Peripheral near-infrared spectroscopy: methodologic aspects and a systematic review in post-cardiac surgical patients

Loss of hemodynamic coherence between macrocirculatory oxygen parameters and the peripheral microvasculature frequently is seen in critically ill patients, including postoperative cardiac surgery patients. Hemodynamic stabilization by volume expansion and pharmacologic cardiovascular support may correct systemic hemodynamic variables but not oxygenation and perfusion of the microcirculation. Persistent microcirculatory abnormalities are associated with adverse patient outcomes. Consequently, there is interest in minimally invasive methods to assess the microvasculature in addition to established systemic hemodynamic monitoring in patients admitted to intensive care units (ICUs).