In medical practice, the monitoring of organ and tissue vitality is a critical need in operating rooms (ORs) as well as in intensive care units (ICUs). The concept of multiparametric monitoring of tissue vitality was described in detail in our previous publication (Mayevsky et al., Proc SPIE 4616:30–39, 2002). The device, called “Tissue Spectroscope” (TiSpec), contained a single light source (325 nm) used as an excitation light. The emitted-reflected light from the tissue was analyzed to provide real-time information on the following three parameters: microcirculatory tissue blood flow (TBF), mitochondrial NADH redox state, and tissue reflectance. Later on, another parameter was added to the developed device, and the new model named CritiView, also monitored the level of blood hemoglobin oxygenation. The main medical application of the CritiView is in critical care medicine of patients hospitalized in the ICUs and intraoperatively in operating rooms. The physiological basis for our clinical monitoring approach is based on the well-known response to the development of body emergency situation, such as shock or trauma. Under such conditions a process of blood flow redistribution will give preference to vital organs (brain and heart) neglecting less vital organs (Skin, GI tract, or the urinary system). Under such conditions, the brain will be hyper-perfused and O2 supply will increase to provide the need of the activated mitochondria. The non-vital organs will be hypo-perfused, and mitochondrial function will be inhibited, leading to energy failure. This differentiation between the two types of organs could be used for the early detection of body deterioration by monitoring of the less vital organ vitality. A fiber optic sensor was embedded in a Foley catheter, enabling the monitoring of Urethral wall vitality, to serve as an early warning signal of body deterioration. The device was tested both in vitro and in vivo in a small animal model and in preliminary clinical trials in patients undergoing vascular or open heart surgery. In patients, the monitoring is started immediately after the insertion of a three-way Foley catheter (urine collection) to the patient and is stopped when the patient is discharged from the operating room. The results show that monitoring the urethral wall vitality provides information in correlation to the surgical procedure performed.