Hemofiltration 'replacement' solution alters the microcirculation.
Continuous venovenous hemofiltration (CVVH) is usually thought of as a water-removal tool for the patient with fluid overload and poor kidney function. However we should consider how the infusion of extraordinary volumes of intravenous 'replacement' fluids during hemofiltration affects the circulation: not just in the bloodstream, but with the flow of water in the tissues and even into and out of the cell. During hemofiltration a crystalloid solution (the ‘replacement fluid’), composed principally of water, sodium, potassium, bicarbonate, chloride and dextrose, is infused continuously to maintain circulating intravascular volume during active plasma water removal by the hemofilter.
Up to 72 liters may be infused intravenously in a single 24-hour period. Much of this crystalloid redistributes to the tissues, to the extravascular space, which in turn stimulates an increase in lymph flow. Proteins in the extravascular space are unavoidably flushed into the newly formed lymph and are then delivered to the plasma via the thoracic duct, effectively maintaining the intravascular content of small and middle molecular weight proteins available for filtration or metabolism.
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