Resuscitation in the ICU was traditionally based on blood pressure (1, 2). An assumption that adequate tissue perfusion cannot be made at pressures of 65 mm Hg, and the number itself has been challenged in other investigations (1, 3, 4). Lactate has long been regarded as an adequate indicator of tissue perfusion and prognosis. Most critical care resuscitation are guided by serial lactate levels as a mean to understand the flow and perfusion side of resuscitative aims (2, 5). Not all high lactate levels are indicators of poor tissue perfusion (6).In 2017, Khanna et al (7) reinvigorated the interest in the renin-angiotensin-aldosterone system (RAAS) as a significant biochemical hormonal axis and feedback mechanism in vasodilatory shock after they published the results of the Angiotensin II in High Output Shock Trial. Gleeson et al (8) showed in 2018 that renin appeared to be a much stronger and significant predictor of ICU mortality compared with lactate in a heterogenous shock population Jeyaraju et al (9) reported that renin kinetics are superior to lactate kinetics for predicting in-hospital mortality in critically ill patients with hypotension, with most being vasodilatory shock (most common diagnosis sepsis, also vasoplegia, acute respiratory distress syndrome [ARDS], liver failure) and those who had hypotension more than 6 hours while of vasopressors included. The bottom line in the previous investigations is that renin was a better marker of poor outcomes in comparison with concurrently measured lactate levels in critically ill ICU patients.
Whole blood lactate concentration is widely used in shock states to assess perfusion. We aimed to determine if the change in plasma renin concentration over time would be superior to the change in lactate concentration for predicting in-hospital mortality in septic shock patients.