Hyponatremia

1. HYPONATREMIA

2. Definition
Serum concentration level less than 135meq/l
Hyponatremia is the most common electrolyte
abnormality in hospitalised patient
It directly correlates with patients morbidity and
mortality of hospitalised patient

3. ● Clinical features
Depends on severity of hyponatremia and
rapidity of progression of hyponatremia
● Nausea
● Vomiting
● Malaise
● Lethargy
● Confusion
● Headache
● Delirium
● Disorientation

4. Clinical features
● Respiratory failure (normocapnic/hypercapnic)
Normocapnic respiratory failure because of non
cardiogenic.Its neurogenic pulmonary edema normal
pcwp
● Seizure
● Coma(<113)
● Death(<100)

6. Hypovolemic Hyponatremia
Hypovolemic hyponatremia-->increased Circulating AVP--
>HTN(mild)V1A+increased reabsorption of water via V2
1.GIT-loss of Na-Cl
U Na<20mM
On IV NS increase of Na
2. Renal-Volume depletion and increases of AVP
U Na>20mM
Hypoaldosteronism
Salt losing nephropathy(Reflex nephropathy)
Increased excretion of osmotically active substances

7. Hypervolemic hyponatremia
Increase of Na-Cl <<< increase of TBW
U Na low
Eg CCF, Cirrhosis

8. Euvolemic Hyponatremia
Hypothyroidism (moderate to severe)
Glucocorticoid deficiency
(Glucocorticoid → × secretion of ADH hence hydrocortisone
replacement rapidly corrects hyponatremia)
SIADH
Inappropriate secretion
Failure to suppress ADH secretion with low osmolality
Reset osmostat
Impaired (gain in function of receptor)

9. Euvolemic Hyponatremia
Low salt intake-->beer Hyponatremia
Endurance exercise-loss of fluid Ave salt via sweat and Intake of
low osmolar fluid intake

10. Plasma osmolality
Plasma osmolality=2Na+BUN/2.8+Glucose/18
● HYPONATREMIA with normal high osmolality should
exclude psuedohyponatremia
● Psuedohyponatremia not causes Brain oedema
● HYPONATREMIA with oedema causes are nephrotic
syndrome, liver cirrhosis, cardiac failure
● Associated with hypokalemia with metabolic alkalosis-
vomiting, diuretic (thiazide)

11. Approach
>Isotonic hyponatremia- measured osmolality Normal but
calculated osmolality will be lower
Eg-Multiple myeloma,hypergammaglobulinemia
>Hypertonic hyponatremia-measured osmolality higher but
calculated calculated osmolality lower,
Eg-hyperglycemia, mannitol

12. Steps in evaluation
Measurement of plasma osmolality
Low-True hyponatremia
High/Normal-psuedohyponatremia
Measure urine osmolality
<100mosm/kg or sp gravity<1.003-primary polydipsia
>100mosm/kg other causes in which water excretion impaired
Urine Na
<15mEq/L-diarrhoea, vomiting
>15mEq/L-SIADH or salt wasting syndrome

13. Treatment
In acute condition rapid correction can be given
In chronic condition rapid correction should not be given as cortical
pontine myelinolysis can occur

14. General guidelines
● Target correction-10-12meq/l on day 1 and<18meq/l in best 2 days
● >25meq/l48hrs:-central pontine myelinolysis
● R/f central pontine myelinolysis
● Hypoxemia
● Hypokalemia
● Malnutrition
● Alcoholism
● Severe malnutrition

15. Treatment of hyponatremia
Treatment principles
1.Treatment should be individualised based on
etiology, severity, clinical symptom
2.NS given to compenstae postsuppy overdiuresis

16. Hyponatremia Treatment
1.Hypovolumia-Salt water supplementation
2.Oedema-- salt and fluid restriction,loop diuretics
3.Normovolumia-fluid restriction

17. Treatment
->Hypovolemic patients should be given isotonic fluid which
increases sodium level
-Patient with cerebral salt wasting syndrome-hypertonic
saline/fludrocort
Psuedohyponatremia -requires no sodium correction.
->acute hyponatremia (eg, exercise-associated hyponatremia) with
severe neurologic manifestations can be reversed rapidly with 100
mL of 3% hypertonic saline infused over 10 minutes
->For severe cases initial 4-6meq correction to be given(can be
repeated twice

18. Treatment
->initial step in hyponatremia management
since excessive free water intake will exacerbate hyponatre-
mia.
->Free water clearance by the kidneys must exceed free
water intake for the serum sodium concentration to rise.
->Free water intake should generally be less than 1–1.5 L/day
->patients with minimal free water clearance, and
hypertonic saline may be necessary in patients with nega-
tive free water clearance.

19. Treatment
For patient with rapid correction in chronic hyponatremia
5%dextrose+ddavp given to be given
HYPONATREMIA correction formula
Sodium deficit = Total body water (TBW) × (Desired serum Na –
Actual serum Na)

20. Hypovolemia-Isotonic fluid (to prevent Hypovolemia-Isotonic induced
ash secretion)
Cerebral salt wasting syndrome-hypertonic saline to prevent
circulatory collapse

21. Specific treatment
● Treat underlying causes-adrenal insufficiency, hypothyroidism,
nephrotic syndrome
● Removal of offending drugs-
Tthiazides,chlorptomide,cyclophosphamide

22. Treatment
Delivery rate
->3% hypertonic saline has a sodium concentration of 513
mEq/1000 mL. The delivery rate for hypertonic saline can be
calculated as:
Delivery rate = Sodium deficit/(513 mEq/1000 mL)/
24 hours

23. Calculate Na deficit
Na deficit=TBW(desired Na-present Na)
Tbw=0.6×Body weight
(0.5for female)

24. References
● CMDT 2018
● HARRISON PRINCIPLES OF INTERNAL MEDICINE
● CLEVELAND CLINIC JOURNAL OF MEDICINE VOLUME
71 • NUMBER 8 AUGUST 2004

25. THANK YOU