Disorders of Sodium

Question 1

How many milliequivalents is one gram of Na+?

Answer 1

43 mEq (aka 43 particles in solution). 
So if someone is on a 2 g Na+ diet, they are taking in 86 mEq.

Question 2

What is normal serum Na+?

Answer 2

140 mEq in every L of water.

Question 3

How can you lower the serum concentration of Na+/ become HYPOnatremic?

Answer 3

1. add more water= NORMAL total body sodium (TBS); from SiADH syndrome!!!
2. lose water and salt (diarrhea)= DECREASED TBS
3. add water and salt (CHF)= INCREASED TBS

Question 4

What happens when you lose Na+ and thus water due to say diarrhea?

Answer 4

you naturally replace it with more water (by drinking when thirsty), thus lowering the amount of sodium in the body (bc you aren’t replacing your fluid loss with saline solution).

Question 5

**How would you know based on physical exam if a patient was hyponatremic due to decreased TBS (aka they lost water and salt; from diarrhea)?

Answer 5

• they will look dehydrated
• increased HR
• decreased BP (perhaps orthostatic hypotension)

Question 6

**How would you know based on physical exam if a patient was hyponatremic due to normal TBS (aka because they just took in more water)?

Answer 6

• they look normal (and you can’t detect it clinically).
• normal HR
• normal BP
• no signs of fluid overload
• Note this is due to the influence of ADH

Question 7

**How would you know based on physical exam if a patient was hyponatremic due to increased TBS (aka because they just took in more salt and water)?

Answer 7

• edema (due to inability to excrete salt and water)
• BP could be high or low
• CHF
• cirrhosis
• nephrotic syndrome
• end-stage renal disease

Question 8

What is important to remember about all of these disorders of hyponatremia?

Answer 8

they will not occur without the influence of ADH

Question 9

Is serum volume more important than serum Na+?

Answer 9

YES. This is why you will maintain volume while hyponatremic in order to maintain cardiac output.

Question 10

What is a urine specific gravity?

Answer 10

How concentrated the urine is (how many particles there are in solution).

Question 11

What is the maximum urine osmolality (in max presence of ADH)?

Answer 11

1200 mOsm/kg (specific gravitity= 1.030)

Question 12

What is the minimum urine osmolality (in minimal presence of ADH)?

Answer 12

50-100 mOsm/kg

Question 13

What would a pt’s urine osmolality be with hyponatremia due to a normal total body sodium (from SiADH)?
(he said he won’t ask this)

Answer 13

200-1200 mOsm/kg, but they can’t maximally dilute the urine due to the presence of ADH.

Question 14

What would a pt’s urine osmolality be with hyponatremia due to an increased total body sodium (say from CHF)?

Answer 14

1200 mOsm/kg (aka a very concentrated urine) because you are trying to hold on to as much fluid as you can to increase the cardiac output.

Question 15

How do we treat someone who is hyponatremic due to decreased TBS?

Answer 15

give them saline (salt)

Question 16

How do we treat someone who is hyponatremic due to normal TBS (i.e SiADH or lung cancer)?

Answer 16

restrict their water

Question 17

How do we treat someone who is hyponatremic due to increased TBS (CHF)?

Answer 17

diuretics to drive off salt and water

Question 18

** A little old lady comes in with diarrhea, systolic BP= 80, HR= 120, urine specific gravity= 1.030. How do you treat her hyponatremia?
(test question)

Answer 18

normal saline because she has both loss of water and sodium.

Question 19

**How do you treat the hyponatremia of a 60 y/o male, who smokes 40 packs/year, has a large hilar mass on CXR, and Na+=125?

Answer 19

restrict water because this is classic SiADH.

Question 20

**How do you treat the hyponatremia of pt who presents with SOB, diaphoretic, BP= 90 systolic, edema, rales on auscultation, and Na+=120?

Answer 20

diuretics and fluid restriction bc pt has CHF