hyponatremia: classification and management DR- KHALID SHAWKEY RAMADAN

2. Khalid Shawkey
Internist and Nephrologist
ICU unit
Internal Medicine Department
Zagazig University Hospitals

4. • Normal serum sodium 135-145 mEq/l
• Osmolality :- number of osmoles per kg of
solvent
• Osmolarity :- number of osmoles per litre of
solution
• Normal plasma osmolality 280-290 mmol/l
• Normal urine osmolality 400-500mmol/l

5. Plasma Osmolality, Calculation
• normally ranges between 280 and 290 mmol/L
5

6. Osmolar gap
• The difference between measured and
calculated plasma osmolality
• A value greater than 10 mosm/kg H2O is
considered elevated and reflects the presence
of unmeasured solutes

9. EPIDEMIOLOGY
• Hyponatremia is the most common
electrolyte disorder
• The disorder is more frequent in females, the elderly,
and in people who are hospitalized.
• A hospital incidence of 15–20% is common, while only
3–5% of people who are hospitalized have a serum
sodium level (salt blood level) of less than 130 mEq/L.
• Hyponatremia has been reported in up to 30% of
elderly patients in nursing homes and is also present in
approximately 30% of depressed patients on selective
serotonin reuptake inhibitors

19. Effects of Hyponatremia on
the Brain and Adaptive
Responses.

20. Diagnosis
• Urine osmolality:-Urine osmolality helps
differentiate between conditions associated
with impaired free-water excretion and
primary polydipsia. A urine osmolality greater
than 100 mOsm/kg indicates impaired ability
of the kidneys to dilute the urine.

21. • Serum osmolality:-Serum osmolality readily
differentiates between true hyponatremia and
pseudohyponatremia secondary to
hyperlipidemia, hyperproteinemia, or
hypertonic hyponatremia associated with
elevated glucose, mannitol, glycine
(posturologic or postgynecologic procedure),
sucrose, or maltose (contained in IgG
formulations).

22. • Urinary sodium concentration:-Urinary sodium
concentration helps differentiate between
hyponatremia secondary to hypovolemia and
syndrome of inappropriate antidiuretic hormone
secretion (SIADH). With SIADH (and salt-wasting
syndrome), the urine sodium is greater than 20-
40 mEq/L. With hypovolemia, the urine sodium
typically measures less than 25 mEq/L. However,
if sodium intake in a patient with SIADH (or salt-wasting)
happens to be low, then urine sodium
may fall below 25 mEq/L.

23. treatment
I. Determine the rate of correction
Acute hyponatremia
Rapid correction at a rate of 1 to 2 mEq/L/hr until plasma Na+ 120 mEq/L
Chronic hyponatremia
Slow correction at a rate of 0.5 mEq/L/hr until plasma Na+ 120 mEq/L
II. Determine the mode of correction
Hypovolemic hyponatremia
Saline
Euvolemic hyponatremia
Fluid restriction; furosemide alone or with saline to replace urine N+ losses
Demeclocycline in SIADH if above is insufficient
Hypervolemic hyponatremia
Treat underlying disease
Fluid restriction
Furosemide alone or with saline to replace urine Na+ losses if above is unsuccessful

25. • Total body water (L) = (body weight in kg) ×
(correction factor) Correction factor is 0.6 for
children and nonelderly men, 0.5 for elderly
men and nonelderly women, and 0.45 for
elderly women.

26. • Total sodium deficit (mEq) = [total body water
in L)] × [(desired Na+) - (actual Na+)] Na+ is in
mEq/L

27. Sodium concentration in IV fluids
• 0 mEq/L in 5% dextrose in water
• 77 mEq/L in 0.45% saline
• 154 mEq/L in 0.9% saline
• 513 mEq/L in 3% saline
Total liters IV fluids needed = total Na+ deficit
(mEq)/Na+ concentration in IV fluid (mEq/L)

28. Pharmacologic treatment
• demeclocyclines:- which interferes with ADH action at
the collecting tubule; hypersensitivity and
nephrotoxicity are the limitations.
• urea, which acts as an osmotic diuretic; palatability
and azotemia limit the use
• vasopressin receptor antagonists, which interfere with
ADH action. Conivaptan is approved for short-term
parenteral use in euvolemic and hypervolemic
hyponatremia. Incomplete data on chronic use and
interactions with cytochrome P450-metabolized drugs
limit use.

29. Central pontine mylinolysis
• a severe neurological disease involving a
breakdown of the myelin sheaths covering
parts of nerve cells .
• During treatment of hyponatremia, the serum
sodium (salt level in the blood) is not allowed
to rise by more than 8 mmol/l over 24 hours.
• The lesion is detectable by both CT and MRI

31. TAKE HOME POINTS
• Symptoms: Usually Na <125 or rapid decline
– N/V, headache, lethargy, AMS, seizures, coma
• WORK-UP in 3 important steps (V-O-U):
– 1) Assess volume status
– 2) Assess serum osmolality
– 3) Check urine sodium and osmolarity
• Treatment varies by etiology, but cautious
correction of sodium important to prevent
demyelination as fluid leaves the brain