Hyponatremia is a common electrolyte disorder in diverse fields of medicine. A sound understanding of Physiology is essential for its management. Real life clinical examples are described

1. Hyponatremia – Fishing in
troubled waters
K.SAMPATHKUMAR .
MD, DNB, DM, FISN,FRCP ( Glasgow)
MEENAKSHI MISSION HOSPITAL
MADURAI, INDIA

2. Homer Smith

3. Crucial role of Kidneys in evolution
‘Mileu interior’
Danger of osmotic lysis

4. Kidneys provide
“milieu interior”

5. Hyponatremia < 135 mEq/L
True = Hypo osmolar Plasma
Water excess state

7. Osmolality of various body fluid compartments
govern the fluid and solute distribution
• Plasma Osmolality:Calculated
Posm = 2 (Na) + glucose + urea
Normal = 2 (140) + 5 + 5 = 290 (275-290 )
• Effective Osm= Remove urea from eq.
• Measured Osmolality- Osmometer- Freezing point
depression
• Osmolal gap= Mannitol,urea,glycine etc

8. S.Na ~ Na e + K e
TBW
280 mOsm
280 mOsm
K 140 Na – 140
25 L 17 L
Na,K
ATPase
H2O balance – ICF Volume
Na balance – ECF Volume

9. Kidney’s capacity to concentrate
and dilute the urine
AVERAGE U Osm = 400. 1.5 L of Urine to excrete 600 mOsm

10. Hyponatremia – Basics
Na + K
Total Body Water
Loss of Na,K
Excess water
Intake
Retention

11. Classic experiments of verney

14. V2R

15. 5
0
1200
50
140
130

16. Osmoreg. Vs Vol.reg
• What is sensed?
• Plasma OSMOLALITY
• Sensor?
• OsmoR
• Effector?
• ADH and thirst
• Final say
• Water excretion /
retention
• What is sensed?
• Eff.Circ.BV
• Sensor?
• CAROTID BARO R,ATR.
• Renal AA
• Effector?
• RAAS,ANP,SS
• Final say
• Urine Na
excretion/Retention

17. In volume depletion states when
ADH is stimulated which takes
precedence ?
Water is retained more and serum sodium lowered

19. Clinical approach to HypoNa
•1% of healthy population
•5-8 % of hospitalised patients
•30% of ICU patients

20. Is it serious ?
• Marker of severity of underlying disease
• CCF.
• Cirrhosis.
• Advanced cancer.
• Marker of increased mortality
• Treatment may be more deleterious in
some !

21. 4 essentials
1. History
2. Plasma osm.
3. Volume status
4. Urine Sodium

23. Don’t jump to treatment!!
Avoid misdiagnosis !
• Sampling error ? Common
• Hyperlipidemia ? Use ISE ( Not Flame
Photometer)
• Multiple Myeloma ? Use ISE ( - do - )
• Hyperglycemia ? Every 100 mg increase in glucose
reduces serum Sodium by 1.6 - 2.4 mEq/L
• Drugs and chemicals? Glycine,Mannitol.

24. Hyperglycemia – Hyperosmolar
hyponatremia
Water
Glucose is osmotically
Active
Translocational
hyponatremia
Serum osmolality will be high

26. LOOP D block both
conc.and dilution
THIAZIDES BLOCK DILUTION
ALONE
Urine Na and K moderate Urine Na and K very high

30. Management and special
situations

31. Therapeutic Strategy Based On
• 1. Volume Status of Patient
• 2. Presence of Absence of Symptoms
• 3. Duration of Hypoosmolality
• 4. Presence of absence of risk factors for
development of neurological complication
(Osmotic demyelination is rare in patients
with initial Na+ > 120mEq/L)

32. Clinical scenario 1
• 28 years old female
• Admitted for delivery
• Prolonged labour
• Had to be taken up for cesarian
• Post op coma
• Seizures
• Fluid orders – NS 3000 ml /24 hrs
• BP 100/80- Serum Sodium 110 mEq/L

33. Why hyponatremia
Source of free water
Was given Normal saline
3 Litres /24 hours
Free water intake due to anxiety
ADH is acting
Post op pain
Anxiety
Nausea due to
analgesics
DESALINATION syndrome

34. e- 300 mOsm x 3
900 Mosm
ADH
CONCENTRATES
URINE
600 Mosm /L = 1.5 L of urine
3 L of Saline
Thus 1.5 Litres of free water
is retained in body !

35. 1.5 L WATER
270 mOsm
270 mOsm
K 135 Na – 135
26 L 17 .5 L
1L
0.5L

36. Cerebral edema and Brain herniation
36
CNS ENCASED IN SKULL
Acute water excess
Neuronal edema
Tentorial herniation
Neurog.Pul.edema

37. Aggressive treatment
• 3% saline 2 ml/kg/hour
• Furosemide 40 mg i.v
• Hourly sodium estimation
• Sodium 118 after 2 hours
• No seizures .

38. Scenario 2
56 years old male
Alcoholic cirrhosis
Edema , Ascites
Oliguria
Sleepiness
S.Sodium 113/K 2.3
?Chronic hyponatremia – beware!
38

41. Chronic hyponatremia – Brain adapts to keep
the edema within limits
Aminoacids.Myoinositol
Rapid correction leads on to
cell shrinkage and Demyelination.

42. Calculation
• 60% of body weight is water
• 65 x 0.6 = 39 L
• 123-113 = 8
• 39x 8 = 312 Meq needed
• 1ml of 3% saline = 0.5 mEq of Na
• Sodium deficit = 624 ml
• 624 /24 hours = 26 ml/hr
• Serum Na measure q2-4 hrs
42

43. Adrogue’s Formula*
• Change in serum Sodium=
(Bottle Na+ + Bottle K+) - serum Na+
total body water + 1
• Easier to calculate
*Horacio J Adrogue, Nicholas E Madias: Hyponatremia; NEJM Vol 342, No 21
May 25 (2000)

44. Janinic and Verbalis formula
• Rate ml/Kg/Hr = Goal rate of rise
mmol/Kg/Hr
• 1ml/kg/hr = 1ml/kg/hr rise in Serum Na
• Ideal for those allergic to Math !!

45. Chronic hyponatremia
• Water restriction
• Demeclorcycline 300 -600 mg tid
• Lithium
• Oral urea
• VAPTANS

46. 19/9/2010
K
Na
moves into cell producing
hyponatremia
46
Tirunelveli API , TVMC Auditorium

47. 19/9/2010
 Treat with Intravenous potassium
 Replenish the IC deficit of Potassium .
 Sodium automatically comes up
 If not replaced , then there is danger of
osmotic demyelination.
47
Tirunelveli API , TVMC Auditorium

48. 19/9/2010 Tirunelveli API , TVMC Auditorium 48

49. Insufficient
Correction
CEREBRAL EDEMA
Herniation
19/9/2010
Too Rapid
Correction
OSMOTIC
DEMYELINATION
49
Tirunelveli API , TVMC Auditorium

50. Vasopressin receptor antagonists

51. Vasopressin-Receptor Antagonists.
Ellison DH, Berl T. N Engl J Med 2007;356:2064-2072.

52. SALT -1 ,SALT-2 and SALTWATER
• Oral Tolvaptan increased the serum sodium
levels significantly and safely in CCF,SIAD and
Cirrhosis.
• NOT USED IN ACUTE SYMPTOMATIC
HYPONATREMIA
• 2 CONCERNS
• INCREASED THIRST
• OVERLY RAPID CORRECTION OCCURRED in 1.8%
• No ODM ENCOUNTERED

53. VAPTANS –PURE WATER EXCRETION

54. Why ODS is not a major threat
• Short acting
• Possible to reverse the effect
• Frequent Na monitoring in major clinical
trials
• No threat of hypok as with diuretic +
Hypertonic saline regimen
• FDA Warning- Liver toxicity on prolonged
use in Cirrhosis

55. Who should be treated with vaptans

56. SIADH v.s. Cerebral Salt Wasting
SIADH CSW
Serum Na ↓ ↓
ECFv Normal ↓
UNa ↑ ↑↑
UOSM ↑ ↑
Urine volume N or ↓ ↑
Serum urate ↓ N or ↓
Urine urate ↑ N or ↑

57. Some Interesting Issues not
discussed
• Reset Osmostat
• Beer Potomania
• Glycine in TURP
• Exertional hyponatremia
• Ecstacy and hyponatremia

58. THANK YOU