Identifying Blood Pressure Target in Patients with AKI on Continuous Kidney Replacement Therapy

Background: To investigate whether a specific blood pressure target is associated with increased mortality in patients with acute kidney injury (AKI) receiving continuous kidney replacement therapy (CKRT) using hourly mean arterial pressure (MAP). Methods: Patients were included if they had AKI and underwent CKRT between 1/1/2012-1/1/2021 at a tertiary academic hospital. Norepinephrine equivalent (NEE) dose was calculated to summarize different vasopressors used. Hourly MAPs were used, while the maximum dose of vasopressor during a 6-hour period were used as predictors. We conducted a time-dependent Cox regression model using piecewise linear spline method to identify a break point of MAP. Results: There were 606 patients with AKI that required CKRT. In-hospital mortality occurred in 285 (47%) patients. Those who died were older (62 vs 57 years), required mechanical ventilation at time of CKRT (80% vs 62%), had higher SOFA score (10.7 vs 9) and lactate (6 vs 3.2 mmol/L). Higher MAP was associated with lower mortality [HR 0.97 (95%CI:0.97-0.98) per 1 mmHg increase] and higher NEE was associated with higher mortality [HR 5 (95%CI:2.8-8.9) per 0.01 mcg/kg/min increase]. The model was adjusted for vasopressor doses and fluid balance prior to CKRT initiation, time-dependent and vasopressor doses, SOFA score, septic shock, age, sex, Charlson comorbidity index, mechanical ventilation, and baseline lactate. Plotting the MAP values with log-hazard ratio using piecewise linear spline identified MAP of 71.67 mmHg as a point of inflection (figure 1). Conclusion: Patients with AKI on CKRT may require a higher MAP target. Prospective studies are required to confirm such association.