80 Questions
Which of the following conditions is most likely to cause hypovolemic hyponatremia?
Severe diarrhea
What is the primary cause of dilutional hyponatremia in the presence of renal failure?
H2O intake without Na+ retention
Which of the following medications is most likely to cause nonosmotic ADH secretion?
All of the above
What is the characteristic of euvolemic hyponatremia?
No significant change to total body Na+
Which of the following conditions is most likely to cause hypervolemic hyponatremia?
CHF and Liver Failure
What is the primary cause of hyponatremia in hypervolemic hyponatremia?
Decrease in effective circulating volume
Which of the following is a common cause of nonosmotic ADH secretion?
All of the above
What is the effect of ADH on the kidneys in hypervolemic hyponatremia?
Antidiuretic effect
What is the osmotic threshold for ADH release in some individuals with SIADH?
Abnormally low
What happens to ADH secretion in some individuals with SIADH?
It is erratic and independent of osmotic control
At what plasma osmolality do symptoms of hyponatremia typically occur?
Below 240 mOsm/kg
What is characteristic of a small group of individuals with SIADH?
Low levels of ADH
What is the primary cause of hyponatremia in SIADH?
Inappropriate ADH secretion
What is the term for the abnormal regulation of ADH secretion in SIADH?
Reset osmostat
What type of hyponatremia is characterized by low levels of ADH?
Euvolemic hyponatremia
What is the term for ADH secretion that is not regulated by osmotic control?
Nonosmotic ADH secretion
Which of the following conditions is most likely to cause hypovolemic hyponatremia?
Diuretic abuse
What is the most common cause of euvolemic hyponatremia?
SIADH
Which of the following is a non-osmotic stimulus for ADH secretion?
Emotional stress
What is the term for hyponatremia caused by excessive water intake?
Dilutional hyponatremia
Which of the following is a cause of hypervolemic hyponatremia?
Heart failure
What is the term for hyponatremia caused by excessive ADH secretion?
SIADH
Which of the following is a cause of euvolemic hyponatremia?
Hypothyroidism
What is the term for hyponatremia caused by excessive sodium loss?
Hypovolemic hyponatremia
Which of the following conditions can cause hypovolemic hypernatremia?
Burns
What is the most common cause of hypernatremia resulting from osmotic diuresis?
Hyperglycemia
Which of the following is a cause of hypernatremia without a disturbance in sodium balance?
Excess sweating
What is the underlying defect in diabetes insipidus?
Defect in production or release of ADH
What can occur in a patient with diabetes insipidus if they do not have access to water?
Hypernatremia without a disturbance in sodium balance
Which of the following can prevent maximally concentrated urine, predisposing to hypernatremia?
Renal insufficiency
What is the consequence of excess loss of water from the body that is not adequately replaced?
Hypernatremia
What can cause hypernatremia in a patient with nonketotic hyperosmolar hyperglycemic coma of diabetes?
Osmotic diuresis
What is the primary mechanism of hypovolemic hyponatremia?
Excessive Na+ loss
Which of the following is a cause of euvolemic hyponatremia?
SIADH
What is the characteristic of hypervolemic hyponatremia?
Total body Na+ is increased
Which of the following is a cause of dilutional hyponatremia?
Infusion of hypotonic fluids
What is the mechanism of nonosmotic ADH secretion?
Stress
Which of the following is a cause of hypovolemic hyponatremia due to extrarenal losses?
Vomiting
Which of the following is a cause of euvolemic hyponatremia due to nonosmotic ADH secretion?
Pain
What is the difference between hypovolemic and euvolemic hyponatremia?
Total body Na+ is decreased in hypovolemic hyponatremia
What is the primary goal of treating hypernatremia?
Replacing water
What is the primary cause of hypernatremia, especially in the elderly?
All of the above
Which of the following signs and symptoms is typically associated with hypernatremia?
All of the above
What is the primary treatment for hypernatremia in patients who cannot drink?
IV fluids with D5W
What type of hypernatremia is associated with hypovolemia?
Hypernatremia with hypovolemia
What is the consequence of excess loss of water from the body that is not adequately replaced?
Hypernatremia
What is a common cause of hypernatremia in the elderly?
All of the above
What is the primary mechanism of hypernatremia in patients with diabetes insipidus?
Excess water loss due to impaired ADH secretion
What is the effect of angiotensin II on the development of hyponatremia?
It potentiates the development of hyponatremia
What is the difference in brain electrolyte content between acute and chronic hyponatremia?
Brain electrolyte content is lower in chronic hyponatremia
What is the characteristic of hyponatremia with hypovolemia?
Decreased total body water and sodium
What is the primary cause of symptoms of CNS dysfunction in acute hyponatremia?
Rapid decrease in brain electrolyte content
What is the characteristic of hyponatremia with euvolemia?
Near normal total body sodium
What is the effect of angiotensin on renal H2O excretion?
It decreases renal H2O excretion
What is the difference in brain water content between acute and chronic hyponatremia?
Brain water content is higher in acute hyponatremia
What is the characteristic of hyponatremia with hypervolemia?
Increased total body water and sodium
What is the primary consideration for decision-making in asymptomatic patients?
Complicating problems
What is a common symptom in the so-called asymptomatic patient?
Crying easily
What is the exception in terms of complications in asymptomatic patients?
Nephrolithiasis
What is the recommended approach for patients with mild symptoms and Ca+ levels below 15 mg/dL?
Conservative approach
What is a characteristic of the so-called asymptomatic patient?
Association with psychiatric and neuromuscular disturbances
What is the significance of Ca+ levels in the decision-making process?
Ca+ levels are irrelevant in asymptomatic patients
What is the relationship between Ca+ levels and symptoms in asymptomatic patients?
Ca+ levels have no impact on symptoms
What is the primary goal in managing asymptomatic patients?
Preventing complications
What is the goal of administering IV 0.9% NS with KCL and Lasix in patients with hypercalcemia?
To expand ECF and increase renal excretion of Ca+
What is the treatment of choice for symptomatic and progressive hyperparathyroidism?
Surgery
What is the purpose of using 99m Tc Sestamibi in parathyroid surgery?
To 'map' the tumor prior to surgery
What is the recommended approach when referring a patient with hyperparathyroidism for surgery?
Send the patient to a surgeon experienced in parathyroid exploration
Which of the following is a treatment approach for mild hypercalcemia in postmenopausal women?
Estrogen therapy
What is the recommended approach for patients with malignancy and hypercalcemia?
Bisphosphonates and NS
What is the role of IV 0.9% NS with KCL and Lasix in treating hypercalcemia?
To expand ECF and increase renal excretion of Ca+
What is the goal of achieving a urine output of at least 3 liters/day in patients with hypercalcemia?
To expand ECF and increase renal excretion of Ca+
What is the primary mechanism leading to hypermagnesemia in patients with renal impairment?
Deficient excretion of magnesium in the urine
What is the characteristic EKG finding in patients with hypermagnesemia?
Prolonged PR interval
What is the most common cause of hypermagnesemia?
Chronic ingestion of magnesium-containing laxatives or antacids
What is the clinical presentation of hypermagnesemia when the plasma level exceeds 12-15 mEq/L?
Respiratory depression and hypotension
What is the indication for surgical therapy in patients with hypercalcemia?
All of the above
What is the characteristic of decreased cortical bone density in patients with hypercalcemia?
Decreased cortical bone density
What is the primary mechanism leading to nephrolithiasis in patients with hypercalcemia?
Increased excretion of calcium in the urine
What is the indication for surgical therapy in patients with hypercalcemia and reduced renal function?
All of the above
Study Notes
Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)
- ADH release is sustained despite low plasma osmolality
- In some cases, ADH secretion is erratic and independent of osmotic control
- In others, ADH levels vary appropriately with plasma osmolality, but the osmotic threshold for ADH is abnormally low (reset osmostat)
- A small group of people have low levels of ADH, which is not suppressed when plasma becomes hypoosmotic
Diagnosing SIADH
- Symptoms of hyponatremia occur when plasma osmolality falls to 120 mmol/L
- Causes of SIADH include:
- Heart failure
- Diarrhea
- Pancreatitis
- Postop narcotics
- Hepatic cirrhosis
- Renal losses
- Diuretics
- Hypothyroidism
- Glucocorticoid deficiency
- Primary polydipsia
- Acute renal failure
- Chronic renal failure
Euvolemic Hyponatremia
- Total body water (TBW) is normal, and there is no significant change to total body Na+
- Dilutional hyponatremia can occur from excessive H2O intake without Na+ retention in presence of renal failure, Addison's disease, myxedema, or nonosmotic ADH secretion (stress, post-op, and certain drugs)
Hypervolemic Hyponatremia
- Increase in TBW and total body Na+ content
- Causes include:
- CHF and Liver Failure
- Decrease in effective circulating volume, leading to release of ADH and angiotensin II
- Hyponatremia results from antidiuretic effect of ADH on kidneys
- Taking loop diuretics
- Burns
- Excessive sweating
Pathogenesis of Hypernatremia
- Usually caused by excess loss of H2O from the body that is not adequately replaced
- Most common cause of hypernatremia from osmotic diuresis is hyperglycemia, seen in nonketotic hyperosmolar hyperglycemic coma of diabetes
- Renal insufficiency can prevent maximally concentrated urine, predisposing to hypernatremia
- When H2O deficit exists, hypernatremia occurs without disturbance in Na+ balance
- Excess sweating can lead to hypernatremia
Pathogenesis of Hypernatremia (con't)
- Diabetes insipidus is a defect in production or release of ADH by posterior pituitary
- Patient cannot secrete a concentrated urine
- Thirst is normal, but patient develops hypernatremia if they do not have access to H2O
Causes of Hypernatremia
- Extrarenal losses:
- Vomiting
- Diarrhea
- Burns
- Excess sweating
- Fever
- Tachypnea
- Hyper-tonic IV fluids
- Hypertonic Saline
- TPN
- Renal losses:
- Intrinsic renal disease
- Osmotic diuresis
- Loop diuretics
- Central DI
- Nephrogenic DI
- Mineralocorticoid excess
- Adrenal tumor secreting deoxycorticosterone
- Congenital adrenal hyperplasia
- Iatrogenic
- Inability to access H2O
- Primary hypodipsia
- Reset osmostat
Hypernatremia
- Common in the elderly, related to inability to access H2O, impaired thirst, impaired renal concentrating ability, and increased insensible H2O loss.
- Diagnosis: signs and symptoms include thirst, CNS symptoms (brain stem shrinkage, confusion, neuromuscular irritability, seizures, and coma).
- Treatment: primary goal is H2O replacement, with IV D5W if the patient cannot drink.
Principle Causes of Hypernatremia
- Hypernatremia with hypovolemia: decreased GFR and excretion by angiotensin II, potentiating development of hyponatremia.
- Hypernatremia with euvolemia: direct impairment of renal H2O reabsorption.
- Hypernatremia with hypervolemia: increased total body sodium and water.
Effects on CNS
- Brain cellular H2O content decreases in acute and chronic hyponatremia.
- Symptoms of CNS dysfunction are more common and greater in acute hyponatremia.
Principle Causes of Hyponatremia
- Hyponatremia with hypovolemia: decreased total body water and sodium, with greater relative decrease in sodium.
- Hyponatremia with euvolemia: near normal total body sodium, with increased total body water.
- Hyponatremia with hypervolemia: increased total body sodium, with relatively greater increase in total body water.
Treatment of Hyponatremia
- If symptoms are mild, Ca+ is 15 mg/dL, and conservative approach is appropriate.
- If symptoms are severe, H2O replacement is primary goal.
The So-Called Asymptomatic Patient
- Most cases are associated with psychiatric and neuromuscular disturbances that are not articulated.
- Prominent symptoms include anxiety, nervousness, daytime sleepiness, loss of energy, crying easily, excessive worry, irritability, and lack of interest.
Therapy
- Rate of complications is low in asymptomatic patients, except for nephrolithiasis.
- Decision for or against surgery is based on complicating problems.
- Mild hypercalcemia in postmenopausal women may respond to estrogens.
- For Vitamin D excess, Prednisone 20-40 mg/day PO usually controls Ca+.
Treatment of Hypercalcemia
- With normal renal function: IV of 0.9% NS with KCL and Lasix to increase renal excretion of Ca+ by expanding ECF.
- In patients with malignancy: bisphosphonates plus NS and Lasix to inhibit osteoclasts from absorbing bone.
- If hyperparathyroidism is symptomatic and progressive: surgery is the treatment of choice.
Surgical vs Conservative Therapy
- Guidelines for surgery: calcium > 12 mg, hypercalciuria >400 mg/24 hrs, nephrolithiasis, cystic bone disease, overt neuromuscular disease, decreased cortical bone density, and reduced renal function.
Hypermagnesemia
- Etiology: rare, deficient excretion of magnesium in urine due to renal disease or renal failure, chronic ingestion of magnesium-containing laxatives or antacids.
- Signs and symptoms: if plasma level is 5-10 mEq/L, EKG shows prolonged PR interval, widening of QRS, and increased T wave amplitude; DTRs decrease or disappear, hypotension, respiratory depression, and cardiac arrest when magnesium >12-15 mEq/L.
This quiz is about hyponatremia, a condition characterized by low sodium levels, and its relation to the release of Anti-Diuretic Hormone (ADH). It covers the osmotic threshold for ADH release and its suppression in certain individuals.
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