Chapter outlines
| Basic Physiology |
| HYPOMAGNESEMIA |
| Etiology |
| Clinical Features |
| Diagnosis |
| History and physical examination |
| Routinely ordered investigations |
| Urinary magnesium excretion |
| Management |
| Correction of underlying etiology |
| Basic principles of therapy |
| Replacement of magnesium |
| - Mild hypomagnesemia |
| - Moderate hypomagnesemia |
| - Severe hypomagnesemia |
| Parenteral magnesium therapy |
Disorder of magnesium, especially hypomagnesemia, is expected particularly in ICU patients and usually occurs due to renal and gastrointestinal (GI) losses. However, hypermagnesemia is a less frequent disorder than hypomagnesemia, and its most common cause is renal failure.
BASIC PHYSIOLOGY
- Magnesium is the fourth most common cation of the body (after Na+, K+, and Ca2+), the second most common intracellular cation (after K+), and the commonest intracellular divalent cation.
- Distribution: About 60% of body magnesium is in bones, 39% is within the cells, and only 1% is in extracellular fluid (ECF). Up to 40% of total plasma magnesium is protein-bound, 5–10% is in complex form, and about 50–55% is in a free, ionized form, which is a biologically active ion (like calcium).
- Normal blood ranges: The normal serum magnesium level is 1.7 to 2.1 mg/dL (0.70 to 0w.85 mmol/L, 1.4 to 1.7 mEq/L), and their values in magnesium disorders are summarized in Table 28.1.
- As the clinical effects of magnesium disorders are determined primarily by tissue magnesium content, serum magnesium levels have limited diagnostic value.
| Table 28.1 Interpretation of serum magnesium concentration |
| Hypomagnesemia |
Normal range |
Hypermagnesemia |
| Severe |
Moderate |
Mild |
Mild |
Moderate |
Severe |
| <1.0 mg/dL |
1.0-1.5 mg/dL |
1.6-1.9 mg/dL |
1.7-2.1 mg/dL |
4.8-7.2 mg/dL |
7.2-12 mg/dL |
>12 mg/dL |
| <0.5 mmol/L |
0.4-0.6 mmol/L |
0.7-0.8 mmol/L |
0.70-0.85 mmol/L |
2.0-3.0 mmol/L |
3.0-5.0 mmol/L |
>5 mmol/L |
| <0.8 mEq/L |
0.8-1.2 mEq/L |
1.4-1.6 mEq/L |
1.4-1.7 mEq/L |
4.0-6.0 mEq/L |
6.0-10 mEq/L |
>10 mEq/L |
| Conversion factors for serum magnesium: 1 mEq/L = 1.2 mg/dL = 0.5 mmol/L |
REFERENCES
- de Baaij JH, Hoenderop JG, Bindels RJ. Magnesium in man: implications for health and disease. Physiol Rev. 2015;95(1):1–46.
- Jahnen-Dechent W, Ketteler M. Magnesium basics. Clin Kidney J. 2012;5(1):i3–i14.
- Fatemi S, Ryzen E, Flores J, et al. Effect of experimental human magnesium depletion on parathyroid hormone secretion and 1,25-dihydroxyvitamin D metabolism. J Clin Endocrinol Metab 1991;73(5):1067–72.
- Lindsay AL, Bazydlo, Needham M, et al. Calcium, Magnesium, and Phosphate, Laboratory Medicine 2014;45(1):e44–e50.
- Eisenbud E, LoBue CC. Hypocalcemia after therapeutic use of magnesium sulfate. Arch Intern Med 1976;136(6):688–91.
- Rodríguez-Ortiz ME, Canalejo A, Herencia C, et al. Magnesium modulates parathyroid hormone secretion and upregulates parathyroid receptor expression at moderately low calcium concentration. Nephrol Dial Transplant. 2014;29(2):282–9.
- Blaine J, Chonchol M, Levi M. Renal control of calcium, phosphate, and magnesium homeostasis. Clin J Am Soc Nephrol. 2015;10(7):1257–1272.
- Swaminathan R. Magnesium metabolism and its disorders. Clin Biochem Rev. 2003;24(2):47–66.
- Yee J. Magnesium: An Important Orphan. Adv Chronic Kidney Dis. 2018;25(3):217–221.
- Schuchardt JP, Hahn A. Intestinal Absorption and Factors Influencing Bioavailability of Magnesium-An Update. Curr Nutr Food Sci. 2017;13(4):260–278.
- Curry JN, Yu ASL. Magnesium Handling in the Kidney. Adv Chronic Kidney Dis. 2018;25(3):236–243.
- Martin KJ, González EA, Slatopolsky E. Clinical consequences and management of hypomagnesemia. J Am Soc Nephrol. 2009;20(11):2291–5.
- Wong ET, Rude RK, Singer FR, et al. A high prevalence of hypomagnesemia and hypermagnesemia in hospitalized patients. Am J Clin Pathol. 1983;79(3):348–352.
- Limaye CS, Londhey VA, Nadkart MY, et al. Hypomagnesemia in critically ill medical patients. J Assoc Physicians India. 2011;59:19–22.
- Cheungpasitporn W, Thongprayoon C, Qian Q. Dysmagnesemia in Hospitalized Patients: Prevalence and Prognostic Importance. Mayo Clin Proc. 2015;90(8):1001–10.
- Cheungpasitporn W, Thongprayoon C, Chewcharat A, et al. Hospital-Acquired Dysmagnesemia and In-Hospital Mortality. Med Sci (Basel). 2020;8(3):37.
- M Kumar A, Naik MK. Prevalence of admission hypomagnesemia in critically ill patients International Journal of Health and Clinical Research, 2021;4(2):129–133.
- Van Laecke S. Hypomagnesemia and hypermagnesemia. Acta Clin Belg. 2019;74(1):41–47.
- Liamis G, Liberopoulos E, Alexandridis G, et al. Hypomagnesemia in a department of internal medicine. Magnes Res. 2012;25(4):149–58.
- Whang R, Ryder KW. Frequency of hypomagnesemia and hypermagnesemia. Requested vs routine. JAMA 1990;263(22):3063–4.
- Huang CL, Kuo E. Mechanism of hypokalemia in magnesium deficiency. J Am Soc Nephrol. 2007;18(10):2649–52.
- Pham PC, Pham PM, Pham SV, et al. Hypomagnesemia in patients with type 2 diabetes. Clin J Am Soc Nephrol. 2007;2(2):366–73.
- Chrysant SG, Chrysant GS. Association of hypomagnesemia with cardiovascular diseases and hypertension. Int J Cardiol Hypertens. 2019;1:100005.
- Ter Braake AD, Shanahan CM, de Baaij JHF. Magnesium Counteracts Vascular Calcification: Passive Interference or Active Modulation? Arterioscler Thromb Vasc Biol. 2017;37(8):1431–1445.
- Assadi F. Hypomagnesemia: an evidence-based approach to clinical cases. Iran J Kidney Dis. 2010;4(1):13–19.
- Tucker BM, Pirkle JL Jr, Raghavan R. Urinary Magnesium in the Evaluation of Hypomagnesemia. JAMA. 2020;324(22):2320–2321.
- Velissaris D, Karamouzos V, Pierrakos C, et al. Hypomagnesemia in Critically Ill Sepsis Patients. J Clin Med Res. 2015;7(12):911–8.
- Agus ZS. Hypomagnesemia. J Am Soc Nephrol. 1999;10(7):1616–22.
- Hansen BA, Bruserud Ø. Hypomagnesemia in critically ill patients. J Intensive Care. 2018;6:21.
- Chonchol M, Smogorzewski MJ, Stubbs JR, et al. Disorders of Calcium, Magnesium, and Phosphate Balance. In: Brenner and Rector’s The Kidney, 11th ed, Yu A, Chertow G, Luyckx V, et al (Eds), W.B. Saunders & Company, Philadelphia 2020.p.603.
- Fulop T. Hypomagnesemia treatment & management. Updated Oct 30, 2020. Available at https://emedicine.medscape.com/article/2038394-treatment#d10 (accessed 18 January 2022).
- Kraft MD, Btaiche IF, Sacks GS, et al. Treatment of electrolyte disorders in adult patients in the intensive care unit. Am J Health Syst Pharm. 2005;62(16):1663–82.
- Neumar RW, Otto CW, Link MS, et al. Part 8: adult advanced cardiovascular life support: 2010 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2010;122(18 Suppl 3):S729–67.
- Tzivoni D, Banai S, Schuger C, et al. Treatment of torsade de pointes with magnesium sulfate. Circulation. 1988;77(2):392–7.
- Hammond DA, Stojakovic J, Kathe N, et al. Effectiveness and Safety of Magnesium Replacement in Critically Ill Patients Admitted to the Medical Intensive Care Unit in an Academic Medical Center: A Retrospective, Cohort Study. J Intensive Care Med. 2019;34(11–12):967–972.
- McDonnell NJ, Muchatuta NA, Paech MJ. Acute magnesium toxicity in an obstetric patient undergoing general anaesthesia for caesarean delivery. Int J Obstet Anesth. 2010;19(2):226–31.