This document discusses hyponatremia, which refers to low sodium levels in the blood. It defines hyponatremia as a change in the ratio of sodium to total body water. Various causes of hyponatremia are described, including thiazide diuretics, liver failure, heart failure, and renal failure. Hypertonic hyponatremia caused by high blood glucose is explained in more detail. Potential treatments discussed include isotonic saline, tolvaptan, demeclocycline, and restricting free water intake. The document cautions that certain treatments like tolvaptan are contraindicated in liver failure due to toxicity risks.
5. Hyponatremia
• Hypo- and hypernatremia are syndromes of altered plasma tonicity and cell
volume that reflect a change in the ratio of total exchangeable body sodium to
total body water ( TBW ).
• Total body sodium can be high in hyponatremia.
• Free water clearance by the kidneys must exceed free water intake for the serum
sodium conc. to rise.
• Hyponatremia is a severe risk factor for morbidity and mortality in patients with
HF and cirrhosis.
• Thiazide diuretics cause hypovolemic hypotonic hyponatremia.
24. Hypertonic
Hyponatremia
• Hypertonic (increased serum osmolality)
hyponatremia is due to the presence of excess
effective osmoles (other than sodium) in the
ECF . Significant hyperglycemia is the most
frequent cause. An elevated serum glucose
concentration initially causes water diffusion
from cells (ICF) into the ECF, thereby
decreasing the ICF volume, expanding the ECF
volume, and diluting the existing sodium
resulting in hyponatremia. The increased ECF
volume results in increased urine output
(polyuria) which triggers the thirst mechanism
(polydipsia). If the hyperglycemia is not
corrected and/or extra fluid is not ingested,
hypovolemia develops.
25. one would predict 1.7 mEq/L decrease in the serum sodium concentration for every 100
mg/dL increase in the serum glucose concentration above 100 mg/dL decrease for every
1 mmol/L increase, and the serum osmolality will increase by 2 mOsm/kg
The presence of other effective osmoles (eg, mannitol) can also cause hypertonic
hyponatremia. The presence of an unmeasured osmole should be suspected in patients
with a normal glucose concentration and hypertonic hyponatremia when there is a
significant osmolal gap, defined as the difference between the measured and calculated
serum osmolalities.
31. • In patients with SIADH, the use of isotonic NaCl can actually worsen
hyponatremia, these patients should be preferentially treated with 3 % NaCl
solution plus loop diuretics.
• Tolvaptan is hepatotoxic, therefore it is C.I in liver failure.
• Tolvaptan shouldn’t be used for longer than 30 days due to the potential for liver
toxicity.
• Dose of tolvaptan; starting dose 15 mg OD, it can be increased to 30 mg daily
and 60 mg daily.
32. • Lack of thyroid hormones increase ADH.
• Lack of cortisol increases ADH.
• Demeclocycline is ttt option for SIADH.
• Demeclocycline is nephrotoxic, and may cause AKI and nephrogenic diabetes
insipidus ( DI ) and hypernatremia.
• The dose of demeclocycline is 300 mg orally twice daily.
• N.b It’s important to recognize that AVP receptor antagonists are C.I in patients
with hypovolemia as their use would worsen the hypovolemia.
33. N.b 3 % NaCl infusion is
used in euvolemic and
hypervolemic hypotonic
hyponatremia ( along with
loop diuretics ).
3 % NaCl is not preferred
to be used in hypovolemic
hyponatremia, because it
will correct the
hyponatremia but will not
correct the hypovolemia.
