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Results for “VASOMOTOR SYSTEM”

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PubMed1991

Experimental studies on the effects of vibration and noise on sympathetic nerve activity in skin.

Multi-unit sympathetic activity was recorded at elbow level from median nerve fascicles supplying glabrous skin of the left hand in five healthy subjects. The resultant vasomotor responses accompanying the neural activity were monitored by simultaneous recordings of skin blood flow using the laser doppler method and skin temperature in the innervation zones. No significant change in sympathetic activity was observed during handgrip exercise of the right hand under a constant gripping force of 2 kg. Subjects maintained the same gripping force of the right hand during exposure in random order to local vibration and/or noise, each type of exposure lasting 5 min with intervals of 20 min. A two-peaked significant increase in outflow from sympathetic nerves was observed during local exposure of the right hand to vibration with a frequency of 60 Hz and an acceleration of 50 m.s-2, followed by a postexposure period which revealed a relative suppression of sympathetic nerve activity and a significant increase in blood flow. Noise at 100 dB(A) showed only an initial effect on skin sympathetic nerve activity (SSA), whereas when combined with local vibration at 60 Hz, a pronounced increase in neural activity was noticed, indicating a combined effect of vibration and noise. These results from direct recordings of SSA suggest a sympathetic vasomotor reflex mechanism triggered by local vibration stimuli to the hand.

Adult↗
PubMed1994

[Periodical blood pressure variation during cardiopulmonary bypass--effects of cervicothoracic epidural anesthesia and phentolamine].

We studied the effects of cervicothoracic epidural anesthesia or intravenous phentolamine on periodical blood pressure variation during cardiopulmonary bypass in 12 adult patients undergoing open heart surgery under fentanyl anesthesia. Spontaneous periodical fluctuation of the blood pressure was analyzed by means of autoregressive power spectrum method. Amplitudes of the low frequency (0.02-0.15 Hz) component of the blood pressure variation amplitudes were calculated. The amplitudes decreased significantly 10 minutes after cervicothoracic epidural block with 15 ml of 2% lidocaine solution (P < 0.05), and after infusion of 0.4 mg.kg-1 of phentolamine (P < 0.05). Since amplitudes of the blood pressure variation were reduced by adequate epidural block or phentolamine, they are likely to reflect sympathetic vasomotor activity.

Adult↗