Preparation: Dried plasma is usually prepared from time-expired citrated blood. The supernatant fluid is separated from the blood by centrifugation process under aseptic conditions. Batches of not more than 10 bottles are pooled, choosing the correct ratio of blood groups to neutralize powerful agglutinins. The pools are kept at 4°C–6°C. Samples from the batch are tested for sterility and no pool is used unless it passes the test. Usually, 400 ml quantities are dispensed into bottles and subjected to freeze-drying.

The steps involved in the freeze-drying process are as follows:

1. Preliminary freezing: The bottles are sealed with bacteriologically efficient fabric pads covered by ring-type closures and then centrifuged at –18°C. The liquid snap-freezes and becomes distributed around the inside of the bottle.
2. Primary drying: The bottles of frozen material are mounted horizontally in the drying chamber and a high vacuum is applied. The ice sublimes on to a condensing coil kept at –50°C, and the heater provides the latent heat required for evaporation. This process takes about two days, after which the residual moisture content is about 2%.
3. Secondary drying: This drying operation is done in another chamber by vacuum desiccation over phosphorus pentoxide. The drying process takes about 18 to 20 hours and the product is left with about 0.5% of moisture.

The fabric seal is then replaced by a closure perforated by a plugged hypodermic needle. The bottles are returned to the secondary drying chamber and re-evacuated, and then the vacuum is broken with dry sterile nitrogen. Finally, the needles are removed and the closure is protected with a sterile viscose cap.

Storage: Dried plasma should be kept below 20°C and protected from light, moisture and oxygen. Under proper storage conditions, it has an expiry date of about five years. After reconstitution, it must be used immediately. Gel formation or incomplete solution indicates deterioration.

Uses: The following are some of the uses of dried plasma:

1. Reconstituted plasma is a satisfactory alternative to whole blood in conditions where there is no loss of red cells.
2. It is important in the treatment of severe burns and scalds.
3. Because of its long storage life at convenient temperature, dried plasma is more suitable than blood as a reserve stock.

Advantages: Dried plasma has the following advantages:

1. If properly stored, it can be used for four to five years.
2. It can be stored at temperature below 20°C if protected from light.
3. It can be given to patients of any blood group.