Development of gangrene during sleep.

A method for continuous measurement of subcutaneous adipose tissue blood flow in the forefoot over 24 h (SBF) is described. The method is based on the radioisotope wash-out principle using 133-Xenon (133Xe). A portable semiconductor detector is placed just above a local depot of 37-74 kBq 133Xe in 0.1 ml isotonic saline, injected into the subcutaneous adipose tissue in the forefoot. The detector is connected to a memory unit allowing for storage of data. Because of the short distance, the recorded elimination rate constant must be corrected for combined convection and diffusion of the radioactive indicator. Characteristic 24-h blood flow patterns were unveiled in patients with normal peripheral circulation and in patients having ischaemic nocturnal rest pain. In normal subjects, SBF doubled from day to night. This is ascribed to the local veno-arteriolar sympathetic axon reflex, which induces vasoconstriction when the transmural pressure of the veins exceeds approximately 25 mmHg. In patients having ischaemic rest pains SBF was reduced by 37% on the average from day to night. This was caused by nocturnal hypotension, which is reflected proportionally in the foot. As the resistance vessels most probably are fully dilatated in feet with rest pain, the blood pressure drop during sleep causes the perfusion pressure and, therefore, blood flow to drop below a certain critical limit. There was a pronounced correlation between the reduction systemic mean arterial blood pressure and SBF. The patients complaining of intermittent claudication, but no rest pains, demonstrated a variety of changes in SBF compatible with the continuous spectrum of peripheral arteriosclerotic disease. The reduced blood flow during sleep in patients having ischaemic rest pains give rise to the concept of the development of gangrene during sleep.