P2.2-SODIUM Flashcards by Dave U.

Major cation of extracellular fluid
o 90% of all extracellular cation
o Most abundant

SODIUM (NATRIUM)

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Normal plasma osmolality of Na

approximately 295 mmol/L,
with 270 mmol/L being the result of Na+ and associated
anions

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Moves three Na+ ions out of the cell in exchange for
two K + ions moving into the cell
 Maintenance of high sodium and high intracellular
potassium concentrations is regulated by

Sodium-potassium pump

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REGULATION of Na osmolality

(1) The intake of water in response to thirst
(2) The excretion of water
(3) The blood volume status

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60% to 75% of filtered sodium is reabsorbed in the

proximal tubule

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decreased blood volume

Hypovolemia

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This stimulates the juxtaglomerular cells of the kidneys to secrete renin

Hypovolemia

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promotes vasoconstriction or a decrease or narrowing in the lumen of the blood vessels.

Angiotensin II

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promotes sodium reabsorption.

aldosterone

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is released by the heart, particularly the myocardial atria, which promotes renal sodium and water expression, and the same time vasodilation in response to hypervolemia

ANP

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Hyperosmolality and Hypernatremia: hypothalamus responds by stimulating ______ to promote water retention or water reabsorption, which corrects now hyperosmolality and hypernatremia.

ADH or AVP

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Most common electrolyte disorder in hospitalized and nonhospitalized.

HYPONATREMIA

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Decreased sodium levels may be caused by

increased sodium loss, increased water retention, or water imbalance

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Increased sodium loss is caused by

o Decreased aldosterone production
o Certain diuretics (thiazides)
o Ketonuria
o Salt-losing nephropathy
o K+ deficiency
o Prolonged vomiting and diarrhea
o Severe burns

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 Aldosterone promotes sodium reabsorption, then
it follows that plasma levels will also be decreased.

o Decreased aldosterone production

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 Promotes urination or increases urine output and
that causes sodium loss

o Certain diuretics (thiazides)

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 Sodium loss with ketones

o Ketonuria

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 Prevalent in some renal tubular disorders due to
decreased sodium reabsorption and increased
excretion of water

o Salt-losing nephropathy

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 Causes sodium loss
 When serum potassium levels are low, the renal tubules will conserve potassium and excrete sodium.

o K+ deficiency

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Increased water retention is caused by

o Acute or chronic renal failure
o Nephrotic syndrome
o Hepatic cirrhosis
o Congestive heart failure

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 Causes dilution of serum or plasma sodium levels, since kidneys cannot properly excrete water, causing dilution

o Acute or chronic renal failure

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 Decreased plasma protein, leading to decreased COP (Colloid Osmotic Pressure) which holds water within the vascular space.
 Low plasma volume causes AVP or ADH to be produced causing fluid retention and dilution of sodium causing hyponatremia.

o Nephrotic syndrome and
o Hepatic cirrhosis

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 Heart does not pump blood as efficiently as it should
 Low blood volume causes the antidiuretic hormone to be produced causing fluid retention and dilution of sodium causing hyponatremia

o Congestive heart failure

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Water imbalance caused by

Excess water intake
SIADH
Pseudohyponatremia

Excess water intake

Polydipsia

There is water retention or imbalance due to increased activity or AVP or ADH

SIADH

 Otherwise known as artifactual low sodium concentration  Occurs when serum concentration is measured with indirect ion selective electrode method, such as in patients with increased lipid levels or protein levels or in cases of hyperlipidemia or hyperproteinemia.  The indirect ISE dilutes the sample prior to analysis and causes falsely decreased sodium levels.

Pseudohyponatremia

Classification by plasma/serum osmolality

Hyponatremia with a normal osmolality Hyponatremia with a normal osmolality Hyponatremia with a low osmolality

Increase in non-sodium cations like calcium, potassium, and magnesium Such as hypermagnesemia, hypercalcemia, hyperkalemia

Hyponatremia with a normal osmolality

elevated magnesium levels in blood

Hypermagnesemia

elevated calcium levels in blood

Hypercalcemia

elevated potassium levels in blood

Hyperkalemia

Caused by Hyperglycemia  In cases of Diabetes mellitus – the elevated levels of glucose increase the serum osmolality, causing shift of water from the cells to the blood, resulting in sodium dilution levels  Associated in the excess levels of glucose in the plasma or serum

Hyponatremia with a high osmolality

 Due to sodium loss or water retention  Sodium retention = sodium osmolality decreased  Most cases are associated with this

Hyponatremia with a low osmolality

Symptoms of Hyponatremia at < 125 mmol/L

neuropsychiatric symptoms, nausea and vomiting, muscular weakness, headache, lethargy, and ataxia

More severe symptoms of hyponatremia at < 125 mmol/L

seizures, coma, and respiratory depression

Hyponatremia at < 120 mmol/L

medical emergency

Treatment of hyponatremia

fluid restriction, hypertonic saline and/or other pharmacologic agents  Correction on the sodium loss

 Plasma or serum sodium concentration is higher than upper limit of normal  Less commonly seen in hospitalized patients than in hyponatremia.

HYPERNATREMIA

HYPERNATREMIA possible causes

 Excess loss of water  Decreased water intake  Increased sodium intake or retention

 Excess loss of water examples

o Profuse sweating or diarrhea o Severe burns o Diabetes insipidus o Renal tubular disease

associated with transdermal fluid losses

o Severe burns

 Problem lies on ADH – deficiency on such causes increase in urine output/urine excretion.

o Diabetes insipidus

 Excess loss of water due to abnormal/decreased capacity of the tubules

o Renal tubular disease

Symptoms of Hypernatremia

o Altered mental status, lethargy, irritability, restlessness, seizures, muscle twitching, hyperreflexes, fever, nausea or vomiting, difficult respiration, and increased thirst

: hyperactivity or repeating reflexes

Hyperreflexes

reference range of hypernatremia that causes 60-75% mortality rate

> 160 mmol/L

Treatment of hypernatremia

correction of the underlying condition that caused the water depletion or Na+ retention

SPECIMEN for Sodium determination

 Serum, plasma, and urine

Plasma anticoagulants used for sodium determination

lithium heparin, ammonium heparin, and lithium oxalate

Urine sodium analysis type of urine specimen used

- 24-hour collection

METHODS used for sodium determination

ISEs Colorimetry

most routinely used method for sodium determination

ISEs

2 types of ISE measurement based on sample preparation

direct and indirect

undiluted sample interacts with the ISE membrane (glass aluminum silicate)

Direct method

a diluted sample is used for measuremen

Indirect method

Colorimetric method of sodium determination

Albanese Lein

Reference Ranges for sodium

Serum, Plasma: 136-145 mmol/L Urine: 40-220 mmol/D Cerebrospinal fluid: 136-150 mmol/L