Renal replacement therapy in critical care

Abstract

Acute kidney injury (AKI) affects up to 60% of intensive care unit (ICU) patients and is associated with mortality rates of between 15 and 60%. Up to two-thirds of patients with AKI go on to require renal replacement therapy (RRT). 1 Without the ability to replace native renal function, mortality from the complications of fluid overload, refractory hyperkalaemia, and metabolic derangement would be far higher. From the 1960s, hollow-fibre dialysers became available as a form of RRT and were able to be mass produced, with Scribner starting the first outpatient dialysis centres in the USA. Haemofiltration, as a form of RRT, began in the 1970s and is now an indispensable tool used as part of modern critical care management. Despite improvements in technologies, there has been only slow improvement in mortality since the 1980s. The reasons postulated for this include the lack of diagnostic tools available to detect early AKI, delayed initiation of RRT, inadequate delivery of RRT, and the inability to replace kidney function fully with current RRT modalities. Little information exists on trends in the epidemiology of AKI; however, there are several reasons to suspect that its incidence is on the rise: the increasing age and comorbidities of the hospitalized population; an increase in the prevalence of risk factors for AKI such as chronic kidney disease and diabetes; and more widespread use of i.v. contrast for cardiovascular and other radiological procedures. Mechanisms of RRT Worldwide, RRT can be provided as peritoneal dialysis, intermittent haemodialysis (IHD), and continuous renal replacement therapy (CRRT), which includes continuous veno-venous haemofiltration (CVVH), continuous veno-venous haemodialysis (CVVHD) and continuous veno-venous haemodiafiltration (CVVHDF). The majority of UK critical care units use either CVVHF or CVVHDF. 2 Some units use hybrid therapies that combine IHD and CRRT; this technique is commonly known as slow low-efficiency daily dialysis. Slow continuous ultrafiltration (SCUF) is an alternative mode of RRT used to control fluid balance particularly in patients with diuretic-unresponsive cardiorenal syndrome. The aims of RRT are solute and water removal, correction of electrolyte abnormalities, and normalization of acid-base disturbances. This is achieved via diffusion or convection which is, respectively, referred to as haemodialysis or haemofiltration. The system comprises an extracorporeal circuit filled by blood arising from a wide-bore double-lumen central venous catheter Key points • Despite improvements in renal replacement therapy (RRT) technology, the mortality associated with acute kidney injury remains high.

First 24-Hour Potassium Concentration and Variability and Association with Mortality in Patients Requiring Continuous Renal Replacement Therapy in Intensive Care Units: A Hospital-Based Retrospective Cohort Study

“…With an increase in the incidence of acute kidney injury (AKI) in recent decades, AKI is now emerging as a global health-care concern. Up to 60% of patients admitted to the intensive care unit (ICU) develop AKI, which may be associated with complications such as fluid overload, refractory hyperkalemia, and metabolic derangement [ 1 ]. In addition, AKI is associated with adverse outcomes including a prolonged stay in the ICU and hospital, higher mortality rates, and subsequent development of chronic kidney disease (CKD).…”

Mortality predictors in critically ill patients with acute kidney injury requiring continuous renal replacement therapy

“…Many studies show that CRRT offers superior hemodynamic stability, metabolic clearance, and volume control. Other advantages of CRRT include enhanced clearance of inflammatory mediators and better preservation of cerebral perfusion among patients with acute brain injury or fulminant hepatic failure [ 12 ].…”

Factors Associated with In-Hospital Mortality after Continuous Renal Replacement Therapy for Critically Ill Patients: A Systematic Review and Meta-Analysis

“…Therefore, renal replacement therapy is vital for critically ill patients with AKI to provide supportive management in critical care settings aimed at speeding up renal recovery and preventing adverse events [6]. The first choice for patients with AKI is continuous renal replacement therapy (CRRT), as most critically ill patients are hemodynamically un-stable [7,8]. CRRT refers to either dialysis or filtration treatments that operate continuously [2].…”