40 Questions
What is the primary cause of hypernatremia in nonketotic hyperosmolar hyperglycemic coma of diabetes?
Hyperglycemia-induced osmotic diuresis
What is the result of renal insufficiency in relation to hypernatremia?
Impaired ability to concentrate urine
What is the consequence of excess water loss without adequate replacement?
Hypernatremia
What is the characteristic of diabetes insipidus?
Defect in production or release of antidiuretic hormone
What is the result of taking loop diuretics?
Excess water loss
What is the consequence of hypernatremia without disturbance in sodium balance?
Water deficit
What is the characteristic of a patient with diabetes insipidus?
Thirst is impaired, but patient develops hypernatremia if they do not have access to water
What is a common cause of hypernatremia?
Excessive sweating
What is a common characteristic of the elderly population that contributes to hypernatremia?
Inability to access H2O
What is the primary cause of inappropriate ADH secretion in SIADH?
Actual cause is often unknown
What is the primary goal of treating hypernatremia?
H2O replacement
Which of the following is a sign or symptom of hypernatremia?
Seizures
Which of the following conditions is associated with increased release of ADH?
Emotional stress
What is the effect of SIADH on urine production?
Less than maximally dilute urine
What is the term for the shrinkage of the brain stem that occurs in hypernatremia?
Brain stem shrinkage
What is the term for the type of hypernatremia that occurs with decreased total body water (TBW) and increased sodium levels?
Hypernatremia with hypovolemia
Which of the following is a cause of renal losses?
Diuretics
What is the effect of diuretics on urine production?
Increased urine production
What is the treatment for hypernatremia in a patient who cannot drink water?
IV with D5W
What is a common underlying cause of hypernatremia in the elderly population?
Impaired thirst
Which of the following is a cause of non-renal losses?
Burns
What is the effect of glucocorticoid deficiency on ADH secretion?
Increased ADH secretion
What is the term for the type of hypernatremia that occurs with increased total body water (TBW) and increased sodium levels?
Hypernatremia with hypervolemia
Which of the following is a characteristic of SIADH?
Plasma hypoosmolality
What is the calcium level threshold for considering treatment?
15 mg/dL
What is the primary concern for asymptomatic patients with a calcium level of 15 mg/dL?
Risk of nephrolithiasis
Which of the following symptoms is NOT typically associated with asymptomatic patients?
Hallucinations
What is the primary factor in deciding whether to pursue surgery for an asymptomatic patient?
Presence of complicating problems
What is the rate of complications in asymptomatic patients, except for nephrolithiasis?
Low
Which of the following is a common symptom of asymptomatic patients?
Crying easily
What is the primary approach for managing asymptomatic patients with a calcium level of 15 mg/dL?
Conservative approach
What is the most common underlying cause of asymptomatic patients' symptoms?
Neuromuscular disturbances
What is the osmotic threshold for ADH release in individuals with hyponatremia?
Subnormally low
What is the characteristic of ADH secretion in some individuals with SIADH?
Erratic and independent of osmotic control
What is the effect of low plasma osmolality on ADH levels in a small group of people with SIADH?
ADH is not suppressed
What is the plasma osmolality level at which symptoms of hyponatremia occur?
12 mg/dL
What is the characteristic of ADH release in classical SIADH?
Sustained ADH release
What is the relationship between ADH levels and plasma osmolality in some individuals with SIADH?
ADH levels vary appropriately with plasma osmolality
What is the term used to describe the abnormal resetting of the osmotic threshold for ADH release in some individuals with SIADH?
Reset osmostat
What is the effect of hypoosmotic plasma on ADH levels in individuals with normal osmotic control?
ADH levels decrease
Study Notes
Hypernatremia
- 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 excess Na+
- When H2O deficit exists, hypernatremia occurs without disturbance in Na+ balance
- Excess sweating can cause H2O loss and hypernatremia
- Diabetes insipidus is a defect in production or release of ADH by posterior pituitary, leading to inability to secrete a concentrated urine
Hypernatremia in the Elderly
- Common in the elderly due to:
- Inability to access H2O
- Impaired thirst
- Impaired renal concentrating ability
- Increased insensible H2O loss
Diagnosis and Treatment of Hypernatremia
- Diagnosis:
- Signs and symptoms: thirst, CNS symptoms (brain stem shrinkage, confusion, neuromuscular irritability, seizures, coma)
- Treatment:
- H2O replacement is primary goal
- If patient cannot drink, IV with D5W
Principle Causes of Hypernatremia
- Hypernatremia with hypovolemia:
- Diarrhea
- Pancreatitis
- 3rd spacing
- Small bowel obstruction
- Rhabdomyolysis
- Burns
- Hypernatremia with euvolemia:
- ADH secretion
- Postop narcotics
- Pain
- Emotional stress
- Hypernatremia with hypervolemia:
- Heart failure
- Hepatic cirrhosis
Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)
- Less than maximally dilute urine in presence of plasma hypoosmolality and hyponatremia
- Etiology: often unknown, but sustained ADH release
- Pathogenesis:
- Classically, SIADH is sustained ADH release
- In some, ADH secretion is erratic and apparently independent of osmotic control
- In others, ADH levels vary appropriately with plasma osmolality, but osmotic threshold for ADH is abnormally low
Diagnosing SIADH
- Symptoms of hyponatremia occur when plasma osmolality falls to 120 mmol/dL, ionized Ca+ is almost 51%
Treatment of SIADH
- If symptoms are mild and Ca+ is 15 mg/dL, conservative approach is appropriate
- If asymptomatic, decision for or against surgery is based on complicating problems
This quiz covers the causes of hypernatremia, including excessive sweating, burns, and taking loop diuretics. Understand the pathogenesis of hypernatremia and its relationship to water loss.
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