A Net Ultrafiltration Challenge to Predict Preload-dependence (UF CHALLENGE)

Diagnostic Performance of a Net Ultrafiltration Challenge to Predict Preload Dependence in Critically Ill Patients Under Continuous Renal Replacement Therapy

Hemodynamic instability episodes are a frequent complication of renal replacement therapies in critically ill patients, and their incidence is associated with worse survival. Hypovolemia, identified by the existence of biventricular preload dependence, is responsible for one episode out of two, and may justify a decrease in or cessation of fluid removal by net ultrafiltration (UF). To date, preload dependence is most frequently identified by evaluating the effects on cardiac output of postural changes (passive leg raising), impact of cardio-pulmonary interactions in ventilated patients, or fluid challenge. However, none of these tests may help identify a patient whose cardiac output is at risk of becoming preload dependent, that is situated at the inflexion point of the Frank Starling curve.

Our study aims to evaluate the effects on cardiac output (measured by a transpulmonary thermodilution technique) of 2 net ultrafiltration challenges, consisting fast removal of 250 ml of ultrafiltrate over 15 and 30 minutes respectively, and compare their diagnostic performance to the reference technique of preload dependence assessed by postural changes (passive leg raising) performed after the UF challenge.

Enrolled participants will undergo both UF challenges, following a randomized crossover design, in which the order of UF challenge duration (15 or 30 minutes) is randomized, separated by a washout period of 24 hours.

Inclusion Criteria:

• adult patient, aged 18 year or older
• under mechanical ventilation and continuous general anesthesia, with a positive end-expiratory pressure of 5 cmH2O or more
• with stage 3 KDIGO acute kidney injury
• treated with continuous renal replacement therapy for less than 14 days
• ongoing continuous cardiac output monitoring
• with a predicted intensive care length of stay of 24 hours or more at time of screening

Exclusion Criteria:

• High arterial lactate concentration, > 4.0 mmol/L at time of screening
• Calibrated cardiac index < 2.0 L/min/m2 or > 4.0 L/min/m2 at time of screening
• Positive postural change maneuver in the last 2 hours preceding screening
• Patient under extracorporeal membrane oxygenation
• Patient with active bleeding requiring emergent transfusion
• Patient under chronic maintenance dialysis or renal transplant recipient
• Acute ischemic or hemorrhagic stroke complicated with coma and requiring mechanical ventilation
• Fulminant hepatitis (acute liver injury, hepatic encephalopathy, icterus and a drop in prothrombin < 50% in less that 15 days
• Impossible postural change maneuver
• Pregnant or lactating patient
• Imminent death
• Patient under legal protection measures as by French regulation
• Patient already enrolled in the present study
• Patient already participates in a study with protocolized net ultrafiltration, ongoing at time of screening