FLUIDS AND ELECTROLYTES

Question 1

List crystalloids, their composition and possible side effects

Answer 1

1. Normal Saline (0.9%): 154 Na, 154 Cl. Can cause hyperchloric acidosis due to lack of bicarb.
2. Lactate Ringers: 130 Na, 109 Cl, 4 K, 3 Ca. Can cause lactate alkalosis with lactate metabolism in the liver.
3. Others: 3% and 5% NS, D5W (5% dextrose in water = 50g dextrose/L).

Question 2

List examples of colloids

Answer 2

• Colloids draw fluids into intravascular compartments due to increase in osmotic pressures. Examples: Albumin, blood products (FFP, packed RBCs, platelets)

Question 3

What level is considered to be high sodium level? What does it indicate?

Answer 3

> 140 mEq/L.

Indicates patient has lost water

Question 4

For ever 3 mEq/L above normal for sodium, how much water has the patient lost?

Answer 4

1 L of water

Question 5

With RAPID loss of water over few hours, how do you treat?

Answer 5

RAPID loss of water indicates brain has not adapted (patient likely in a coma). Tx to reverse rapidly: give D5W over a few hours.

Question 6

WIth SLOW loss of water, how do you treat?

Answer 6

SLOW loss of water indicates the brain has adapted (patient not in a coma). Tx is to reverse gradually - would be deadly to reverse rapidly. Give D5 1/2 NS. This will replenish the volume rapidly, but slowly change the tonicity.

Question 7

If there has been evidence of SLOW loss of water, and you resuscitate too rapidly, what can occur?

Answer 7

Myelopontine degeneration: central pontine myelinolysis. The myelin sheath of nerve cells are damaged due to the rapid rise in serum tonicity.

Question 8

What level is considered to be low sodium level?

Answer 8

<140 mEq/L. Indicates that the patient has retained water.

Question 9

with RAPID increase in water, how do you treat?

Answer 9

Reverse effects with hypertonic solutions: 3-5% normal saline at 300cc or 100cc bolus respectively at a time.

Question 10

with SLOW increase in water from cancer with SIADH, how do you treat?

Answer 10

Since this has occurred slowly and the brain has adapted, treat with water restriction

Question 11

With SLOW increase in water due to persistent vomiting (GI loss) and replacement of fluids with pure water (thus resulting in decreased tonicity of Na), how do you treat?

Answer 11

First treat with isotonic fluids.
If patient is acidotic, use Lactate Ringers.
If patient is alkalotic, use Normal Saline.

Question 12

How is potassium movement into/out of cells affected by acidosis?

Answer 12

Acidosis is due to high levels of H. Cells responds by exchanging K for H: So there is an increase in potassium outside the cell in an effort to bring H into the cells. Potassium is then urinated out => can eventually result in profound hypokalemia

Question 13

In Diabetic ketoacidosis, how do you treat the patient?

Answer 13

first treat the acidosis, and look for good urine output. Once corrected, we should worry about hypokalemia, and thus provide 20 mEq/hr of Potassium. (although normal rates should be around 10 mEq/hr, we are worried about profound hypokalemia).

Question 14

What occurs in our fluid and electrolyte dynamics during a crush injury?

Answer 14

With a crush injury, the contents of cells are suddenly released: Potassium can rapidly rise. Acidosis occurs as cells try to take in the K resulting in higher hyperkalemia. Treatment: hemidialysis. If this is not immediately available, give calcium to protect the myocardium from being exposed to too much potassium

Question 15

What is the step by step way to tell if someone is in respiratory/metabolic acidosis/alkalosis?

Answer 15

1. pH - is it acidosis or alkalosis?
2. normal PCO2 is 40. Can it be Respiratory?
3. normal bicarb is 24. Can it be metabolic?

Question 16

How do you treat most metabolic alkalosis?

Answer 16

5-10 mEq/hr of KCl.