Effects of prolonged tourniquet ischaemia and short-term venous stasis on plasma endothelin-1 levels in man

Abstract

In vitro studies have indicated increased endothelial release of endothelin during tissue and cellular hypoxia. Therefore, we studied the effect of tourniquet ischaemia and venous stasis on plasma endothelin-1 (ET-1) levels in humans in vivo. The effect of hypoxia on plasma ET-1 levels in 16 patients subjected to an orthopaedic operation and six healthy volunteers was studied by (a) tourniquet ischaemia, in which a limb is totally emptied of blood and kept ischaemic by means of a pneumatic tourniquet, and (b) venous stasis in an upper arm. The mean (SEM) basal plasma ET-1 concentration in the patients subjected to tourniquet ischaemia of a lower limb was 4.1 (1.0) pg ml-1. No significant change in plasma ET-1 levels during or after tourniquet ischaemia was found. The mean (SEM) plasma ET-1 concentration in six healthy subjects prior to venous occlusion in the right upper arm was 3.3 (0.7) and 2.7 (0.3) pg ml-1 in the right and left arm, respectively. A significant increase in plasma ET-1 concentration after 20 min was observed in the arm subjected to venous stasis, but not in the other, control, arm. Mean arterial blood pressure did not change significantly. Local tissue hypoxia may not be an important stimulus for ET-1 release in humans in vivo, whereas short-term venous occlusion in an upper arm leads to local release of ET-1 by an as yet unknown mechanism.

Plasma endothelin-1 concentrations in patients with retinal vein occlusions

“…39 It is possible that, at least in some patients, increased basal ET-1 circulating levels could directly promote or favour vascular retinal occlusions, or otherwise reflect a baseline condition predisposing to RVO. However, findings from our study better fit a scenario in which the ET-1 plasma increase may represent a marker of the occlusion, possibly as a “spillover” phenomenon from a locally activated system 41. This possibility is supported by several lines of evidence.…”

The Vasodilatory Effect of Juxta-arteriolar Microinjection of EndothelinAReceptor Inhibitor in Healthy and Acute Branch Retinal Vein Occlusion Minipig Retinas

“…[33][34][35][36][37][38][39] Previous studies have demonstrated that the development of extended areas of nonperfused capillaries after BRVO in humans correlates with the secondary constriction of the arteriole that crosses the occluded area. 40 Arteriolar constriction of the apparently nonaffected arterioles irrigating the territory of the occluded veins occurs within hours of the occlusive phenomenon and can persist for months.…”

Plasmakonzentrationen von Endothelin-1 nach myokutaner Latissimus dorsi-Transplantation - Bedeutung für den Reperfusionsschaden

“….Ebenso war es uns aus medizinisch-ethischer Sicht nicht möglich, eine entsprechende Kontrollgruppe gesunder Probanden zu rekrutieren, denen man im Rahmen einer Operation zusätzlich ein Tourniquet mit vergleichbaren Ischämiezeiten hätte anlegen müssen, um zu statistisch verwertbaren Ergebnissen zu kommen. Dies könnte zudem erklären, warum es bisher nur einige vergleichbare Arbeiten mit ähnlichem Studiendesign gibt[10,13].Die Etablierung von Endothelin-1 als laborchemischen Parameter zur präoperativen Beurteilung drohender Zirkulationsstörungen bei der Latissimus dorsi-Transplantation ist aufgrund unserer Ergebnisse nicht sinnvoll.Bereits Sokolovsky[21] ließ im Ausblick zu seiner Arbeit erkennen, dass es schwierig sein werde, die Rolle für freies und lokal wirksames ET-1 exakt zu unterscheiden. Er verweist ebenso auf den medizinisch-ethischen Aspekt wie auf den nicht nachgewiesenen Zusammenhang erhöhter ET-1-Konzentrationen und biologischer Aktivität im Rahmen verschiedener Krankheitsprozesse.…”