الفهرس 
Pathophysiology of Renal DiseasesOnly 14 pages are availabe for public view
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Abstract
The prevalence of acute renal failure in critically ill patients remains high and mortality is up to 60%. Both the practice of renal replacement therapy (continuous against intermittent, haemofiltration against haemodialysis) and patient outcomes vary widely between studies. In most developed countries, the prevalence of acute renal failure (ARF) in critically ill patients ranges from 1 to 25%. Approximately 4% of this group receive renal replacement therapy (RRT) .
Currently available modalities of renal replacement therapies for treatment of acute renal failure includes peritoneal dialysis, intermittent hemodialysis, continuous renal replacement therapy and the newly developed hybrid technique, Sustained low-efficiency daily dialysis. Each of these modalities has its own advantages and disadvantages. In addition, newer devices such as bioartificial membrane show great promise, but must be well investigated.
The optimal choice between different modalities of RRT in ARF remains uncertain. It is well accepted that initiation of RRT in patients with progressive azotaemia prior to the development of overt uremic manifestations is associated with improved survival, however, this effect is still uncertain as retrospective and observational studies suggesting improved survival with very early initiation of RRT have not included patients with ARF who recover renal function or die without ever receiving RRT.
One large epidemiological study found that the main (but not the only) reasons for starting RRT were severe diuretic unresponsive oliguria/anuria followed by uncontrolled uraemia and fluid overload. There are no universally accepted levels of urea, creatinine, potassium or pH or decreased level of glomerular filtration rate (GFR) at which to start the therapy. Urea and creatinine are easily measured but are not the only uraemic toxins and are affected by non-renal factors. Urine output may be more sensitive to changes in renal haemodynamics, but oliguric and non oliguric AKI can occur and urine volume may be influenced by diuretic use.
The patients on RRT may have series of complications which involve in each system of whole body, such as combined cardiovascular system disease including hypertension, hypotension, heart failure, arrhythmia, percarditis, coronary artery blood supply shortage, myocardial infarction and so on. Accompanying infection: since the immunity of uremic patients is very low, the long-term dialysis is likely to cause infection with the bacterial infection of vascular access, respiratory system and urinary system being most commonly seen, nephrotuberculosis and virus hepatitis as well.
Recent data suggest that the modality of RRT used does not impact either survival or recovery of renal function and all dialysis strategies should be mastered and utilized in the appropriate indications for ARF patients. So far, no hard evidence is available that one technique above another is superior, if they are used for the correct indications and applied by a skilled ICU and dialysis team.
In cardiogenic shock after massive myocardial infarction or low-output syndrome caused by cardiomyopathy, acute renal failure and loss of diuresis caused by renal perfusion impairment is frequent. This leads to fluid and electrolyte imbalance and the accumulation of toxic metabolites, which also further suppresses cardiac function. These factors contribute to marked cardiovascular instability. In these patients, the performance of intermittent hemodialysis is not recommended because of severely compromised hemodynamics. Therefore, CVVH is administered in order to remove excess body fluid, to correct metabolic acidosis, and to eliminate uremic metabolites. As a result, an improvement of the cardiovascular situation is observed. Therefore, CVVH in patients with cardiogenic shock and acute renal failure is the first choice for renal replacement therapy
Currently, continuous renal replacement therapy (CRRT) is the best way to support patients with advanced AKI and cardiogenic shock. It allows controlling volume and correction of electrolyte and acid-base disorders with less hemodynamic impact. In recent years, other forms of extracorporeal fluid removal have been developed (e.g., aquaphoresis), but existing data provide no evidence of advantage relative to CRRT, and the absence of solute clearance is a significant disadvantage.