Investigation of a haemolytic transfusion reaction

Investigation of a haemolytic transfusion reaction

HAEMOLYTIC TRANSFUSION REACTIONS


INTRODUCTION

Haemolytic transfusion reactions (HTR) occur because of the transfusion of incompatible blood. They can be immediate or delayed. Immediate HTRs are usually due to ABO incompatibilities, for example due to group A red cells being given to a group O patient. Rarely, antibodies to other blood group antigen systems may also be involved in immediate HTR. Immediate HTR are usually due to clerical errors. Because anti-A, B and AB antibodies are naturally occuring (i.e. without prior sensitization), the reaction occurs immediately. Because these antibodies are IgM and hence, efficient at fixing complement, intravascular haemolysis can occur due to the action of the final products of the complement cascade. In addition effects due to other complement cascade intermediates such as fever, hypotension, chest pain, bronchospasm, DIC, etc.

Delayed HTR are not so dramatic and are usually noticed a week or two after a transfusion. Antibodies to antigens other than ABO, eg.,the Rh, Kell, Duffy, Kidd antigen systems are commonly responsible. Delayed HTR occur because of an anamnestic response to blood group antigens that the patient has previously encountered, either by way of transfusions or pregnancies. The antibody screen on the patient’s serum sample and the cross-match between the patient’s serum and the donor RBCs may well have been normal during the initial testing. They are subtle in their manifestations and may present only as a mild jaundice or as a failure of the Hb to rise as expected.
 
Fortunately, HTR are rare but they can be fatal. According to one US study, this happens with 1 in every 200,000 transfusions and that 41% of transfusion related fatalities are supposed be to be related to immediate HTR. Most serious HTR occur because of clerical errors and are therefore preventable.

IMMEDIATE STEPS

  • Stop the transfusion.
  • Keep the line open with normal saline.
  • Obtain additional venous access.
  • Provide respiratory support with 100% oxygen if bronchospasm is significant.
  • Monitor vital signs such as pulse, BP, respiratory rate, temperaure urine output and oxygen saturation.
  • Consider giving iv Frusemide if oliguric.
  • Collect samples for tests (see below).
  • Keep all records pertaining to the transfusion, the blood bag, iv lines, etc.
  • Check records (patient identification, identification on the unit, etc.) to see if an obvious error has been made.
  • Contact the transfusion centre or blood bank.
  • Attend to other complications such as DIC, bronchospasm and hypotension.

INVESTIGATIONS

  1. Full blood count }
  2. Baseline urea and electrolytes } on the post reaction sample
  3. Baseline coagulation screen and FDP }
  4. Repeat ABO and Rh grouping including the direct antiglobulin test (DAT) (on pre-reaction and post-reaction patient RBCs, on the stored RBC sample from the donor unit and also if possible on an RBC sample drawn from the transfused unit itself).
  5. Repeat antibody screening (on the pre and post reaction patient samples)
  6. Cross match pre-and post-reaction serum samples from the patient with RBCs from the stored sample of the donor unit and if possible, with RBCs drawn from the transfused unit itself.
  7. Blood cultures from the patient as well as from the unit.
  8. Urine sample to see if Haemoglobinuria (? iv haemolysis) or haematuria (?DIC) are occuring

 Of these, tests 4 – 6 will be done at the blood transfusion centre and the others in other appropriate laboratories.

INTERPRETATION OF RESULTS

 
 

TEST  RESULT  INTERPRETATION 
a. Grouping I. Donor group not as labelled on donor unit Labelling or grouping error
ii. Pre and post reaction patient RBC sample groups not the same Error in patient identification (i.e. pre transfusion sample from X but transfusion given to person Y) or grouping error.
iii. Mixed Field Reaction (MFR) on post-reaction patient RBC sample Presence of cells of 2 different groups in the sample (e.g. a few group B cells mixed with a lot of A group cells will give a MFR reaction when tested with anti – B)
b. DAT Positive on the post reaction patient RBC serum sample Sensitized RBCs
c. Antibody Screening Negative on the pre-reaction patient serum sample but positive on the post-reaction serum sample (using the screening cells)Note: Ab screening may be negative with both pre and post reaction patient samples using the usual screening cells even if a haemolytic transfusion reaction has occurred. This is because most such reaction are due to incompatibilities in ABO matching and the screening cells being group O will not detect this Anamnestic reaction or pre and post reaction samples are not from the same person 
d. Cross matching of donor RBC with patient pre and post reaction serum samples i. Compatible with pre reaction sample, incompatible with the post reaction sample As above 
ii. Both pre and post reaction samples are incompatible Error during pre-reaction testing or incompatible unit administered by mistake.

 

 
PREVENTION

  • Avoid unnecessary transfusions.
  • Avoid ’emergency’ transfusions whenever possible. Avoid transfusing at night.
  • Send patient samples to the transfusion centre well in time (say 12 to 24 hrs prior to requirement) to allow proper selection of units and cross-matching. If however the patient has had a transfusion or pregnancy in the previous 3 months, the sample for compatibility testing must be sent as close to the intended time of transfusion.
  • Provide donor details especially with respect to prior sensitizing events like pregnancies and transfusions.
  • Take great care during patient, sample and unit identification.
  • Attention to detail in the laboratory and the use of approved methods.

Dr.K.G.Badami MD,MRC (Path)
Consultant Haematologist
Email : [email protected] 

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