Emergency Transfusion with Anti-K and Limited K-Negative Inventory
A 27-year-old woman at 38 weeks' gestation is admitted with placenta previa and active vaginal bleeding. Blood pressure is 90/60 mmHg, pulse 120/min, Hb 5.8 g/dL, platelets 110 × 10⁹/L, INR 1.3 and fibrinogen 2.0 g/L. The blood bank types her as group B RhD negative; the antibody screen is positive, and the panel identifies anti-K with a titre of 1:16. There is no anti-D. Inventory: two units B RhD-negative, both K-positive; four units O RhD-negative, K-negative; six units B RhD-positive, K-negative. The obstetrician requests four units urgently and says, 'Give whatever is fastest.' The patient continues to bleed and the blood bank has one technologist on duty.
1. Which units would you issue first and why? Address ABO/RhD compatibility, anti-K and emergency release.
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Anti-K is a clinically significant IgG antibody associated with delayed haemolytic transfusion reactions and haemolytic disease of the fetus and newborn. K-positive units should not be given while K-negative units are available. The first choice is O RhD-negative K-negative packed red cells: O red cells are ABO-compatible with a group B recipient, and the units are D- and K-negative. B RhD-positive K-negative units would avoid anti-K but risk anti-D alloimmunisation in a woman who may have further pregnancies; reserve them only for catastrophic exsanguination when no D-negative units remain. Do not use the two B RhD-negative K-positive units.
Issue by emergency release with a signed request and compatibility label, and continue the antibody workup. Telephone the obstetrician to explain why 'fastest' must not mean K-positive. Activate the massive transfusion protocol, call in backup, and switch to group-specific B RhD-negative K-negative units if they become available. A titre of 1:16 does not override the need to avoid the antigen; the decision is based on the antibody's clinical significance and the patient's history.
2. After 15 minutes of the first unit she develops fever, chills, flank pain and dark urine. What is the differential and immediate workup, and how does it change your transfusion plan?
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This is an acute haemolytic transfusion reaction until proven otherwise; septic transfusion reaction and febrile non-haemolytic reaction are also in the differential. Stop the transfusion immediately, keep the vein open with saline, and check the patient's identity and the unit label at the bedside. Notify the clinician and blood bank. Send post-transfusion samples for repeat ABO/Rh, direct antiglobulin test, antibody screen and elution if indicated; check plasma free haemoglobin, LDH, haptoglobin, urine haemoglobin, coagulation and renal function; culture the unit and the patient's blood. Maintain urine output and monitor for disseminated intravascular coagulation.
Do not restart the same unit. The transfusion plan changes: give only O RhD-negative K-negative red cells, and support with fluids and blood products as clinically indicated. Report the reaction to the hospital transfusion committee and, if a clerical error is found, review the entire emergency-release process.
3. If no K-negative units remain and the patient is exsanguinating, how would you decide and document the next step?
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The decision is a risk-benefit judgement. If bleeding is immediately life-threatening, the risk of withholding transfusion may exceed the risk of giving a K-positive unit, but that should be a documented clinical decision, not a default. First look for any remaining O RhD-negative K-negative units, including from a nearby blood bank, and call a haematologist. If none exist, use crossmatch-compatible units after discussion with the clinician, document the indication and the known risk of anti-K, and monitor closely for haemolysis. Do not assume that an immediate-spin-compatible unit is safe: anti-K is IgG and may not react at immediate spin. Premedication does not prevent haemolysis. Continue uterotonics, tranexamic acid, balloon tamponade and early transfer. If the patient refuses blood, document capacity and informed refusal.