Comparison of renal resistivity index in critically ill trauma patients with and without shock: a prospective observational study

Trauma remains one of the leading causes of morbidity and mortality worldwide, with critically ill trauma patients often facing a myriad of life-threatening complications, including acute kidney injury (AKI) and hemodynamic instability. Shock, defined as inadequate tissue perfusion leading to cellular dysfunction, is a common occurrence in trauma patients, and its management often requires immediate and precise interventions. The pathophysiology of shock involves complex hemodynamic changes that can adversely affect renal blood flow, leading to acute kidney injury (AKI) or worsening of pre-existing renal dysfunction. It is therefore critical to monitor renal perfusion accurately in these patients to guide therapeutic interventions. Among the markers of renal function, the renal resistivity index (RRI), measured via Doppler ultrasonography, has emerged as a promising tool for assessing renal perfusion and predicting adverse outcomes in critically ill patients.

Renal resistivity index (RRI) is an index derived from Doppler ultrasound assessment of intrarenal blood flow and reflects resistance to blood flow in renal vasculature. It is a non-invasive, bedside assessment. The specific utility in trauma patients remains less well defined. Recent studies have suggested that the RI may be a valuable predictor of AKI in trauma patients, particularly in those who present with hypoperfusion states such as shock. However, only few prospective studies have directly compared the renal RI between trauma patients with and without shock, which is essential for understanding its prognostic implications in this cohort.

This prospective observational study aims to compare the renal resistivity index in critically ill trauma patients with and without shock, to explore its utility as a biomarker for renal dysfunction and its potential as a prognostic tool. By analyzing RI values in the context of trauma-induced shock, this study seeks to provide valuable evidence to support its use in clinical practice and improve patient outcomes through early identification of renal compromise.

METHODOLOGY

After obtaining ethics committee approval, student researcher will receive training for the measurement of RRI using Doppler ultrasound. Patients above the age of 18 years who are admitted in trauma ICU will be recruited within 24 hours of their admission. Informed written consent will be obtained from a legally appointed representative (LAR). Baseline characteristics and laboratory parameters will be noted, and patients will be classified as having or not having shock.

RRI assessment will be done for all patients and the readings will be repeated on days 2 and 3. Bedside ultrasound examination will be done with A 5MHz convex transducer, placed on the posterior axillary line to identify interlobular artery using the color Doppler. Pulse waveforms will be obtained and an image with three clear continuous waves is considered ideal. Average of RRI of right and left kidneys are obtained.

Patient will be followed up for 7 days to monitor urine output and serum creatinine to assess for development, duration and severity of AKI.