Hyponatremia Anthony R Mato, MD Remember the basics of the body’s fluid compartments. TBW = WEIGHT x .5 (women) or .6 (men) TBW x 1/3 = ECF TBW x 2/3 = ICF ECF x 2/3 = Interstitial compartment ECF x 1/4 = Intravascular compartment
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Anthony R Mato, MD
ECFV overload results from too much sodium in the ECF compartment.
ECFV depletion results from too little sodium in the ECF compartment.
It’s NOT IMPORTANT TO MEMORIZE THE PATHWAYS.
IMPORTANT TO KNOW : that when ECFV increases mechanisms are triggered to excrete Na as the response.
When ECFV decreases mechanisms are triggered to retain Na as the response.
NOTE THAT WE HAVE NOT YET MENTIONED THE CLINICAL MEASURE OF SODIUM CONCENTRATION.
[Na] is a measure of Na relative to water.
It tells you NOTHING about the total body sodium. Abnormalities in the Na concentration tell us that there are abnormalities in the amount of WATER in the ECF compartment.
ALL OF THE CLINICAL DISORDERS PRODUCING HYPER AND HYPONATREMIA MAY BE UNDERSTOOD AND REMEMBERED BASED ON ABNORMALITIES OF THESE MECHANISMS.
Goals of the body
ATTACK VOLUME AND SODIUM CONCENTRATION AS TWO SEPARATE PROBLEMS.
THIS TABLE WILL HELP BREAK IT DOWN.
Hyponatremia with hypotonicity: impaired renal water excretion in the setting of continued water intake.
THE REASON WHY THE KIDNEY CAN NOT CONCENTRATE THE URINE IS THE KEY TO DIAGNOSING THE CAUSE OF HYPONATREMIA.
PUTTING IT ALL TOGETHER
An Alternative Approach.
23 yr old male develops watery diarrhea. He comes to your ER lightheaded and orthostatic. He has dry MM and tachycardia. Neuro exam is normal and he is alert.
Labs: Na 129, K 3, HCO3 20, BUN 20, Cr 1, Glucose 75, Urine Na 5, Urine osm 520.
72 yr old woman with DM presents to ER with polyuria and polydipsia x 5 days. PE is normal. Labs:
Na 129, K 4.2, Cl 89, HC)3 24, BUN 5, Cr.08, Glucose 780.
What is the osm?
Why is he hyponatremic?
What is the corrected Na?
What is the treatment?
38 yr old woman with Hep C is brought to ED unresponsive. She is obtunded with elevated JVP, rales b/l, massive ascites, and 2 + edema. Labs:
Na 112, K 4.1, Cl 89, HCO3 24, BUN 32, Cr .7, Glucose 90, Urine Na 2, Urine OSM 800.
What is the osm?
What is the volume status?
Why is she hyponatremic?
What is the treatment(s)?
You are called as a curbside consult for an outpatient hyponatremia case.
Serum Na is 120. Pt is asymptomatic. Other data: Cl 80, K 4.5, HCO3 24, BUN 14, glucose 90.
What further questions do you ask?
A 50 yr old male with h/o hyperlipidemia has the following labs:
Na 125, M-Osm 270, TGs 1000, total protein 8.5. The blood is lipemic.
Is this a case of pseudohyponatremia?
Mr. T has 3 days of N/V, polyuria and polydipsia. Exam: poor turgor and orthostatic. Labs: glucose 360, Na 120, BUN 28. M-OSM 270.
What is the cause of this hyponatremia?
What will Na be once glucose is corrected to 100?
Mrs. NA has polyuria, polydipsia, and delta MS.
Exam shows poor turgor and orthostasis. Labs: glucose 2100, Na 130, BUN 40. M-OSM = 395.
What is the cause of the hyponatremia?
What will Na be once glucose is corrected?
What fluid should you use?
Mr. JD comes to the ER staggering and smelling foul.
Na is 140, glucose 180, and BUN 28. M-OSM = 330.
What is your diagnosis?
How could you confirm it using the above lab data?
RR has a classic exam in addition to his new onset edema after eating some chips. He has elevated JVP, crackles, S3.
CXR shows b/l pulmonary edema. Labs Na 125, urine Na 5, M OSM 270.
Why is serum Na low?
How would you treat this?
RR return to clinic in florid CHF. This time his Na is 138.
What treatments would you now offer him?
Jenny a 46 yr old female presents with N/V and abdominal pain. MM are dry, skin has poor turgor, and she is orthostatic. She notes a h/o PUD.
Labs: Na 125, U Na 5, M OSM 270.
What is happening?
What therapy do you implement?
72 yr old male who is a heavy smoker presents with cough and hemoptysis. His physical exam is completely normal in terms of volume status. CXR reveals a 6 cm left sided chest mass. Labs: Na 125, K 4.2, Cr 1.1, M OSM 270, Urine Na is 45. He takes no meds. TSH and am cortisol are normal.
What is causing the hyponatremia?
50 yr old 60 kg advertising executive is recovering from TOA surgery. She has been getting D5 ½ NS x 36 hours. You are called s/p a seizure preceded by confusion. You send off the stat labs and find Na 116 (baseline 136), M OSM 258.
What has happened?
What do you do?
A man with SIADH has a fixed urine osm of 600 mosm/L. Solute excretion is measured to be 600 mosm/day.
What amount of water could he safely drink?
What could you do to improve this to a more reasonable amount?