CURRENT Essentials of Critical Care.pdf

Chapter 5 Fluids, Electrolytes, & Acid-Base 57■■■HypermagnesemiaEssentials of Diagnosis• Serum magnesium [Mg ] 2.7 mg/dL• Reduced deep-tendon reflexes• May progress to respiratory muscle failure• Hypotension with reduced vascular resistance• Somnolence and coma with extremely elevated levels• Decreased serum calcium may be seen• Progression of ECG changes: interventricular conduction delay,prolonged QT interval, heart block, asystole• Generally occurs with renal insufficiency and excessive intake• Other risk factors: nephrotoxic agents, hypotension or hypovolemiawith oliguria, preeclampsia-eclampsia receiving largetherapeutic dosesDifferential Diagnosis• Renal failure: acute and chronic• Excess ingestion: antacids, laxatives• Intravenous administration: parenteral nutrition, intravenousfluidsTreatment• Eliminate infusion of all magnesium-containing compounds• Intravenous calcium gluconate or chloride reverses acute cardiovasculartoxicity and respiratory failure• Hemodialysis with magnesium-free dialysate• Monitor deep tendon reflexes when treating with “therapeutichypermagnesemia” as in obstetric patients• Correct renal insufficiency■ PearlMagnesium can be thought of as “nature’s calcium channel blocker.”ReferenceTopf JM: Hypomagnesemia and hypermagnesemia. Rev Endocr Metab Disord2003;4:195. [PMID: 12766548]