hypernatremia, diabetes insipidus, Cl- imbalances

Question 1

symptoms of hypernatremia

mild to moderate
severe

• [Na+] > 145 mmol/L (severe when >160 mmol/L)

Answer 1

• Thirst mechanism (activated by release of vasopressin) isbusually sufficient to resolve transient episodes of hypernatremia
– Impairment in children, elderly, disabled
• Mild to Moderate: weakness, lethargy, restlessness, irritability, twitching, and confusion
• Severe: seizures, coma, and an increased risk of death

Question 2

what is classification of hypernatremia based on?

what are the 3 types?

Answer 2

status of ECF

hypovolemic, hypervolemic, euvolemic

Question 3

describe hypovolemic hypernatremia

Answer 3

water loss (renal, GI, lung, skin) ‘faster’ than
sodium loss
– sweating, diarrhea, vomiting, exposure to high temperatures
– Usually thirst mechanism will correct this imbalance

Question 4

describe hypervolemic hypernatremia

Answer 4

odium overload (e.g., overcorrect
hyponatremia using 3% NaCl, sodium bicarbonate, salt tablets)

Question 5

describe euvolemic hypernatremia

Answer 5

: water loss with little or no loss of sodium

– Diabetes Insipidus is the most common cause

Question 6

Causes of Diabetes Insipidus (Daily urine volume > 3L)

central causes

Answer 6

low levels of vasopressin
– Polyuria develops suddenly
– Unreplaced water loss from skin & lung
– Medical Conditions: Hypodipsia, TB, head trauma, CNS malignancy
– Other: ethanol ingestion (transient)

Question 7

Causes of Diabetes Insipidus (Daily urine volume > 3L)

nephrogenic causes

Answer 7

renal tubules do not respond to vasopressin
– Polyuria develops gradually
– Medical Conditions: hypokalemia, hypercalcemia, kidney disease
– Drug Induced: lithium, demeclocycline, amphotericin B

Question 8

Management of Hypovolemic Hypernatremia

Answer 8

• Initially treat with normal saline (0.9% NaCl) until
hemodynamically stable
– Adults 200 to 300 mL/h
– Children 10 to 20 mL/kg/h
• Once patient is hemodynamically stable, switch to half normal saline (0.45% NaCl), 5% dextrose (D5W), or other hypotonic solution

Question 9

Management of Diabetes Insipidus

Answer 9

• Central: replace vasopressin
– Desmopressin acetate: intranasally every 12-24h
• Nephrogenic:
– Correct the underlying cause (e.g., hypercalcemia)
– If drug-induced, stop or decrease dose (e.g., Li+)
– Limit sodium intake and add a thiazide diuretic
• Creates a mild deficit in extracellular fluid volume, which can lower urine output by ↑water reabsorption in renal tubule

Question 10

Management of Sodium Overload

Answer 10

• Administer D5W (5% Dextrose in Water) and a loop diuretic (e.g., furosemide) to facilitate sodium elimination
– Measure sodium concentration every 2-4 hours until < 148 mmol/L and symptoms of hypertonicity have resolved

Question 11

define hypochloremia and hyperchloremia

• Chloride (Cl-) is a major extracellular anion
– Passively follows Na+
– Normal concentration is 96-106 mmol/L

Answer 11

Hypochloremia (<96 mmol/L)
– Associated with hyponatremia as well as loss of large volumes of stomach
acid (e.g., vomiting)
– Diuretics may also cause hypochloremia
– Metabolic alkalosis

Hyperchloremia (>106 mmol/L)
– Associated with metabolic acidosis and hypernatremia