Regulation and disorders of salt and water

Question 1

How is total body water (TBW) calculated for both men and women?

Answer 1

Men: TBW = .6 x wt
women: TBW = .5 x wt

Question 2

How much of total body water is in the ECF?

Answer 2

1/3 of TBW

Question 3

How much of total body water is in the ICF?

Answer 3

2/3 of TBW

Question 4

How much of the ECFV is in the ISF?

Answer 4

3/4 of the ECFV

Question 5

Total body Na+ (TBNa) is synonymous with what?

Answer 5

ECFV

Question 6

What indicates a change in TBNa?

Answer 6

Clinical signs and symptoms give clues about TBNa

Question 7

What is the formula for Serum Na?

Answer 7

Serum Na = TBNa/ TBW

Question 8

T or F: Total body Na+ = Serum Na+

Answer 8

FALSE

Serum Na = TBNa/ TBW

Question 9

How is sodium balance regulated?

Answer 9

Only by Effective Circulating Volume (ECV)

Question 10

How and where does Angiotensin II regulate sodium?

Answer 10

Increase Na reabsoprtion

• proximal tubule!

Question 11

How and where does Aldosterone regulate sodium?

Answer 11

Increases Na+ reabsorption

• Distal tubule!

Question 12

How and where does ADH regulate sodium?

Answer 12

Increases WATER reabsorption

• distal tubule

Question 13

Effects of ADH on urine osmolarity?

Answer 13

Increases U osmlarity (concentrates)

• due to increased water reabsorption

Question 14

What is the effective circulating volume?

Answer 14

• relates to the fullness and tension within the arterial compartment
• usually correlates with total ECFV

Question 15

When does effective circ. volume not correlates with total ECFV?

Answer 15

1. CHF
2. Liver disease

• ECF is decreased due to either dec CO (CHF) or arterial vasodilation (splanchnic vasodilation in liver failure)

Question 16

What occurs if the effective circ. volume decreases?

Answer 16

Angiotensin II: increases
Thirst: Increases
ADH: Increases

=> Na+ retention (RAAs)
=> Water absorption (ADH)

Question 17

Clinical features of volume depletion?

Answer 17

1. Reduction in blood pressure
2. Poor skin turgor, absence of dependent edema
3. Disproportionate increase in BUN relative to serum creatinine:prerenal azotemia and reduced urine output
4. Reduced urine Na except in cases with renal losses of Na
5. Mental obtundation and cool extremities.

Question 18

Effects of volume depletion due to extra renal losses (i.e. Diarrhea or burns) on urine with normal renal function?

Answer 18

Urine: highly concentrated ( inc. Osm) but low Na+

• Because Water and Salt are being reabsorbed

Question 19

Effects of volume depletion due to renal losses (i.e. Diuretics) on urine with normal renal function?

Answer 19

Urine: Inappropriately diluted (dec Osm) and somtimes high Na+

Question 20

When does Volume expansion occur?

Answer 20

When salt and water intake exceeds renal and extrarenal losses

• usually Na+ and water retention by kidney

Question 21

Clinical features of volume expansion?

Answer 21

1. Edema
2. Distended JVD
3. Crackles, pleural effusion
4. ascites

Question 22

When are ADH levels high?

Answer 22

Water deprivation

Question 23

When are ADH levels low?

Answer 23

After consuming Water

Question 24

How is water balance regulated?

Answer 24

1. Plasma osmolarity (osmoreceptor)
2. Volume status (baroreceptor - non-osmotic)

• note diff between this ans Na+ balance: Na+ only regulated by volume status!

Question 25

disease caused by too much ECFV?

Answer 25

Hyponatremia (low Na concentration)

Question 26

Disease caused by too little ECFV?

Answer 26

Hpernatremia (High Na conc. )

Question 27

Normal serum Na+ level?

Answer 27

~135 -140 mEq/L

Question 28

The cause of hyponatremia depends on what?

Answer 28

Changes in ECFV - so can be: 1. Hypovolemic (hyponatremia) 2. Hypervolemic (hyponatremia) 3. Euvolemic (hyponatremia) - *excess TBW relative to TBNa**

Question 29

Causes of Hypovolemic Hyponatremia?

Answer 29

(decreased ECFV and ECV) - Renal/extra renal Na losses 1. Diarrhea 2. Burns 3. Pancreatitis 4. Diuretic Rx

Question 30

Causes of Hypervolemic Hyponatremia? (two types)

Answer 30

(inc ECFV) A. Decreased ECF 1. CHF 2. Liver disease B. Increased ECF 1. Acute Kidney injury 2. Chronic Kidney disease

Question 31

Causes of Euvolemic Hyponatremia?

Answer 31

[no change in ECFV (clinical symptoms)] 1. SIADH 2. Glucocorticoid def. 3. Hypothyroidism 4. Drugs 5. Primary polydipsa 6. poor solute intake

Question 32

Name that natremia: - Sodium depletion with reduction in ECF volume and secondary water retention due to non-osmotic stimulation of vasopressin release

Answer 32

Hypovolemic Hyponatremia - TBNa: vv - TBW: v

Question 33

Name that natremia: - Water retention due to autonomous or altered regulation of vasopressin release(SIADH)

Answer 33

Euvolemic Hyponatremia - TBNa: No Change - TBW: ^^

Question 34

Name that natremia: - Retention of both sodium and water in which the latter is sufficient to lower the sodium concentration despite an increase in total body sodium

Answer 34

Hypervolemic Hyponatremia - TBNa: ^ - TBW: ^^

Question 35

Clinical findings: Edema, Distended JVD, crackles, pulmonary effusion TBNa?

Answer 35

TBNa = ECFV - Increased ^

Question 36

Clinical findings: Normal TBNa?

Answer 36

TBNa = ECFV - No Change

Question 37

Clinical findings: Hypotension, reduced skin turgor, flat neck veins, no recent fluid intake, vomiting, diarrhea, severe burns TBNa?

Answer 37

TBNa = ECFV - Decreased v

Question 38

How does osmolarity reflect ADH levels?

Answer 38

1. High ADH = High Urine Osmolarity - Due to inc. water reabsorption 2. Low ADH = Low Urine Osmolarity - due to dec. water reabsorption - **value of Urine Osm relative to Plasma Osm.

Question 39

Usual cause of hypernatremia?

Answer 39

Excess water loss - rather than by sodium gain

Question 40

Causes of Hypernatremia?

Answer 40

1. Inability to sense thirst (Disease of brain) 2. Inability to obtain water 3. Absent or resistance to ADH (along with insufficient water intake) 4. Diabetes Insipidus

Question 41

Hypernatremia w/ U osm

Answer 41

Diabetes Insipidus | - excessive urination leading to hypernatremia