Hyponatremia Flashcards
What % of body weight is salt water?
60%
What is the equation for blood [Na+]?
Blood [Na+] = total body sodium/total body water
Describe the physiological regulations of Na+ conc after a large intake of water
Large water intake Lower [Na+] Less ADH release from post pituitary Less thirst Less H2O reabsorption in renal collecting ducts Normalization of [Na+]
Where is ADH synthesized?
Hypothalamus
Where is ADH stored?
Posterior pituitary
What physiological value tends to most sensitively regulate ADH levels?
Serum osmolality
Small changes in osmolality will lead to ADH release/inhibition
Define hyponatremia
Excess of total body water relative to total body sodium
Almost always indicates impaired renal water excretion
Intrarenal factors that cause Hyponatremia
- Filtration at glomeruli
- Delivery of solute to distal nephron sites
- Reabsorption of solute at distal nephron sites
List some causes of hypovolemic hyponatremia
Renal Na+ losses
Diuretics
Primary adrenal insufficiency (Addison’s Disease)
Salt wasting nephropathies
Extrarenal Na+ losses
Diarrhea
Vomiting
Excess sweating
List some symptoms of hypovolemic hyponatremia
Flat neck veins
Decreased skin turgor
Orthostatic hypotension
List some causes of euvolemic hyponatremia
SIADH
Hypothyroidism
Psychogenic polydipsia
List some causes of hypervolemic hyponatremia
CHF
Liver cirrhosis
Renal failure
List some symptoms of hypervolemic hyponatremia
Edema
What does a normal Urine conc of Na+ indicate? (>20 mEq/L)
Renal loss of Na+ or excess ADH
What does a low Urine conc of Na+ indicate? (
Extrarenal loss of Na+ or an edematous disorder
Treatment for Hypervolemic hyponatremia
Fluid restriction and diuretics
Treatment for Hypovolemic hyponatremia
Physiologic saline
Treatment for Euvolemic hyponatremia
Asymptomatic -> water restriction
Symptomatic -> medical emergency; use hypertonic saline with or without diuretics
Define Hypernatremia
Increased [Na+] relative to total body water
List some symptoms of hypovolemic hypernatremia
Renal Na+ losses
Duretics with inadequate water intake
Post obstructive diuresis
Tubular injury
Extrarenal Na+ losses
Sweating
Diarrhea
Vomiting with inadequate water intake
List some symptoms of euvolemic hypernatremia
Central diabetes insipidus
Nephrogenic diabetes insipidus
Decreased thirst and water intake
List some symptoms of hypervolemic hypernatremia
Hypertonic fluid administration
Mineralocorticoid excess states
Salt poisoning (sea water ingestion)
Treatment for Euvolemic hypernatremia
Water administration
May also give ADH in central diabetes insipidus
Treatment for Hypovolemic hypernatremia
Hypotonic fluids
Treatment for Hypervolemic hypernatremia
May require both water administration plus diuretics or dialysis to remove excess Na+
