A pitfall of measuring lithium levels in neonates

Area of Science:

• Neonatal Medicine
• Clinical Chemistry
• Pharmacology

Background:

• Lithium therapy during pregnancy or lactation necessitates neonatal serum lithium monitoring.
• Neonatal blood samples are frequently collected using devices containing lithium heparin.
• Oversight in recognizing the impact of lithium-heparin devices can lead to misinterpretation of lithium levels.

Observation:

• Two neonatal cases presented with falsely elevated serum lithium levels.
• Initial high lithium readings in neonates were not associated with clinical signs of toxicity.
• Subsequent analysis revealed that lithium-heparin sampling devices caused spurious lithium level elevations.

Findings:

• Lithium levels exceeding 3 mmol/L are possible with small blood volumes in lithium-heparin tubes.
• Case 1: A 3-day-old infant showed a falsely toxic lithium level of 4.19 mmol/L.
• Case 2: An infant's lithium levels rose to 1.1 mmol/L, later identified as spurious.

Implications:

• Mismanagement of neonatal lithium exposure is a risk if spurious results are not identified.
• Healthcare providers must be aware of lithium-heparin contamination in neonatal blood samples.
• Accurate interpretation of neonatal lithium levels requires careful consideration of sample collection methodology.