CAN TRANSCUTANEOUS OXIMETRY DETECT NUTRITIVE PERFUSION DISTURBANCES IN PATIENTS WITH LOWER-LIMB ISCHEMIA

Transcutaneous oximetry (TcpO(2)) performed at 37 and 44 degrees on th e dorsum of the foot and capillary microscopy of the nailfold of the b ig toe were applied to 85 patients with various (including asymptomati c) stages of lower limb ischemia to appreciate the relationship betwee n (disturbances in) capillary perfusion and skin oxygen tension. In mi ldly diseased patients, capillary perfusion as measured by direct obse rvation, was preserved. In critically ischemic patients in the supine position, red blood cell-perfused capillary density was reduced. Nutri tive perfusion was severely reduced and showed an absent reactive hype remia after a 1-min arterial occlusion. Also, postural vasoconstrictiv e activity was reduced. TcpO(2) measured at 37 degrees was very low al ready in mildly diseased patients, illustrating the poor oxygen diffus ion toward the skin. At 44 degrees, TcpO(2) was severely reduced in cr itically ischemic patients. Reactive hyperemic response and postural v asoconstriction were suppressed, due to local heating of the skin. Mea surement of the TcpO(2) has limitations in the assessment of nutritive perfusion, as opposed to capillary microscopy, since it is an indirec t measure of skin perfusion, not necessarily derived from capillaries only. The obligatory local skin heating impairs physiological studies as to hyperemic reserve capacity or postural constriction mechanisms. Thus, transcutaneous oximetry is a poor method of characterizing patho physiological mechanisms occurring in skin nutritive microcirculation. However, capillary microscopy and transcutaneous oximetry can give ad ditive information as to the severity of peripheral ischemia. Peak red blood cell velocity during reactive hyperemia using capillary microsc opy and the resting TcpO(2) at 44 degrees, both measured in the supine position, appeared to be valuable microcirculatory parameters in dete cting critical limb ischemia. (C) 1995 Academic Press, Inc.