A pitfall in the evaluation of medical therapy for occlusive arterial disease using the xenon wash-out technique.

In a double-blind cross-over trial an oral thromboxane synthetase inhibitor (TSI) or placebo was given to 15 patients with severe foot ischaemia. After TSI therapy, rest pain remitted in nine out of 14 legs, while remission during placebo was seen in three out of 11 legs (NS). The ankle and toe systolic blood pressures remained constant during both study periods. Nocturnal adipose tissue blood flow in the forefoot was measured by the xenon wash-out method. A significant increase of the nocturnal perfusion rate constant during TSI therapy was found. A slight oedema developed during TSI therapy. This causes a change of the composition of the tissue under study and thus of lambda-xenon. The perfusion rate in the present study thus merely illustrates the latter and not a true increase in blood flow.