Project Overview: This project is focused on the early diagnosis and management of septic shock using tissue near infrared spectroscopy (tNIRS) for continuous and non-invasive assessment of microcirculatory vasoreactivity as a diagnostic and prognostic indicator in critically ill patients. A novel aspect of this study is that point of entry of patients will be via the Critical Care Outreach Team (CCOT) which will ensure patients are assessed in the early phases of their disease prior to and co-incident with admission to Critical Care Unit (CCU). The investigators will employ tNIRS to assess peripheral tissue oxygen saturation (StO2) in all patients assessed by CCOT (n = 1031 patients in 2009) and in addition, the investigators will employ the NIRS vascular occlusion test (VOT) using a brief episode of forearm ischemia to quantify microvascular (dys)function.