Platelets are a component of blood essential in coagulation. When tissue has suffered injury, platelets collect at the site, forming a barrier and activating other coagulation factors. Platelet apheresis is a method of platelet collection in which blood is taken from a donor and processed to have the platelets removed. Medical professionals then return the remaining blood components to the donor.
To perform platelet apheresis, a nurse inserts a cannula into either one or both of the donor's arms. Blood then travels down the tube from the donor's arm and into a specialized apheresis machine, which acts as an automated cell separator. Inside the machine, the blood combines with an anticoagulant, such as sodium citrate, to prevent it from clotting.
The blood spins inside a sterile, single-use centrifuge, which separates the platelets from the rest of the blood. Separated platelets divert into a designated bag, and the blood, plus some saline, is returned to the patient via the other arm. If only a single cannula is used, then the blood is returned via that arm. Generally, three to four cycles are carried out per donation. This process normally takes 90 to 120 minutes.
Although platelets can be separated and used from whole-blood donations, platelet apheresis is much more effective at obtaining sufficient amounts. Each donation using platelet apheresis can result in up to three usable units, whereas six units of blood are required to produce a single dose. Using a single donor per dose also minimizes the occurrence of transfusion-transmitted infections or reactions that may be more common with pooled products from a number of donors.
Due to a smaller amount of blood being removed, and because the body replaces the amount taken within 48 hours, a person can donate platelets more often than blood. This is very useful because of the high demand for platelets due to their relatively short shelf life of five days. They are used to treat a number of conditions where excessive bleeding may become a problem, such as in burn victims, bone marrow or organ transplants, and heart surgery.
To donate using platelet apheresis, donors must be over 18 and in good health. Even though the platelets are tested for viruses such as HIV before they are transfused to a patient, donors also have to undergo health screening before they are allowed to donate. Platelets can be donated at specific hospitals, clinics, and donation centers.