Kidney Essentials BONUS Minipodcast Blooper

In this podcast Drs Blaine, Ambruso and Young review an error they made in their first podcast tiled " can you drink too much water?"  Can you find the error they made?  Listen to them explain all the different ways you could have picked up on their mistake

Sophia Ambruso DO @Sophia_Kidney, Sarah Young MD @kidneycritic, Judy Blaine MD, Parisa Mortaji, MD

Transcript

Outline mini BONUS  podcast- titled BLOOPERS

Welcome to Kidney essentials

A podcast for Medical students, residents, and advanced practitioners at the University of Colorado and beyond

Introductions: 

Judy 

,Sophie

 & sarah

 a few Housekeeping notes BEFORE our next case

Mission statement (Sophie):

• Make nephrology more accessible, less intimidating
• Provide concise nephrology “pearls” in each episode to help listeners understand renal pathophysiology
• “Making nephrology sexy one episode at a time”

Legal disclaimer (Judy):

This podcast is for educational purposes only. The views and statements expressed on this podcast are soley those of the hosts.  This podcast should not be used as medical advice or for treatment purposes

sarah: Not surprisingly in our first podcast we had an oversight which fortunately was noticed by the esteemed Dr Tom Berl who knows a little about salt and water. 

Sophie: Our first mistake, but certainly won’t be our last

Judy: Please contact us if you find a mistake because it is really helpful for us and helps improve the podcast

Sarah: In an attempt to simplify the case for teaching purposes we made up values for our hyponatremic fellow Matt who drank too much water.  The values in retrospect defied the laws of chemistry!

Now my explanation of this is going to test how well we are meeting our mission of making nephrology more accessible and less intimidating

Soo.... this is the mistake we made, Matts Uosm was 75 and his urine Na was 100meq/L

There are several ways in which you could have heard those numbers and realized we were full of BEEP 

1. We explained during the podcast that osmolality in the serum is a measure of the total number of particles in solution. In serum osmolality it is 2 X PNa + glu/18 +BUN/2.8.

The same holds true for the urine osmolality which is also a measure of the number of particles in solution in the urine. Like plasma, NA is the major particle in the urine contributing to the osmolality so you can not have an osmolality LOWER then your urine sodium (like matt had in our case with a Usom of 75 and a urine  Na of 100meq/L) 

Sophie: So, in our case, if we took into account all the other solutes excreted, which include mainly urea sodium and potassium, which I might add urine potassium is in much higher concentrations in the urine compared to the small concentration in the serum, we would expect a urine osm closer to 300.

Judy: teaching point of distribution of k intracellular vs extracellular & tight regulation of 3.5-4.5

Sarah: Why Judy does it have to maintain such a narrow range?

Judy: arrythmias

The other way you could have noticed that we had made a mistake was by noting the following

1. If Matts Urine Na was 100meq/L and he was producing 20 Liters of urine he would have excreted 2000meq in 24 hours!

Sophie: whoa! 2000meq of sodium in your would be like eating 46g of salt a day. A normal american diet is between 8-15g a day! 

Judy : That is a lot. Not even americans can do that!!!!

The 3rd way your could have figured out our mistake was

1. if you know a normal 24 hour NA excretion is 200meq and the urine output was 20 liters – 200/20🡪 Una of 10 meq/L.  

Judy: THIS IS THE FINAL AND MOST IMPORTANT POINT BECAUSE PATIENTS WITH PRIMARY POLYDIPSIA WILL HAVE A LOW SPOT UNA BECAUSE IT IS MEASURED AS A CONCENTRATION NOT BECAUSE THEY ARE IN SODIUM DEFICIT. 

Sophie: So to summarize ( in your own words SOPHIE): 

• you cannot have a Usom lower then your Una
• NORMAL 24 HOUR URINE NA EXCRETION ON A REGULAR DIET IS 100-300 meq/day
• Una in primary polydipsia is low because of the denominator (the volume is so great)

Sy:- Please DM us if you have any questions about this

SY:- lastly before we go, we had a listener ask what is “free water”. When we use the term free water we are referring to electrolyte free water. So IV electrolyte free water would be D5W (dextrose 5% water) or enteral water administration,

Judy: t interns and residents should never write fluid restriction as free water restriction because that means the nurses will let them drink everything that is not plain water. Patients should always be written for fluid restriction not free water restriction

Thanks for listening to kidney essentials and We will try to not defy the laws of chemistry again but if we do let us know...KEEP US HONEST

JOIN US FOR OUR NEXT PODCAST WHERE WE will review common urine studies and what they mean

BYE AND STAY SAFE!

JUDY SAYS GOODBYE

SOPHIE SAYS GOODBYE

Credits:

Seamus Klingsporn for editing

Josh strong for graphics

And of course the University of Colorado division of RENAL disease and HTN  for giving us our jobs!