Beer potomania......

 Recently we had a gentle man who presented to us with seizures nearly 10 hours after drinking in a pub.His sodium was 115. He is someone who drinks 2-3 beers a day.Binges on weekends. Night before admission he had atleast 10 beers (as per friends). He had a low serum osmolality, and a urine osmolalty of 152 mosm/L. His Na was initially corrected with 3% NS upto 120, and then by water restriction. This guy had beer protomania.

The mechanism - Beer has a lot of water with  very low sodium and protein.Someone on a beer diet will roughly get 200 msosm/day(1L of beer has roughly 30 gm of Sodium) compared to an american diet which has 750mosm/day. Still the serum osmolaltiy is maintained.This is because ....with ingestion of so much water(in the form of beer), ADH secretion is at its lowest, and so the kidneys excrete a dilute urine.The kidneys can dilute the urine to a maximum of 50mosm/L. So for a guy who drinks 4L of beer and roughly takes 200 osmoles a day, can excrete the osmotic load in 4L of urine (50 mosm/L x 4 = 200 mosm). If he drinks a 5th litre of beer, then he would develop hyponatremia.

The Urine flow depends on the the number of osmoles excreted. So to call it beer potomania...you should have some one who has binged on a lot of beer(water) without eating anything(especially with salt). A low serum osmolality/ low urine osmolality with the above history will clinch this diagnosis. In many of these alcoholics..the situation may be complicated by the need for  5% dextrose following Vit B1 to prevent Wernicke's encephalopathy. Close monitoring and replacement is needed in those situations.