Approach to Hypernatremia

1. HYERNATREMIA
DR GERARD VINODH
DNB Nephrology
Apollo Hospital

2. DEFINE HYPERNATREMIA
Hypernatremia Serum Na+ > 145 mEq/L
Acute < 48 hrs
Chronic > 48 hrs or if cannot be classified

3. WATER & ELECTROLYTE DISTRIBUTION

4. WATER & ELECTROLYTE DISTRIBUTION

5. PLASMA OSMOLALITY & HYPERNATREMIA
PLASMA OSMOLALITY
INCREASED
STIMULATION OF THIRST
INTAKE OF WATER
STIMULATION OF
VASOPRESSIN
CONCENTRATED URINE

6. PLASMA OSMOLALITY & HYPERNATREMIA

7. VASOPRESSIN ACTION

8. VASOPRESSIN
• supraoptic & paraventricular magnocellular
nuclei in hypothalamus
• OSMOTIC STIMULI
• NONOSMOTIC STIMULI
– Decreased effective circulatory volume (Heart failure,
cirrhosis, vomiting)
– Hypovolemia
– Nausea, Postoperative pain, pregnancy

9. APPROACH TO HYPERNATREMIA
• HISTORY ( RECENT DRUGS)
• EXAMINATION
• LABORATORY VALUES

10. HISTORY & EXAMINATION
• Elderly
• Infants
• ICU patients
• Sensation of Thirst
• Polyuria
• Watery stools – osmotic diarrhoea
• Postural Hypotension

11. REDUCED WATER INTAKE
1. Cognitive impairement
2. ICU patients
3. Hypodipsia of elderly
4. Osmoreceptor dysfunction
Urine osmolality Maximal
Ur spot Na+ < 25
Urine output decreased

12. INCREASED WATER LOSS
• Renal water loss
1. Diabetes Insipidus
a. Central
b. Nephrogenic
c. Gestational
2. Osmotic diuresis
3. Diuretics
• GI water loss
1. Vomiting
2. Osmotic diarrhoea
• Cutaneous water loss

13. CENTRAL DI

14. • Post traumatic
• Post Surgical – trans-phenoidal surgery
• Tumors
• Infections – TB, Influenza, Histiocytosis
• Hereditary – Neurophysin II
• Adipsogenic – Craniopharyngioma
CENTRAL DI

15. Acquired
Disease
Medullary
tonicity defect
cAMP
defect
AQP 2 ↓ Other
Lithium Yes ENaC
Amp B
Damage apical
membrane
Yes Frequent K+ ↓
Demeclocycline yes
CKD Medullary cystic Yes Yes V2R
↓ K+ Interstitial damage Yes ↓ polyuria
↑ Ca++ CaSR localise with AQP2
CaSR in TAL
Pregnancy Vasopressinase
NEPHROGENIC DI
Hereditary V2R gene – X
recessive
AQP2 – Autosomal
recessive
Barters

16. CENTRAL & NEPHROGENIC DI
Urine osmolality < 300
Ur spot Na+ < 25
Urine output polyuria

17. DDAVP 1-4mcg i.v
DISEASE URINE OSMOLALITY
CENTRAL >50% raise within 1-2 hrs
NEPHROGENIC <10% raise
INDETERMINATE 10% to 50%

18. • Water intake is restricted until
1. ↓ 3 to 5% body wt
2. 3 consecutive hrly Urine osm change < 10%
3. Aq vasopressin 5U s/c Urine osm after 60 min
WATER DEPRIVATION TEST

19. WATER DEPRIVATION TEST
Condition
U oSm (water
deprivation)
Plasma vasopressin
U oSm (Exogenous
vasopressin)
Normal >800 >2 Little or no increase
Complete central
diabetes insipidus
<300 Undetectable ↑ >750
Partial central
diabetes insipidus
300-800 <1.5 >10% ↑
Nephrogenic
diabetes insipidus
<300-500 >5 No or < 10 % ↑
Primary polydipsia >500 <5 No or < 10 % ↑

20. OSMOTIC DIURESIS
• Hyperglycemic Hyperosmolality
– Effective osmole in tubular fluid
• ↑ Urea
– ICU, Hyperalimentation, Catabolism, GI bleed
Urine osmolality > 300
Ur spot Na+ > 25
Urine output polyuria

21. EXTRA RENAL WATER LOSS
• GI loss
• Osmotic diarrhoea
• Prolonged vomiting
• Cutaneous
• Burns
• Excessive sweating Urine
osmolality
maximal
Ur spot Na+ <25
Urine output ↓

22. GAIN OF SODIUM
• Hypertonic fluids
• Excessive sodium in oliguric patient
Urine
osmolality
maximal
Ur spot Na+ >25
Urine output N or↓

23. ↑ Na+
Ur spot Na+ >25
Sodium gain
Ur spot Na+ <25
Reduced water
intake
U osm max
Polyuria↓ Urine/Normal
Diabetes
Insipidus
Uosm > Sr osm
Ur spot Na+ > 25
U osm < Sr osm
Ur spot Na+ < 25
Osmotic diuresis
Response to DDAVP
U osm ↑ <10%
Nephrogenic
U osm ↑ >50%
Central

24. LAB INVESTIGATION
BLOOD URINE
Sr osmolality Ur osmolality
Na+ Ur spot Na+
K+ Ur spot K+
Ca++
Glucose
Urea
Creatinine

25. CLINICAL FEATURES
• CNS Dysfunction
• Thirst
• Polyuria
• Postural Hypotension
Acute Chronic
Cerebral Hemorrhage
Cerebral edema –
overzealous treatment

26. EFFECT ON BRAIN

27. STEPS IN TREATMENT
STEPS
Assess
1. Acute or Chronic
2. Cause
Correct ECV if Hypotension
Set Target
Check progress

28. ACUTE HYPERNATREMIA
• Correct @ 1mEq/L/hr
• Measure Na+ 2nd hrly, then 4th hrly

29. CHRONIC HYPONATREMIA
• Correct more slowly
• <0.5 mEq/L/h
• Not > 10mEq/L/day
• Correct 50% water deficit in 24 hrs
• Remaining in next 24 to 48 hrs
• Measure Na+ 2nd hrly then 4th hrly

30. WATER DEFICIT
• Water deficit
= TBW x {(Sr Na+/140) – 1}
TBW = 0.6 x body wt ( males)
= 0.5 x body wt (females, Age >65)
50 yrs old 70kg man with Na+-170
=0.6 x 70 x {(170/140)-1}
=42 x (0.21)
=9 litres

31. CORRECTION
• Change in Na+
= Infusion Fluid Na – Na for 1000ml of infusion
TBW+1
Using 5%D
Change in Na+ = (0-170)/43= -3.95 mEq/L
So 1 L 5%D needed to bring Na+ to 166mEq/l
Aiming to correct 0.5 mEq/h = 1L/8 = 125ml/hr
Using ½ NS
250ml/hr
Oral intake if feasible

32. TREATMENT OF CENTRAL DI
DRUGS
DESMOPRESSIN NASAL SPRAY 10-20mcg intranasal
Q12-24H
AQUEOUS VASOPRESSIN 5-10U s/c Q6-8H