CNS Toxicants Tutorial

Question 1

What are the 2 causes of sodium ion toxicosis? What is the overall issue?

Answer 1

1. DIRECT - excess salt intake, ECF Na+ content increases relative to free water content
2. INDIRECT - water deprivation, free water in ECF is lost without compensatory decrease in Na+ concentration

free water deficit

Question 2

What is the treatment goal of sodium ion toxicosis?

Answer 2

gradually correct free water deficit —> total body water should be 60% of BW

• 40% = intracellular
• 20% = extracellular

Question 3

What does the treatment of hypernatremia require?

Answer 3

knowledge of the degree of elevation of serum Na+ concentration

Question 4

What 3 conditions does hypernatremia present with?

Answer 4

1. HYPOVOLEMIA - decreased total body water and total body Na+, from excessive diarrhea, vomiting, or sweating
2. HYPERVOLEMIA - increased body Na+ with normal or increased total body water, from seawater intake or administration of hypertonic saline/bicarbonate
3. EUVOLEMIA - normal body Na+ and decreased total body water from poor water intake

Question 5

What is the initial step in treating hypernatremia? What is treated first?

Answer 5

evaluate perfusion deficits - CRT, heart rate, pulse strength, blood pressure

free water deficit

Question 6

Estimation of free water deficit (FWD):

Answer 6

Question 7

What happens upon rapid correction of hypernatremia? Why should gradual correction be done?

Answer 7

water uptake exceeds accumulated electrolytes and osmolites, causing cells to swell and CNS impairment

establishes normal osmolality because electrolytes and osmolites can keep up with the increased fluid

Question 8

Too rapid fluid correction:

Answer 8

Question 9

What type of fluid is recommended for treating free water deficit? Why? How should the concentration of Na+ levels compare to serum levels?

Answer 9

hypertonic saline —> reduces incidence of iatrogenic cerebral edema

parenteral and oral fluids should have similar Na+ concentrations to serum Na+ levels to prevent the movement of water into CSF

Question 10

What is the sodium concentration of physiologic saline? What is required in clinical cases of hypernatremia?

Answer 10

154 mEq/L Na+

additional Na+ is required - if unknown, initial fluids should contain 170 mEq/L and be decreased as clincal signs improve

Question 11

Following deprivation of water for 4 days, the serum of a 180-lb finisher pig was analyzed and found to contain 4020 ppm Na+. If the normal serum Na+ concentration in pigs is 145 mEq/L, calculate the free water deficit for this pig. (Na atomic weight = 23, valence = +1)

a. 10.1 L
b. 59.2 L
c. 16.8 L
d. 40.7 L

Answer 11

Question 12

A 30-lb dog presents with a serum Na+ level of 176 mEq/L. If the normal serum Na+ level for dogs is 155 mEq/L, calculate the free water deficit.

a. 1.1 L
b. 5.8 L
c. 7.2 L
d. 2.4 L

Answer 12

Question 13

The oral LD50 for sodium fluoroacetate in dogs is 0.066-0.35 mg/kg. If field rodent bait contains 0.15% sodium fluoroacetate, how much would a 50-lb dog need to consume to attain the LD50?

a. 1 g
b. 2 g
c. 8 g
d. 5 g

Answer 13