Beer Potomania: Mechanism

WHAT IS IT? Hyponatraemia (dilutional) secondary to excessive alcohol consumption and undernourishment (i.e low protein/salt)

HOW? Malnourished chronic alcoholics with minimal solute/ protein intake are susceptible to water toxicity at small volumes (due to loss of urea concentrating gradient) compared to healthy individuals with normal renal function (normal adults can drink up to 20L a day without subsequent hyponatremia).

*Fluid intake over 4-5 L can push them into hyponatremia [Obligatory solute loss is ~250mOsm/day]

MECHANISM:

• Free water excretion from the kidney depends on both urinary dilution capacity AND solute excretion
• MAX urine diluting capacity= 50 mOsm/L
• Beer potomania= LOW osmoles due to poor diet 
• Hence the low solutes makes the kidneys HOLD onto the fluid because there are insufficient osmoles to allow for excretion of the water
• So when you give solute, they undergo diuresis rapidly and are at risk of over correcting! ADH is SUPPRESSED due to all the volume retention!

REFERENCES

1. Bhattarai N, Kafle P, Panda M. Beer potomania: a case report. BMJ Case Reports. 2010;2010:bcr10.2009.2414. doi:10.1136/bcr.10.2009.2414.
2. Sanghvi, S. R.,Kellerman, P. S. & Nanovic, L. Beer potomania: an unusual cause of hyponatremia at high risk of complications from rapid correction. Am. J. Kidney Dis. Off. J. Natl. Kidney Found. 50,673–680 (2007).
3. Shalin R. Sanghvi, Paul S. Kellerman, Lisa Nanovic. Beer Potomania: An Unusual Cause of Hyponatremia at High Risk of Complications From Rapid Correction. AJKD. October 2007 Volume 50, Issue 4, Pages 673–68