Can you drink too much water?

In this podcast Drs. Blaine, Ambruso and Young discuss a case of a young man who presents with a serum Na of 120meq/L.  Listen as they take you through how they approach a case of hyponatremia.
Please not there is an addendum at the end of the case, because there was an error in the urine parameters. It is not possible to have a  Uosm of 75 and Una of 100. The osmolality has to be higher if the Una is 100. The Una should have been lower (15-25)

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

Transcript

Please not there is an addendum at the end of the case, because there was an error in the urine parameters. It is not possible to have a  Uosm of 75 and Una of 100. The osmolality has to be higher if the Una is 100. The Una should have been  15-25
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Kidney Essentials

Podcast episode # 1 TITLE:  Can you drink too much water?

PRESS RECORD

Welcome to Kidney essentials

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

Introductions: 

Sarah, Judy and Sophie

Name/Our institution/Areas of interest/ COI statement

First a few Housekeeping notes:

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

Getting to know your hosts- in order to help our audience get to know us better we thought we would start off with a fun non medical question for our hosts. This episodes question is:

 What is a weird renal mom thing you do? 

SOPHIE, THEN JUDY THEN ME

Case 

35 yo male presents with a serum Na of 120meq/L to the ER. The ER calls you saying I got this guy with a serum Na of 120 I want to admit to you

SY: Sophie, what would you ask and why?

Sophie ASK about  MENTATION-review SYMPTOMS OF HYPONATREMIA

SY: Judy, in your experience what kinds of symptoms would a patient with a serum Na of 120 have?

Judy: PROBABLY AT 120 ASYMPTOMATIC, unless high risk group: elderly

SY: ER tells you  he has a mild headache and complains of fatigue. They want to give him 2 L NS for hyponatremia for presumed volume depletion

SY: sophie, what questions do you want to ask? 

Sophie: Why do they think that he is volume depleted? SY: because that is the most common cause of hyponatremia in the ER so they usually just treat with a bunch of fluids

What is his BP? SY: 140/80

Is he tachycardic? SY: NO! pulse of 80

Does he have edema? SY: they did not look (chuckle)

Is he urinating?  SY: ER says he is urinating all the time in fact he is getting up so much to urinate they gave him a bedside urinal

SY: Judy- how to you feel about the 2 LNS? IS there urgency? What are you worried about regarding NS given in a hyponatremic patient whose etiology is not entirely clear?

                Judy- don’t give NS, doesn’t sound like there is evidence of volume depletion and NS c     ould exacerbate his hyponatremia if he has a high ADH state

SY: Sophie, what other questions regarding his medical history would your want to ask the ER about?

Sophie: 

·         Medical history targeted questions about: 1. Psychiatric 2 etoh, 3. cirrhosis ,4 heart failure 5. Kidney function

·         History about water intake

SY: Judy  & sophie, what labs would you like the ER to get?  And what do those labs tell you?

Sophie to discuss: Creatinine , Una, U osm

Judy to discuss: plasma osmolality, glucose, TSH

SY: creatinine is 1.0mg/dL , Una is 100 (ERROR should have been 25) and Usom is 75

Sophie, what does that mean for this patient?

                Sophie: Una is 100à no intravascular volume depletion

U osm 75à maximally dilute urine so NO ADH around not. Mention usom range of functional kidney

                Normal creatinine means renal function is not preventing water excretion

SY:  plasma osmolality 248, TSH 2 Random cortisol is 25

Judy, what does that mean for this patient?

Judy: Plasma osmolality as expected for serum Na of 120 (2x120) mention this equation Plasma osmolality: 248=  2(120) + 80/18+ 10/2.8

TSH- discuss normal TSH excludes low serum Na due to hypothyroidism

Cortisol- discuss cortisol level

SY: The patient, Matt, comes to the floor and you finally get to meet him. He is accompanied by his roommate. You ask him how much water he drinks in a day and he says he really likes water and he wants to flush out his body.  He had not been feeling well so he thought if he just drank more water he would flush all those bad humours out and feel better. 

His roommate, Ryan, chimes in that he has never seen anyone drink so much…Ryan had bought 10x 2 liter bottles of seltzer water for an upcoming party  and Matt had emptied them in 24 hours.

Sy: judy, how much water is too much water?

                Judy- 20Liters is a lot! (20% of GFR)

SY: how are u calculating GFR/creatinine clearance

                Judy- cockrault, CKD epi

Creatinine 1--> GFR 100ml/min x 60min x 24 hrs/day= 144,000ml/d X 0.20 =28,800ml/day= 28.8L/day

SY: Sophie, do you have enough information to make a diagnosis. What is it and how do  you know?

                Sophie- Uosm, U na, plasma osm and history all confirm primary polydipsia

SY: Judy, how would you like to treat this patient? Are you worried at all about him correcting too fast?

Judy: Treatment: don’t let him drink 20 liters/dayà 

If only acute-à not worried

If more prolonged history of drinking this much would want his serum Na to not rise > 6meq/24 hours

SY: Judy & Sophie, are there any additional points you would like  to make about this case?

SY: Our take home messages that we hope you learned from this case are:

Sarah: Hyponatremiea: is excess of water in relation to solute (main solute is Na)

No ADHà U osm can be as low as 50-100mosm, maximum water excretory capacity that can exceed 10 liters

 Normal fluid intake is 2.5L/day

Need to know creatinine is normal and that renal failure is not the cause of impaired water clearance

                Sophie: Need to know plasma osmolality to r/o pseudohyponatremia

Sophie: Pseudohyponatremia refers to disorders in which marked elevations of substances (ie lipids) results in a reduction in the fraction of plasma that is water and an artificially lowered serum na concentration (meq?l)

Need to know glucose is normal to confirm it is not a shifting of water from intracellular to extracellular space and actual excess of total body water

Plasma osmolality: 248=  2(120) + 80/18+ 10/2.8

Judy: In this case Una is not as crucial for making the diagnosis because we know from the U som of 75 there is no ADH.  What does Una tell you in the setting of hyponatremia? U na- need to know to distinguish appropriate ADH excretion from volume depletion (appropriate because it is stimulated by barocepters detection of decreased pressure) and inappropriate ADH secretion in the absence of volume depletion

That ends episode one of Kidney Essentials. We hope you learned that you can indeed drink too much water! Thanks for tuning in! Stay safe and remember THERE ARE NO EMERGENCIES IN A PANDEMIC SO TAKE TIME TO PUT ON YOUR PPE AND WE LOOk FORWARD TO YOU TUNING IN TO EPISODE 2

Sophie says goodbye

Judy says goodbye