conditions of Na+ imbalance Flashcards
- Daily sodium intake _____ (Adequate Intake)
* Sodium is a primary driver of ______
1000-1500 mg
– About ½ a teaspoon of table salt
osmolality in the extracellular fluid compartment
how is Na+ actively transported out of cells
– Via the Na+-K+-ATPase pump
*Also involved in cell depolarization (nerves, muscles)
Kidneys are responsible for sodium _______
excretion
– Responsive to changes in serum sodium concentrations to maintain osmolality
– Will conserve sodium if required
• Sodium is a primary driver of osmolality in the extracellular fluid compartment
how do you calculate serum osmolality
– Serum Osmolality = (2 x [Na+]) + [Glucose] + [Blood Urea Nitrogen]
– Normal is 280-300 mOsm/kg
define hyponatremia
• extra note: Normal serum sodium concentration
– 135-145 mmol/L (mEq/L)
Low sodium concentration (<135 mmol/L)
most common electrolyte abnormality encountered
clinically
define hypernatremia
High sodium concentration (>145 mmol/L)
- always associated with hypertonicity and can cause
significant reduction in intracellular fluid volume
symptons of mild/chronic hyponatremia
[Na+] 125-134 mmol/L – Asymptomatic – Impaired attention – Gait changes – Postural Changes – Fall risk increased
Symptom severity may also depend on rate of change in [Na+] 9
symptoms of moderate/severe hyponatremia
[Na+] <124 mmol/L – Nausea – Vomiting – Headache – Lethargy – Altered mental status – Seizures – Respiratory arrest – Risk of death increased
3 types of hyponatremia
MEASURE SERUM OSMOLALITY Low (<280 mOsm) - Hypotonic hyponatremia (most common) Normal (~280 mOsm) -Isotonic hyponatremia]
hypertonic (elevated)
what is isotonic hpyonatremia caused by?
SEE PICTURE ON SLIDE 10 OF NOTES
AKA PSUEDONATREMIA Artificially decreased c/o • Elevated lipid level • Elevated protein level Reduces the proportion of water in the serum.\
Caused by other components in srum that could be elevated (lipid, proteins), water content in serium decreased, looks like there is low sodium level
what is hypertonic hyponatremia caused by?
Hyperglycemia
- Caused by presence of elevated amounts of other
effective osmoles
• Elevated glucose level
3 types of hypotonic hyponatremia
hypovolemic
euvolemic/isovolemic
hypervolemic
describe hypovolemic hypotonic hyponatremia
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- Hypovolemic: loss of fluids that are hypotonic relative to serum
○ More water be lost than sodium
○ Serum levels go down because water loss more than sodium, body senses that sodium levels are high/concentration
○ Stimulate release of vasopressin frrom CNS
○ Vasopressin increases thirst and increases water reabsorption and sodium exretion
○ Hyponatremia nw develops as the sodium is being lost more than water
○ Pt may have orthosstatsis, change in bp whten they sit or stand rapid heartbeat, dry muc membranes
○ Do urine sample test, conc of urine
○ Also at whether kidnets are retaing sodium
○ If sodium lvls in urine are low, the case of Na loss is exrtrarenal, could be from GI source ro lungs
○ If urinary sodium is high, loss of sodium is likely renal
describe hypervolemic hypotonic hyponatremia
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- Hypervolemic: low sodium level, low serum osmolality
a. Fluid that should be retained within vascular space si moving out into interstitial space, fluid is collecting elsewhere (edema)
b. Elevated urine concentration as body is trying to retain fluid as it thinks blood volume is low
c. Sodium level is still low
d. Body not perfusing kidneys well
due to heart failure, cirrhosis, nephrosis
describe euvolemic/isovolemic hypotonic hyponatremia
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a. Urine is normal, maybe low
b. Decrease in sodium conc is cuased by polydipsia, pt thristy all the time - elevated water volume relateive to sodium conc
c. IF URINE OSMOLALITY IS CONCENTRATED AND NA excretion IS > 20 mEQ need to look at other medical causes
* *** IF someone has elevated urince conc and elevated Na excretion, there are 2 possible conditions *hypovlemic, euvolemic/isovolemic)
- Extremely elevated, caused by diuretics
- Not extrenely elevated, look for drugs
what is hypovolemic caused by?
- extrarenal losses, GI, skin, lung if Na excretion is low
- renal losses, diuretics, adrenal insuff if Na excretion is high
what is euvolemic caused by?
- primary poldipsia if UNa <20 mEq/L
- hypothyroidism, hypocortisolism, kidney failure, SIADH if UNa > 20 mEq/L
what is hypervolemic hypotonic hyponatremia caused by?
heart failure failure
cirrhosis
nephrosis
Syndrome of Inappropriate Secretion of Antidiuretic
Hormone (SIADH)
Disease Induced causes (3)
– Tumors (lung, pancreas)
– CNS disorders (head trauma, stroke,
meningitis, pituitary surgery)
– Pulmonary disease (TB, pneumonia)
Syndrome of Inappropriate Secretion of Antidiuretic
Hormone (SIADH)
Drug Induced causes
– Tricyclic antidepressants – Phenothiazines – Opioids – Nicotine – Carboplatin – Cisplatin – Bromocriptine – NSAIDs – Acetaminophen
Syndrome of Inappropriate Secretion of Antidiuretic
Hormone (SIADH)
SIADH - body makes too much ADH and body retains too much water
Might be missed clinically
Cause of low sodium
Level of release is not as high as if somebody dehydrated
Urine conc is not as high as dehydration
pt assessment
symptoms
- asymptomiatic
- neurologic, severity depends on magnitude, rate of onset
- other symptoms depend on cause (dry mucus membranes, hypotension with hypovol)
pt assessment
lab tests to look at
– Serum sodium concentration
– Plasma osmolality
– Urine analysis for osmolality and sodium concentration
– Glucose, lipid, renal function, thyroid function
treating hyponatremia
goals (2)
what is ODS
Acute changes in serum osmolality can result in rapid and excessive
water movement out of cells
– Rapid decline in brain cell volume can cause osmotic demyelination syndrome (ODS)
• Hyperreflexia, para- or quadriparesis, parkinsonism, or death
Goals:
– Treat the underlying cause of hyponatremia
– Slowly correct the sodium and water imbalance
Acute or Severely Symptomatic Hypotonic
Hyponatremia
- how to treat?
• Intravenous solution until severe symptoms resolve
– 3% NaCl (hypertonic saline)
– 0.9% NaCl (normal saline)
• Symptoms will usually resolve with a small increase in [Na+]
– e.g., 5% increase, or reaching 120 mmol/L
• To minimize risk of osmotic demyelination syndrome, the [Na+] should be corrected at a rate that does not exceed 6 to 12 mmol/L during the first 24 hours
Hypovolemic Hyponatremia
- how to treat?
- treat vomiting, diarrhea, asses need of direutics
- reduce elevated vasopressin release by restoring intravascular volume
- use solutions that remain in the extracellular / intravascular fluid compartment
- Serum [Na+] will increase because the replacement solution stays in the ECF / intravascular fluid compartment not from the Na+ content of the solution
– Oral replacement: water, WHO-ORS (oral rehydration salts), water+salt, sports drinks
– Sodium chloride infusion (e.g., 0.9% NaCl solution)
Hypervolemic Hyponatremia
- how to treat?
Treat the underlying cause of fluid retention
– Heart failure, nephrosis, cirrhosis
Fluid restriction (1000-1200 mL/day)
– Creates a negative water balance
Sodium restriction (1000-2000 mg/day)
Vasopressin receptor antagonists (tolvaptan, conivaptan*)
– V2 receptor: located on the distal nephron; blockade of vasopressinnbinding decreases water reabsorption from the collecting duct
⟹ large volume of water excretion, ↓urine osmolality, ↑serum [Na+]
Euvolemic Hyponatremia
- how to treat?
• Correct the underlying cause if possible
– e.g., stop the drug that causes SIADH
• Fluid restriction (1000-1200 mL/day)
– Create a negative water balance
• Chronic SIADH may also require increased solute (NaCl tablet) intake +/- loop diuretic
• Vasopressin receptor antagonists
