Diastolic Shock Index for Predicting Hemodynamic Instability During Continuous Renal Replacement Therapy (DSI-CRRT)

Background: CRRT-associated hemodynamic instability (CRRT-HI) complicates 19-43% of CRRT sessions and is independently associated with increased mortality and impaired renal recovery. The diastolic shock index (DSI = heart rate / diastolic arterial pressure) reflects both vascular tone (diastolic pressure) and neurohumoral compensation (heart rate) and has been proposed as an early marker of vasoplegia. Its predictive value for CRRT-HI has not been prospectively evaluated.

Objective: To evaluate the diagnostic performance of pre-CRRT bedside DSI in predicting CRRT-HI in critically ill adults.

Design and setting: Prospective observational cohort study conducted in the general intensive care units of Basaksehir Cam and Sakura City Hospital, Istanbul, Turkey. Approximately 70 adult patients (≥18 years) starting CRRT for acute kidney injury will be enrolled.

Definition of CRRT-HI: An event meeting at least one of the following criteria: mean arterial pressure below 65 mmHg; initiation of a new vasopressor or an increase of ≥20% in the norepinephrine dose; crystalloid fluid bolus exceeding 250 mL; or reduction or discontinuation of ultrafiltration.

Data collection: Demographic and clinical characteristics (APACHE II, SOFA-2, comorbidities, CRRT indication and AKI stage), CRRT settings (modality, blood flow, dialysate and replacement fluid rates, ultrafiltration rate, anticoagulation), and baseline laboratory parameters (arterial blood gas, lactate, complete blood count, renal and liver function tests, electrolytes, CRP, procalcitonin) will be recorded. Heart rate, systolic, diastolic and mean arterial pressures, vasopressor/inotrope use and doses will be recorded at CRRT initiation (T0) and at 15, 30, 60 and 180 minutes. DSI, the classic shock index (HR/SAP) and the modified shock index (HR/MAP) will be calculated from these routine monitoring data. No additional blood sampling, tests or invasive procedures will be performed for the study.

Statistical analysis: The predictive performance of DSI, the classic shock index, the modified shock index and mean arterial pressure will be assessed by ROC curve analysis and compared using the DeLong test. Optimal cut-off values will be determined by the Youden index, with corresponding sensitivity and specificity. Independent risk factors for CRRT-HI will be identified by multivariable logistic regression. Associations of DSI and CRRT-HI with 28-day mortality, ICU and hospital length of stay, duration of mechanical ventilation and renal recovery will be evaluated as secondary analyses.

Sample size: Assuming a CRRT-HI incidence of approximately 50% and an expected AUC of 0.75 for DSI, at least 60 patients are required (α = 0.05, power = 80%). Allowing for approximately 15% data loss, 70 patients will be enrolled.