Hyponatremia Definition and Causes
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Questions and Answers

What serum/plasma level defines hyponatremia?

  • 135 mmol/L (correct)
  • 120 mmol/L
  • 145 mmol/L
  • 130 mmol/L

Which condition is least likely to cause increased sodium loss in urine?

  • Decreased aldosterone production
  • Cirrhosis (correct)
  • Thiazide diuretics
  • Ketonuria

What serum potassium level correlates with sodium loss in response to renal tubular activity?

  • Medium potassium levels
  • Low potassium levels (correct)
  • High potassium levels
  • Normal potassium levels

Which of the following conditions typically results in urine sodium levels of less than 20 mmol per day?

<p>Severe burns (B)</p> Signup and view all the answers

What is a predominant effect of decreased colloid osmotic pressure (COP) in conditions like cirrhosis?

<p>Fluid retention leading to serum sodium dilution (C)</p> Signup and view all the answers

What is a common clinical significance of hyponatremia when serum sodium levels fall below 130 mmol/L?

<p>It indicates a severe electrolyte imbalance. (D)</p> Signup and view all the answers

Which of the following is the most likely cause of increased Na+ loss in the urine?

<p>Diuretic therapy (B)</p> Signup and view all the answers

In terms of sodium retention, what is the primary action of arginine vasopressin (AVP)?

<p>Increase renal sodium reabsorption (D)</p> Signup and view all the answers

What mechanism explains the relationship between low K+ levels and Na+ loss?

<p>Sodium and potassium compete for excretion (B)</p> Signup and view all the answers

Which symptom is least associated with acute hyponatremia due to water retention?

<p>Increased thirst (A)</p> Signup and view all the answers

Flashcards

What is hyponatremia?

A low serum/plasma sodium level, less than 135 mmol/L. It's a common electrolyte problem in hospitals.

When does Hyponatremia become clinically significant?

Levels below 130 mmol/L are considered clinically significant, meaning they may require medical attention.

How can Hyponatremia be assessed?

Hyponatremia can be assessed by determining the cause of low sodium or by looking at the osmolality levels.

What can cause increased sodium loss in urine?

Increased loss of sodium through urine can occur due to low aldosterone, certain diuretics, ketonuria (sodium lost with ketones), or kidney problems.

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How does low potassium affect sodium levels?

Low potassium (K+) levels can lead to sodium loss because of their inverse relationship in the renal tubules.

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What are some causes of sodium loss outside of the urinary system?

Prolonged vomiting, diarrhea, or severe burns can lead to sodium loss. The urine sodium levels are usually lower than 20 mmol per day in these cases.

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How can water retention cause low sodium levels?

Increase in water retention dilutes the serum/plasma sodium, a situation seen in acute or chronic kidney failure.

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How do conditions like nephrotic syndrome and cirrhosis contribute to hyponatremia?

Nephrotic syndrome and hepatic cirrhosis can decrease plasma proteins, causing fluid to move out of blood vessels causing edema. This triggers AVP production leading to further water retention and sodium dilution

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Explain how water imbalance can lead to hyponatremia.

Excessive water intake can lead to dilution of sodium and hyponatremia.

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What are the major causes of hyponatremia?

Hyponatremia can be caused by increased sodium loss, increased water retention, or a combination of both.

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Study Notes

Hyponatremia Definition and Significance

  • Hyponatremia is a condition where serum/plasma sodium levels are below 135 mmol/L.
  • It's a common electrolyte disorder in both hospitalized and non-hospitalized patients.
  • Levels below 130 mmol/L are considered clinically significant.

Causes of Hyponatremia

  • Increased Sodium Loss: This can occur due to:
    • Decreased aldosterone production
    • Certain diuretics (thiazides)
    • Ketonuria (sodium lost with ketones)
    • Salt-losing nephropathy (some renal tubular disorders)
    • Potassium deficiency (inverse relationship with sodium in renal tubules; low K+ leads to Na+ loss)
    • Prolonged vomiting or diarrhea
    • Severe burns
  • Increased Water Retention: This can result from:
    • Acute or chronic renal failure
    • Nephrotic syndrome (low plasma proteins -> decreased colloid osmotic pressure -> fluid shifts, edema)
    • Hepatic cirrhosis (low plasma proteins -> decreased colloid osmotic pressure -> fluid shifts, edema)

Diagnosing Hyponatremia

  • Urine Sodium Levels:
    • Increased urine sodium levels (≥ 20 mmol per day) often indicate causes related to increased sodium loss in the urine.
    • Low urine sodium levels (< 20 mmol per day) are more common with conditions like vomiting, diarrhea, and burns.

Fluid Retention and Hyponatremia

  • Fluid Retention and Dilution: Increased water retention leads to dilution of serum sodium.
  • Decreased Colloid Osmotic Pressure: Conditions like nephrotic syndrome and hepatic cirrhosis decrease plasma protein, lowering the colloid osmotic pressure (COP) and prompting fluid shifts into the tissues (edema).
  • Antidiuretic Hormone (AVP): The low plasma volume stimulates AVP (arginine vasopressin) release, promoting fluid retention and further diluting sodium.

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Description

This quiz covers the definition, significance, and various causes of hyponatremia. It explores how electrolyte imbalance occurs due to sodium loss or water retention, presenting common conditions and mechanisms involved. Test your knowledge on the important aspects of this critical health issue.

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