RESUMEN
Non-invasive clinical examination has well-recognized limitations in detecting compensated and uncompensated low flow states and their severity. This paper describes the principles of near-infrared absorption spectroscopy (NIRS) and the basis for its proposed use in heart failure/cardiogenic and septic shock to assess global and regional tissue oxygenation. The vascular occlusion test is explained. Limitations of NIRS, current controversies, and what is necessary in the future to make this technology a part of the initial and ongoing assessment of a patient are also discussed. The ultimate goal of such techniques is to prevent miss-assessment and inadequate resuscitation of patients, two major factors in the development of multisystem organ failure and death.