Conditions of Sodium Imbalance

Question 1

What is the role of sodium in fluid balance

Answer 1

The primary driver of osmolarity in Extracellular Fluid Compartment

Question 2

Formula to calculate Serum Osmolarity

Answer 2

(2 x Na+) + (Glucose) + Blood Urea Nitrogen

Question 3

Most common electrolyte abnormality?

Answer 3

Hypotonic Hyponatremia
- Low Electrolytes

Question 4

Symptoms of Mild Hyponatremia (5)

Answer 4

Mild:
- Asymptomatic
- Impaired Attention
- Postural Changes
- Gait Changes
- Increased Fall Risk

Question 5

Symptoms of Moderate/Severe Hyponatremia (8)

Answer 5

• Nausea
• Vomiting
• Headache
• Lethargy
• Altered Mental Status
• Seizures
• Respiratory Arrest
• Increased Risk of Death

Question 6

How to assess Hyponatremia

Answer 6

1. Patient is determined to have low sodium levels
2. Measure Serum Osmolarity
3. If Hypovolemic measure Volume Status
4. If Hypovolemic measure Urine Osmolarity
5. If Hypovolemic measure Urine Concentration

Question 7

1. Low Sodium
2. Normal Serum Osmolarity

Answer 7

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

Question 8

1. Low Sodium
2. High Serum Osmolarity

Answer 8

Hypertonic Hyponatremia
- Hyperglycemia

Question 9

Explain Hypotonic Hyponatremia (Dehydrated)

Answer 9

1. Low Sodium level
2. Low Serum Osmolarity
   –> Dehydrated
3. Hypovolmic
4. 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

Question 10

How does Hypotonic Hyponatremia (Hypovolemic) occur

Answer 10

1. Excessive fluid loss (Diuretic, Diarrhea, Sweating)
2. Body is in a hypernatremia state
3. Body releases vasopressin
4. Water is retained, sodium is excreted
5. Very concentrated urine

Question 11

What would be Extrarenal Losses

Answer 11

GI: Diarrhea
Skin: Sweating
Lungs: Hyperventilation

Question 12

What would be Renal Losses

Answer 12

Adrenal Insufficiency: Not enough aldosterone
Diuretics: Too strong
Renal Losses

Question 13

Explain Hypotonic Hyponatremia (Edema)

Answer 13

1. Low Sodium Levels
2. Low Serum Osmolarity
   –> Edema
3. Hypervolemia
4. Low Osmotic Pressure in Vasculature
5. Water moves into interstitial spaces
6. Urine Osmolarity will be low as blood volume is low
7. Sodium Concentration in urine will be less than 20 mEq/L because it is not being released in kidneys

Question 14

What causes Hypotonic Hyponatremia (Hypervolemic)

Answer 14

Heart Failure
Cirrhosis
Nephrosis

Question 15

Explain Hypotonic Hyponatremia (Isovolumic and Low Urine Osmolarity)

Answer 15

1. Low Sodium Levels
2. Low Serum Osmolarity
3. Isovolumic/Euvolemic
4. Low Urine Osmolarity
5. Low Sodium Concentration in Urine

Primary polydipsia causes excessive drinking of water because of high glucose levels
- Water dilutes urine

Question 16

Explain Hypotonic Hyponatremia (Isovolumic and High Urine Osmolarity)

Answer 16

1. Low Sodium Levels
2. Low Serum Osmolarity
3. Isovolumic/Euvolemic
4. High Urine Osmolarity
5. High Sodium Concentration in Urine

Caused by hypothyroidism, hypocortisolism, Kidney failure, SIADH

Question 17

What is SIADH, relation to hypoantremia

Answer 17

Can cause hypotonic hyponatremia (Euvolemic)
- Causes release of vasopressin
–> Water is retained, sodium is excreted

Thus, increases urine osmolarity and sodium concentration in urine

Question 18

Hypotonic Hyponatremia
- Which conditions involve High Serum Osmolarity + High Urine Osmolarity

Answer 18

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

Question 19

Hypotonic Hyponatremia
- Which conditions involve Low Serum Osmolarity + High Urine Osmolarity

Answer 19

None

Question 20

Hypotonic Hyponatremia
- Which conditions involve High Serum Osmolarity + Low Urine Osmolarity

Answer 20

Edema (Hypervolemic)
- Low Osmolarity Pressure in Vasculature
- Water moves into interstitial space
- Low Blood Volume and Low Blood Pressure

1. Urine is more concentrated due to less blood volume
2. Sodium is not excreted through kidneys

Question 21

Hypotonic Hyponatremia
- Which conditions involve Low Serum Osmolarity + Low Urine Osmolarity

Answer 21

Primary Polydipsia (Euvolemic)
- Excessive drinking of water
- Urine is very dilute

Question 22

Diseases that can induce SIADH

Answer 22

• Tumours (Lungs, Pancreas)
• CNS Disorders (Head trauma, stroke, meningitis, pituitary surgery)
• Pulmonary Disease (TB, Pneumonia)

Question 23

Drugs that can induce SIADH

Answer 23

• Tricyclic Antidepressants
• Phenothiazines
• Opioids
• Nicotine
• Carboplatin
• Cisplatin
• Bromocriptine
• NSAIDs
• Acetaminophen

Question 24

How to treat severe Hypotonic Hyponatremia

Answer 24

3% NaCl (Hypertonic Saline)
0.9% NaCl (Normal Saline)

Do not exceed 6 to 12 mmol/L during the first 24 hours

Question 25

How to treat Hypovolemic Hyponatremia - Mechanism?

Answer 25

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

Question 26

How to treat Hypervolemic Hyponatremia

Answer 26

- 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

Question 27

How to treat Euvolemic Hyponatremia

Answer 27

- 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

Question 28

Symptoms of Hypernatremia Mild to Moderate (6)

Answer 28

- Weakness - Restlessness - Lethargy - Irritability - Twitching - Confusion

Question 29

Symptoms of Hypernatremia Severe (3)

Answer 29

Seizures, Coma, Increased chances of death

Question 30

Hypovolemic Hypernatremia - Cause

Answer 30

Water loss faster than sodium loss

Question 31

Hypervolemic Hypernatremia - Cause

Answer 31

Sodium overload - Too much salt, water follows salt

Question 32

Euvolemic Hypernatremia - Cause

Answer 32

Water loss with little to no sodium loss - Diabetes Insipidus is the most common cause

Question 33

Causes of Diabetes Insipidus

Answer 33

- Lots of Water being lost through urine - Central (Low levels of Vasopressin) - Renal tubules not responding to Vasopressin (Nephrogenic)