الفهرس 
Renal FunctionOnly 14 pages are availabe for public view
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Abstract
Acute renal failure could be defined as a syndrome characterized by rapid decline in glomerular filtration rate (hours to days), retention of nitrogenous waste products, and perturbation of extracellular fluid volume and electrolyte and acid-base homeostasis. ARF complicates approximately 5% of hospital admissions and up to 30% of admissions to intensive care units.
Mortality rates of ARF in ICU patients remain high, from 28 to 90% in studies of heterogenous populations.
Certain preexisting conditions are known to increase the risk for ARF. These chronic risk factors include preexisting renal impairment, atherosclerosis, hypertension, diabetes mellitus, congestive heart failure, chronic liver failure, and advanced age.
Etiology of ARF is divided into three categories, Pre renal ARF (55% to 60%), intrinsic ARF (35% to 40) and post renal ARF (<5%).
Clinical feature and physical examination may aid in providing clues to the cause of ARF. Assessment of urine output is required as patients of ARF are usually oliguric (urine output less than 0.3 ml/Kg/h for at least 24 hours). Anuria (urine volume < 100 or complete absence of urine) is rare and usually indicates acute urinary tract obstruction or vascular occlusion, but may complicate severe cases of prerenal or intrinsic renal failure. whereas patients with partial urinary tract obstruction can present with polyuria due to impairment of urine concentrating mechanisms.
To aid in appropriate hemodynamic support, invasive monitoring has been used to guide therapy. Technique such as the pulmonary artery catheter rely on the measurement of filling pressures, such as central venous pressure and pulmonary artery occlusion pressure, to estimate preload responsiveness.
Urinalysis, fractional excretion of Na+, blood urea, serum creatinine and creatinine clearance are considered leading laboratory diagnostic criteria for ARF. In addition to imaging studies and abnormal serologic markers, searching for various autoantibodies as a apart of the basic workup of immunologically mediated renal disease, including glomerulonephritis.
Intensive care unit patient with oliguric AKI presents adilemma with limited therapeutic options. These would include optimization of systemic hemodynamics, added fluid therapy, administration of loop diuretics, or finally, the instillation of renal replacement therapy.
Extracorporeal blood purification techniques can be applied to prevent these complications and improve homeostasis. Various techniques of renal replacement therapy include continuous venovenous hemofiltration, intermittent hemodialysis, and peritoneal dialysis, each with its technical variations but with a common fundamental principle of removing unwanted solutes and water through a semipermeable membrane. The membranes used are either biologic (peritoneum) or artificial (hemodialysis or hemofiltration membranes) and have characteristic advantages and disadvantages.
For many years, intermittent hemodialysis (IHD) was the only treatment option for patients with ARF in the ICU. In numerous countries, it is still the most frequently used modality. Continuous venovenous hemofiltration (CVVH) was subsequently proposed as an alternative to IHD in the critically ill, because it was better tolerated by hypotensive patients, and the continuous regulation of fluid and nutritional support avoided cycles of volume overload and depletion.
Other new approaches to intermittent therapy (so-called hybrid techniques), such as slow extended dialysis, slow low-efficiency daily dialysis, and intermittent extended hemofiltraiton, are emerging. These techniques seek to adapt intermittent hemodialysis to the clinical circumstances and increase its tolerance and its clearances. Such hybrid approaches represent a welcome improvement in dialysis support and a clear recognition that acute renal failure patients should not receive the dialysis offered to patients with end-stage renal failure.