CRRTnet: Observational Study of Prescription and Delivery of Continuous Renal Replacement Therapy

More than half of admission to the intensive care unit (ICU) are complicated by acute kidney injury (AKI), and approximately 5% to 6% of patients admitted to the ICU require renal replacement therapy (RRT). Among patients with hemodynamic instability, continuous RRT (CRRT) is the dialysis modality of choice in high-income nations.

According to Michael Heung, MD, MS, and colleagues, there have been significant changes in CRRT since its inception 30 years ago, including improvements that allow for more widespread and routine use. Improvements include peristaltic pump driven venovenous circulation, sophisticated hardware and software engineering that allows for precise application of the prescribed treatment and enhanced safety and alarms, improved biocompatibility and other membrane characteristics, regional anticoagulation protocols, and enhancements in user interface.

The 2012 Kidney Disease: Improving Global Outcomes AKI guidelines suggest using CRRT over intermittent dialysis options for hemodynamically unstable patients; benefits include improved hemodynamic stability, better overall solute clearance, and better fluid balance. However, despite the established clinical role of CRRT in this patient population, there is great variability in how the modality is prescribed and delivered.

The research team recently initiated a prospective, multi-national, observational study of patients undergoing CRRT (NCT02034448). They described the study protocol online in BMC Nephrology [doi:10.1186/s12882-017-0650-2]. The study is designed to develop a large repository of data on CRRT practices and outcomes (CRRTnet). Over the next 5 years, enrollment will continue at four academic medical centers in North America with >50 eligible patients per year; target enrollment is 2000 patients.

Inclusion criteria are adult patients ≥18 and <89 years of age with AKI receiving CRRT as part of their standard of care. Exclusion criteria are receiving CRRT for <24 hours and initiation of CRRT at an outside hospital prior to transfer resulting in incomplete available data. Of the patients who require multiple courses of CRRT during an ICU admission, only the data from the first course will be utilized. Pre-existing end-stage renal disease requiring maintenance dialysis is also an exclusion.

The primary outcome of interest is patient survival at discharge from the ICU. Patients outcomes at hospital discharge will also be recorded. Secondary outcomes include length of stay in the ICU and in the hospital, recovery of renal function during hospitalization, and adverse events related to CRRT.

Recovery of renal function is defined as return of serum creatinine to within 50% of baseline. Adverse events include (1) major bleeding related to heparin anticoagulation (drop in hemoglobin of ≥1.0 g/dL within a 24-hour period, and transfusion requirement of ≥2 units of packed red cells); (2) development of heparin-induced thrombocytopenia (fall in platelets of at least 30% and positive confirmatory rest for heparin-induced thrombocytopenia; (3) hypocalcemia event related to citrate anticoagulation (fall in systemic ionized calcium below 0.8 mmol/ and one of (a) worsening hypotension/increasing pressure requirement or (b) cardiac arrhythmia.

Particular areas of interest for initial analyses are anticoagulation protocols, approach to fluid overload, CRRT-related workload, and patient safety. Standard statistical methods will be utilized in the analyses of all descriptive data. CRRTnet will assess for potential associations between patient characteristics, CRRT initiation and prescription parameters, and patient outcomes (mortality, length of stay, duration of AKI) using ANOVA for normally distributed variables or Kruskal-Wallis for non-normally distributed variables.

Recruitment is currently active at the four academic medical centers: University of Michigan Health System (Ann Arbor, Michigan); University of Alberta Hospital, University of Alberta (Edmonton, Alberta); University Hospital London Health Sciences Centre (London, Ontario); and University of Mississippi Medical Center (Jackson, Mississippi). A fifth center is being evaluated for inclusion in CRRTnet.

In summary, the researchers said, “Over the past 30 years, CRRT has developed into an important tool for the management of critically ill patients with renal failure. Despite overall improvements, there remains marked variation in CRRT practices which is driven in part by lack of evidence-based guidance. The primary goal of CRRTnet is to develop a large data repository of CRRT patients with detailed information regarding specific CRRT practices which can then be compared in relation to outcomes. We anticipate that CRRTnet will provide the nephrology and critical care communities with an important resource for planning future clinical trials as well as for benchmarking clinical outcomes.”



Researchers describe study protocol for, a prospective, multi-national, observational study of CRRT practices.

The study is currently enrolling participants at four academic medical centers: two in the United States (Michigan and Mississippi) and two in Canada (Alberta and Ontario); target enrollment over 5 years is 2000.

The primary outcome of interest is patient survival at discharge from the intensive care unit. Secondary outcomes include length of stay in the ICU and hospital, recovery of renal function during hospitalization, and CRRT-related adverse events.