When to consider transfusion
Unfortunately, there are no strong randomized controlled trials to definitively dictate when simple transfusions or exchange transfusions are indicated. Acute simple transfusions should be considered in certain circumstances including acute chest syndrome, acute stroke, aplastic anemia, preoperative transfusion, splenic sequestration plus severe anemia, acute hepatic sequestration, and severe acute intrahepatic cholestasis.2
Exchange transfusion (erythrocytapheresis) should be considered for seriously ill patients, including those with multisystem organ failure, severe acute chest syndrome, and acute stroke.2 It may also be used for hepatic sequestration and acute intrahepatic cholestasis.1,2 The benefits of removing sickled cells include an increased percentage of Hb A and the ability to transfuse a greater volume with a lower net volume to decrease hyperviscosity and iron overload. Exchange transfusion increases the volume of donor blood exposure, increasing the risk of alloimmunization.
Few studies compare simple transfusion and exchange transfusion.2 The decision to use exchange transfusion over simple transfusion often is based on availability of exchange transfusion, ability of simple transfusion to decrease the percentage of hemoglobin S, and/or the patient’s current hemoglobin to avoid hyperviscosity from simple transfusion.3 Exchange transfusion should be considered for hemoglobin greater than 8-9 g/dL.2
Acute hepatic sequestration (AHS) occurs with the sequestration of RBCs in the liver and is marked by greater than 2 g/dL decrease in hemoglobin and hepatic enlargement, compared with baseline. The stretching of the hepatic capsule results in right upper quadrant pain. AHS often develops over a few hours to a few days with only mild elevation of liver function tests. AHS may be underestimated as two-thirds of SCA patients have hepatomegaly. Unless the hepatomegaly is radiographically monitored it may not be possible to determine an acute increase in liver size.2
Severe acute intrahepatic cholestasis (AIC) is characterized by the sudden onset of right upper quadrant pain, increasing hepatomegaly, light-colored stools, and jaundice due to total serum bilirubin greater than 50 mg/dL. Thrombocytopenia, hypoalbuminemia, elevated alkaline phosphatase, increased prothrombin time, and partial thromboplastin time are also present. This presentation is suggestive of cholestatic jaundice or choledocholithiasis but without evidence of common duct obstruction or cholangitis. AIC may prove fatal if not recognized and treated promptly.2
Aplastic crisis presents as a gradual onset of fatigue, shortness of breath, and sometimes syncope or fever. Physical examination may reveal tachycardia and occasionally frank heart failure. The hemoglobin is usually far below the patient’s baseline level with an inappropriate, severely low reticulocyte count. Aplastic crisis should be transfused immediately because of the markedly short life expectancy of hemoglobin S RBCs, but does not need to be transfused to baseline.2
Acute splenic sequestration presents as a decrease in hemoglobin by greater than 2 g/dL, elevated reticulocyte count and circulating nucleated red blood cells, thrombocytopenia, and sudden splenomegaly.2 The goal of transfusion is for partial correction because of the risk of hyperviscosity when the spleen releases the sequestered RBCs.
Acute chest syndrome (ACS) presents as a pneumonia radiographically consistent with a respiratory tract infection caused by cough, shortness of breath, retractions, and/or rales. ACS is the most common cause of death in SCA. ACS is usually from infection but may be because of fat embolism, intrapulmonary aggregates of sickled cells, atelectasis, or pulmonary edema.2 If ACS has a hemoglobin decrease of greater than 1g/dL, consider transfusion.1,2
Severe acute chest syndrome is distinguished by radiographic evidence of multilobe pneumonia, increased work of breathing, pleural effusions, and oxygen saturation below 95% with supplemental oxygen. Severe ACS may have a decrease in hemoglobin despite receiving transfusion. Exchange transfusion is recommended because of the high mortality in severe ACS.2
Preoperative transfusion is used to decrease the incidence of postoperative vaso-occlusive crisis, acute stroke, or ACS for patients receiving general anesthesia. The goal for transfusion hemoglobin is 10g/dL. In SCA patients with a hemoglobin greater than 9g/dL, exchange transfusion may be considered to avoid hyperviscosity.1,2
Multisystem organ failure (MSOF) is severe and life-threatening lung, liver, and/or kidney failure. MSOF may occur after several days of hospitalization. It is often unanticipated and swift, frequently presenting with fever, a rapid increase in anemia, thrombocytopenia, and altered mental status. Lung failure often presents as ACS. Liver failure is marked by hyperbilirubinemia, elevated transaminases, and coagulopathy. Kidney failure is marked by elevated creatinine, with or without change in urine output and hyperkalemia. Rapid treatment with transfusion or exchange transfusion reduces mortality.
The incidence of acute ischemic stroke in SCA decreases with prophylactic transfusion of patients with elevated transcranial Dopplers. Acute stroke is usually secondary to stenosis or an occlusion of the internal carotid or middle cerebral artery. Acute hemorrhagic stroke may present as severe headache and loss of consciousness. Acute stroke should be confirmed radiographically, then exchange transfusion instituted rapidly.2