Peripheral Perfusion Index Trajectory to Predict 28-Day Mortality in Patients With Sepsis in the Intensive Care Unit

Sepsis is a life-threatening condition caused by the body's overwhelming response to infection, and it remains a leading cause of death in intensive care units. Even when standard treatment targets such as blood pressure are met, blood flow to the small vessels of the skin and other tissues may remain impaired. This "hidden" poor perfusion may not be detected by routine monitoring, yet it may be linked to worse outcomes. The perfusion index is a simple number obtained from the standard pulse oximeter already placed on a patient's finger. It reflects blood flow in the peripheral tissues, requires no additional procedure, and causes no discomfort. This prospective observational cohort study will examine whether the perfusion index, and especially how it changes over the first 24 hours in the intensive care unit, can help predict death within 28 days in adults with sepsis or septic shock. Capillary refill time and skin mottling score will be recorded as additional bedside measures of peripheral perfusion. No treatment will be changed for the purpose of this study, and no additional blood samples or invasive procedures will be performed. All care decisions remain with the treating team. Measurements will be taken at intensive care admission and at 6 and 24 hours. Participants will be followed for 28 days, with survival status also recorded at 90 days. The study will be conducted at two centers. A prediction model will be developed in the first center and then tested, without modification, in patients enrolled at the second center.

Inclusion Criteria: * Age 18 years or older * Diagnosis of sepsis or septic shock according to Sepsis-3 criteria (suspected or confirmed infection with an acute increase in SOFA score of 2 points or more) * Enrollment possible within the first 6 hours of intensive care unit admission * Written informed consent obtained from the patient or, when the patient lacks decision-making capacity, from a legal representative, in accordance with the approved consent procedure Exclusion Criteria: * Conditions precluding valid peripheral perfusion measurement at both measurement sites, including severe peripheral arterial disease, limb ischemia or amputation, extensive edema or burns, or local trauma at the measurement site * Intensive care unit stay of 24 hours or longer at another facility prior to admission * Decision to withdraw or limit life-sustaining treatment planned within the first 24 hours * Pregnancy * Severe Raynaud phenomenon or vasospastic disease of the extremities * Persistent tremor or agitation precluding standardized measurement * Concurrent enrollment in an interventional study