Magnesium

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    Magnesium

    Hypomagnesemia

    • Causes:
      • GI Losses:
        • vomiting, diarrhea, pancreatitis
        • Use of PPIs (especially diuretics). Through intestinal receptor dysregulation
      • Renal Losses
        • Diuretics (most common)
          • Loop & Thiazide diuretics (NOT K sparing diuretics)
        • Nephrotoxic drugs
          • Aminoglycosides, amphotericin B, cisplatin, Pentamidine, cyclosprine)
        • Alcohol (common in EtOH patients)
          • Prevlanece was 30% in pts admitted to hospital for an EtOH problemm.
            • Mechanism:
              • 1. Defect in urinary excretion due to EtOH induced tubular dysfunction.  (reversible in 4 weeks of abstinence)
              • 2. Co-existing dietary deficiency
              • 3. Other factors: pancreatitis, diarrhea etc..
        • Uncontrolled DMII
          • Causes glycosuria - drags magnesium with it, and insulin induced magnesium into cells.
        • Hypercalcemia (mg and Ca compete for same receptor in thick ascending loop)
    • Treatment:
      • Fix the underlying issue
      • Magnesium Supplementation
        • IV: 1-4g of Magnesium Sulfate IV
        • PO:  (Many options - can cause diarrhea, GI absorption can be erratic)
          • Magnesium Glucoheptinate
          • Magnesium Oxalate 420mg po q...
      • NOTE: Magnesium stores can take a long time to replenish
        • Moderate Magnesium Deficiency:
          • Add 6g MgSO4 (48mEq) to 250 or 500mL of NS and infuse of 3h
          • Follow with 5g of MgSO4 (40 mEq) in 250 - 500 mL of NS infuse over 6h
          • Continue with 5g MgSO4 q12h (by continuous infusion) for 5 days
        • Severe Life-Threatening Mg Deficiency
          • Same as above, except give 2g of MgSO4 (16 mEq) IV over 2-5m first (then follow 6h and 5 day protocol)

    Hypermagnesemia

    • Very rare, usually in context of (DKA, adrenal insufficiency, hyperPTH, lithium toxicity), but often transient.
    • Symptoms:
      • > 4 mEq/L (>2 mmol/L SI - Canada) --> Hyporeflexia
      • > 5 mEq/L (> 2.5 mmol/L SI) --> 1st deg AV block
      • > 10 mEq/L (> 5 mmol/L SI) --> Complete Heart Block
      • > 13 mEq/L (> 6.5 mmol/L SI) --> Cardiac Arrest
    • Causes
      • Renal failure + large intake
      • Obstetrics (pre-eclampsia rx?)
      • Laxatives
    • Toxicity Findings:
      • Hyporeflexia

      • AV block

      • Cardiac Arrest

    • Management:
      • Stop offending agent
      • Diuretics
      • If Serious:
        • Can temporize with Calcium Gluconate  (1g IV over 2-3min) until dialysis
        • Dialysis
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