Blood transfusion in Sickle Cell Patients
Author: Joseph E Maakaron, MD; Chief Editor: Emmanuel C Besa, MD more... (Used, Courtesy of Medscape)
Transfusions are not needed for the usual anemia or episodes of pain associated with SCD. Urgent replacement of blood is often required for sudden, severe anemia due to acute splenic sequestration, parvovirus B19 infection, or hyperhemolytic crises. Transfusions are helpful in acute chest syndrome, perioperatively, and during pregnancy. Acute red cell exchange transfusion is indicated in the following situations:
Acute infarctive stroke
Severe acute chest syndrome
Multiorgan failure syndromes
Right upper quadrant syndrome
Priapism that does not resolve after adequate hydration and analgesia
Regular blood transfusions are used for primary and secondary stroke prevention in children with SCD. See Stroke Prevention, below.
Transfusion-related complications include alloimmunization, infection, and iron overload. Treatment of iron overload is becoming easier with the new oral chelators.
Alloimmunization is a common problem that arises from the differences in certain minor red cell antigens found in the predominantly black patient population and the mostly white blood donors. Matching for C, E, Kell, JKB (Kidd), and Fya (Duffy) antigens can significantly reduce alloimmunization.
Transfusion and surgery
Intraoperative and postoperative complications may result from hypoxia, dehydration, or hypothermia that occurs during or after a surgical procedure. More complex procedures or longer duration of anesthesia times are more likely to lead to acute chest syndrome or other complications. Providing preoperative transfusion may decrease the risk.
Although one study demonstrated no overall difference in the complication rate among subjects who received either preoperative exchange or simple transfusion, it provided little guidance for what type of transfusion would be best in individual situations.
In general, raising the hemoglobin concentration to between 10 g/dL and 12 g/dL provides the patient with approximately 20-30% hemoglobin A. The presence of this fraction of normal hemoglobin may provide some protection from complications. Many anesthesiologists require a hemoglobin concentration of more than 10 g/dL prior to the procedure. [46]
When the patient’ baseline hemoglobin level is above 10 g/dL, the approach is less certain. If the complexity of the surgical procedure or the duration and risk of anesthesia is considerable, exchange transfusion or erythrocytapheresis can reduce the hemoglobin S concentration to 30%, while keeping the total hemoglobin level below 12 g/dL.
In patients undergoing retinal surgery, the HbS concentration or combined concentration of HbS and HbC needs to be reduced to less than 30% (increase the hemoglobin A concentration to 70%).
Individualize all other situations based on the complexity of the procedure and underlying medical condition.
Treatment of iron overload
With continued transfusion, iron overload inevitably develops and can result in heart and liver failure, and multiple other complications. Serum ferritin is an inaccurate means of estimating the iron burden; liver iron evaluation, or perhaps MRI, is a more accurate means of determining tissue iron concentration and the response to chelation.
Three agents are available for iron chelation: deferoxamine, deferasirox, and deferiprone.
Deferoxamine is an efficient iron chelator. It is administered as a prolonged infusion intravenously or subcutaneously for 5-7 days a week. Although effective, there are significant challenges associated with its use that can result in non-compliance. [47]
Deferiprone and deferasirox, oral iron chelators, are effective for iron overload treatment and have differences (eg, different pharmacokinetics and adverse effect profiles). Deferasirox has a capacity similar to deferoxamine in chelating iron, but it is administered orally. Renal toxicity might be a limiting factor in its use, but it is generally safe. Deferiprone does not seem to be as effective as the other 2 agents and is considered a second-line therapy. Unlike deferasirox and deferoxamine, it selectively removes cardiac iron; is most effective when used in combination with deferoxamine or deferasirox.
A novel new iron chelator is being developed but is still in the clinical testing phase. [48]
Erythrocytapheresis
Erythrocytapheresis is an automated red cell exchange procedure that removes blood that contains HbS from the patient while simultaneously replacing that same volume with packed red cells free of HbS. [49] Transfusion usually consists of sickle-negative, leuco-reduced, and phenotypically matched blood for red cell antigens C, E, K, Fy, and Jkb.
The procedure is performed on a blood cell processor (pheresis machine) with a continuous-flow system that maintains an isovolemic condition. RBCs are removed and simultaneously replaced, with normal saline followed by transfused packed RBCs along with the patient's plasma. The net RBC mass/kg is calculated for each procedure based on the measured hematocrit of the transfused and removed blood and the total RBC volume transfused.
Erythrocytapheresis thus has the advantage of controlling iron accumulation in patients with SCD who undergo long-term transfusion, as well as the ability to achieve adequate Hb and HbS concentrations without exceeding the normal concentration. This precision is achieved because, before the start of the transfusion, the computer in the pheresis machine calculates the expected amount of packed RBCs required to obtain a specific posttransfusion hemoglobin level, using various physiologic parameters (eg, height, weight, Hb level). Further, erythrocytapheresis requires less time than simple transfusion of similar blood volumes.
Although erythrocytapheresis is more expensive than simple transfusion, the additional costs associated with simple transfusions (ie, those of chelation and organ damage due to iron overload) make erythrocytapheresis more cost-effective than simple transfusion programs. Central venous access devices can safely be used for long-term erythrocytapheresis in patients with SCD with a low rate of complications.
