Hemodynamic monitoring is a diagnostic tool. Hemodynamic monitoring is used for early identification of hypoperfusivestate, to identify its probable cause and rapidly restore cellular perfusion. Hemodynamic monitoring can be invasive or noninvasive, or continuous or intermittent. Monitoring devices can measure physiologic variables directly or derive these variables through signal processing. The purpose of hemodynamic monitoring in critically ill patients is to assess tissue oxygenation, establish the diagnosis and to guide therapeutic interventions to optimize oxygen balance. Oxygen delivery (DO2) and oxygen consumption (VO2) are two components of oxygen balance. Central venous pressure, pulmonary artery catheter, minimally invasive cardiac output monitoring are the monitoring invasive arterial blood pressure. Serum lactates and venous oximetry are the types of downstream markers. Microcirculation is the part of the circulation. Gastric tonometry, sublingual capnometry, indocyanine green clearance and near infrared spectroscopy are techniques of microcirculation.