Hyper Mg


Plasma Mg concentration >2.3 mg/dL [0.95 mmol/L], symptoms present usually when > 3.0 mg/dL [1.2 mmol/L]

Diagnosis

  • Anorexia, nausea, vomiting
  • Paresthesias, hypotension, confusion, hyporeflexia, paralysis, apnea, coma, seizures, respiratory depression, cardiac arrest
  • Acute hypermagnesemia suppresses PTH secretion & can produce hypo Ca+
  • ECG
    • PR prolongation
    • Heart block, arrhythmias
    • Variable QRS and QT prolongation

Pathophysiology

  • Renal failure (decr GFR)
  • Decr renal excretion due to salt depletion
  • Abuse of antacids & laxatives containing Mg in patients with renal insufficiency
  • Endocrinopathies (deficiency of mineralocorticoid or thyroid hormone)
  • Incr tissue breakdown

Treatment

  1. Identify & correct underlying disorder
  2. Intracardiac conduction abnormalities can be Rx with:
    • Ca Gluconate 10%, 10-20 mL IV over 15 min
  3. Rx decr BP w/ NS, pressors
  4. Dialysis for severe hypermagnesemia

Disposition

  • Admit:
    •  Mg+ > 3.0 mg/dL [1.2 mmol/L] or if symptomatic