The presence of symptoms related to gut failure on the first day in an ICU stay is associated with a three-fold increase in mortality. 
Shock is a life-threatening, generalized form of acute circulatory failure associated with inadequate oxygen utilization by the cells and increased blood lactate levels. If left untreated, shock results in sustained multiple organ dysfunction (MODS), and end-organ damage with possible death, so routine screening of patients at risk is recommended to allow earlier identification of impending shock to implement adequate therapy on time and prevent complications and death [1, 2].
Shock is often first suspected by low or declining blood pressure and acute deterioration in vital signs, reduced level of consciousness, or decreased urinary output. The usage of a single variable is not recommended, so nursing staff and doctors use patient-at-risk scores based which are based on the combination of the values of several physiological variables .
During the last three decades, the gut has been hypothesized to play a major role on the damage to distant organs and the development of MODS .
 Cecconi, Maurizio, et al. "Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine." Intensive care medicine 40.12 (2014): 1795-1815.
 Nee, P., & Brown, J. (2015, November 2). Shock. In BMJ best practice. Retrieved from http://bestpractice.bmj.com
 Meng, Mei, Nathan J. Klingensmith, and Craig M. Coopersmith. "New insights into the gut as the driver of critical illness and organ failure." Current opinion in critical care 23.2 (2017): 143-148.
 Reintam Blaser, Annika, Stephan M. Jakob, and Joel Starkopf. "Gastrointestinal failure in the ICU." Current opinion in critical care 22.2 (2016): 128-141.