hypernatraemia

1. HYPERNATRAEMIA
Qusyairi
Defined as serum sodium >145mmol/L
Normal range: 135-145 mmol/L

2. Outline
Definition
Causes
Signs & symptoms
Investigation
Managements

3. Definition Serum [Na+]
(mmol/l)
Mild Hypernatremia 146 - 149
Moderate
Hypernatraemia
150 - 169
Severe
Hypernatraemia
≥ 170

4. Introduction
Serum sodium concentration is controlled by
1. Urine concentration and it’s production (ADH influence)
2. Thirst response (increase water intake)

5. Clinical features
Affects all ages
• Tremulousness
• Irritability
• Ataxia
• Spasticity
• Mental confusion
• Shortness of breath
• Vomiting
• Coma

6. Causes of Hypernatraemia
Excess sodium intake Inappropriate IV therapy(hypertonic saline,
NaBicarbonate)
salt ingestion (seawater, accidental, Munchausen-
by-proxy),,
sodium bicarbonate, blood products
Increased water losses 1) Renal: diabetes insipidus(central DI and
nephrogenic DI), diuretics, medullary damage
2) GI: diarrhea, vomiting, colostomy/ileostomy
output, malabsorption
3) Insensible: fever, tachypnea, burns
4) Esssential hypernatraemia
Decreased water intake Ineffective breastfeeding,
poor access to water,
impaired thirst mechanisms,
Adipsia(lack of thirst perception)

7. Hypernatraemia caused by increased renal
water loss
1. Central diabetes insipidus- failure of synthesis of antidiuretic
hormone (ADH)
• Eg: langerhans cell histiocytosis, tumour such as craniopharyngioma, damage
caused by meningitis or encephalitis, infarction of pituitary stalk (Sheehan’s
syndrome)
2. Nephrogenic diabetes insipidus- resistance/insensitivity of
renal tubule to ADH action
• Presented with polyuria and polydipsia
• Lithium, tetracycline, amp B, Acute tubular necrosis, HHS
3. Acquired renal disease eg; Renal medullary damage
- Sickle cell disease, reflux nephropathy, medullary cystic disease
4. Essential hypernatraemia- uncommon

8. Hypernatraemia caused by non-renal water
loss
1. Increased evaporative water loss
- Lost in desert, military on duty in desert area
2. Hypernatraemic(hypertonic) dehydration
- Defined as dehydration with plasma sodium conc. above
150mmol/l
- Hypertonicity causes osmotic extraction of water from the cells 
contraction of ECF and ICF
- Eg: gastroenteritis—poor absorption

9. Hypernatraemia caused by non-renal water
loss
3. Hypernatraemia caused by sodium excess:
a. Iatrogenic hyperNa
• Eg: result from the administration of repeated doses of
hypertonic Na bicarbonate to correct acidosis
b. Non-accidental salt poisoning
• Abuse:Adding salt in to the feed or directly into child’s mouth
c. Accidental salt poisoning
• Use of as anti-emetic as treatment
• Use of hypertonic saline to induce an abortion

11. Investigation
Urinalysis
Plasma osmolality
Blood urea serum electrolyte
#urine osmolality is low in diabetes insipidus
#plasma osmolality is high in hyperNa
#hypernatraemia

12. Treatment
• Depends on type of hydration, cause, and time period of development
• Target fall in serum Na conc of 10mmol/L/day except with long-standing
hyperNa
• Long-standing hyperNa: to lower extracellular hypertonicity slowly in
hypertonically-dehydrated patients eg; 0.5 mmol/hr
(prevent cerebral oedema)
• If acute eg: with accidental Na loading, do rapid correction (eg 1mmol/hr)
• Treat the aetiology!!!!!!

13. 1. Water depletion
• Give water orally if tolerated
• If not, set up IV infusion of D5% or 0.45% NaCl
• Rate: hypertonicity should resolved slowly
- Plasma osmolality should not be corrected at a rate
greater than 1mmol/L/hr
- Change in Na conc not exceed 1mmol/L/hr

14. Water depletion
Fraction
of body
water
Children 0.6
Men 0.6
Women 0.5
Elderly
Men
0.5
Elderly
Women
0.45
Method 1: Formula for sodium
correction and volume required

15.  Ongoing free water loss (urine from the electrolyte-
free water clearance (EFWC)):
EFWC = volume of urine (1 - ((urinary [Na+] +
urinary [K+] + urinary glucose/2)/ serum [Na+]))
(Where volumes are in L and concentrations in mmol/L.)
Method 2: Calculation of
volume required

16. 1. Water depletion
#Diabetes insipidus
- Central DI: desmopression through intranasal 5-10ug
once or twice daily or aqueous vasopressin SC 5-10 U
twice daily. SC/IV: 1-2 µg od/bd in acute care
- Nephrogenic DI: thiazide diuretic with or without
prostaglandin synthetase inhibitors eg: indomethacin,
or amiloride + modest Na restiction

17. 2. Salt gain
• Aim: to remove sodium rapidly using a potent diuretic (IV
frusemide) + D5% infusion
• In severe and difficult cases dialysis may be necessary