Exam #2: Sodium Disorders Flashcards
What does “TIE 60, 40, 20” refer to?
- TBW = 60% of total body weight
- ICF = 40% of total body weight
- ECF = 20% of total body weight
What is the primary ECF ion, and is it a cation or anion?
Na+ (cation)
If fluid is moved from ECF → ICF, what happens to cells?
Cells SWELL
If fluid is moved from ICF → ECF, what happens to cells?
Cells SHRINK
If there is an abnormal serum [Na+], what does this indicate?
Water regulation disorder
- Serum [Na+] refers to amount of water relative to Na+ in ECF
What is the major determinant of ECF volume?
Total amount of Na+ in ECF
If Na+ is LOW, what does this mean for ECF volume, and what is another name for this?
How does this present clinically?
Low Na+ → low ECFV = hypovolemia
- Presents as poor skin turgor, dry mucous membranes (dehydration)
If Na+ is HIGH, what does this mean for ECF volume, and what is another name for this?
How does this present clinically?
High Na+ → high ECFV = hypervolemia
- Presents as edema/fluid retention
What general condition is associated with etiologies of GI loss, renal loss, skin loss, sequestration without loss?
Hypovolemia
What general condition is associated with etiologies of liver disease, HF, acute/chronic renal failure, nephrotic syndrome, primary hyperaldosteronism, Cushing’s, pregnancy?
Hypervolemia
What are the three major causes of Hypervolemia?
- Liver disease
- HF
- Renal failure (acute/chronic)
What general condition is associated with increased thirst, decreased sweating; poor skin turgor, dry mucous membranes; oliguria, CNS depression; weakness and muscle cramps; low BP with postural dizziness; high pulse?
Hypovolemia
What general condition is associated with edema, SOB, orthopnea, PND, JVD, hepatojugular reflux, crackles?
Hypervolemia
What two factors influence water retention?
- Thirst
- ADH
What is the primary factor that influences salt retention, and what are the two main results?
RAAS
- Na+ retention
- K+ excretion
- Also ANP and general renal function (GFR, RBF)
What is the most common electrolyte abnormality in hospitalized patients?
Hyponatremia
What constitutes Hyponatremia? With what two populations is it more common in?
Serum [Na+] below 125 (or symptomatic)
- More common in very young or very old
What condition involves falsely low serum [Na+] BUT normal osmolality (isoosmolar)?
Pseudohyponatremia
What two causes are often associated with Pseudohyponatremia?
- Hyperlipidemia
- Hyperproteinemia
What condition involves hyperosmolar state due to increased solute in ECF causing shift of water from ICF to ECF → lower serum [Na+]?
Redistributive/Hyperosmolar hyponatremia
What is often the cause of Redistributive/Hyperosmolar hyponatremia, and why?
Hyperglycemia
- High glucose in ECF causes shift of water from ICF → ECF = lowers serum Na
What are the three primary causes of Hypervolemic Hyponatremia?
How do you treat it?
- Liver failure
- HF
- Renal failure
Treat underlying cause (diuretics, dialysis, fluid restrictions)
What are the five possible causes of Hyponatremia?
- Pseudohyponatremia
- Redistributive/Hyperosmolar hyponatremia
- Hypovolemic Hyponatremia
- Euvolemic Hyponatremia
- Hypervolemic Hyponatremia
What condition is considered a laboratory artifact?
Pseudohyponatremia
With Hypovolemic Hyponatremia, if urine Na+ >20, what is the primary cause?
Diuretics (Thiazides)
- Also cerebral salt wasting or RTA
With Hypovolemic Hyponatremia, if urine Na+ <20, what is the primary cause?
Gastroenteritis (V/D)
- Also, third space losses (burns, pancreatitis)
What is the primary treatment for Hypovolemic Hyponatremia?
Replace fluids lost
What are the four primary causes of Euvolemic Hyponatremia?
- SIADH
- Hypothyroidism
- Adrenal insufficiency
- Psychogenic polydipsia
What is the primary treatment for Euvolemic Hyponatremia?
Fluid restriction
What general condition involves HA, dizziness, N/V, lethargy, weakness, confusion, hypoventilation, seizures, coma, death?
HYPOnatremia
Severity of symptoms of Hyponatremia depends on level of…
Cerebral edema
- If ECF → ICF = brain cells swell
What should always be considered in the diagnosis of Hyponatremia?
FLUID STATUS (hyper vs. eu vs. hypo)
What condition involves concentrated urine with low serum osmolality and euvolemia?
SIADH
- Possible cause of Euvolemic Hyponatremia
What condition is diagnosed as high urine osmolality and low serum osmolality?
SIADH
- Possible cause of Euvolemic Hyponatremia
What condition involves too much ADH but has normal cortisol and thyroid levels?
SIADH
- Possible cause of Euvolemic Hyponatremia
What is a possible cause of SIADH?
Pulmonary disease (SCLC)
What is the recommended treatment for Hyponatremia (if serum [Na+] <125 OR symptomatic)?
Hospitalize
What is a possible complication of Hyponatremia if Na+ is not corrected slowly (especially chronic)?
Cerebral Pontine Myelinolysis (CPM)
- Focal demyelination in pons and extra-pontine areas that is NOT reversible
What is the recommended rate of correction for Hyponatremia?
Less than 8 mEq/L in first 24 hours
- Should be about 4-6 mEq/L in first 24 hours
What constitutes Hypernatremia?
Serum [Na+] above 145
What is the general etiology of Hypernatremia? What are two other possible causes?
Excessive water loss from body
- Also too little dietary water or too much dietary salt
Is Cerebral Pontine Myelinolysis (CPM) reversible? How and when would this present?
NOT reversible
- Dysarthria, dysphagia, seizures, AMS
- Begins 1-3 DAYS after over-correction
What general condition is often asymptomatic… Thirst/signs of volume depletion; AMS, weakness; NM irritability; focal neuro deficits; seizures, coma?
HYPERnatremia
What are three possible causes of Hypernatremia?
- Osmotic diuresis = hyperglycemia, Mannitol
- Diuretics (Loops)
What is the body’s normal response to Hypernatremia (2 steps)?
- Create thirst to increase fluid intake
2. Concentrate urine to prevent further water loss
What condition involves urinary water loss but high serum [Na+] = urine dilute but should be concentrated, and what type of natremia is it associated with?
Diabetes Insipidus (DI) - Associated with HYPERnatremia
What are the two types of Diabetes Insipidus (DI), and what is the cause of each?
- Neurogenic/Central DI: due to impaired ADH secretion
- Nephrogenic DI: lack of kidney response to ADH (sufficient ADH present though)
How do you treat Neurogenic/Central DI?
Desmopressin
How do you treat Nephrogenic DI (2)?
Thiazides, Amiloride
- CANNOT be treated with Desmopressin
What is the general treatment of Hypernatremia (2)?
- STOP water loss
- REPLACE water loss (but not too rapidly - should take days)
