Core-to-Big-Toe Temperature Gradient as a Marker of Peripheral Perfusion in Adult Patients With Septic Shock

Septic shock is a life-threatening condition caused by severe infection that leads to dangerously low blood pressure and impaired blood flow to body tissues and organs. In the intensive care unit (ICU), restoring adequate tissue perfusion (blood flow) is essential during resuscitation. While doctors routinely monitor overall blood pressure, microcirculatory blood flow in peripheral tissues, such as the skin of the feet, can remain poor even after general blood pressure targets are reached. The difference between core body temperature and big-toe skin temperature (known as the core-to-big-toe temperature gradient, or ΔT) reflects blood vessel constriction in the extremities. When peripheral blood flow improves, skin temperature rises and this gradient narrows. This prospective observational study aims to evaluate whether serial measurements of the core-to-big-toe temperature gradient significantly change during the first 12 hours of ICU resuscitation in adult patients presenting with septic shock. The study also examines whether changes in this gradient correlate with standard indicators of clinical recovery, including blood pressure, vasopressor medicine requirements, and blood lactate clearance. All enrolled participants will receive standard, evidence-based medical care for septic shock in accordance with current international clinical guidelines; study participation will not interfere with, alter, or delay clinical treatment. Non-invasive measurements will be collected at three time points: at ICU admission (Hour 0), at 6 hours, and at 12 hours. These assessments include core body temperature, big-toe skin temperature measured with a calibrated infrared thermometer, finger capillary refill time, routine arterial blood pressure, and arterial blood lactate levels. If effective, this temperature gradient could provide clinicians with a simple, non-invasive, and cost-effective bedside indicator to monitor peripheral perfusion during critical care resuscitation.