What is the procedure for performing an exchange transfusion?

Exchange Transfusion Procedure

Exchange transfusion in neonates with severe hyperbilirubinemia should be performed using modified whole blood (red cells and plasma) that is crossmatched against the mother and compatible with the infant, with the procedure initiated immediately when total serum bilirubin reaches exchange levels despite intensive phototherapy or when signs of acute bilirubin encephalopathy are present. 1

Pre-Procedure Preparation

Blood Product Selection and Testing

• Send blood for immediate type and crossmatch when TSB is at or approaching exchange level 1
• Use modified whole blood (red cells and plasma) crossmatched against the mother and compatible with the infant 1
• For sickle cell disease patients requiring operative shunting, consider simple transfusion of packed red blood cells to raise hemoglobin to 9-10 g/dL prior to general anesthesia 1

Patient Assessment

• Measure serum albumin level and calculate bilirubin/albumin (B/A) ratio to use in conjunction with TSB level 1
• Assess for signs of acute bilirubin encephalopathy (hypertension, arching, retrocollis, opisthotonos, fever, high-pitched cry) which mandate immediate exchange even if TSB is falling 1
• Repeat TSB measurement every 2-3 hours if level is above exchange threshold 1

Indications for Exchange Transfusion

Neonatal Hyperbilirubinemia

• Exchange is recommended when TSB rises to threshold levels despite intensive phototherapy during birth hospitalization 1
• For readmitted infants with TSB above exchange level, consider exchange if TSB remains above indicated levels after 6 hours of intensive phototherapy 1
• Immediate exchange is mandatory for any jaundiced infant manifesting intermediate to advanced acute bilirubin encephalopathy, regardless of whether TSB is falling 1

Risk-Stratified Thresholds

The B/A ratios that should trigger consideration of exchange transfusion alongside TSB levels are 1:

• Infants ≥38 weeks: B/A ratio 8.0 (mg/dL per g/dL) or 0.94 (mmol/L per mmol/L)
• Infants 35-36 6/7 weeks (well) or ≥38 weeks with higher risk/isoimmune hemolytic disease/G6PD deficiency: B/A ratio 7.2 or 0.84
• Infants 35-37 6/7 weeks with higher risk/isoimmune hemolytic disease/G6PD deficiency: B/A ratio 6.8 or 0.80

Exchange Transfusion Techniques

Automated Red Blood Cell Exchange

• Automated exchange uses apheresis devices to simultaneously remove patient RBCs while returning other blood components along with normal RBCs, providing isovolemic transfusion 2
• Requires specialized equipment, trained personnel, and appropriate vascular access 2
• Efficiently decreases abnormal hemoglobin while limiting iron loading and hyperviscosity 2
• Increases RBC exposure compared to simple or manual exchange 2

Manual Exchange Transfusion

• Manual exchange is based on sequential phlebotomies with isovolemic replacement 3
• Can be performed with packed red blood cells (PRBC), whole blood, or started with PRBC and continued with whole blood 4
• Whole blood decreases sickleable cell concentration rapidly and increases hematocrit slowly without markedly increasing viscosity 4
• PRBCs decrease sickleable cell concentration more slowly and increase hematocrit faster, potentially increasing blood viscosity to dangerous levels 4

Modified Whole Blood Exchange

• Whole blood exchange replaces patient's plasma with albumin and saline in addition to erythrocyte replacement 5
• Performed using standard pheresis equipment with relatively simple technique 5
• Addresses potential role of plasma factors in pathogenesis of vaso-occlusive events 5

Vascular Access

Access Requirements

• High blood flow is critical for successful collection and return phases, especially since most patients require multiple treatments over days to weeks 6
• Options include peripheral venous access, arteriovenous grafts and fistulas, central venous catheters, and tunneled central venous catheters with ports 6

Critical Monitoring During Procedure

Hemoglobin Targets

• Maintain hemoglobin below 10 g/dL in sickle cell disease patients to prevent hyperviscosity and associated complications 7
• Do not increase hemoglobin by more than 4 g/dL in a single transfusion episode 7
• For patients with hemoglobin >9-10 g/dL requiring exchange, target post-transfusion levels of 10-11 g/dL 7

Exchange Planning

• The two most important determinants are the patient's initial hematocrit and desired final concentration of sickleable cells 4
• Rate and type of exchange (continuous or discontinuous) are not important factors 4
• Final hematocrit depends on the blood product used 4

Important Caveats

Sickle Cell Disease Considerations

• Exchange transfusion should NOT be used as primary treatment for acute ischemic priapism in sickle cell patients 1
• Delaying intracavernosal phenylephrine and corporal aspiration to perform exchange transfusion is not warranted 1
• Exchange transfusion preparation typically requires 6+ hours for extended red cell antigen matched products, increasing risk of complications during prolonged ischemic events 1

Hyperviscosity Risk

• Exceeding hemoglobin threshold of 10 g/dL increases risk of vaso-occlusive complications, stroke, venous thromboembolism, and hyperviscosity syndrome 7
• Careful monitoring of post-transfusion hemoglobin is critical to avoid exceeding target levels 7