[Pathophysiology, diagnosis, and laboratoy examination in critical limb ischemia].

The term critical limb ischemia (CLI) is defined as chronic ischemic pain at rest, ulcers, or gangrene lasting more than 2 weeks attributable to objectively confirmed occlusive arterial disease. Patients with ischemic pain at rest generally have ankle pressure (AP) of less than 50 mmHg or toe pressure (TP) of less than 30 mmHg, while patients with ulcers or gangrene usually have AP of less than 70 mmHg or TP of less than 50 mmHg. Healing requires an inflammatory response and additional perfusion above that required for supporting intact skin and underlying tissues. The AP and TP levels needed for healing are, therefore, higher than the pressures found in ischemic pain at rest. A combination of blood-flow reduction due to multisegmental lesions of the proximal artery and blood-flow imbalance in the local tissue lead to CLI. It is important to evaluate not only the macroscopic blood flow but also the microcirculation to understand the pathophysiology of CLI. Transcutaneous oxygen tension measurement (critical level <30 mmHg) and skin perfusion pressure measurement (critical level < 30 mmHg) are useful methods to evaluate the microcirculation.