Lecture 12 CNS Toxicants II - Part 1

Question 1

• The use of strychnine and fluoroacetate is ______
• A few ___ states still use them
• Fluoroacetate is widely used in _______ and _____ __________
• Most _________ are banned in US and Canada
• ____ re-approved for malaria control by WHO in 2006

Answer 1

• The use of strychnine and fluoroacetate is
  limited
• A few US states still use them
• Fluoroacetate is widely used in Australia and New Zealand
• Most organochlorines are banned in US and Canada
• DDT re-approved for malaria control by WHO in 2006

Question 2

What are the DIRECT causes of sodium toxicosis?

What happens to the ECF as a result?

Answer 2

• Direct Na+ toxicity: excess salt intake
• ECF Na+ content increases relative to the free water content

Question 3

What are the INDIRECT causes of sodium toxicosis?

Answer 3

• Indirect toxicity: water deprivation
• Free water in ECF is lost without compensatory decrease in Na+ concentration

Question 4

What is the main issue with sodium toxicosis?

Answer 4

Free water deficit

Question 5

What is the treatment goal in a case of sodium toxicosis?

Answer 5

• Correct free water deficit
  Body water
• Total body water is 60% of body weight
• This is the 0.6 in the free water deficit (FWD)
  calculation equation
• 40% (2/3) intracellular; 20% (1/3) extracellular

Question 6

What do treating a hypernatremic patient require?

Answer 6

• Treating hypernatremia requires knowledge of the degree of elevation of serum Na+
  concentration

Question 7

Hypernatremia may be present with?

Answer 7

hypovolemia, euvolemia or hypervolemia

Question 8

What is the initial step in evalutaing perfusion deficits?

Answer 8

• Capillary refill time, heart rate, pulse strength, blood pressure

Question 9

What do you treat first?

Answer 9

• Treat the volume deficit first –> Correct the free water deficit

Question 10

What are the three ways to evaluate the free water deficit?

Answer 10

Question 11

Over how long should Na+ levels be lowered?

Answer 11

• Na+ levels should be lowered no faster than 0.5 - 1 mEq/h to avoid development of edema

Question 12

Question 13

What is recommended to correct a free water deficit? Explain why.

Answer 13

• Hypertonic saline is recommended –> Reduces incidence of iatrogenic cerebral edema

Question 14

Na+ levels of the parenteral and oral fluids should closely match ?
Explain why.

Answer 14

serum Na+ levels
* Prevents movement of water into CSF
* Physiologic saline contains 154 mEq/L Na+. In clinical cases serum
Na+ levels are >160 mEq/L so additional Na+ is required
* If Na+ levels are not known initial IV fluid should contain 170
mEq/L Na+ and should be decreased as clinical signs improve

Question 15

Once Na+ levels of the parenteral and oral fluids match up, what should be done next?

Answer 15

Na+ levels in fluids should then be decreased as clinical signs improve

Question 16

Question 17

Question 18

Question 19

Watch videos and fill in treatment file on brightspace

Question 20

Acute (severe) hypernatremia that develops in minutes to hours, e.g., from a massive salt
overdose, causes the brain to _______ –> can cause _______ of blood vessels resulting in ______________ hemorrhage.
If the hypernatremia is sustained (e.g., > ___ hours), there is an adaptation of brain cells in which an increase in _________ and organic _______ occurs.

Answer 20

shrink, rupture, intracranial, 48, electrolytes, osmolytes

Question 21

Electrolytes and organic osmolytes draw water _______ the brain cells which partly corrects the
initial cell ______, but ____ osmolality persists.
The rapid correction of hypernatremia results in _______ _____ because water _____ by brain
cells exceeds the ________ of accumulated electrolytes and organic osmolytes.
The cerebral edema causes the serious signs of CNS impairment seen when hyponatremia is
corrected _______.
In contrast, slow correction of the hypernatremia reestablishes normal brain osmolality without
causing _______ _______ because this allows the dissipation of _________ electrolytes and
organic osmolytes to keep pace with water ________.

Answer 21

into, shrinkage, high, cerebral edema, uptake, dissipation, rapidly, cerebral edema , accumulated, replacement