The relationship between renal resistive index, tissue hypoperfusion parameters and prognosis in septic shock patients

Introduction: Sepsis and septic shock are an inflammatory response following microbial invasion and is associated with cardiovascular disorders leading to tissue hypoperfusion and is one of the leading causes of mortality worldwide. Early diagnosis of hypoperfusion is critical in reducing mortality. Since traditional hypoperfusion markers may require costly and invasive procedures, the search for alternative methods continues. This study aims to investigate the utility of RRI measurement, a rapid and noninvasive ultrasound-based method, in recognizing tissue hypoperfusion and predicting prognosis in septic shock patients. Materials and Methods: Our study was designed as a prospective observational study on patients with central venous catheter and invasive arterial monitoring who received invasive mechanical ventilation and vasopressor or inotrope support in the intensive care unit for septic shock. Patients with renal artery stenosis, structural kidney injury and atrial fibrillation were excluded. Measurements of patients admitted to the intensive care unit with a diagnosis of septic shock were performed within the first 24 hours. As part of routine treatment, an invasive arterial catheter and a central venous catheter were placed in the internal jugular or subclavian vein. Patients were placed in supine or left lateral position before measurement. A 2-5 MHz convex probe was used for RRI measurement. Interlobar or arcuate arteries were identified with color doppler and then the artery was aligned with pulse wave doppler. Three measurements were taken from the upper, middle and lower parts of the kidney in duplex setting with the P-mode option and the average of these measurements was calculated and recorded. Central venous and arterial blood gas samples were taken simultaneously during RRI measurement. Routine hemodynamic variables and capillary refill time (CRT) were also recorded. The ratio of central venous-arterial carbon dioxide pressure difference to arterial-central venous oxygen difference (P(cv-a) CO2/C(a-cv) O2), lactate and CRT were considered as global tissue hypoperfusion indices. Results: This study demonstrated that RRI may be useful in assessing renal perfusion but does not provide sufficient prognostic value on its own and that a more comprehensive approach is critical for patient outcomes.