RRT treatment for AKI: is more always better?

Abstract

Acute kidney injury (AKI) is an increasingly common condition, occurring in up to 25% of critically ill patients admitted to the intensive care unit (ICU) [1]. It is associated with significant morbidity and up to 60% in-hospital mortality in its most severe form, necessitating renal replacement therapy (RRT) [2]. In the absence of effective pharmacological therapy, the treatment of patients with AKI is predominantly supportive, managing haemodynamic and volume status, correcting electrolyte and acid–base disturbances, providing adequate nutrition and adjusting drug doses. In patients with sustained, severe renal failure, RRT is indicated for the management of volume overload, hyperkalaemia, acidosis and symptoms of uraemia while awaiting the recovery of kidney function. Most clinicians are convinced that RRT is life saving and not starting RRT will lead to death in severely ill AKI patients, but data are lacking to support this opinion. Conservative treatment for AKI has only been considered as the treatment option for less severe patients. In recent years, several controlled studies [3–7] and metaanalysis [8–10 ]s howed similar benefit with continuous and intermittent dialysis modalities. Critics of the published studies, however, pointed to different shortcomings in these studies [11, 12]. However, hard data remain absent or conflictive regarding when to start dialytic therapy and what constitutes the appropriate dose [13]. In 2011, the Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline for AKI was developed, aiming to assist practitioners caring for adults and children at risk for or with AKI [14]. They recommend to initiate RRT emergently when life-threatening changes in fluid, electrolyte and acid–base balance exist. Continuous RRT (CRRT) and intermittent RRT (IRRT) are considered as complementary therapies, but they suggest using CRRT, rather than standard IRRT, for haemodynamically unstable patients. The dose of RRT to be delivered should be prescribed before starting each session of RRT. KDIGO recommend delivering a Kt/V of 3.9/week when using IRRT or extended RRT and an effluent volume of 20–25 mL/kg/h for CRRT. This will usually require a higher prescription of effluent volume. Numerous modalities of RRT can be used in the treatment of patients with AKI. These include various modalities of intermittent haemodialysis (IHD), of CRRT, ‘hybrid’ modalities such as sustained low-efficiency dialysis (SLED), that combine aspects of both conventional IHD and CRRT, and peritoneal dialysis. Although there are many arguments favouring the use of continuous therapies in critically ill patients with AKI [15], the predominance of current evidence does not support a benefit of CRRT compared with IRRT. Nonetheless, the use of CRRT versus IRRT remains a subject of ongoing controversy, in particular because studies of modality must