TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: Magnesium is a major intra-cellular divalent cation. It is essential for multiple metabolic and physiological processes. It plays a crucial role in enzymatic actions, electron transporters, and the synthesis of nucleic acids. CASE PRESENTATION: A 73-year-old Caucasian male patient with a past medical history of Hypertension, Diabetes Mellitus type two, chronic constipation and chronic lower back pain presented to emergency department with 2-day history of diffuse abdominal pain. Acute abdominal series failed to show significant abnormality other than constipation and hence he was given one dose of oral magnesium citrate, one dose of GI cocktail (contains Maalox) and a fleets enema on day one of hospital stay. Overnight patient had a near syncopal episode and worsening of his abdominal pain while having a bowel movement. He was noted to be hypotensive with blood pressure of 84/47 mmhg, heart rate 132 and with a lactic acidosis level of 8.3 mmol/l, hence an abdominopelvic CT was done and showed free air in abdomen (Figures 1 and 2). Patient was taken to emergent laparotomy and underwent pyloric ulcer perforation repair with omental patch.On post-operative day 1 he was noted to have flaccid paralysis including lack of deep tendon and brain stem refluxes. Due to concerns of anoxic brain injury, brain imaging was done with no acute findings. Ionized Calcium, Phosphate levels and Potassium levels were within normal limits. He was noted to have Magnesium level of 9.2 mg/dl. This was thought to be cause of his flaccid paralysis and hence was initiated on Intravenous fluids along with Lasix. In view of oliguric kidney injury, emergent Hemodialysis was initiated. Patient received two hemodialysis sessions with Magnesium levels returning to physiologic levels. Over the next 48-72 hours patient has significant improvement in his hypotension and bradycardia. His mentation and muscle strength and acute kidney injury also improved. He was successfully liberated from the ventilator and subsequently discharged to rehab DISCUSSION: Our patient had acute respiratory failure with failure to extubate due to flaccid paralysis of his respiratory muscles. This was found to be a result of extremely high serum magnesium levels which was unexpected given he received only two doses of magnesium containing agents (magnesium citrate and Maalox) within the last 2 weeks. Hypermagnesemia is most commonly seen in the setting of renal impairment along with concomitant excessive magnesium intake. Neuromuscular and cardiac toxicity are common complications of hypermagnesemia. [2] Our patient had all the features usually described in hypermagnesmia but with only a small intake of Magnesium in setting of acute kidney injury. We hypothesize that the pyloric perforation allowed for increased uptake of magnesium through the inflamed peritoneum CONCLUSIONS: N/A REFERENCE #1: Cascella, Marco, Sarosh Vaqar et al. "Hypermagnesemia." StatPearls, StatPearls Publishing, 2020. REFERENCE #2: Agus, Z. S., M. Morad et al. "Modulation of cardiac ion channels by magnesium." Annual review of physiology 53.1 (1991):299-307. REFERENCE #3: Lee, Jay Wook. "Fluid and electrolyte disturbances in critically ill patients." Electrolytes & Blood Pressure 8.2 (2010):72-81. DISCLOSURES: No relevant relationships by Khalid Sawalha, source=Web Response