Severe hypermagnesemia presenting with abnormal electrocardiographic findings similar to those of hyperkalemia in a child undergoing peritoneal dialysis
An 11-year-old boy on CCPD was admitted to the emergency room (ER) after 1 week of lethargy, decreased oral intake and poor function of CCPD. He had a medical history of mild cerebral palsy and steroid resistant focal segmental glomerulosclerosis leading to end stage renal disease. He had been managed with CCPD for 5 months. His medications included 4 types of antihypertensive drugs (nifedipine, enalapril, losartan, and amlodipine), 3 types of antiepileptic drugs (oxcarbazepine, clobazam, and lamotrigine), iron, calcium, and vitamin supplementation for chronic renal failure. Additionally, as a laxative for chronic constipation, lactulose had been administered for 5 months. Since lactulose didn't improve his symptom much, magnesium oxide was administered for 2 weeks prior to admission.\nAt admission, his blood pressure was 112/75 mmHg, his heart rate was 135 bpm, and his respiratory rate was 32 breaths/min. Physical examination revealed no specific abnormalities. Laboratory tests showed a leukocyte count of 7,900/mm3, a hemoglobin concentration of 10.7 g/dL, a serum sodium concentration of 132 mmol/L, a serum potassium concentration of 7.2 mmol/L, a blood urea nitrogen concentration of 53 mg/dL, a serum creatinine concentration of 9.3 mg/dL and a C-reactive protein concentration of 1.1 mg/dL. His dialysate fluid was clear. While in the ER, his temperature rose to 38.4℃ and his lethargy persisted. He was diagnosed with a viral infection and hyperkalemia and was admitted for general supportive care. After admission, an electrocardiography (ECG) revealed a tall T wave, a wide QRS complex and irregular conduction. CCPD was much frequently performed every 1 hour and he was administered intravenous calcium gluconate and regular insulin with glucose to correct his supposed hyperkalemia. Follow-up laboratory tests from blood drawn 4 hours later showed that his potassium concentration had decreased to 6.3 mmol/L, but his ECG findings did not improve and even became aggravated to wide QRS complex with irregular conduction abnormalities (). At that time, we found that his serum concentration of magnesium was markedly elevated, to 8.9 mg/dL (7.4 mEq/L), and he was diagnosed with symptomatic severe hypermagnesemia.\nThe patient was transferred to the pediatric intensive care unit and emergently hemodialyzed for hyperkalemia and hypermagnesemia. The patient underwent hemodialysis for three hours with dialysate containing 2.0 mEq/L (2.4 mg/dL) of magnesium, without heparin treatment. His serum concentration of magnesium decreased to 5.7 mg/dL (4.7 mEq/L) after 30 minutes. An ECG performed during the dialysis revealed a normal sinus rhythm with mild T wave changes (). The patient tolerated hemodialysis well and showed no hemodynamic instability. After 3 hours of hemodialysis, his serum concentrations of magnesium and potassium had decreased to 3.7 mg/dL and 4.8 mmol/L, respectively. On the following day, he was transferred to a general ward and continued CCPD every 2 hours. After two days, however, his serum magnesium concentration rose slightly, to 4.7 mg/dL. A repeat session of hemodialysis reduced his serum magnesium concentration to 3.17 mg/dL, which was thereafter maintained within a normal range with CCPD. At the time of discharge, his serum electrolytes and ECG findings were within the normal range.