[Hypoalgesia by voluntary hyperventilation in the healthy subject].
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Biomedical subjects
Publications and source records attributed to G Leftheriotis.
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The role of nitric oxide (NO) in cerebral autoregulation is controversial. The purpose of this study was to compare the effects on the lower limit of the cortical cerebral autoregulation of the inhibition of NO synthesis by N omega-nitro-L-arginine (L-NNA) infusion to saline and phenylephrine in pentobarbital-anaesthetized rats. Variations of the cortical cerebral blood flow (CBF), the cortical cerebrovascular resistances, the mean arterial pressure and the lower limit of cerebral autoregulation were compared in three groups: a group pretreated with L-NNA (n = 8), a group pretreated with saline (n = 8) and a group pretreated with phenylephrine (n = 5). The laser-Doppler flowmetry continuously measured CBF. Controlled haemorrhage was performed after the intravenous infusion of L-NNA, saline, or phenylephrine. The lower limit of cerebral autoregulation of each rat was computed by the least-squares method. The lower limit of cerebral autoregulation was significantly higher after L-NNA infusion (74 +/- 5 mm Hg) than after saline (43 +/- 3 mm Hg; p < 0.01) or phenylephrine infusions (52 +/- 5 mm Hg; p < 0.05). In conclusion, the role of NO on the cerebral autoregulation has been controversial; our results confirm the hypothesis that NO exerts a significant role in maintaining the lower limit of cerebral autoregulation in pentobarbital-anaesthetized rats.
Forty-eight cyclists were studied for suspected external iliac artery endofibrosis with ultrasound B-mode imaging. In highly trained competition cyclists, symptoms of external iliac artery endofibrosis were characterized by lower limb claudication during maximal effort that was caused by fibrosis thickening of the intima of the external iliac arterial wall. Typical ultrasound imaging aspects consisted of parietal thickening, enhanced echogenicity of the arterial wall, straightness of the abnormal arterial segment, and mild narrowing of the arterial diameter of the proximal or medial segment of the diseased external iliac artery. Although ultrasound B-mode imaging study seems to be useful in the diagnosis of external iliac artery endofibrosis, results with this technique must be compared with results of clinical examination, physiologic tests, and arteriography.
The recent description of exercise-induced intimal fibrosis affecting mainly the iliac artery (and therefore usually described as external iliac artery endofibrosis) has dramatically changed the diagnostic approach of unexplained recurrent lower limb exercise pain, especially in cyclists. Because arterial disease is often associated with the aftereffect of various concomitant musculotendinous lesions, several months may pass before an arterial origin is suspected. The arterial origin of the pain must not be eliminated on normal ankle-to-arm index or normal Doppler velocity profiles at rest. Ultrasound examinations taken at rest may show the lesions in 80% of endofibrotic patients and allow for the diagnosis of popliteal entrapment syndrome during dorsiflexion of the foot. However, the hemodynamic consequences of a stenosis on the aortoiliofemoral axis can only be proved by measurement of the ankle-to-arm index after exercise. A cutoff of this index <0.5 provides an 85% sensitivity in the detection of endofibrosis. Invasive investigations (arteriography or angioscopy) will confirm the diagnosis before surgery is discussed. Although long-term results in endofibrosis are unknown, most of the surgically treated patients return to competition.
73 oral facial surgery have been performed using controlled-hypotension induced with nitroglycerin (NTG) to reduce surgical bleeding. Surgical bleeding has been reduced in more than 45% of cases. But frequent lack of correlation between blood pressure, heart beat and bleeding might imply vascular reflex mechanisms induced by controlled-hypotension using NTG. Hemodynamic parameters such as blood pressure and heart rate seem to be insufficient to monitor controlled hypotension efficiency on surgical bleeding. The use of peroperative tissues blood flow monitoring may help for the better understanding of surgical bleeding during controlled-hypotension using NTG.
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