Disorders of Salt and Water Balance Flashcards
Hyponatriemia
- Low plasma sodium concentration
- Induces fluid movement into cells
Hypernatriemia
- High plasma sodium concentration
- Induces fluid movement out of cells
Hypovolemia
ECF volume contraction
Hypervolemia
ECF volume expansion
Hyponatriemia
-In virtually all patients, hyponatriemia results from?
the intake (oral or intravenous) and subsequent retention of water
What happens in a normal individual when they have water load?
The water will be rapidly excreted as the dilutional fall in serum osmolality suppresses the release of ADH thereby allowing excretion of the excess water in a dilute urine
What happens in patients who develop hyponetriemia?
They typically have an impairment in renal water excretion, most often due to an inability to suppress ADH secretion
Hyponatriemia
-Exception?
Patients with primary polydipsia
-drink such large quantities of fluid that they overwhelm the excretory capacity of the kidney even though ADH release is appropriately suppressed
Causes of hyponatriemia
-Pseudohyponatriemia?
- Hyperproteinemia
- Hyperproteinemia
- Hyperlipidemia
- Hypercholesterolemia
- Unmeasured osmol
Causes of hyponatriemia
- Hyperproteinemia, hyperproteinemia, hyperlipidemia
- Lead to?
Errors in lab measurement of Na
Causes of hyponatriemia
-Hyperglycemia and unmeasured osmol?
-Water is pulled via osmotic gradient into vasculature with resulting dilutional hyponatriemia
True hyponatriemia
-Dilute urine and low ADH?
- Reset osmostat (e.g. pregnancy)
- Psychogenic polydipsia
True hyponatriemia
-Concentrated urine, high ADH?
- Decreased ECV (e.g. CHF, cirrhosis)
- SIADH (syndrome of inappropriate ADH)
- Cortisol deficiency
- Hypothyroidism
Hyponatriemia
- Usually indicates hypotonicity of ECF
- Cell swelling due to water movement into cells
- Can cause neurological problems with rapid onset
- Not due to loss of sodium but excess volume relative to amount of sodium in ECF
True hyponatriemia
-Plasma Na concentration and osmolality?
Both are below normal
Diabetes insipidus
- Patient has excess dilute urine-Give them ADH
- If there is no change?
- If the problem is corrected?
If there is no change-nephrogenic DI
If the problem is corrected-Central or neurogenic DI
Hypernatriemia
- Always associated with hypertonicity
- Usually due to unreplaced water loss, not Na gain (unless hypertonic saline is administered)
Hypernatriemia
- Extrarenal water loss
- Symptoms?
- Excessive sweating, fever, diarrhea, vomiting
- Low urine output, high circulating ADH
Hypernatriemia
-Renal water loss
- ADH mechanism for retaining water isn’t working
- Central or nephrogenic DI
ADH MOA?
Increases permeability (reabsorption) of late DT, CD via V2 receptors and insertion of aquaporin channels
Signs of hypovolemia?
- Orthostatic hypotension
- Orthostatic tachycardia
- Loss of skin turgor
- Dry mucous membranes
