Sodium Disorders Flashcards
Dr. Covert EXAM III
Which electrolytes are present intracellularly?
-Potassium (K): 3.5 - 5 meq/L
-Magnesium (Mg): 1.5 - 2 meq/L
-Phosphorus (P): 2.5 - 4.5 mg/dl
Which electrolytes are present extracellularly?
-Sodium (Na): 135 - 145 meq/L
-Chloride (Cl)
-Bicarbonate (HCO3-)
Normal range of sodium (Na)
135 - 145 meq/L
Hyponatremia VS Hypernatremia
Hyponatremia: Na < 135 mEq/L
Hypernatremia: Na > 145 mEq/L
Most common electrolyte disorder
Hyponatremia
-low serum sodium
Categorization of Hyponatremia
-Hypotonic Hyponatremia: low serum Osm
(< 275mOsm/kg)
-Hypertonic Hyponatremia: high serum Osm
(>290 mOsm/kg)
Symptoms and Signs of Hyponatremia
-generally asymptomatic
-symptoms if Na < 120 mEq/L:
N/V, headache, confusion, fatigue, muscle weakness, seizure, coma
Factors that determine the treatment of Hyponatremia
-Cause of hyponatremia
-Presence or absence of symptoms
-chronicity of hyponatremia (how long has the patient been hyponatremic)
Meaning and most common cause of HYPERTONIC Hyponatremia
-Meaning: excess of solutes
-most common cause: Hyperglycemia, patient admitted with diabetic ketoacidosis (DKA)
-Calculation of corrected Na (it might actually not be hyponatremic after accounting for the glucose)
Equation for corrected Na value
NOT on the EXAM
NAPLEX
Na(corrected) =
Na measured + [(BGmeasured - 100) / 100] *1.6
Treatment of Hypertonic Hyponatremia
-treat the underlying disease state: often diabetes -> treat the blood sugar
-don’t give sodium or fluids due to low Na levels
What would happen?
Types of HYPOTONIC Hyponatremia
-Hypovolemic: low volume of water + greater deficit in sodium
-Euvolemic: slight excess in body water, normal body sodium,
-Hypervolemic: significant excess of body water, slight excess in body sodium
Causes of HYPOTONIC HYPOVOLEMIC Hyponatremia
(great sodium deficit, low body volume)
Renal or Extra-renal
S/sx: dehydration, dry mouth, low UOP
-> Use urine Na U(Na) to differentiate between renal and extra-renal
How to differentiate between Renal or Extra-renal causes of HYPOTONIC HYPOVOLEMIC Hyponatremia
-Use urine Na U(Na) to differentiate between renal and extra-renal
How to treat HYPOTONIC HYPOVOLEMIC Hyponatremia
Fluids
outpatient: electrolyte replacement solution: Gatorade, Powerade, Pedialyte
inpatient: IV Fluids containing sodium salt
What are the urine sodium levels in a HYPOTONIC HYPOVOLEMIC Hyponatremic patient -> with a renal cause?
Renal cause: high U(Na): > 20 mEq/L
-the kidney is not able to keep the sodium
-> due to drugs: diuretics
-> due to disease: renal tubular acidosis, osmotic diuresis, cerebral salt wasting
-electrolyte replacement solution + HOLD diuretics
What are the urine sodium levels in a HYPOTONIC HYPOVOLEMIC Hyponatremic patient -> with Extra renal cause?
Extra-renal: low U(Na): <20 mEq/L
low volume, low sodium
but here the kidney is able to retain the sodium -> U(Na) is low -> so the problem would be somewhere else -> probably GI related
-N/V, third spacing (fluid collection in a third space - abdomen f.e.), burns (drainage from burned tissue)
Calculate Na deficit
- Subtract current sodium from desired sodium
- multiply by 0.6 * wt (kg) = … mEq needed to replace
Causes of Hypotonic Euvolemic Hyponatremia
-no sodium deficit, slight excess in body water (dilutional effect)
-Causes:
SIADH (most common)
small cell lung cancer, pancreatic cancer
head trauma
Meds: Carbamezapin (CBZ), SSRis
Glucocorticoid deficiency (when you get off steroids abruptly?)
Beer protomania
SIADH Pathophysiology
the patient produces too much ADH -> causing water to be transported into the blood via aquaporins
-Euvolemic Hyponatremia
Treatment of Hypotonic Euvolemic Hyponatremia
-DC offending agent
-water restriction (restrict from water intake)
-diureses +/- hypertonic saline
-Vasopressin antagonists (aquaretics)
-Demeclocycline
Vasopressin Antagonists
-Conivaptan (Vaprisol)
-Tolvaptan (Samsca) - oral, avoid in liver impairment
-Demeclocycline works the same way
-selective water diuresis (aquaresis): no change in sodium or potassium excretion
-short-term fix
-not seen often, costly
MOA of Vasopressin Antagonists
Blockage of V2 receptors on the convolute tube -> water diuresis (elimination of free water)
Hypotonic Hypervolemic Hyponatremia
-low serum Osm, excess in body water + slight excess of body sodium
Causes of Hypotonic Hypervolemic Hyponatremia
-HFrEF
-Cirrhosis
-CDK
Treatment of Hypotonic Hypervolemic Hyponatremia
-fluid restriction
-diuresis
-treatment of underlying conditions (CKD, cirrhosis, HFrEF)
-treatment based on diuresis, not sodium replacement (unless symptomatic)
When to treat patients with saline in Hypotonic Hypervolemic Hyponatremia?
-Hypertonic saline (3% (common), 7%, 23.4%)
-when symptomatic: seizure, coma, evidence of cerebral edema) Na: <120 mEq/L
How to approach sodium correction
-treat with saline treatment, but not aggressively
-maximum sodium correction in asymptomatic patients is 6-8 mEq/L per 24h, complete correction in 48-69h
-rapid correction (>12 mEq/L in 24h) can cause central pontine myelinolysis/ osmotic demyelination syndrome
-paralysis, dysphagia, loss of consciousness
-irreversible brain damage
Central pontine myelinolysis/ osmotic demyelination syndrome
rapid rise of serum sodium can cause a quick efflux of water out of the brain
-> dehydration of the myelin sheath (myelin layer)
-correction should not be more than 6-8 mEq/L in 24h
Causes of Hypernatremia
-often due water loss - less commonly due to sodium gain
-Causes:
diabetes insipidus (central or nephrogenic)
insensible losses
GI losses (diarrhea)
Iatrogenic (Na-rich IV fluids)
Symptoms and signs of Hypernatremia
-generally asymptomatic
-confusion, coma
Hypovolemic, Euvolemic, Hypervolemic Hypernatremia
Hypovolemic: Water losses
Euvolemic: Diabetes insipidus
Hypervolemic: Exogenous sodium
Which lab values are expected in Hypovolemic Hypernatermia?
low volume, high osmolality, concentrated urine: >6: UOsm: >600 mOsm/kg (highly concentrated)
U(Na): < 20 mEq/L
-water replacement (PO or IV (with D5W))
Treatment of Euvolemic Hypernatremia
-Treat the disease
-Cause: Diabetes Insipidus
if central: pituitary injury or disease
if nephrogenic: drugs (lithium), genetic disorders
Labs: UOsm: <300 mOsm/kg
Pathophysiology of Diabetes Insipidus
Normally: The pituitary gland produces ADH -> Aquaporins in the convoluted tube
-> increase in plasma volume and concentrated urine
-diabetes insipidus: loss of the ability to concentrate the urine
urine volume goes up (diluted urine), plasma volume goes down
Treatment of Diabetes Insipidus
-Central: related to the pituitary gland (could be a timer) -> ADH (Vasopressin) deficiency -> treat with Desmopressin (DDAVP)
-Nephrogenic: renal ADH deficiency;
treat with NSAID/diuretic combo
Treatment of Hypervolemic Hypernatremia
-high volume, high sodium
-due to aggressive administration of Na IV fluids
-DC fluids or medications causing it
How to correct sodium levels in Hypervolemic Hypernatremia
-similar to Hypotonic Hypovolemic Hyponatremia
-do not lower sodium by more than 6-8 mEq/L over 24 h
-it may cause rapid efflux into the brain, resulting in cerebral edema
