Case 34 – summary

This was a varied case centered around an unwell patient with sickle cell anaemia post surgery.

There were a number of themes to cover in this case reminding us that patients with sickle cell anaemia can be complex and require careful medical management.

The assessment of the unwell patient with sickle cell anaemia

It is essential to follow some of the basic management principles for patients with sickling disorders, especially when they are acutely unwell.  These include:

  • Keeping the patient warm
  • Ensuring the patients are well hydrated
  • Oxygen therapy if evidence of hypoxia
  • Adequate analgesia whilst monitoring respiratory function
  • Prevention of further complications by incentive spirometry/chest physiotherapy
  • Low threshold for antibiotics (remembering they are hyposplenic)
  • Transfusion support when indicated
  • Careful VTE assessment
  • Avoid acidosis
  • Early haematology input

Management of drop in haemoglobin

Patients with sickle cell disorders are anaemic and it is not necessary to transfuse to the reference ranges. Sudden onset anaemia needs further investigation and causes identified:

  • Blood loss (especially if post operative) – menorrhagia, GI bleeding etc.
  • Haematinic deficiency
  • Medications – e.g. hydroxycarbamide
  • Parvovirus B19 (and other viral infections or infective insults that result in temporary reduction in marrow function)
  • Splenic sequestration
  • Haemolytic transfusion reaction
  • Hyperhaemolysis syndrome

Transfusion in sickle cell anaemia

Care must be taken to transfuse patients only when necessary. Complications of red cell transfusion include:

  • Circulatory overload
  • Allergic reactions
  • Wrong blood resulting in major haemolytic transfusion reaction (usually labelling errors)
  • Infections – very rare
  • Development of red cell antibodies
  • Iron overload leading to liver and cardiac damage in addition to endocrinopathies

In order to prevent red cell antibodies patients with sickle cell anaemia and other disorders where chronic transfusions are needed have blood that is matched more closely. In the UK patients with sickle cell anaemia will be matched for ABO, Rh c/C/D/e/E and K/k. Ideally patients would also be matched for Fya and Fyb (Duffy) but this would make transfusion very difficult due to the blood donation demographic. Other ‘normal’ patients would just be matched for ABO and possibly RhD. Prior to transfusion patients are therefore ‘phenotyped’ – this is where the transfusion lab will see what antigens are on the red cell surface. This enables us to match for the Rh and Kell system and also makes it easier to rule out certain antibodies if an antibody is detected (i.e. someone that is known to have RhD will not develop anti-D).

However transfusion can be lifesaving in the following situations:

  • Post stroke or abnormal transcranial doppler
  • In acute crisis – especially chest crisis
  • Pre operations
  • Severe anaemia due to aplastic crisis

For major surgery/stroke the HbS concentration should ideally be less than 30%. If the haemoglobin is already on the high side then exchange transfusion is used.  Transfusion is thought to help by increasing oxygen carrying capacity, suppressing erythropoiesis (abnormal HbS) and reducing HbS concentration.  In general for most procedures a simple top up transfusion is required pre op to obtain Hb >90g/L. For major/prolonged surgery (e.g. cardiovascular), or previous chest crisis an exchange tranfusion is preferred aiming HbS <30%.

Our patient and hyperhaemolysis

She had sudden drop in Hb about 6 days post op. She had a pre operative transfusion. There was no evidence of blood loss. The main differential was delayed haemolytic transfusion reaction, however there was not a reticulocytosis, the Hb dropped to lower than pre transfusion levels and no antibody was found (save for the known antibodies) and the direct antiglobulin test was negative. If this was a delayed haemolytic transfusion reaction one would expect (not always!) a reticulocytosis, a new red cell antibody to be found and the DAT to be positive.  In addition the red cell panel was similar to prior transfusion.  HPLC may be helpful to prove

Acute hyperhaemolysis is thought to be a rare condition characterised by a drop in Hb to lower than pre transfusion sample with evidence of haemolysis but no reticulocytosis. It happens within seven days of transfusion. The patient’s red cell, donor red cells and new reticulocytes are destroyed, possibly due to a ‘macrophage activation syndrome’. Macrophages are potentially activated by sickling or infection or due to complement activation causing bystander haemolysis. This is exacerbated by relative erythropoietic suppression caused by the transfusion.  Previously both HbS and HbA have been found in patients’ urine following hyperhaemolysis suggesting that both donor and patient blood is haemolysed.

It appears that further transfusion (even with matched blood) exacerbates the problem with further haemolysis of the donated blood with associated complications. Intravenous immunoglobulin plus/minus steroids and avoiding transfusion along with supportive care appear to be key here.

In our patient we initially persisted with transfusion but then following investigation changed tact and following IvIg the patient’s haemoglobin gradually started to rise.

References:

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