II. Pathophysiology
- Water Intoxication, beer potomania, Tea and Toast Syndrome share a similar mechanism for Hyponatremia
- Patient with excessive hypoosmolar fluid intake (free water, beer, tea) and low solute diet (low Sodium intake)
- Intake exceeds the renal capacity for free water excretion (50 to 100 meq/L or mOsm/L, specific gravity <1.003)
- Example: Normal Patient
- Patient ingests 600 mOsms solute (e.g. salt, Potassium) per day (10 mOsm/kg/day for a 60 kg person)
- If urine most dilute at 50 mEq/L, they could excrete 12 liters worth of free fluid intake without Hyponatremia
- However, renal excretion of dilute urine would be overwhelmed at 13 liter intake, and Hyponatremia would begin
- Example: Low solute intake (e.g. beer potomania, Tea and Toast Syndrome)
- Patient ingests only 100 mOsms solute per day (the remainder is beer, tea)
- Renal excretion of dilute urine is overwhelmed at only 2 Liters/day
- Example: Exercise Associated Hyponatremia
- Extrarenal Solute Losses Replaced with Free Fluid
- Excessive extrarenal losses (e.g. sweating) replaced with large volume of free fluid intake
III. Causes
- See Exercise Associated Hyponatremia
- Water Intoxication (Psychogenic Polydipsia)
- Free water intake exceeds free water excretion
- Seen in Psychosis (Schizophrenia, Bipolar Disorder)
- Beer Potomania Syndrome
- Excessive Alcohol intake (esp. beer) and low solute dietary intake
- Tea and Toast Syndrome (esp. elderly)
- Diet lacking in salt and Protein but with excessive oral free water intake
- Compounded by the typically low Glomerular Filtration Rate (GFR) in the elderly (increases fluid reabsorption)
-
Hypotonic Saline infusion
- Affects 4-5% of post-operative patients
-
Methylenedioxymethamphetamine (MDMA, Ecstasy, Molly)
- May result in Water Intoxication to point of severe Hyponatremia (deaths have occurred)
IV. Findings
- See Hyponatremia
V. Labs
- See Isovolemic Hypoosmolar Hyponatremia
- See Hyponatremia
- Diagnosis
- Hyponatremia
- Hypoosmolality
- Normal extracellular fluid (normovolemic)
- Urine Sodium < 10 (Urine Osmolality <100 mOsm/kg, maximally dilute urine)
VI. Differential Diagnosis
VII. Management
VIII. References
- Glaser (2022) EM:Rap 22(6): 9-11
- Peechakara (2022) Water Toxicity, StatPearls, Treasure Island, accessed online 6/2/2022
- Lodhi (2017) Cureus 9(12): e2000 [PubMed]
- Miller (2023) Am Fam Physician 108(5): 476-86 [PubMed]