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1a/14
It’s 1:34 p.m. and the ED pages you for hyponatremia.
A 45 y/o M with no known medical history presents after a seizure with a sodium of 102 mEq/L.
#tweetorial #MedTwitter #Nephtwitter #hyponatremia @theskeletonkeygroup
What's your first move?
It’s 1:34 p.m. and the ED pages you for hyponatremia.
A 45 y/o M with no known medical history presents after a seizure with a sodium of 102 mEq/L.
#tweetorial #MedTwitter #Nephtwitter #hyponatremia @theskeletonkeygroup
What's your first move?
1b/14
The initial evaluation of hyponatremia must “evaluate osmolality excluding hyperglycemia and other causes of non-hypotonic (SOsm >275) hyponatremia.” - per the European Guidelines (PMID: 24569125)
We find a hyperosmolar hyponatremia:
The initial evaluation of hyponatremia must “evaluate osmolality excluding hyperglycemia and other causes of non-hypotonic (SOsm >275) hyponatremia.” - per the European Guidelines (PMID: 24569125)
We find a hyperosmolar hyponatremia:
2a/14
What is the most likely cause of hyponatremia?
What is the most likely cause of hyponatremia?
2b/14
Hyperglycemia-related hyponatremia is staring us in the face.
In insulin deficiency/hyperglycemia, glucose is “effective” osmole, drawing fluid
from the intracellular
extracellular space, diluting sodium.
Glucose Up
, Sodium Down
Hyperglycemia-related hyponatremia is staring us in the face.
In insulin deficiency/hyperglycemia, glucose is “effective” osmole, drawing fluid
from the intracellularextracellular space, diluting sodium. Glucose Up
, Sodium Down
3/14
Reminder
“Effective” osm (gluc, Na, mannitol)
-create osmotic gradient, increase tonicity, cause water to shift out of cells
“Ineffective “ osm (BUN, EtOH, glycine)
-no osmotic gradient, no change in tonicity, no water shifts
Reminder“Effective” osm (gluc, Na, mannitol)
-create osmotic gradient, increase tonicity, cause water to shift out of cells
“Ineffective “ osm (BUN, EtOH, glycine)
-no osmotic gradient, no change in tonicity, no water shifts
4a/14
Hold on…
Glucose >4000 — greater than the laboratory limit of detection.
Did our patient set a new Guinness World Record for the highest sodium?
Hold on… Glucose >4000 — greater than the laboratory limit of detection.
Did our patient set a new Guinness World Record for the highest sodium?
4b/14
A sodium >4000 is probably incompatible with life and likely a laboratory error.
Houston, we have a problem.
A sodium >4000 is probably incompatible with life and likely a laboratory error.
Houston, we have a problem.
5/14
Osmolality, the concentration of solute per kg of water, is used to help estimate a more accurate glucose measurement.
NA
2
BUN
2.8
Glucose 18
Osmolality, the concentration of solute per kg of water, is used to help estimate a more accurate glucose measurement.
NA
2 BUN
2.8 Glucose
18
6a/14
Can we account for all the 350 mOsm we measured?
Na 102 x 2 = 204 mOsm
BUN of 50 / 2.8 = 18 mOSm
Normal osmol gap = 10 mOsm
Glucose of 
=
Can we account for all the 350 mOsm we measured?
Na 102 x 2 = 204 mOsm BUN of 50 / 2.8 = 18 mOSm Normal osmol gap = 10 mOsm Glucose of =
6b/14
Measured: 350 mOsm
Calculated: 232 mOsm
The remaining 118 mOsm are due to glucose.
Measured: 350 mOsm
Calculated: 232 mOsm
The remaining 118 mOsm are due to glucose.
7a/14
POP QUIZ
What is the conversion factor from mOsm/kg to mg/dL of glucose?
POP QUIZWhat is the conversion factor from mOsm/kg to mg/dL of glucose?
7b/14
18 x 118 mOsms = 2,124 mg/dL
Not quite the Guinness World Record glucose of 2,656 mg/dl, but certainly an impressive value and much less than the laboratory reported >4000.
18 x 118 mOsms = 2,124 mg/dL
Not quite the Guinness World Record glucose of 2,656 mg/dl, but certainly an impressive value and much less than the laboratory reported >4000.
8a/14
To correct sodium for hypernatremia:
for every
mg/dL of glucose over we add a correction factor 
What correction factor do you like to use?
To correct sodium for hypernatremia:
for every
mg/dL of glucose over we add a correction factor What correction factor do you like to use?
8b/14
Traditionally 1.6 is used.
Hiller et al proposed 2.4 (PMID: 10225241).
The nephrology fellows @NephBCM like @SaynaNorouzi use 2.0 to make it easy.
Traditionally 1.6 is used.
Hiller et al proposed 2.4 (PMID: 10225241).
The nephrology fellows @NephBCM like @SaynaNorouzi use 2.0 to make it easy.
9/14
Using measured gluc >4000, Na corrects to >164
Using calculated gluc 2,124, Na corrects to 134
We’ve done the mathematical heavy lifting
Using measured gluc >4000, Na corrects to >164
Using calculated gluc 2,124, Na corrects to 134
We’ve done the mathematical heavy lifting
10/14
This is a case of hyperglycemia-related hyponatremia in the setting of Hyperglycemic Hyperosmolar State (HHS)
hyperglycemia
hyperosmolality (>320)
AMS/seizure
absent ketones
This is a case of hyperglycemia-related hyponatremia in the setting of Hyperglycemic Hyperosmolar State (HHS)
hyperglycemia hyperosmolality (>320) AMS/seizure absent ketones
11/14
Let’s treat the patient.
With insulin, cells consume glucose, fluid shifts back from the extracellular intracellular, correcting Na in the process.
Timing
of correcting blood glucose is a rate of 50 - 75 mg/dL/hr per the ADA (PMID: 19564476)
Let’s treat the patient.
With insulin, cells consume glucose, fluid shifts back from the extracellular
intracellular, correcting Na in the process. Timing
of correcting blood glucose is a rate of 50 - 75 mg/dL/hr per the ADA (PMID: 19564476)
12a/14
So why did the patient have a seizure?
So why did the patient have a seizure?
12b/14
HHS may cause altered mental status, seizures, and death, but the exact pathophysiology is unclear.
Whereas rapid changes in osmolality cause cerebral edema in children
, it very rarely occurs in adults 
.
Idunno, bro!
HHS may cause altered mental status, seizures, and death, but the exact pathophysiology is unclear.
Whereas rapid changes in osmolality cause cerebral edema in children
, it very rarely occurs in adults .Idunno, bro!
13/14
In this case, the patient was admitted to ICU, received intravenous fluids and insulin per HHS protocol.
Glucose Down, Sodium Up
Sodium improved to 134, exactly our estimation!
In this case, the patient was admitted to ICU, received intravenous fluids and insulin per HHS protocol.
Glucose Down
, Sodium Up Sodium improved to 134, exactly our estimation!
14/14
To summarize:
Glucose is “effective” osmole, drawing fluid from the intracellular to the extracellular space, diluting sodium.
Accurate measurements of serum osmolality and glucose help to predict the corrected sodium.
To summarize:
Glucose is “effective” osmole, drawing fluid from the intracellular to the extracellular space, diluting sodium. Accurate measurements of serum osmolality and glucose help to predict the corrected sodium.
Check out the visual abstract and full blog post at: https://renalfellow.org/2020/05/11/skeleton-key-group-electrolyte-case-8/
Special thank you to these great people, among others!
@DTomacruzMD, @amyaimei, @SaynaNorouzi, @kkalra_22, @iheartkidneys, @NephroGuy, @RyannSohaney, @drM_sudha, @kidney_boy, @TheSkeletonKG
Special thank you to these great people, among others!
@DTomacruzMD, @amyaimei, @SaynaNorouzi, @kkalra_22, @iheartkidneys, @NephroGuy, @RyannSohaney, @drM_sudha, @kidney_boy, @TheSkeletonKG
