In an emergency medicine patient, accurate measurement of change or lack thereof from non-shock, non-ischemimc, non-inflammation, non-tissue injury, non-immune dysfunction conditions is important and is provided, as practical, real-time approaches for accurately characterizing a patient's condition, using Raman spectroscopy with a high degree of accuracy, Resonance Raman spectroscopy is used to monitor tissue nitric oxide activity either in vivo or in vitro, especially as a function of its interaction with hemoglobin or other metalloproteins. Measurement times are on the order of seconds. High-accuracy measurement is achieved with Raman spectroscopy interrogation of tissue. Measurements may be non-invasive to minimally invasive. The invention may be used to monitor the effect of instituting therapies using nitric oxide or disease processes that produce nitric oxide.