Dialysate

Contents:

Composition and function of dialysate

Acetate Dialysate

Bicarbonate Dialysate

 The term dialysate refers to the fluid and solute that have crossed a membrane i.e. effluent dialysis fluid. However, in current renal jargon all dialysis fluid, fresh or used is called dialysate. Dialysate is sometimes called “bath". The composition of dialysate is nearly correspond  to that of plasma water.

• Composition and function of dialysate

Composition of dialysate:

There are five compounds

1. Sodium chloride

2.Sodium acetate or Sodium bicarbonate

3. Calcium chloride

4. Potassium chloride

5. Magnesium chloride.

Glucose may be included in some formulas.

The use of bicarbonate in concentrate causes calcium and magnesium precipitate because of high pH.  

Function of Dialysate:

   1.It carries away the waste materials and fluid removed from the blood by dialysis.

   2.It prevents removal of essential electrolytes.

   3.It avert excess water removal during dialysis.

Types of dialysate: 

Two types of dialysis solutions are discussed in the following 2 tips

1-Acetate Dialysate

2-Bicarbonate Dialysate

• Acetate Dialysate

Acetate is physiologically compatible with blood and metabolized to bicarbonate in the liver. It is mixed with water in proportioning system, usually 1 part concentrate and 34 parts of water, to form the dialysate. A typical composition of acetate containing dialysate (after mixing) contains, Sodium 135-145 mEq/L, potassium 0-4 mEq/L, Calcium2.5-3.5 ,Magnesium 0.5-1 mEq/L, Acetate 35-38 mEq/L, Chloride 100-119 mEq/L, Dextrose 11 mEq/L ,PCo2  0.5 mmHg.

Advantages:

1.Stable during storage

2. Not prone to bacterial contamination

3.A wide variety of formulations are available 

4.The delivery system is simple and less costly

Disadvantages:

1.Serum bicarbonate may decrease early during dialysis.

2.Acetate accumulation contribute to cardiovascular instability with vasodilatation and hypotension, nausea , vomiting, and post dialysis fatigue.

3.Acetate dialysate is not suited for high efficiency or high flux dialysis. Serum bicarbonate is depleted and acetate level may exceed the rate at which the liver can metabolize it. Therefore cardiovascular instability may be severe and disequilibrium may occur.

• Bicarbonate Dialysate

Calcium and magnesium will not remain in solution with bicarbonate because of low hydrogen ion content (high pH). To solve this problem, two separate concentrate are used. The proportioning (delivery) system mix and monitor three liquids instead of two.

1.The “A” concentrate 

2.The “B” concentrate OR powder. 

3. Purified water

·      The “A” -indicating acidified- concentrate contains sodium ,calcium , magnesium and potassium, chloride. To maintain low pH enough to keep the calcium and magnesium in solution when mixed into dialysate  a small amount of acetic acid is included.

·      The “B” -indicating bicarbonate-concentrate contains the sodium bicarbonate. Sodium chloride may be included in some preparation to raise the total conductivity.

·      Dry concentrates:  Manufacturers utilizes a delivery system that accepts a closed container of dry (powder) bicarbonate onto a special holder. Warm water passes  through the column producing a saturated solution of bicarbonate that is proportioned with water then with the A concentrate by conductivity controlled feed back system (e.g. Bicart.). The advantage of this technique avoid the problems of bacterial growth in bicarbonate concentrate and reduces the cost of storage.

• Chemicals in bicarbonate concentrates in mEq/L(after mixing)

 The proportioning system mix the two components simultaneously with purified water to form the product of dialysis solution, just before it goes to dialyzer. During mixing carbon dioxide will be generated as a result acid and bicarbonate reaction. The carbon dioxide generated will form carbonic acid , which lower the pH of the final bicarbonate containing solution to ~ 7-7.4 . In this pH calcium and magnesium remain in solution.

• Negative features of bicarbonate dialysate

 1-Liquid “B” is not stable. Some stabilizer or dry sodium bicarbonate may be mixed. The mixing process requires care to avoid much loss of Co2 ; it must be used within 24 hours.

 2-Bicarbonate concentrate is very susceptible to bacterial contamination which should be avoided . If the container has been opened for more than 72 hours it should not be used. All containers for mixing, holding, or dispensing B concentrate must be scrupulously sanitized at regular intervals.

 3-Many formulation of “A” concentrate are available therefore care must be exercised to ensure that the concentrates selected are correct for the delivery system being used.