MEDI7111 Lecture Notes - Lecture 15: Solution, Radial Artery, Dietitian
Therapeutics
Diuretics
Dialysis
Dialysis is the removal of toxic waste products and excess water, from blood across a
semipermeable membrane. It can help to combat some consequences of chronic renal failure
such as accumulation of nitrogenous wastes, electrolyte imbalance, salt/water overload and
acidosis.
Dialysis works through the formulation of a fluid (dialysate) which varies in content and
concentration to establish a concentration gradient of waste products out of the blood, when
passed beside a semipermeable membrane. There are two major categories of dialysis;
haemodialysis and peritoneal dialysis.
Haemodialysis
The patients’ blood is pumped through a dialyzer exposing it to a partially permeable
membrane, which consists of a multitude of hollow synthetic fibres, the blood passes through
these fibres with a dialysate solution on the outside, thus allowing water and wastes to flow
between the two.
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Document Summary
Dialysis is the removal of toxic waste products and excess water, from blood across a semipermeable membrane. It can help to combat some consequences of chronic renal failure such as accumulation of nitrogenous wastes, electrolyte imbalance, salt/water overload and acidosis. Dialysis works through the formulation of a fluid (dialysate) which varies in content and concentration to establish a concentration gradient of waste products out of the blood, when passed beside a semipermeable membrane. There are two major categories of dialysis; haemodialysis and peritoneal dialysis. Ultrafiltration is achieved by applying a negative pressure to for a greater hydrostatic pressure. The blood flows through the dialyser at ~200-400ml/min (with the pressure driven by map) whereas the dialysate flows at 500ml/min allowing for greater exchange. Additionally, there is counter current flow between the two fluids, further encouraging product exchange. Access for haemodialysis in the short term/initial stages of treatment is done by venous catheter but ideal access is from an arterio-venous fistula.
