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Hypervolemic hyponatremia is seen in

  • Burns
  • Capillary leak due to sepsis
  • Diabetes Mellitus
  • Hyperaldosteronism
Correct Answer : Hyperaldosteronism
Ref: Harrisons 17th edition page 1445, 277
 
In Hypervolemic hyponatremia like CCF, Nephrotic syndrome and Cirrhosis there is decreased effective intravascular volume leading to activation of the Renin – Angiotensin system. This leads to hyperaldosteronism and further water retention. There is primary sodium gain due to hyperaldosteronism but this increase is exceeded by the amount of  secondary water gain – resulting in increased dilution of sodium in water  – hyponatremia
 
In Burns and Capillary leak due to sepsis – the patients are hypovolemic not hypervolemic
 
In Diabetes Mellitus –  Hyponatremia is due to increased plasma osmolality ( because of high glucose
level) – Pseudohyponatremia. For every 100mg/dl increase in glucose level the sodium level will decrease by 1.6mmol/L
 
 
Causes of Hyponatremia

I. Pseudohyponatremia

A. Normal plasma osmolality

1. Hyperlipidemia
2. Hyperproteinemia
3. Posttransurethral resection of prostate/bladder tumor

 

B. Increased plasma osmolality

1. Hyperglycemia
2. Mannitol

 

II. Hypoosmolal hyponatremia

A. Primary Na+ loss (secondary water gain)

1. Integumentary loss: sweating, burns
2. Gastrointestinal loss: vomiting, tube drainage, fistula, obstruction, diarrhea
3. Renal loss: diuretics, osmotic diuresis, hypoaldosteronism, salt-wasting nephropathy, postobstructive diuresis, nonoliguric acute tubular necrosis

 

B. Primary water gain (secondary Na+ loss)

1. Primary polydipsia
2. Decreased solute intake (e.g., beer potomania)
3. AVP release due to pain, nausea, drugs
4. Syndrome of inappropriate AVP secretion
5. Glucocorticoid deficiency
6. Hypothyroidism
7. Chronic renal insufficiency

 

C. Primary Na+ gain (exceeded by secondary water gain)

1. Heart failure
2. Hepatic cirrhosis
3. Nephrotic syndrome

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