Hypermagnesemia
Adult-Gerontology Acute Care Practice Guidelines
Definition
A.See Box 5.4.
B.Mild hypermagnesemia 2.5 to 4 mg/dL.
C.Moderate hypermagnesemia 4 to 12.5 mg/dL.
D.Severe hypermagnesemia greater than 12.5 mg/dL.
BOX 5.4
Magnesium in Humans
•Normal serum range is 1.5 to 2.4 mg/dL.
•Found primarily in soft tissue, bone, and muscle.
•Approximately 1% of total body magnesium is found in the extracellular fluid.
•Homeostasis managed primarily by the kidneys, but gastrointestinal tract, parathyroid hormone, and serum magnesium concentrations also involved.
•Serves as a cofactor in many enzymatic and biochemical reactions, including reactions involving adenosine triphosphate.
Incidence
A.Hypermagnesemia is rare in patients with normal renal function.
Pathogenesis
A.Magnesium is the second most abundant intracellular cation in the body after potassium.
B.It is critical in the functioning of neuromuscular, cardiac, and nervous system functions.
C.Magnesium is vital to vascular tone, heart rhythm, bone formation, and muscle contraction among many other critical functions.
Predisposing Factors
A.Excessive intake of magnesium.
B.Lithium.
C.Hypothyroidism.
D.End-stage renal disease.
Subjective Data
A.Common complaints/symptoms.
1.Typically asymptomatic until serum concentrations exceed 4 mg/dL.
2.Mild hypermagnesemia.
a.Nausea and vomiting.
b.Loss of deep tendon reflexes.
c.Hypotension.
d.Bradycardia.
e.EKG changes such as increased PR interval, and increased QRS interval.
3.Severe hypermagnesemia.
a.Respiratory paralysis.
b.Refractory hypotension.
c.Atrioventricular block.
d.Cardiac arrest.
Physical Examination
A.Check reflexes.
B.Check blood pressure.
C.Perform cardiac examination.
Diagnostic Tests
A.Serum magnesium.
B.Serum creatinine/blood urea nitrogen (BUN).
C.EKG.
D.Evaluation for pregnancy.
Differential Diagnosis
A.Ingestion.
1.Magnesium-containing laxatives or antacids.
2.Accidental ingestion of Epsom salts (magnesium sulfate).
B.Intravenous magnesium infusion (intentional overdose).
1.Therapy for preeclampsia and eclampsia.
2.Parenteral nutrition or magnesium supplementation.
C.Reduced excretion.
1.Reduced renal function due to chronic kidney disease or acute kidney injury.
D.Theophylline intoxication.
E.Acromegaly.
F.Tumor lysis syndrome.
G.Familial hypocalciuric hypercalcemia.
H.Adrenal insufficiency.
Evaluation and Management Plan
A.Step 1—If severe cardiac symptoms exist, give intravenous calcium immediately. It can transiently stabilize the cardiac effects of severe, symptomatic hypermagnesemia.
1.Calcium chloride 1 gm or calcium gluconate 3 gm (see section “Hypocalcemia” for safety details regarding intravenous calcium).
B.Step 2—Determine the cause.
1.Intentional overdose for medical reasons should not be corrected.
2.If indicated, restrict or discontinue all magnesium-containing agents.
C.Step 3—Treat other electrolyte and acid–base disorders.
D.Step 4—Accelerate renal magnesium clearance.
1.Loop diuretics, which can increase urinary excretion of magnesium.
2.Hemodialysis, which can remove excess magnesium.
Follow-Up
A.Hypermagnesemia is a rare occurrence. Follow-up with nephrology if persistent.
Consultation/Referral
A.Nephrology should be consulted if hypermagnesemia cannot be explained or requires intervention such as dialysis.
Special/Geriatric Considerations
A.This is a rare condition that is typically caused by ingestion of excessive magnesium.
Bibliography
Kraft, M. D., Btaiche, I. F., Sacks, G. S., & Kudsk, K. A. (2005, August). Treatment of electrolyte disorders in adult patients in the intensive care unit. American Journal of Health System Pharmacy, 62(16), 1663–1682. doi:10.2146/ajhp040300
Moe, S. M., &Daoud, J. R. (2014). Disorders of mineral metabolism: Calcium, phosphorous, and magnesium. In D. S. Gipson, M. A. Perazella, & M. Tonelli (Eds.), National Kidney Foundation’s primer on kidney diseases (6th ed., pp. 100–112). Philadelphia, PA: Elsevier Saunders.