Prolonged intermittent renal replacement therapy in the intensive care unit.
OBJECTIVE
To present a review on the use of prolonged intermittent renal replacement therapy in the intensive care patient.


METHODS
Articles and abstracts reporting the use of renal replacement therapy.


RESULTS
Standard intermittent haemodialysis (IHD) has significant shortcomings in the treatment of the acute renal failure (ARF) of critical illness. These shortcomings include haemodynamic instability, the need to remove excess fluid over a short period of time, the episodic nature of small solute control, the limited ability to achieve middle molecular weight solute control and the episodic nature of acid-base control. Over the last 20 years, these limitations have stimulated the evolution and increased application of continuous renal replacement therapy (CRRT) which provides major biochemical, biological and physiological advantages compared with IHD, although it remains unclear as to whether such advantages translate into a survival advantage. However, CRRT is technically demanding, requires supervision 24 hr per day and is often associated with the need for continuous anticoagulation, which, in some patients, might be undesirable. In some institutions, CRRT changes the nurse to patient ratio from 1:2 to 1:1, an alteration which has cost implications and might affect resource availability for other patients. Accordingly, techniques which prolong the duration of intermittent therapy and avoid the need for 24 hr treatment may offer "best value" in the management of ARF in the intensive care unit (ICU). These techniques will be referred to as prolonged intermittent renal replacement therapies (PIRRT) in this article. They are characterised by several fundamental principles: 1. Use of a modified or standard dialysis machines, 2. Use of diffusion, convection or any combination of the two, 3. Application of a decreased intensity of solute removal compared with IHD, 4. Extended duration of treatment beyond the typical 3 or 4 hr of standard IHD (hence the term prolonged) but not beyond an 8-12 hr period (hence the term intermittent) and 5. Use of "on-line" generation of dialysate or replacement fluid from tap water.


CONCLUSIONS
Information is now being obtained on the efficacy and safety of PIRRT in the ICU. Several units in Australia have started applying this technology to patient care. It is now important that critical care physicians and nurses become familiar with its principles and practice.
Department of Intensive Care, Austin & Repatriation Medical Centre, Heidelberg, Victoria. rinaldo.bellomo@armc.org.au
R
R
Bellomo
I
I
Baldwin
N
N
Fealy