Emergency Requests For Blood
When blood is required immediately for an emergency, its safety and availability will be dependent on whether pretransfusion compatibility testing has been completed and whether the antibody screen is negative. The transfusion of uncrossmatched blood is a clinical decision determined by the level of urgency. It is important for the requestor to clearly state to the laboratory staff the degree of urgency for the provision of blood.
Dependent on the laboratory's logistics, timeframes for the availability of blood in an emergency situation are shown in the table below:
|
Immediate
| Immediate release of group specific blood
| Provision of Group O Rh(D) negative red cells taken without pre-transfusion testing. It is essential to collect a blood sample for subsequent testing prior to the administration of uncrossmatched blood.
|
10 minutes
| Crossmatch compatible blood (see note below)
| Provision of group-specific ABO and Rh(D) compatible red cells taken without compatibility testing. |
20 minutes
| Crossmatch compatible blood (see note below)
| Crossmatch compatible blood (see note below). |
Note: Should these emergency procedures detect the presence of a red cell antibody, considerable delays in the supply of compatible red cells may occur.
Clinical judgement is required as to whether the immediate correction of blood loss or anaemia outweighs the risk of acute or delayed immune haemolysis. To avoid this dilemma, it is recommended that where possible patients be prospectively typed and screened when a need for blood transfusion may arise.
Maximum Blood Order Schedules
The available shelf life of a unit of red cells decreases each time the red cell unit is held or crossmatched for a patient who does not use it.
When more blood is crossmatched and set aside for a patient than is required, it is unavailable for other patients and increases the chance that the blood will expire before it is used.
Providing guidelines such as a policy to use 'group and hold' wherever possible, a maximum blood order schedule (MBOS) and monitoring crossmatch-to-transfusion (C/T) ratios is helpful in preventing blood expiring unnecessarily.
The MBOS defines the number of units required to meet the needs of 80-90% of patients undergoing a specific procedure and assists in ordering blood. The hospital transfusion laboratory, however, must give special consideration to patients with a positive antibody screen.
The ANZSBT guidelines contain a suggested maximum blood order schedule (1). However, institutions should also take into consideration their own particular circumstances, including patient demographics (which may have special requirements) and local surgical practice and experience.