Sodium Disorders Flashcards by o e

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

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Which electrolytes are present extracellularly?

-Sodium (Na): 135 - 145 meq/L

-Chloride (Cl)

-Bicarbonate (HCO3-)

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Normal range of sodium (Na)

135 - 145 meq/L

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Hyponatremia VS Hypernatremia

Hyponatremia: Na < 135 mEq/L

Hypernatremia: Na > 145 mEq/L

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Most common electrolyte disorder

Hyponatremia
-low serum sodium

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Categorization of Hyponatremia

-Hypotonic Hyponatremia: low serum Osm
(< 275mOsm/kg)

-Hypertonic Hyponatremia: high serum Osm
(>290 mOsm/kg)

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Symptoms and Signs of Hyponatremia

-generally asymptomatic
-symptoms if Na < 120 mEq/L:
N/V, headache, confusion, fatigue, muscle weakness, seizure, coma

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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)

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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)

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Equation for corrected Na value
NOT on the EXAM
NAPLEX

Na(corrected) =
Na measured + [(BGmeasured - 100) / 100] *1.6

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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?

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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

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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

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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

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How to treat HYPOTONIC HYPOVOLEMIC Hyponatremia

Fluids

outpatient: electrolyte replacement solution: Gatorade, Powerade, Pedialyte

inpatient: IV Fluids containing sodium salt

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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

Sodium Disorders Flashcards

Dr. Covert EXAM III