Hyper/hyponatremia Flashcards
Distribution of body solids and fluids?
In both men and women
- solids - 45% females and 40% males
- fluids - 55% female and 60% males
> 2/3 intercellular fluid
> 1/3 extracellular fluid
- 80% interstitial fluid
- 20% plasma
Normal plasma ranges of electrolytes?
- Mg - 1.6-2.6 mg/dl
- PO4 - 1.9-4.3 mg/dl
- Ca2+ - 2.0-2.5 mmol/L
- K+ - 3.5-5.5 mmol/L
- Cl- - 102-116 mmol/L
- Na+ - 135-145 mmol/L
Function of sodium?
- to conduct nerve impulses
- contract and relax muscles
- maintain the proper balance of water and minerals
Hypernatremia?
Hypernatremia is characterized by a serum sodium level above 145 mEq/L (SI, 145 mmol/L) or ULN
Causes of hypernatremia?
- the body has an excess of sodium relative to water
- Water deficit or excess sodium intake can lead to hypernatremia, making body fluids more hypertonic
Release of Antidiuretic hormone (ADH)?
- released from hypothalamus and stored in posterior pituitary
- Released with high plasma osmolality and hypovolemia
Function of ADH hormone?
- Increases water permeability in distal tubule and renal collecting ducts
- results in water retention thus reducing the concentration of solutes such as sodium
When is ADH pathologically released?
Syndrome of inappropriate ADH secretion (SIADH)
e.g. pain, tumour, trauma
Release of Aldosterone?
from adrenal cortex in the adrenal gland
Function of aldosterone?
acts on the distal tubules and collecting ducts of the kidney to cause the:
1. conservation of sodium
2. secretion of potassium
3. increased water retention
4. increased blood pressure
Causes of hypernatraemia - water deficit?
- fever
- heat stroke
- pulmonary infections
- extensive burns
- severe diarrhea
- hypersomolar hyperglycemic nonketotic syndrome
- urea diuresis
- diabetes insipidus
Causes of hypernatremia - excess sodium?
- overconsumption of dietary sodium
- use of certain drugs
- near drowning in salt water
- Cushings syndrome
- hyperaldosteronism
Drug causes of hypernatremia?
- antacids
- NaCl IV
Diagnostic tests for hypernatrmia?
- Measure serum osmolality (formula)
- Serum Osmolality above 300m/Osm/kg
- Serum sodium level above 145 meq/L or ULN - Urine specific gravity above 1.030 (or less than 1.005 in DI)
Calculating serum osmolality?
2(Na+) + Glucose (mg/dl/18) + BUN (mg/dl/2.8)
Rapid correction of severe hypernatremia can cause?
cerebral edema
Hypernatremia signs and symptoms?
you are FRIED
- Fever (low grade), flushed skin
- Restless (irritable)
- Increased fluid retention and increased BP
- Edema (peripheral and pitting)
- Decreased urinary output, dry mouth
Hypernatremia sign and symptoms?
SALT
- Skin flushed
- Agitation
- Low-grade fever
- Thirst
Hyponatremia?
Hyponatremia is characterized by a serum sodium level below 135 mEq/L (SI, 135 mmol/L)
- In hyponatremia, body fluids are diluted and cells swell from decreased extracellular fluid osmolality
- Severe hyponatremia (sodium level below 110 mEq/L [SI, 110 mmol/L]) can lead to seizures, coma, and permanent neurologic damage
Hyponatremia can be triggered by?
- sodium loss
- water gain
- dilutional hyponatremia - inadequate sodium intake
- depletional hyponatremia
Types of hyponatremia?
- hypovolemic
- with decreased extracellular fluid volume - hypervolemic
- with increased extracellular fluid volume - isovolumic
- with extracellular fluid volume equal to intracellular fluid volume
Causes of hypovolemic hyponatremia causes - urinary Na+ >20 mmol/L?
renal loses
1. diuretic excess
2. mineralocorticoid deficiency
3. salt losing nephropathy
4. bicarbonaturia with renal tubular acidosis and metabolic alkalosis
5. ketonuria
6. osmotic diuresis
7. cerebral salt wasting
Causes of hypovolemic hyponatremia causes - urinary Na+ <20 mmol/L?
extrarenal loses
1. vomiting
2. diarrhea
3. third spacing of fluids in burns
4. pancreatitis
5. trauma
Euvolemic hyponatremia causes?
- glucocorticoid deficiency
- hypothyroidism
- stress - physical or psychological
- drugs
- SIADH
Hypervolemic hyponatremia causes - urinary Na+>20mmol/L?
acute or chronic renal failure
Hypervolemic hyponatremia causes - urinary Na+<20mmol/L?
- nephrotic syndrome
- cirrhosis
- cardiac failure
Drugs that cause hyponatremia?
- anticonvulsants
- antineoplastics
- antidiuretics
Diagnostic tests for hyponatremia?
- Serum osmolality below 280 mOsm/kg (dilute blood).
- Serum sodium level below 135 mEq/L (SI, 135 mmol/L) or less than LLN
- Urine specific gravity below 1.010 (or increased urine specific gravity and urine sodium level in a patient with SIADH secretion).
Rapid correction of severe hyponatremia can cause?
osmotic demylination of the cord (Central Pontine Myelinosis)
