1. By
Dr:-FATIMA EYAD AL GLAD

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Definition
Epidemiology
Physiology
Pathophysiology
Types
Clinical Manifestations
Diagnosis
Treatment

3. • Definition:
– Commonly defined as a serum sodium concentration
135 meq/L
– Hyponatremia represents a relative excess of water in
relation to sodium.

4. : Epidemiology
ocw.jhsph.edu
Frequency
Hyponatremia is the most common electrolyte
disorder
incidence of approximately 1%
prevalence of approximately 2.5%
surgical ward, approximately 4.4%
of patients treated in the intensive care unit 30%

5. . Epidemiology Cont

Mortality/Morbidity ›
Acute hyponatremia (developing over 48 h or 
less) are subject to more severe degrees of
cerebral edema
sodium level is less than 105 mEq/L, the mortality is 
over 50%
Chronic hyponatremia (developing over more 
than 48 h) experience milder degrees of
cerebral edema
Brainstem herniation has not been observed in 
patients with chronic hyponatremia

6. . Epidemiology Cont

Age ›
Infants 
fed tap water in an effort to treat symptoms of 
gastroenteritis
Infants fed dilute formula in attempt to ration 
Elderly patients with diminished sense of thirst, 
especially when physical infirmity limits
independent access to food and drink

7. Physiology

Serum sodium concentration ›
:regulation
stimulation of thirst 
secretion of ADH 
feedback mechanisms of the 
renin-angiotensin-aldosterone
system
renal handling of filtered sodium 

8. . Physiology Cont

Stimulation of thirst ›
Osmolality increases 
Main driving force 
Only requires an increase of 2% - 3% 
Blood volume or pressure is reduced 
Requires a decrease of 10% - 15% 
Thirst center is located in the anteriolateral 
center of the hypothalamus
Respond to NaCL and angiotensin II 

11. www.merricks.com/tech_electrolyte_new.htm

12. . Physiology Cont

extracellular-fluid and intracellular-fluid ›
compartments make up 40 percent and 60
percent of total body water
renal handling of water is sufficient to ›
excrete as much as 15-20 L of free water per
day
sodium is the predominant osmole in the ›
extracellular fluid (ECF) compartment and
serum

13. Pathophysiology

hyponatremia can only occur when some ›
condition impairs normal free water
excretion
:acute drop in the serum osmolality ›
neuronal cell swelling occurs due to the water 
shift from the extracellular space to the
intracellular space
Swelling of the brain cells elicits 2 responses for 
:osmoregulation, as follows
It inhibits ADH secretion and hypothalamic thirst 
center
immediate cellular adaptation 

14. Types 
Hypovolemic hyponatremia 
Euvolemic hyponatremia 
Hypervolemic hyponatremia 
Redistributive hyponatremia 
Pseudohyponatremia 

15. develops as sodium and free
water are lost and/or
replaced by inappropriately
hypotonic fluids
Sodium can be lost through
renal or non-renal routes
www.grouptrails.com/.../0-Beat-Dehydration.jpg

16. Nonrenal loss
GI losses ›
Vomiting, Diarrhea, fistulas, pancreatitis 
Excessive sweating ›
Third spacing of fluids ›
ascites, peritonitis, pancreatitis, and burns 
Cerebral salt-wasting syndrome ›
traumatic brain injury, aneurysmal 
subarachnoid hemorrhage, and intracranial
surgery
Must distinguish from SIADH 
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17. Renal Loss ›
Acute or chronic renal insufficiency 
Diuretics 
www.ct-angiogram.com/images/renalCTangiogram2.jpg

19. Normal sodium stores and a total body
excess of free water
Psychogenic polydipsia, often in psychiatric
patients
Administration of hypotonic intravenous or
irrigation fluids in the immediate postoperative
period

20. administration of hypotonic maintenance ›
intravenous fluids
Infants who may have been given ›
inappropriate amounts of free water
bowel preparation before colonoscopy or ›
colorectal surgery

21. SIADH

downward resetting of the osmostat ›
Pulmonary Disease ›
Small cell, pneumonia, TB, sarcoidosis 
Cerebral Diseases ›
CVA, Temporal arteritis, meningitis, 
encephalitis
Medications ›
SSRI, Antipsychotics, Opiates, Depakote, 
Tegratol

22. Total body sodium increases, and TBW
. increases to a greater extent
Can be renal or non-renal
acute or chronic renal failure
dysfunctional kidneys are unable to excrete the
ingested sodium load
cirrhosis, congestive heart failure, or nephrotic
syndrome

23. Water shifts from the intracellular to the ›
extracellular compartment, with a resultant
dilution of sodium. The TBW and total body
. sodium are unchanged
This condition occurs with hyperglycemia 
Administration of mannitol 

24. Pseudohyponatremia
The aqueous phase is diluted by excessive ›
proteins or lipids. The TBW and total body
. sodium are unchanged
hypertriglyceridemia 
multiple myeloma 


25. Clinical Manifestations
most patients with a serum sodium
concentration exceeding 125 mEq/L are
asymptomatic
Patients with acutely developing
hyponatremia are typically symptomatic at
a level of approximately 120 mEq/L
Most abnormal findings on physical
examination are characteristically
neurologic in origin
patients may exhibit signs of hypovolemia or
hypervolemia
›
›
›
›


26. Diagnosis
CT head, EKG, CXR if symptomatic
Repeat Na level
Correct for hyperglycemia
Laboratory tests provide important initial
information in the differential diagnosis of
hyponatremia
Plasma osmolality 
Urine osmolality 
Urine sodium concentration 
Uric acid level 
FeNa 
›
›
›
›


27. .Laboratory tests Cont
Plasma osmolality ›
normally ranges from 275 to 290 mosmol/kg 
: If >290 mosmol/kg 
Hyperglycemia or administration of mannitol 
:If 275 – 290 mosmol/kg 
hyperlipidemia or hyperproteinemia 
:If <275 mosmol/kg 
Eval volume status 


28. .Laboratory tests Cont

Plasma osmolality < 275 mosmol/kg ›
:Increased volume 
CHF, cirrhosis, nephrotic syndrome 
Euvolemic 
SIADH, hypothyroidism, psychogenic polydipsia, beer 
potomania, postoperative states
Decreased volume 
GI loss, skin, 3rd spacing, diuretics 

29. .Laboratory tests Cont
Urine osmolality ›
Normal value is > 100 mosmol/kg 
:Normal to high 
Hyperlipidemia, hyperproteinemia, hyperglycemia, 
SIADH
mosmol/kg 100>
hypoosmolar hyponatremia 
Excessive sweating
Burns
Vomiting
Diarrhea
Urinary loss








30. .Laboratory tests Cont

Urine Sodium ›
mEq/L 20< 
SIADH, diuretics

mEq/L 20> 
cirrhosis, nephrosis, congestive heart failure, GI loss, 
skin, 3rd spacing, psychogenic polydipsia
Uric Acid Level ›
mg/dl consider SIADH 4>

FeNa ›
Help to determine pre-renal from renal causes 

31. Treatment
four issues must be addressed ›
Asymptomatic vs. symptomatic 
(acute (within 48 hours 
(chronic (>48 hours 
Volume status 
1st step is to calculate the total body water ›
total body water (TBW) = 0.6 × body weight 

32. .
Treatment Cont
•
next decide what our desired correction rate ›
should be
Symptomatic ›
immediate increase in serum Na level by 8 to 10 
meq/L in 4 to 6 hours with hypertonic saline is
recommended
acute hyponatremia
›
more rapid correction may be possible 
to 10 meq/L in 4 to 8 hours 8

chronic hyponatremia
slower rates of correction
meq/L in 24 hours 12

›


33. Symptomatic or Acute ›
!!!Treatment Cont. - Here comes the Math 
estimate SNa change on the basis of the amount of 
Na in the infusate
(ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1 
ΔSNa is a change in SNa 
Na + K]inf is infusate Na and K concentration in 1 liter of] 
solution
!!!!!!!!!!!!!!!!!!OH MY GOD, what did he just say 

34. IV Fluids
:One liter of Lactated Ringer's Solution contains ›
mEq of sodium ion = 130 mmol/L 130 
mEq of chloride ion = 109 mmol/L 109 
mEq of lactate = 28 mmol/L 28 
mEq of potassium ion = 4 mmol/L 4 
mEq of calcium ion = 1.5 mmol/L 3 
:One liter of Normal Saline contains ›
mEq/L of Na+ and Cl 154 
−
:One liter of 3% saline contains ›
mEq/L of Na+ and Cl 514 
−


35. :Example

a 60 kg women with a plasma sodium of 110 ›
meq/L
:Formula ›
(ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1 
?What is the TBW ›
How high will 1 liter of normal saline raise the ›
? plasma sodium
:Answer
TBW is 30 L ›
Serum sodium will increase by approximately ›
1.4 meq/L for a total SNa of 111.4 meq/L


36. :Example

a 90 kg man with a plasma sodium of 110 ›
meq/L
:Formula ›
(ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1 
?What is the TBW ›
How high will 1 liter of 3% saline raise the ›
? plasma sodium
:Answer
TBW is 54 L ›
Serum sodium will increase by approximately ›
7.3 meq/L for a total SNa of 117.3 meq/L


37. Asymptomatic or Chronic
SIADH ›
response to isotonic saline is different in the
SIADH
In hypovolemia both the sodium and water
are retained
sodium handling is intact in SIADH
administered sodium will be excreted in the
urine, while some of the water may be
retained
possible worsening the hyponatremia 






38. Asymptomatic or Chronic

SIADH ›
Water restriction 
liter/day 0.5-1 
Salt tablets 
Demeclocycline 
Inhibits the effects of ADH 
Onset of action may require up to one week 

39. :Example
y/o male with weakness and head ache 85
SNa is 118 mEq/L
Plasma osmolality is 254 mosmol/kg
Urine osmolality is 130 mosmol/kg
Urine sodium >20 mEq/L
Uric acid is 3mg/dl
What type of hyponatremia does this
?patient have
What additional labs/studies would you
?want

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–
–
–
–
–
•
•

40. Ouch!!!!!
.:Example Cont

Noncontrast CT ›
:Head
Tx
Call Neurology ›
and neurosurgery
Free water ›
restriction

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41. :Example
•
y/o female at 75 Kg with N/V/D for 4 days 63 –
SNa is 108 mEq/L –
She has had one seizure in the ambulance –
•
Plasma osmolality is 251 mosmol/kg
•
Urine osmolality is 47 mosmol/kg
Uric acid is 6mg/dl •
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What type of hyponatremia does this •
?patient have
What additional labs/studies would •
?you want

42. ?How will you Tx her

Calculate the total body water
x weight = 37.5 L 0.5
›

?What rate of correction do you want
to 10 mEq/L in 6 to 8 hours 8
?What fluid will you use
Saline 3%
›

›

How will you calculate the amount of sodium ›
?to give her
(ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1 
How will her sodium increase after 1 liter of 3% ›
?saline
By 10.8 mEq/L to 118.8 mEq/L


43. ?What other medication will she need

Lasix and a foley ›
Her sodium increases to 118.8 mEq/L over
the next 8-10 hours. How will you continue to
?correct her hyponatremia

(ΔSNa = {[Na + K]inf − SNa} ÷ (TBW + 1 ›
ΔSNa = 154mEq/L – 118.8mEq/L ÷ 38.5L = 0.9 ›
mEq/L
So 2 liters of normal saline over the next 14
hours


44. The syndrome of inappropriate antidiuretic hormone secretion or
SIADH (other names: Schwartz-Bartter syndrome, SIAD—syndrome of
immoderate antidiuresis) is characterized by excessive release
of antidiuretic hormone from the posterior pituitary gland or another
source. The result is often dilutional hyponatremia in which Athe
sodium remains normal but total body fluid increases. It was originally
described in people with small-cell carcinoma of the lung, but it
can be caused by a number of underlying medical conditions. The
treatment may consist of fluid intake restriction, various medicines,
And management of the underlying cause.

45. Gastro-intestinal
•Anorexia
• Nausea
Skeleto-muscular
Muscle aches
•Generalised muscle weakness
Neuro-muscular
•Myoclonus
•Hyporeflexia
•Ataxia
•Pathological reflexes
•Tremor
Asterixi
Respiratory
•Cheyne-Stokes respiration
Neurologica
•Dysarthria
•Lethargy
•Confusion
•Delirium
•Seizures

46. Some common causes of SIADH include:[
citation needed]
•Meningitis
•Head injury
•
Subarachnoid hemorrhage
•Cancers
•
Lung cancer (especially small-cell
lung cancer, as well as other smallcell malignancies of other organs)
•Infections
•
Brain abscess
•
Pneumonia
•
Lung abscess
•Guillain-Barré syndrome
•Drugs
•
Chlorpropamide
•
Ciprofloxacin[2]
•
Clofibrate
•
Moxifloxacin[2]
Phenothiazine

49. !Congrats!!!!!!!! You saved her

????Questions
