Info
🌱 來自: Huppert’s Notes
Magnesium🚧 施工中
Magnesium
Magnesium homeostasis (Mg2+ 1.8–2.5 mg/dL)
• Distribution:
- 99% intracellular, two-third of that in bones
- 1% extracellular, 30% bound of that to albumin
• Regulation:
- Intake: Passive intestinal absorption
- Storage: Intracellular shift by insulin and glucocorticoids
- Excretion: Inhibited by ADH, PTH, and hypomagnesemia
Hypomagnesemia (Mg2+ <1.8 mg/dL)
• Clinical features:
- Neurologic: Tremors, hyperreflexia, seizures, altered mental status
- ECG: Prolonged QT, T-wave flattening, torsade de pointes
- Often also hypocalcemia (low PTH), hypokalemia (in muscle/myocardium Mg2+ and K+ move together)
• Etiology:
- Poor intake: Alcohol use, diarrhea, short bowel, fasting, malabsorption
- Intracellular shift: Insulin, hungry-bone (post-parathyroidectomy), pancreatitis, catecholamine excess
- Renal wasting: Alcohol, diuretics, calcineurin inhibitors, aminoglycosides, cisplatin, amphotericin B, Gitelman syndrome
• Treatment: Mild: PO magnesium oxide. Severe: IV magnesium sulfate
Hypermagnesemia (Mg2+ >2.5 mg/dL)
• Clinical features: Loss of deep tendon reflexes (earliest sign), nausea, weakness, ECG similar to hyperkalemia (increased PR interval, widened QRS, peaked T)
• Etiology:
- Endogenous: Renal failure, burns/trauma, adrenal insufficiency, rhabdomyolysis
- Exogenous: Magnesium enemas, excessive PO supplementation, IV magnesium for treatment of other pathology (e.g., preeclampsia)
• Treatment:
- Stop exogenous magnesium
- Give IV calcium gluconate for cardioprotection
- Consider IVF/furosemide, dialysis if anuric