressure in the range of 90-130 mmHg. Because vasa recta velocity remains constant within this range, pressure diuresis cannot be caused by the lack of autoregulation of vasa recta blood flow, at least to 130 mmHg.

Animals↗