Situation: A nurse in the delivery room and newborn nursery of a provincial hospital receives newborns at birth and during the first days of life. A 2-day-old with Rh hemolytic disease is undergoing a double-volume exchange transfusion with citrate-anticoagulated blood. Midway through, the newborn becomes jittery and the monitor shows a prolonged QT interval. Results drawn at that time: Glucose: 68 mg/dL (3.8 mmol/L) Potassium: 5.0 mmol/L Total serum bilirubin: lower than before the exchange The newborn is alert with normal tone. Which problem MOST likely explains the findings?

Citrate in the donor blood binds ionized calcium, and hypocalcemia shows as jitteriness with QT prolongation or dysrhythmia. Glucose and potassium are within normal limits, and falling bilirubin with an alert, normally toned infant argues against encephalopathy. The nurse pauses the exchange and reports; calcium gluconate may be ordered.

Clinical context
A double-volume exchange transfusion replaces roughly twice the neonate’s circulating blood volume with donor blood. When the donor unit is anticoagulated with citrate, the citrate is infused along with the red cells. Citrate works by chelating ionized calcium, which is the physiologically active fraction of serum calcium. Because ionized calcium is required for myocardial repolarization and neuromuscular stability, a falling ionized calcium level produces the classic picture seen here: jitteriness, irritability, and QT prolongation on the monitor.

Key point! The glucose of 68 mg/dL (3.8 mmol/L) is within the normal neonatal range, and the potassium of 5.0 mmol/L is also acceptable for a 2-day-old. Therefore, hypoglycemia and hyperkalemia do not explain the findings.

Why the other options are less likely
Hyperkalemia from stored red cells can occur during massive transfusion, but the measured potassium is normal, and hyperkalemia more typically produces peaked T waves and bradycardia rather than isolated jitteriness with a prolonged QT interval.
Acute bilirubin encephalopathy is a concern in Rh hemolytic disease, but the total serum bilirubin is falling, and the newborn is alert with normal tone. Encephalopathy would be expected to present with lethargy, poor feeding, hypotonia, or a high-pitched cry rather than isolated jitteriness.
Hypoglycemia from a dextrose load is not consistent with a glucose of 68 mg/dL. In fact, donor blood contains dextrose, which would tend to raise rather than lower glucose.

Mechanism of citrate-induced hypocalcemia
Citrate binds free ionized calcium in a reversible manner. During an exchange transfusion, the citrate load can temporarily exceed the neonate’s hepatic metabolic capacity and parathyroid hormone response, especially in a newborn with immature liver function. The resulting decline in ionized calcium delays ventricular repolarization, which is seen on the ECG as a prolonged QT interval. Neuromuscular irritability from hypocalcemia presents as jitteriness or tetany.

The ASFA guidance on apheresis-related electrolyte management reinforces this mechanism. In procedures using citrate-based anticoagulants such as ACD-A, citrate chelates ionized calcium to prevent clotting in the extracorporeal circuit, and the electrolytes most frequently affected include calcium, magnesium, and potassium ^[2]. The same principle applies to exchange transfusion in the neonate, where the citrate in donor blood produces a similar effect.

Nursing priorities during the exchange
The nurse should pause the exchange, maintain a secure airway and IV access, and report the findings immediately because worsening hypocalcemia can progress to tetany, laryngospasm, or dysrhythmia. Calcium gluconate may be ordered, and it should be given slowly through a separate line while monitoring the heart rate and QT interval. Continuous cardiorespiratory monitoring is essential during the remainder of the procedure.

Finding	Value	Interpretation
Glucose	68 mg/dL (3.8 mmol/L)	Normal; rules out hypoglycemia
Potassium	5.0 mmol/L	Acceptable for a neonate; rules out hyperkalemia
Total bilirubin	Lower than before exchange	Exchange is working; encephalopathy less likely
Neurologic status	Alert, normal tone, jittery	Irritability without encephalopathy; consistent with hypocalcemia
ECG	Prolonged QT interval	Delayed repolarization from low ionized calcium

Watch out! A normal total serum calcium does not exclude hypocalcemia during citrate infusion. Citrate lowers the ionized calcium fraction, which is the clinically active form. If only total calcium is checked, the result may appear normal because the bound fraction is unchanged. Ionized calcium or clinical signs plus ECG changes are more useful during the procedure.

Key point! The combination of jitteriness and QT prolongation during an exchange transfusion with citrate-anticoagulated blood should immediately suggest hypocalcemia from citrate binding, not a glucose or potassium problem, when those laboratory values are normal and the bilirubin is improving.