Wednesday, March 11, 2009

Beer Potomania


One of the admittedly rare causes of hyponatremia is beer potomania--the excessive consumption of beer in the absence of much food. How does beer potomania work?

Beer has a very low content of sodium and protein--and if an individual subsists solely on beer they have a very limited solute intake. This is important because the limit on how much free water excretion can be achieved in a day is dependent on urine osmolality (urine flow rate = rate of solute excretion / urine osmolality). For an individual drinking predominantly beer, they are taking in only about 300mosm of solute per day, which is then eliminated in the urine. This puts a cap of only about 4-5 Liters of electrolyte-free water that can be excreted in a day. Thus, if an individual drinks more than 4-5 Liters of beer in a day, in the absence of additional solute, they will become hyponatremic. On top of this mechanism, beer drinkers may also have non-osmotic secretion of ADH as a result of volume depletion from chronic GI losses or vomiting. This can result in profoundly low serum sodium levels and all the neurologic complications which go along with it. The same general mechanisms (low solute intake, high fluid intake) are also at play in elderly women eating a "tea and toast" diet.

8 comments:

nr1215 said...

FWC = V ( 1 - Uosm/Sosm )
EFWC = V [ 1 – (UK+ UNa)/SNa ]

To be more precise, we are using the EFWC and not FWC as we want to 'ignore' the non osmotic molecules from the picture.

Alcohol also has a direct action as a V2 receptor antagnoist and so we pee a lot when we drink beer, further worsening the hyponatremia.

Dont forget your salted nuts with next dose of beer. Cheers!!

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Joel Topf said...

nr1215, a V2 receptor antagonist would increase water excretion, but that would increase not decrease the serum Na. Beer drinker's potomania and Tea and Toast stand alone with psychogenic polydipsia as the only ADH independent causes of hyponatremia.

nr1215 said...

Dear Joel!!

I agree with you, yes u r right!

I presented it other way around. Thanks for correcting me and thanks a ton for the post.

david k said...

I think of it this way. A normal diet generates around 750 mosm of solute per day. A patient with normal renal function can dilute the urine to about 50 mosm/L. Therefore, if a patient like this drinks more than 15 liters of fluid per day he will become hyponatremic because he can't excrete any more than 15 liters of urine per day. Each liter of urine contains the minimum amount of solute at 50 mosm. After the 15th liter of urine there is no longer any solute left to excrete the 16the liter and it is retained. The calcluation is 750 mosm/( 50 mosm/L)= 15 L. This is the classic form of psychogenic polydipsia and this is why a quantity of 15 liters is often quoted when asked about the maximum amount of water one can drink in a day before becoming hyponatremic.

Now take a case of beer potomania where the person has a very low protein and sodium diet. Remember the "osm" in urine osmolarity consists of urea ( from dietary protein) and also sodium. A beer diet consists of mostly carbohydrate but little sodium or protein.

For example, if a patient's diet generates 200 mosm of solute per day then that person can ingest only 4 Liters of fluid before he becomes hyponatremic. 200 mosm/(50 mosm/L)= 4 liters. If he drinks a 5th liter there is no solute left to allow excretion of the 5th liter and he becomes hyponatremic.


Even worse, if he has a defect in diluting capacity, say to 100 mosm/L and if he ingests a 200 mosm/day diet then he can only drink 2 liters before becoming hyponatremic.

nathanhellman said...

Thanks for the comments all, hopefully everybody can enjoy a beer (without developing potomania) this Friday after work.

Dr. Burhan Ahmed said...

for better info visit:
http://medicalopedia.org/1361/beer-potomania-syndrome-2/

Anonymous said...

i have a question. How do you share with a heavy beer drinker that this is his fate? the facts speak for themselves, but one cant speak with the beer drinker! shall we call this the catch 22 of potomania....statistics and solutions abound but when ones life sit is the source of all these facts and figures its a fair mile from any real help....su