Talk:Hemofiltration
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Is this lifted from another source?Felix-felix 11:50, 30 March 2006 (UTC)
I suspect strongly that it is, and not only that, but its pretty poorly written with multiple factual errors. Unless there are any objections, I will do a rewrite, when I get around to it.Felix-felix 11:53, 31 March 2006 (UTC)
Here's the previous version; Hemofiltration (Haemofiltration) is the replacement of blood plasma with an electrolyte solution by filtering plasma out of the bloodstream. It may be necessitated by acute renal failure.
Haemofiltration is a term used synonymously with Haemodialysis and is a common renal replacement therapy used in critical care settings. Renal replacement therapies mimic normal renal function by introducing a semi-permeable membrane in between the patient’s blood and a collection vessel. It’s use is confined to patients with moderate to severe renal failure.
Kidney dialysis is a medical treatment used to remove waste materials from the blood of patients lacking sufficient renal function. Blood from an artery is pumped through a dialyser, or artificial kidney, where it flows past a semi-permeable membrane. Dialysis fluid passing on the other side of the membrane removes unwanted elements in the blood by the process of diffusion. The blood is then returned to the body through a vein.
dialysis (daι’ælιsιs) the separation of small molecules from large molecules and colloids in a solution by the selective diffusion of the small molecules through a semi-permeable membrane.
filtration (filtrā’shen) a type of haemodialysis in which there is convective transport of solute through ultrafiltration across a semi-permeable membrane; reported to be more effective than diffusion in removing large molecular weight solutes (creatinine) from blood, particularly in uraemia.
Whilst used synonymously, the two terms Haemofiltration and Haemodialysis differ in that Haemodialysis is usually only employed in hospitals with integral renal units. It involves the pumping of large volumes of blood through a circuit with a flow of “dialysate” (a solution subjected to dialysis) flowing in the opposite direction to ensure rapid removal of excess fluids and electrolytes.
However, haemodialysis has complications which are significantly problematic in critically ill patients, these include; · Cardiovascular compromise, i.e.; hypovolaemia, hypotension and dilutional anaemia. · Disequilibrium syndrome, a chemical imbalance caused by rapid removal of toxins, resulting in neurological problems. · Immunological problems. · Water and solute removal and transfer of extravascular fluid to intravascular spaces.
Haemofiltration overcomes many of the problems of haemodialysis. It is a convective process in which there is mass movement of water and solutes across a permeable membrane.
Blood on one side of the membrane exerts hydrostatic pressure, via the use of a pump, which allows plasma, water and solutes to move across the membrane by hydrostatic ultrafiltration to become “filtrate” (liquid that has been filtered). A pump controls the amount of filtrate removed.
Constant draining of the filtrate compartment creates negative pressure on the other side of the membrane, ensuring a pressure gradient.
Due to their molecular size, proteins and cellular constituents of blood are not able to move across the membrane, but waste products, which can be approximately measured by markers urea and creatinine are. Removal of waste products can only be achieved by removal of an accompanying volume of water and other solutes and should be replaced using an isotonic fluid, i.e.; having the same osmotic pressure as the fluid removed. Fluid replacement should also aim to replace solutes lost in the filtrate that would normally be re-absorbed by the normally functioning kidney such as Sodium and Calcium.
There are various types of haemofiltration, some of which depend purely on the systolic blood pressure of the patient as a driving force and some that depend on the introduction of a pump to ensure driving pressure.
The type of haemofiltration used on this unit is “Continuous Veno-Venous Haemofiltration” (CVVH). This is a pumped method using a double lumen cannula sited in a large vein (usually femoral or sub-clavian) for removal from and return of blood to the patient.
Indications for Haemofiltration. · Metabolic acidosis (pH < 7.3 and continuing to fall) · Hyperkalaemia. · Fluid overload. · Severe uraemia resulting in confusion, nausea and vomiting. · Elevated renal function results, i.e.; urea > 30 mmol/l and creatinine > 300 μmmol/l.
Ultimate aims of any type of renal replacement therapy are to relieve fluid overload, maintain fluid balance, remove waste products and to maintain metabolic and electrolyte homeostasis.
Hope you prefer my versionFelix-felix 08:47, 3 April 2006 (UTC)
