Since the electrolyte composition of the filtrate is similar to plasma water, adaptation of the composition of the replacement solution can correct almost every electrolyte disturbance. The sole restriction is the correction of severe hyperkalemia with arteriovenous hemofiltration; in a patient with a plasma potassium above 6 mmol/l, a daily filtration rate of 10 l eliminates only 60 mmol which represents a small fraction of the total body content. Commercially available replacement solutions do not contain phosphate. Large sodium losses can occur if filtrate replacement is partial.
Correction of metabolic acidosis may present a problem when lactate is used in patients whose capacity to metabolize lactate is not high enough to compensate for bicarbonate losses in the ultrafiltrate.
A filtration rate of 10 ml/min is considered necessary to compensate uremia. In hypercatabolic patients these relatively low filtration rates may be inadequate.
Efficiency can be increased by addition of dialysis or by the use of a blood pump.
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