Elevated Lithium Level

INTRODUCTION: We present the case of a minimally symptomatic patient found to have an elevated lithium level after a blood sample was inadvertently obtained in a green-top tube containing lithium heparin. CASE REPORT: A 33-year-old woman presented 8 hours after ingesting an unknown quantity of sustained-release lithium carbonate, venlafaxine, clonazepam, and valproic acid. The patient was noted to be slightly drowsy but could be easily aroused. No gastrointestinal symptoms or electrocardiographic changes were observed. The patient was admitted to the intensive care unit for observation. The patient's lithium level 21 hours after ingestion was 5.6 mEq/liter, but she was clinically asymptomatic. The disagreement between symptoms and lithium level led to the discovery that this blood sample had been collected in a lithium heparin tube, thereby falsely elevating the level. CONCLUSIONS: This case illustrates the wisdom of the old adage to "treat the patient, not the levels." Caution should be used by physicians, nurses, technicians, and other personnel when obtaining blood samples.