30 Questions
What is the total body water content in liters for a 70 kg person?
42 L
What percentage of the total body water is intracellular fluid (ICF) in a 70 kg person?
66.7%
What is the volume of interstitial fluid in liters for a 70 kg person?
10.5 L
What is the daily recommended water intake in liters?
1.5-2 L
How do aging and breathing affect the appearance of oral mucous membranes?
They may appear dry in patients breathing through their mouths.
What are the clinical manifestations of intracellular fluid loss?
Lethargy, confusion & coma
What is a rare autosomal dominant disorder causing recurrent attacks of muscle weakness or paralysis?
Hypokalemic periodic paralysis
What is a common cause of hypokalemia?
Refeeding
What should be avoided when giving intravenous potassium for hypokalemia?
Faster than 20 mmol/hour
Which symptom is associated with hyperkalemia?
Cardiac arrhythmia
What is used to treat severe hyperkalemia by stimulating cellular uptake of potassium?
Insulin
What is a cause of pseudohyperkalemia?
Potassium movement out of cells during or after drawing blood
What plays a crucial role in regulating water reabsorption in the kidneys?
Antidiuretic hormone (ADH)
What is the principal extracellular cation?
Sodium
What indirectly indicates the presence of osmotically active substances other than sodium, urea, or glucose?
Osmolal gap
What is affected by sodium concentration, which in turn is influenced by blood volume?
Osmolality
What physical property is crucial for hypothalamic responses and is affected by sodium concentration?
Osmolality
What regulates thirst and the secretion of antidiuretic hormone (ADH)?
Hypothalamic osmoreceptor center
What percentage of filtered sodium is normally reabsorbed in the proximal tubule?
60-75%
Which hormone stimulates sodium reabsorption in the distal parts of the distal convoluted tubules and collecting ducts?
Aldosterone
What is the most common cause of hyponatremia due to water retention?
SIAD (syndrome of inappropriate antidiuretic hormone secretion)
What are the symptoms of hyponatremia?
Nausea, malaise, and headache
What does ECF volume depend on?
Total body sodium content
What is the treatment for hyponatremia dependent on?
Severity of symptoms
Which of the following is a clinical feature of hypernatraemia?
Altered mental status and seizures
What is the recommended maximal rate for correcting hypernatraemia to avoid cerebral edema and death?
$0.5 mmol/L$ per hour
What is the serum sodium level associated with a mortality rate of 60-75% in hypernatraemia?
160 mmol/L
What is the role of potassium (K) in determining the resting membrane potential of cells?
It stabilizes the resting membrane potential
What can hyperkalaemia cause that warrants serum potassium checks after cardiac arrest?
Muscle weakness, cardiac arrest, and ECG changes
What is the reciprocal relationship between potassium and hydrogen ions in acidosis and alkalosis?
Increased potassium in alkalosis and decreased potassium in acidosis
Study Notes
Hypernatraemia and Hyperkalaemia: Key Points
- Hypernatraemia is defined as a serum sodium level above the reference interval of 133–146 mmol/L, developing due to water loss or sodium gain.
- Causes of hypernatraemia include excess water loss, decreased water intake, and increased sodium intake or retention (salt poisoning).
- Clinical features of hypernatraemia include altered mental status, seizures, fever, nausea, vomiting, lethargy, restlessness, and muscle twitching.
- Hypernatraemia with a serum sodium level of more than 160 mmol/L is associated with a mortality rate of 60-75%.
- Urine osmolality of 700 mOsm/kg, loss of thirst, insensible loss of water, GI loss of hypotonic fluid, and excess intake of sodium are related to hypernatraemia.
- Treatment of hypernatraemia involves correcting pure water loss with oral or IV water, administering sodium for dehydration, and using diuretics and natriuresis for salt poisoning and sodium overload.
- The maximal rate for correcting hypernatraemia should be 0.5 mmol/L per hour to avoid cerebral edema and death.
- Sodium can be measured in serum, plasma, urine, and sweat, and hemolysis does not significantly affect serum or plasma values of sodium.
- Potassium (K) disorders are important due to K's role in determining the resting membrane potential of cells, and changes in plasma K levels can cause fatal consequences such as arrhythmias.
- Factors affecting plasma K concentration include intracellular K reservoir, K intake and excretion routes, and redistribution of potassium.
- There is a reciprocal relationship between potassium and hydrogen ions in acidosis and alkalosis, affecting urinary loss of potassium.
- Hyperkalaemia, the commonest and most serious electrolyte emergency, can cause muscle weakness, cardiac arrest, and ECG changes that mimic other conditions, warranting serum potassium checks after cardiac arrest.
Test your knowledge of hypernatraemia and hyperkalaemia with this quiz. Learn key points about the causes, clinical features, and treatment of hypernatraemia, as well as the importance of potassium disorders and the implications of hyperkalaemia. Brush up on essential information for understanding and managing these electrolyte imbalances.
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