This is a pilot observational cohort study to understand whether advanced monitoring techniques can be applied during continuous kidney replacement therapy (CKRT), which is the most common form of dialytic therapy provided in critically ill patients.

The CritLine-IV® monitor is a non-invasive device which integrates into the dialysis circuitry to continuous provide hematocrit and oxygen saturation values during dialysis. This monitoring has been used both in clinical and research settings with good accuracy over 4 hours of hemodialysis and has been used to guide real-time decisions on fluid management during intermittent hemodialysis. Given its non-invasive application, continuous measurements, and ease of integration into the dialysis circuitry, this technology has great potential for use in the critical care setting, where changes in clinical status and acuity of illness often require frequent reassessment and adjustment of dialysis settings. However, the reliability of Critline-IV® measurements over longer periods of time is unknown. In this study, we intend to determine the accuracy over time of Critline-IV® monitoring during CKRT, establish whether it impacts CKRT performance (primarily dialysis filter patency), and explore potential signal changes during various interventions commonly performed in the intensive care unit.

Inclusion Criteria:

1. Patients who have been admitted to the Medical ICU or Cardiothoracic ICU at the Hospital of the University of Pennsylvania (HUP).
2. Patients who have been prescribed continuous venovenous hemodialysis (CVVHD) or Continuous Veno-Venous Hemofiltration (CVVH), the predominant modalities of continuous kidney replacement therapy (CKRT) at HUP.
3. Patients who have central venous catheters placed in either the left or right internal jugular veins.

Exclusion Criteria:

1. Patients who are prescribed other forms of CKRT, namely continuous venovenous hemofiltration (CVVH), slow continuous ultrafiltration (SCUF), or prolonged intermittent kidney replacement therapy (PIKRT).
2. Patients who have femoral vein dialysis catheters placed.
3. Patients who cannot provide consent or have a legal proxy to provide consent.

Patients admitted to one of the Medical ICUs and the Cardiothoracic ICU who have been prescribed CKRT.