By Raashid Ahsaan
Among the diseases than can be transmitted via transfusion are:
- HIV-1 and HIV-2
- Human T-lymphotropic virus (HTLV-1 and HTLV-2)
- Hepatitis C virus
- Hepatitis B
- Treponema pallidum
- Chagas Disease
- variant Creutzfeldt-Jakob Disease or “Mad Cow Disease” has been shown to be transmissible in blood products. No test exists for this, but various measures have been taken to reduce risks.
When a person’s need for a transfusion can be anticipated, as in the case of scheduled surgery, autologous donation can be used to protect against disease transmission and eliminate the problem of blood type compatibility. “Directed” donations from donors known to the recipient were a common practice during the initial years of HIV. These kinds of donations are still common in developing countries.
Processing of blood prior to transfusion
Donated blood is usually subjected to processing after it is collected, to make it suitable for use in specific patient populations. Examples include:
- Component separation: red cells, plasma and platelets are separated into different containers and stored in appropriate conditions so that their use can be adapted to the patient’s specific needs. Red cells work as oxygen transporters, plasma is used as a supplement of coagulation factors, and platelets are transfused when their number is very scarce or their function severely impaired. Blood components are usually prepared by centrifugation.
- Leukoreduction, also known as Leukodepletion is the removal of white blood cells from the blood product by filtration. Leukoreduced blood is less likely to cause alloimmunization (development of antibodies against specific blood types), and less likely to cause febrile transfusion reactions.
- Chronically transfused patients
- Potential transplant recipients
- Patients with previous febrile nonhemolytic transfusion reaction
- Patients with hereditary immune deficiencies
- Patients receiving blood transfusions from relatives in directed-donation programs
- Patients receiving large doses of chemotherapy, undergoing stem cell transplantation, or with AIDS (controversial).
- Neonatal transfusionTo ensure the safety of blood transfusion to pediatric patients, hospitals are taking additional precaution to avoid infection and prefer to use specially tested pediatric blood units that are guaranteed negative for Cytomegalovirus. Most guidelines recommend the provision of CMV-negative blood components and not simply leukoreduced components for newborns or low birthweight infants in whom the immune system is not fully developed. These specific requirements place additional restrictions on blood donors who can donate for neonatal use. Neonatal transfusions are usually top-up transfusions, exchange transfusions, partial exchange transfusions. Top-up transfusions are for investigational losses and correction of mild degrees of anemias, up to 5-15 ml/kg. Exchange transfusions are done for correction of anemia, removal of bilirubin, removal of antibodies and replacement of red cells. Ideally plasma-reduced red cells that are not older than 5 days are used.
- If an exchange transfusion is necessary, compatible blood must be ordered. If a severely affected ( i.e. hydropic) infant with Rh hemolytic disease is anticipated at birth, it may be necessary to have blood available in the nursery prior to the delivery. The request should be for O negative packed red blood cells of the specific volume needed and of the appropriate CMV status. This blood may be utilized in any one of the following ways:
- The RBC’s may be given as a simple transfusion (with or without additional Plasmanate) while stabilization of the infant is accomplished.
- The RBC’s may be used for a partial exchange transfusion to acutely elevate the hematocrit without changing the blood volume in a severely anemic baby.
- When the need for an emergency, complete exchange transfusion is virtually certain, arrangements can be made in advance for O negative whole blood or O negative PRBC’s resuspended in fresh frozen plasma.
- For double-volume exchange transfusions for hemolytic disease of the newborn or for hyperbilirubinemia without hemolysis, the blood used will be packed cells (type O, Rh specific for the infant) resuspended to the esired hematocrit in compatible fresh frozen plasma.
- A partial exchange transfusion is often done for polycythemia (see section on polycythemia). II. Although the standard anticoagulant (CPD) is acidic, the blood need not be buffered. If the infant is severely acidemic, consult the staff neonatologist. III. If possible, the infant should be NPO and the stomach contents aspirated prior to the procedure. IV. The exchange transfusion should be done under a radiant warmer using sterile technique.V. The donor blood should be warmed using the blood warmer to a temperature not exceeding 37oC. VI. The infants blood pressure, respiratory rate, heart rate and general condition should be monitored during the exchange transfusion according to standard nursing protocol.
VII. If the serum bilirubin concentration is at a dangerous level and the blood for exchange transfusion is not yet ready, consider priming the infant with 1 gram/kg (4 ml/kg) of a 25% solution of salt-poor albumin to bind additional bilirubin and keep it in the circulation until the exchange can be accomplished..
VIII. The umbilical vein catheter should be inserted until there is free flow of blood immediately prior to starting the exchange transfusion. See section on placement of umbilical catheters for technique. The exchange transfusion should not be done through an umbilical artery line unless the UAC is used only for blood withdrawal with simultaneous replacement through the umbilical vein or peripheral IV. At the beginning of the exchange transfusion, the first blood sample withdrawn should be sent for 1)total and direct bilirubin; 2) hemoglobin and hematocrit; 3) glucose; and 4) calcium.
- Use the “exchange transfusion kit”, which contains catheters, stopcocks, waste bag, and calcium gluconate.
- Ideally, blood (or colloid in the event of a partial volume exchange) should be infused through a peripheral vein at a rate equal to blood withdrawal from the UVC. If the “push-pull” (single catheter) technique is utilized, no more than 5 ml/kg body weight should be withdrawn at any one time.
- The exchange volume is generally twice the infant’s blood volume, (generally estimated to be 80 ml/kg). The total volume exchange should not exceed one adult unit of blood (450-500 ml). A standard two-volume exchange will remove approximately 85% of the red cells in circulation before the exchange and reduce the serum indirect bilirubin level by one-half. The exchange of blood should require a minimum of 45 minutes.
XII. The need for giving supplemental calcium is controversial. If used give 0.5 to 1.0 ml of 10% calcium gluconate IV, after each 100 ml of exchange blood. Monitor heart rate for bradycardia.
XIII. At the end of an exchange transfusion blood should be sent for sodium, glucose, calcium, total and direct bilirubin, and hemoglobin and hematocrit.
XIV. At the end of an exchange transfusion, the umbilical vein catheter is usually removed. In the event of a subsequent exchange, a new catheter can be inserted.
- Hypoglycemia often occurs in the first or second hour following an exchange transfusion. It is therefore necessary to monitor blood glucose levels for the first several hours after exchange.
XVI. The serum bilirubin concentration rebounds to a value approximately halfway between the pre- and post- exchange levels by two hours after completing the exchange transfusion. Therefore, the serum bilirubin concentration should be monitored at two to four hours after exchange and subsequently every three to four hours.
XVII. Feedings may be attempted two to four hours after the exchange transfusion.
The terms type and screen are used for the testing that (1) determines the blood group (ABO compatibility) and (2) screens for alloantibodies. It takes about 45 minutes to complete (depending on the method used). The blood bank technologist also checks for special requirements of the patient (eg. need for washed, irradiated or CMV negative blood) and the history of the patient to see if they have a previously identified antibody.
A positive screen warrants an antibody panel/investigation. An antibody panel consists of commercially prepared group O red cell suspensions from donors that have been phenotyped for commonly encountered and clinically significant alloantibodies. Donor cells may have homozygous (e.g. K+k-), heterozygous (K+k+) expression or no expression of various antigens (K-k+). The phenotypes of all the donor cells being tested are shown in a chart. The patient’s serum is tested against the various donor cells using an enhancement method, eg Gel or LISS. Based on the reactions of the patient’s serum against the donor cells, a pattern will emerge to confirm the presence of one or more antibodies. Not all antibodies are clinically significant (i.e. cause transfusion reactions, HDN, etc). Once the patient has developed a clinically significant antibody it is vital that the patient receive antigen negative phenotyped red blood cells to prevent future transfusion reactions. A direct antiglobulin test (DAT) is also performed as part of the antibody investigation.
Once the type and screen has been completed, potential donor units will be selected based on compatibility with the patient’s blood group, special requirements (eg CMV negative, irradiated or washed) and antigen negative (in the case of an antibody). If there is no antibody present or suspected, the immediate spin or CAC (computer assisted crossmatch) method may be used.
In the immediate spin method, two drops of patient serum are tested against a drop of 3-5% suspension of donor cells in a test tube and spun in a serofuge. Agglutination or hemolysis in the test tube is a positive reaction and the unit should not be transfused.
If an antibody is suspected, potential donor units must first be screened for the corresponding antigen by phenotyping them. Antigen negative units are then tested against the patient plasma using an antiglobulin/indirect crossmatch technique at 37 degrees Celsius to enhance reactivity and make the test easier to read.
If there is no time the blood is called “uncross-matched blood”. Uncross-matched blood is O-positive or O-negative. O-negative is usually used for children and women of childbearing age. It is preferable for the laboratory to obtain a pre-transfusion sample in these cases so a type and screen can be performed to determine the actual blood group of the patient and to check for alloantibodies.