Hyponatremia classification

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Saeedeh Kowsarnia M.D.[2]

Overview

Hyponatremia (serum sodium less than 135 mEq/L) may be classified based upon serum ADH level, duration of hyponatremia, serum osmolality and volume status. The various classification systems enable accurate identification of the cause of hyponatremia and hence translate into optimal management based on the condition of the patient.

Classification

Hyponatremia is defined as serum sodium less than 135 mEq/L (mmol/L) ^[1] .There are different classifications for hyponatremia based on duration, severity, volume status, ADH level and serum osmolality.

Classification based on serum sodium level

Hyponatremia is classified based on serum sodium level into the following types ^[2] :

Mild : Serum sodium 130– 135 mmol/L
Moderate: Serum sodium ≤125–129 mmol/L
Severe: Serum sodium <124 mmol/L

Classification based on duration

Hyponatremia may be classified based on duration into the following types:^[3]

Hyper acute ^[4]: Develops in a few hours, excess water intake, impaired water excretion, runners, users of the recreational drug (Ecstasy)

Acute: Rapid onset <48 hours, surgeries, colonoscopy preparation, polydipsia, diuretics
Chronic: Gradual onset >48 hours, caused by chronic disease ( including cardiac, renal, hepatic and other conditions)

( Etiologies cause hyperacute and acute hyponatremia are applicable to each category interchangeably depending on the onset of symptoms)

Classification based on ADH level

Hyponatremia may be classified into the following types based on ADH levels:

↑ ADH: Volume depletion (GI loss, Renal loss) , decreased perfusion ( CHF, Cirrhosis), increased ADH secretion, reset osmostat

↓ ADH: Primary polydipsia, ↓ dietary solute intake, advanced renal failure

Classification based upon osmolality

Hyponatremia may be classified into the following types based on serum osmolality:^[5]

Hypertonic hyponatremia: Serum osmolality >295 mOsm/kg
Hypotonic hyponatremia: Serum osmolality < 275 mOsm/kg
Normotonic hyponatremia: Serum osmolality 275–295 mOsm/kg

Classification based on volume status

Hyponatremia may be classified into the following types according to volume status :

Volume status	Sodium status	Causes
Hypovolemic Hyponatremia	total body water ↓ total body sodium ↓↓	True volume depletion: GI loss, renal loss, insensible loss
Euvolemic Hyponatremia	total body water ↑ total body sodium ↔	Drugs, increased ADH level, reset osmostat, low dietary salt intake
Hypervolemic Hyponatremia	total body water ↑↑ total body sodium ↑	Decrease effective arterial volume: Cirrhosis, Renal disease, CHF

References

↑ Upadhyay, Ashish; Jaber, Bertrand L.; Madias, Nicolaos E. (2006). “Incidence and Prevalence of Hyponatremia”. The American Journal of Medicine. 119 (7): S30–S35. doi:10.1016/j.amjmed.2006.05.005. ISSN 0002-9343.
↑ Laczi, Ferenc (2008). “Etiology, diagnostics and therapy of hyponatremias”. Orvosi Hetilap. 149 (29): 1347–1354. doi:10.1556/OH.2008.28409. ISSN 0030-6002.
↑ Sterns, Richard H.; Ingelfinger, Julie R. (2015). “Disorders of Plasma Sodium — Causes, Consequences, and Correction”. New England Journal of Medicine. 372 (1): 55–65. doi:10.1056/NEJMra1404489. ISSN 0028-4793.
↑ Thomas, Sarah Beth (2017). “Acute hypervolemic hyponatremia”. Nursing. 47 (10): 53–57. doi:10.1097/01.NURSE.0000522006.83149.20. ISSN 0360-4039.
↑ A. I. Arieff & H. J. Carroll (1972). “Nonketotic hyperosmolar coma with hyperglycemia: clinical features, pathophysiology, renal function, acid-base balance, plasma-cerebrospinal fluid equilibria and the effects of therapy in 37 cases”. Medicine. 51 (2): 73–94. PMID 5013637. Unknown parameter |month= ignored (help)

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[UpadhyayJaber2006-1] Upadhyay, Ashish; Jaber, Bertrand L.; Madias, Nicolaos E. (2006). “Incidence and Prevalence of Hyponatremia”. The American Journal of Medicine. 119 (7): S30–S35. doi:10.1016/j.amjmed.2006.05.005. ISSN 0002-9343.

[Laczi2008-2] Laczi, Ferenc (2008). “Etiology, diagnostics and therapy of hyponatremias”. Orvosi Hetilap. 149 (29): 1347–1354. doi:10.1556/OH.2008.28409. ISSN 0030-6002.

[SternsIngelfinger2015-3] Sterns, Richard H.; Ingelfinger, Julie R. (2015). “Disorders of Plasma Sodium — Causes, Consequences, and Correction”. New England Journal of Medicine. 372 (1): 55–65. doi:10.1056/NEJMra1404489. ISSN 0028-4793.

[Thomas2017-4] Thomas, Sarah Beth (2017). “Acute hypervolemic hyponatremia”. Nursing. 47 (10): 53–57. doi:10.1097/01.NURSE.0000522006.83149.20. ISSN 0360-4039.

[5] A. I. Arieff & H. J. Carroll (1972). “Nonketotic hyperosmolar coma with hyperglycemia: clinical features, pathophysiology, renal function, acid-base balance, plasma-cerebrospinal fluid equilibria and the effects of therapy in 37 cases”. Medicine. 51 (2): 73–94. PMID 5013637. Unknown parameter |month= ignored (help)

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