FEN: Hypertonic Saline

Question 1

What are typical concentrations of hypertonic saline, expressed in W/V% and osmolarity?

Answer 1

1. 3% (954 mOsm/L)
2. 7.5% (2393 mOsm/L)
3. 23.4% (7462 mOsm/L)

Question 2

What concentrations of hypertonic saline are available commercially?

Answer 2

1. NaCl 3%

2. NaCl 23.4%

Question 3

How to prepare hypertonic saline extemporaneously?

Answer 3

1. Choose base solutions (for example, NaCl 23.4% vials and sterile water)
2. Set up alligation using desired final concentration
3. Add and subtract to come up with total parts, and parts from each base solution
4. Divide parts of each base solution by total parts and set up proportion based on desired final volume to solve for number of mL of each base solution

Question 4

Set up calculations to calculate 1000 mL of 7.5% hypertonic saline (HS)

Answer 4

1. 23.4% and 0% are base solutions
2. 7.5% is desired final concentration

23.4% 7.5 parts
7.5%
0% 15.9 parts
23.4 total parts

3. (7.5 parts 23.4% HS/23.4 total parts) = x/1000mL; x = 320.5 mL of 23.4% HS
4. (15.9 parts water/23.4 total parts) = (x/1000mL); x = 679.5 mL of sterile water.

Question 5

What sort of venous access is preferred for hypertonic saline?

Answer 5

1. Use central intravenous access because the osmolarity of HS 3% is greater than the cutoff range for peripheral administration (900 mOsm/L)

Question 6

If hypertonic saline must be administered through peripheral intravenous access, what are two strategies?

Answer 6

1. Use 2% hypertonic saline
2. Use 3% hypertonic saline because it is close to cutoff range. Use large vein, monitor for phlebitis, and obtain central access ASAP.

Question 7

Describe use of hypertonic saline in traumatic brain injury

Answer 7

Used to reduce an elevated intracranial pressure and increase cerebral perfusion pressure. It is typically used if sustained ICP is greater than 20 mmHg as measured with an ICP monitor.

Question 8

Describe use of hypertonic saline for symptomatic hyponatremia

Answer 8

1. Some practitioners treat asymptomatic or moderately symptomatic (lethargy, confusion) hyponatremia before concentrations of serum sodium drop very low
2. Symptoms typically start at Na+ 120 mEq/L
3. Symptoms of severe hyponatremia include coma and seizures

Question 9

Describe the inappropriate use of hypertonic saline in chronic asymptomatic hyponatremia (e.g. asymptomatic SIADH)

Answer 9

1. Hyponatremia is generally a water problem rather than a deficiency of Na; thus, HS makes little sense in absence of symptoms.
2. Asymptomatic syndrome of inappropriate secretion of antidiuretic hormone (SIADH) is usually treated with fluid restriction of less than 800 mL of fluid per day.

Question 10

Describe the inappropriate use of hypertonic saline in hyponatremia associated with severe hyperglycemia (pseudohyponatremia, i.e. diabetic ketoacidosis)

Answer 10

1. Typically, serum Na+ decreases in a nonlinear fashion in response to increasing blood glucose.
2. As hyperglycemia is corrected with insulin, serum sodium will normalize.

Question 11

What is the formula for corrected sodium in presence of hyperglycemia?

Answer 11

1. Corrected Na+ = serum Na+ plus [1.6 (glucose-100)]100]
2. In other words Na decrease by about 1.6-2.4 (depending on model used) per 100 mg/dL elevated in glucose above 100 mg/dL.

Question 12

Describe the pathophysiology of hypervolemia 2/2 HF causing hyponatremia

Answer 12

1. heart failure leads to tissue hypoperfusion
2. this triggers ADH secretion
3. water reabsorbed from kidneys leading to hyponatremia

Question 13

Describe the inappropriate use of hypertonic saline in hyponatremia associated with hypervolemia, e.g. heart failure

Answer 13

1. In general this situation is treated with fluid restriction or diuresis
2. Symptomatic hyponatremia is uncommon in patients with heart failure
3. Hypertonic saline could be considered in symptomatic patients, however they may also need diuresis to prevent worsening volume overload.

Question 14

List two hypertonic saline dose options for traumatic brain injury or other neurological injuries

Answer 14

1. 3% HS 250 mL or 2-4 mL/kg IV over 1-15 minutes administered for elevated ICP
2. 23.4% HS 30 mL over 20-30 minutes administered for elevated ICP

Question 15

What is a common standing order for HS 23.4% in setting of TBI or other neurological injury?

Answer 15

HS 23.4% 30 mL every 4-6 hours as needed for sustained ICP greater than 20 mmHg

Question 16

What HS dosing option is often recommended for patients requiring a prolonged reduction in intracranial pressure?

Answer 16

Continuous infusion of hypertonic saline, which rate of which should be based on frequent reassessment (~4 hours) of Na+, ICP and urinary excretion of sodium.

Question 17

What are the clinical goals for administering hypertonic saline in patients with symptomatic hyponatremia?

Answer 17

1. Stop symptoms
2. An immediate goal is not necessarily a normal serum sodium, however than rage is typically 120-125 mEq/L.
3. Reach a maximum safe amount of change in serum sodium.

Question 18

What is a maximum safe amount of change in a 24-hour period and a 48-hour period in serum sodium?

Answer 18

1. Some practitioners suggest a maximum change of 8 mEq/L in 24 hours.
2. Generally regarded as 10-12 mEq/L in 24 hours.
3. Changes more than 18 mEq/L in 48 hours should be avoided to minimize risk of osmotic demyelination syndrome.

Question 19

How often should serum sodium be monitored in setting of symptomatic hyponatremia?

Answer 19

1-4 hours, depending on severity of symptoms

Question 20

Describe the maximum safe amount of change in sodium on an hourly basis?

Answer 20

1. For severe symptoms, it is reasonable to increase serum sodium by up to 2 mEq/L/hour for a short time.
2. Generally an hourly increase of 0.75-1 mEq/L/hour up to a concentration of 120 mEq/L.
3. For concentrations above Na 120 mEq/L, generally infusion should be reduced so that Na increases by 0.5 mEq/L hour.
4. Maximum 24-hour change of 8-12 mEq/L.

Question 21

What weight is used to estimate infusion rate of 3% hypertonic saline in setting of symptomatic hyponatremia and why?

Answer 21

Ideal body weight to avoid overdosing patients with obesity

Question 22

How to estimate infusion rate of 3% hypertonic saline in setting of symptomatic hyponatremia?

Answer 22

1. Multiple Ideal Body Weight (IBW) by desired rate of sodium increase per hour.
   For example, 70 kg x 1 mEq/L = 70 ml/hour to increase sodium by 1 mEq/L in 1 hour.
2. The infusion can then be adjusted to achieve goal changes.

Question 23

Describe two HS bolus dosing options for patients with symptomatic hyponatremia

Answer 23

1. HS 2-3% 250 mL bolus over 30 minutes

2. HS 3% 50 mL bolus every 30 minutes x 2 doses.

Question 24

When consider hypertonic saline for symptomatic hyponatremia, why should you check potassium levels?

Answer 24

1. Hypokalemia can cause hyponatremia, so you should correct K+ depletion if present.
2. As K+ is replaced, serum sodium will increase.

Question 25

What complication of hypertonic saline results from rapid correction of serum sodium?

Answer 25

osmotic demyelination syndrome (includes central pontine and extrapontine myelinolysis)

Question 26

Describe early and late presentation of osmotic demyelination syndrome

Answer 26

1. Early: lethargy and affect changes

2. Late: permanent neurologic damage, including paraparesis, quadriparesis, dysarthria, dysphagia and coma.

Question 27

Rapid correction of what type of hyponatremia is most likely to cause osmotic demyelination syndrome?

Answer 27

chronic hyponatremia (vs. acute hyponatremia).

Question 28

List three electrolyte abnormalities that would show up on a BMP that can be a complication of hypertonic saline

Answer 28

1. Hypokalemia can occur with large volumes of HS
2. Hyperchloremic acidosis
3. Hypernatremia

Question 29

What is a strategy to avoid hyperchloremic acidosis as a complication of hypertonic saline?

Answer 29

1. Administer hypertonic saline in a 1:1 or 2:1 ratio of sodium chloride and sodium acetate or using a fluid with less chloride content. (e.g. 3% sodium chloride/acetate)

Question 30

What complication can result from administering hypertonic saline in a peripheral vein?

Answer 30

Phlebitis

Question 31

Describe the pathophysiology, initially and overtime, that causes hypertonic saline to have a complication with heart failure

Answer 31

1. initially: fluid overload can result from volume expansion
2. over time: hypertonic saline can have a diuretic effect leading to intravascular volume depletion.

Question 32

Describe the complication of hypertonic saline (and hyperosmolar therapy in general) on coagulopathy

Answer 32

Postulated to cause coagulopathy (e.g. decreased ability to clot blood, increased risk of bleeding) by causing platelet dysfunction

Question 33

Describe the impact on blood pressure if hypertonic saline is administered too rapidly

Answer 33

Hypotension

Question 34

List 8 complications of hypertonic saline

Answer 34

1. Osmotic demyelination syndrome
2. Hypokalemia
3. Hypernatremia
4. Hyperchloremic acidosis
5. Phlebitis
6. Heart failure
7. Coagulopathy
8. Hypotension