Citations

Plethysmography can be used to detect and assess venous incompetence in the lower extremities. The authors recently evaluated a new device designed for this purpose that uses strain gauges to determine changes in lower extremity cir cumference occurring with (and immediately after) exercise. The device plots a curve of volume against time for each limb and automatically calculates key values such as the volume of blood expelled from the lower limb veins during exercise and the time required for the veins to refill following exercise. The ap paratus was incorporated into their noninvasive vascular laboratory and used (along with other standard tests) to study patients referred for suspected venous incompetence. They observed the following: (1) A shortened postexercise refilling time ac curately identified limbs with venous incompetence. (2) The clinical severity of venous incompetence was inversely related to the refilling time. (3) Exercise- induced changes in lower extremity volume correlated well with simultaneously determined changes in venous pressure. (4) Valvular incompetence could be local ized to the deep or superficial veins based upon the improvement in refilling times seen following placement of elastic tourniquets around the lower limb. (5) The type of exercise performed (knee bends while the patient was standing versus ankle reflexes while sitting) had little effect on results. The authors conclude that exercise venous plethysmography is a useful noninvasive tool for assessing low er limb venous incompetence.

Thromboangiitis obliterans (Buerger's disease) is an occlusive vascular disease that occurs almost exclusively in young male tobacco users. A unique case is documented here in which Buerger's disease affecting the upper limbs was diagnosed in a sixty-two-year-old man who was a cigarette smoker but had stopped smoking fifteen years earlier.

The authors evaluated the relationship between sympathetic nerve activity and transcutaneous oxygen tension (TcpO 2 ) in normal and ischemic lower extremities. Dorsal foot TcpO 2 was measured by using oxygen-sensing electrodes with surface temperatures of 42 ° C and 45°C; in theory, changes in sympathetic activity should affect vasomotor tone and TcpO 2 in skin beneath an electrode at 42 °C (submaximal vasodilation), but not at 45°C (maximal vasodilation). The vasodilation index (TcpO 2 at 42°C/TcpO 2 at 45°C) was created as an index of vasomotor tone (vasodilation index increases as tone decreases). In normal limbs (n=24) averages for TcpO 2 at 42°C, TcpO 2 at 45°C, and vasodilation index were 30.3 mmHg, 62.1 mmHg, and 0.47, respectively. In subjects (n=5) with quadriplegia and reduced sympathetic tone secondary to cervical cord trauma, TcpO 2 at 42 ° C and vasodilation index were increased (45.0 mmHg and 0.61); TcpO 2 at 45 ° C did not change. When normal subjects (n=7) were chilled for twenty minutes with a cooling blanket at 5 ° C (to increase sympathetic tone) average vasodilation index dropped from 0.50 to 0.29. Among ischemic limbs (n = 34) vasodilation index was highly variable (range: 0-0.77); in general, vasodilation index fell as the ischemia worsened. In a subset of patients with ischemic limbs, the vasodilation index increased after the limb was wrapped in a warm dressing (average vasodilation index=0.25without dressing, 0.37 with dressing). The authors conclude: (1) TcpO 2 can be used to assess the degree of vasomotor tone (and sympathetic activity) in skin; (2) tone generally increases as ischemia worsens; and (3) local warmth can improve cutaneous circulation in ischemic limbs.

Persistent digital ischemia is an uncommon paraneoplastic syndrome. We describe a 71-year-old man whose only manifestation of an underlying adeno carcinoma was digital ischemia. His symptoms responded dramatically to bilat eral dorsal sympathectomies. A thorough search for the mechanism producing the ischemia failed to provide an explanation. We assume that unknown neuro- humoral factors produced by the tumor were responsible.