Hyponatremia and Hypernatremia (chemical pathology) Flashcards
What is the normal range of sodium ECF concentration?
135-145 mmol/L
What are the symptoms of hyponatremia?(4)
Weakness, dizziness, confusion and coma.
What are the signs of hyponatremia? (6)
- Oliguria, tachycardia, weight loss, peripheral circulatory failure, hypotension, decreased skin turgor.
Symptoms of acute hyponatremia.
Severe cerebral oedema, coma, seizures and respiratory distress.
True or false:
Chronic hyponatremia is a medical emergency.
False, it is acute hyponatremia that is a medical emergency.
What are the symptoms of chronic hyponatremia (5)
Headache, restlessness, muscle cramps, vomiting, lethargy.
What are the three causes of hyponatremia and their examples?
Decreased ECF volume-Thiazide diuretics, addison’s disease.
Increased ECF volume- Cirrhosis, impaired renal water excretion, heart failure.
Normal ECF volume- SIADH, hypothyroidism, Excessive water intake, psychogenic polydipsia.
Three circumstances in which hyponatremia can occur
- Sodium depletion (Hypovolemic hyponatremia)
-Water excess, sodium normal (euvolemic hyponatremia)
-Both water and sodium excess- Hypervolemic hyponatremia
How do we calculate osmolal GAP
Osmolal GAP = Osmolality - Osmolarity
Three things a clinician should do when assessing a patient with hypoNa
- History- time frame to development of hyponatremia.
-Establish fluid status (water retention/fluid loss) - Establish true hyponatremia
What is true hyponatremia?
Hypotonic hyponatremia
What causes isotonic hyponatremia? (2)
- Hyperlipidemia
Hyperproteinemia
What causes hypertonic hyponatremia? (2)
Hyperglycemia
Mannitol
What’s the next step to take in case of a hypotonic hyponatremia?
Assess volume status
What can be the causes of hypovolaemic hypotonic hyponatraemia ? (7)
Renal losses (urine sodium is high >40)
-Addison’s disease
-Diuretics
-Osmotic diuretics
Ketonuria
Extra-renal losses
-Diarrhoea
-Burns
-3rd space losses
What causes euvolaemic hypotonic hyponatraemia? (4)
-Psychogenic polydipsia
-SIADH
-Hypothyroidism
-Secondary adrenal insufficiency
What causes hypervolaemic hypotonic hyponatraemia? (5)
Urine sodium levels are high
-Renal failure
Low urine sodium levels
-Nephrotic syndrome
-Liver cirrhosis
Hypoalbuminaemia
-CCF
What are the symptoms of hypernatremia? (6)
Thirst, nausea and vomiting, diarrhoea, muscle twitching, confusion.
What are the signs of hypernatremia?
Irritability, hypovolemia, decreased skin turgor, dehydration.
What causes persistent hypernatremia?
Defect in thirst mechanism.
What is the first step in assessing hypernatremia?
Assess volume status
What can cause hypovolaemic hypernatraemia?
Renal losses(urine sodium is high)
-Osmotic diuretics
-ATN polyuric phase
Extra-renal losses (urine sodium is low)
-Diarrhoea
-Burns
-Sweating
What can cause euvolemic hypernatremia?
Renal losses (urine osmolality is low)
-Diabetes insipidus
Extra-renal losses (urine osmol is high)
-Insensible losses
What causes hypervolaemic hypernatraemia? (4)
-Ingestion of sea water
- Overconcentrated formula milk
- Hypertonic saline IV of NaHCO3
- Hypertonic dialysis
How does the brain adapt to:
A. Hypernatraemia
B. Hyponatraemia
A. Accumulating intracellular idiogenic molecules.
B. Secreting idiogenic molecules out of brain cells to ECF.
What are the effects of hyponatraemia on the brain? (5)
-Low sodium levels on the ECF causes water to move into the brain, which can cause cerebral oedema.
- Adaptation (1) rapid loss of water and salts, tonicity remain low.
- Adaptation (2) slow loss of osmolytes and water to eliminate the oedema.
Note: Rapid correction can lead to brain shrinkage.
Effect of hypernatremia on brain (5)
- Extracellular hypertonicity causes water to move out of the brain.
- This causes cerebral shrinkage.
- Adaptation (1) rapid gain of water and salts from ECF, tonicity remains high.
- Adaptation (2) slow gain of osmolytes and water to correct the shrinkage.
Note: Rapid correction may lead to cerebral oedema.
