Iatrogenic Hypermagnesemia in a Patient With Preeclampsia Caused by Misinterpretation of the Magnesium Reporting Unit Following Magnesium Sulfate Administration

Because of the lack of standardization, different laboratories report plasma magnesium sulfate or magnesium level in different units, leading to errors in diagnosis and case management; especially when a patient's workup was done in a hospital and then transferred to another hospital. Failure to recognize or understand the reporting units can confuse clinicians and healthcare workers, leading to erroneous interpretations and, consequently, to misdiagnosis of hypermagnesemia or hypomagnesemia. In this report, we present a 32-year-old female patient at 31 weeks of gestation with a history of a multi-substance use disorder who was transferred to the hospital after taking 2.5mg of fentanyl. At the ER, her blood pressure and liver function tests were found to be high. Her albumin was 3.4 g/dl, aspartate transaminase (AST) was 104 IU/l, alanine transaminase (ALT) was 19 IU/l, and anaplastic lymphoma kinase (ALK) phosphatase was 148 IU/l; however, the renal function test was within the normal range. She had a few twitching movements. Her troponin I was high at 648 ng/L, and her B-type natriuretic peptide was 186.1 pg/mL, but her ECG showed a normal result. Magnesium was initiated on a 6 mg bolus, then 2 mg/dl due to preeclampsia concerns. She was transferred to another hospital ICU that used mEq/L as a reporting unit for magnesium and magnesium sulfate levels. The travel nurse did not alert the physician, thinking that magnesium sulfate was still within with therapeutic range of 4.8-8.4 mg/dL. However, considering 4.0-7.0 is the therapeutic range of magnesium sulfate utilizing mEq/L as a reporting unit instead of mg/dL, the patient was found to be at a supratherapeutic level, reaching up to 8.2 mEq/L. The physician discounted the magnesium sulfate. Her blood picture showed normocytic normochromic anemia. Her hemoglobin was 10.9 g/dl, her hematocrit was 33.8%, her mean corpuscular volume (MCV) was 92.5 fL, and her mean corpuscular hemoglobin (MCH) was 29.5 fL. Her platelets were within the normal range (169 10exp9/L). Her temperature was 99.6 F with increased white blood cells (17.7 10e9/L). The fetus was delivered via C-section on the third day of admission in the setting of persistently low fetal heart rates. The patient was extubated on the fourth day of admission and later transferred to the ward and discharged on the fifth day. Monitoring the magnesium level while administrating magnesium sulfate is essential to avoid iatrogenic hypermagnesemia. Utilizing different units at the same laboratory or across different laboratories could lead to the healthcare providers misinterpreting the result, which can lead to misdiagnosing iatrogenic hypermagnesemia. Therefore, standardizing magnesium units across the Clinical Laboratory Improvement Amendments (CLIA) and College of American Pathologists (CAP)-accredited laboratories is highly recommended. A unified unit reporting protocol will allow healthcare providers, constantly and correctly, to interpret the results and avoid misdiagnosing iatrogenic hypermagnesemia, and it will facilitate reporting and exchange of results among the different laboratories.