Q: 26 year old is admitted to ICU with Sickle cell crisis/disease (SCD). Intern on call 'reflexly' ordered three units of blood after hemoglobin level found to be lower than 7 g/dL. Post transfusion Hb is reported 13 g/dL. Now Attending is not happy! and wants to do phlebotomy. What is the target value for Hgb and HgbS, when phlebotomy is implied for SCD?


Answer:

Ideally blood transfusion should be avoided as much as possible in SCD. Hyperviscosity is a significant risk factor after blood transfusion in Sickle cell Disease (SCD). Risk for hyperviscosity goes high with Hgb above 10 g/dL and HgbS more than 50 percent of total Hgb.

Phlebotomy has been employed as one mean to decrease the level of Hgb and HgbS. If phlebotomy is considered to prevent or treat the hyperviscosity in SCD, target is to decrease Hgb below 10 g/dL (and HgbS less than 50 percent of total Hgb).


Note: Above question is an academic exercise. Other means to decrease viscosity in SCD should be considered like exchange blood transfusion, by obtaining proper hematology service consult



Recommended reading:

Schmalzer EA, Lee JO, Brown AK, et al. Viscosity of mixtures of sickle and normal red cells at varying hematocrit levels. Implications for transfusion. Transfusion 1987; 27:228.