Uncrossmatched Blood

Emergency release provides blood without completed pretransfusion testing when delay would risk death. Use is justified in life-threatening haemorrhage when waiting for full compatibility testing is unsafe. The trade-off is a small risk of haemolysis from undetected antibodies in return for immediate oxygen carrying capacity.

Authorisation. A senior clinician requests the units and signs a form accepting the risk. The blood bank documents the release.

Before release.

1. Take a correctly labelled sample before any blood is given, so testing can continue.

2. Use the patient's emergency identifiers if the identity is unknown (for example a trauma number), and do not change identifiers during the episode.

3. Alert the blood bank to the anticipated number of units.

Special groups.

• Women of childbearing potential and girls: RhD negative and, where available, K negative red cells.

• Males and older women: RhD positive red cells are acceptable when RhD negative stock is limited.

• Known antibody history: tell the blood bank, since the risk is highest in those previously transfused and in multiparous women.

• Neonates: group O RhD compatible blood with low risk from maternal antibodies.

Products.

• Red cells: group O, uncrossmatched.

• Whole blood: low titre group O whole blood in systems that use it.

• Plasma: AB or group A low titre plasma in systems that use it, or thawed plasma as supplied.

• Platelets: group O or ABO compatible, depending on blood bank supply.

Equipment. Intravenous access of large gauge, a blood giving set with filter, a rapid infuser or blood warmer if available, and monitoring.

Bedside checks. Even in an emergency, the patient identity and the unit label are checked by two staff. Emergency labels or numbers must be accurate.

Timeline in practice.

1. Recognise life-threatening haemorrhage and call for senior help.

2. Take the sample and send it urgently.

3. Request emergency units. Group O red cells are usually available immediately.

4. Start transfusion and control the source of bleeding.

5. When the sample reaches the blood bank, the group is determined (usually within 10 to 15 minutes) and group specific blood replaces group O.

6. Full crossmatch is completed in about 45 minutes while transfusion continues.

7. Switch to crossmatched products when ready.

Balanced resuscitation. Give plasma and platelets as the massive haemorrhage plan directs, and consider early tranexamic acid.

If transfusion is stopped early. Return unused units promptly if within validated time and temperature limits.

Complications. Acute haemolysis from antibodies, alloimmunisation in RhD negative recipients receiving RhD positive blood, and the usual risks of massive transfusion.

After release. The laboratory completes the crossmatch. If an incompatibility is found, inform the clinician at once. Monitor for haemolysis: urine colour, haemoglobin, bilirubin, lactate dehydrogenase, haptoglobin and direct antiglobulin test. Consider anti-D immunoglobulin or specialist advice when RhD positive blood is given to an RhD negative woman of childbearing potential.

Documentation. Time of request, who authorised, products and units given, patient identifiers and results of retrospective testing.

Quality assurance. Audit the time from request to first unit, the use of emergency blood and the rate of incompatibility. Review each release case with the team.