Conditions of Sodium Imbalance Flashcards
What is the role of sodium in fluid balance
The primary driver of osmolarity in Extracellular Fluid Compartment
Formula to calculate Serum Osmolarity
(2 x Na+) + (Glucose) + Blood Urea Nitrogen
Most common electrolyte abnormality?
Hypotonic Hyponatremia
- Low Electrolytes
Symptoms of Mild Hyponatremia (5)
Mild:
- Asymptomatic
- Impaired Attention
- Postural Changes
- Gait Changes
- Increased Fall Risk
Symptoms of Moderate/Severe Hyponatremia (8)
- Nausea
- Vomiting
- Headache
- Lethargy
- Altered Mental Status
- Seizures
- Respiratory Arrest
- Increased Risk of Death
How to assess Hyponatremia
- Patient is determined to have low sodium levels
- Measure Serum Osmolarity
- If Hypovolemic measure Volume Status
- If Hypovolemic measure Urine Osmolarity
- If Hypovolemic measure Urine Concentration
- Low Sodium
- Normal Serum Osmolarity
Isotonic Hyponatremia
- Pseudohyponatremia
Displacement in fluid volume from elevations in cholesterol/protein levels
- Sodium level is normal, but, when drawing blood sample sodium is low because other components in the blood is displacing it
- Low Sodium
- High Serum Osmolarity
Hypertonic Hyponatremia
- Hyperglycemia
Explain Hypotonic Hyponatremia (Dehydrated)
- Low Sodium level
- Low Serum Osmolarity
–> Dehydrated - Hypovolmic
- Urine is very concentrated
5a. If Sodium concentration is less than 20 mEq/L sodium loss is from extra renal sources
5b. If Sodium concentration is greater than 20 mEq/L sodium loss is from renal source
How does Hypotonic Hyponatremia (Hypovolemic) occur
- Excessive fluid loss (Diuretic, Diarrhea, Sweating)
- Body is in a hypernatremia state
- Body releases vasopressin
- Water is retained, sodium is excreted
- Very concentrated urine
What would be Extrarenal Losses
GI: Diarrhea
Skin: Sweating
Lungs: Hyperventilation
What would be Renal Losses
Adrenal Insufficiency: Not enough aldosterone
Diuretics: Too strong
Renal Losses
Explain Hypotonic Hyponatremia (Edema)
- Low Sodium Levels
- Low Serum Osmolarity
–> Edema - Hypervolemia
- Low Osmotic Pressure in Vasculature
- Water moves into interstitial spaces
- Urine Osmolarity will be low as blood volume is low
- Sodium Concentration in urine will be less than 20 mEq/L because it is not being released in kidneys
What causes Hypotonic Hyponatremia (Hypervolemic)
Heart Failure
Cirrhosis
Nephrosis
Explain Hypotonic Hyponatremia (Isovolumic and Low Urine Osmolarity)
- Low Sodium Levels
- Low Serum Osmolarity
- Isovolumic/Euvolemic
- Low Urine Osmolarity
- Low Sodium Concentration in Urine
Primary polydipsia causes excessive drinking of water because of high glucose levels
- Water dilutes urine
Explain Hypotonic Hyponatremia (Isovolumic and High Urine Osmolarity)
- Low Sodium Levels
- Low Serum Osmolarity
- Isovolumic/Euvolemic
- High Urine Osmolarity
- High Sodium Concentration in Urine
Caused by hypothyroidism, hypocortisolism, Kidney failure, SIADH
What is SIADH, relation to hypoantremia
Can cause hypotonic hyponatremia (Euvolemic)
- Causes release of vasopressin
–> Water is retained, sodium is excreted
Thus, increases urine osmolarity and sodium concentration in urine
Hypotonic Hyponatremia
- Which conditions involve High Serum Osmolarity + High Urine Osmolarity
Dehydration From Renal Sources (Hypovolemic)
- Body losses water
- Body responds by retaining water
- Body excretes sodium
- Concentrated urine
SIADH (Euvolemic)
- Vasopressin is released
- Water is retained, sodium is excreted
- Concetrated Urine
Hypotonic Hyponatremia
- Which conditions involve Low Serum Osmolarity + High Urine Osmolarity
None
Hypotonic Hyponatremia
- Which conditions involve High Serum Osmolarity + Low Urine Osmolarity
Edema (Hypervolemic)
- Low Osmolarity Pressure in Vasculature
- Water moves into interstitial space
- Low Blood Volume and Low Blood Pressure
- Urine is more concentrated due to less blood volume
- Sodium is not excreted through kidneys
Hypotonic Hyponatremia
- Which conditions involve Low Serum Osmolarity + Low Urine Osmolarity
Primary Polydipsia (Euvolemic)
- Excessive drinking of water
- Urine is very dilute
Diseases that can induce SIADH
- Tumours (Lungs, Pancreas)
- CNS Disorders (Head trauma, stroke, meningitis, pituitary surgery)
- Pulmonary Disease (TB, Pneumonia)
Drugs that can induce SIADH
- Tricyclic Antidepressants
- Phenothiazines
- Opioids
- Nicotine
- Carboplatin
- Cisplatin
- Bromocriptine
- NSAIDs
- Acetaminophen
How to treat severe Hypotonic Hyponatremia
3% NaCl (Hypertonic Saline)
0.9% NaCl (Normal Saline)
Do not exceed 6 to 12 mmol/L during the first 24 hours
How to treat Hypovolemic Hyponatremia
- Mechanism?
Treat the underlying cause
0.9% NaCl / Oral Replacement: Water, WHO-ORS, Water+Salt, Sports Drinks
- Once infused it remains in extracellular / intravascular fluid compartment
–> Restores intravascular fluid volume thus, reducing elevated vasopressin release
How to treat Hypervolemic Hyponatremia
- Treat underlying cause: Heart failure, Nephrosis, Cirrhosis
- Fluid Restriction: Creates a negative water balance, fluids are moves out of interstitial spaces into the intravascular spaces
- Sodium Restriction: Moves fluids out of the interstitial spaces into the intravascular spaces
- Vasopressin Receptor Antagonists (Tolvaptan, Conivaptan): Prevents reabsorption of water, more water is excreted creating less concentrated urine. Urine osmolarity decreases, Serum Sodium Concentration increases
How to treat Euvolemic Hyponatremia
- Correct the underlying cause: Stop the cause of SIADH
- Fluid Restriction: Creates a negative water balance
- For chronic SIADH may need to increase NaCl intake or add/remove loop diuretic
- Vasopressin Receptor Antagonist: Prevents water reabsorption, more water excreted
Symptoms of Hypernatremia Mild to Moderate (6)
- Weakness
- Restlessness
- Lethargy
- Irritability
- Twitching
- Confusion
Symptoms of Hypernatremia Severe (3)
Seizures, Coma, Increased chances of death
Hypovolemic Hypernatremia
- Cause
Water loss faster than sodium loss
Hypervolemic Hypernatremia
- Cause
Sodium overload
- Too much salt, water follows salt
Euvolemic Hypernatremia
- Cause
Water loss with little to no sodium loss
- Diabetes Insipidus is the most common cause
Causes of Diabetes Insipidus
- Lots of Water being lost through urine
- Central (Low levels of Vasopressin)
- Renal tubules not responding to Vasopressin (Nephrogenic)
