Regulation and Disorders of Salt and Water - Gyamlani

Question 1

What percent of weight is TBW?

Answer 1

60% males

50% females

Question 2

As a core principle, what is water balance regulated by?

Answer 2

Plasma osmolality

Question 3

As a core principle, what is Na balance regulated by?

Answer 3

Plasma volume

Question 4

What is total body sodium proportional to?

Answer 4

TBW

Question 5

What is an equation for plasma osmolarity?

Answer 5

2*Na + glucose / 18 + urea / 2.8

Question 6

What is a normal plasma Na?

Answer 6

140 mEq / L

Question 7

What is the effect of hypovolemia on EABV, ECFV, plasma volume, and CO?

Answer 7

EABV - decreased
ECFV - decreased
Plasma volume - decreased
CO - decreased

Question 8

What is the effect of CHF on EABV, ECFV, plasma volume, and CO?

Answer 8

EABV - decreased
ECFV - increased
Plasma volume - increased
CO - decreased

Question 9

What is the effect of cirrhosis on EABV, ECFV, plasma volume, and CO?

Answer 9

EABV - decreased
ECFV - increased
Plasma volume - increased
CO - increased

Question 10

What are sensors of plasma osmolality?

Answer 10

Hypothalamic osmoreceptors?

Question 11

What are effectors of plasma osmolality regulation?

Answer 11

ADH

Thirst

Question 12

What is manipulated through osmoregulation?

Answer 12

Urine osmolality

Water intake

Question 13

What are sensors of EABV?

Answer 13

Macula densa
Afferent arteriole
Atria
Carotid sinus

Question 14

What are effectors of EABV regulation?

Answer 14

RAS
Aldosterone
ANP
Norepinephrine
ADH

Question 15

What is manipulated through volume regulation

Answer 15

Urine Na

Thirst

Question 16

What stimulates RAS?

Answer 16

Decreased sodium
Decreased ECFV
Decreased arterial pressure

Question 17

What stimulates aldosterone?

Answer 17

Increased AT II

Increased plasma potassium

Question 18

What are the actions of AT II?

Answer 18

Vasoconstriction

Increased Na absorption in PT

Question 19

What are the actions of aldosterone?

Answer 19

Increased Na reabsorption in DT

Increased K secretion

Question 20

What are the actions of atrial natriuretic peptide (ANP)?

Answer 20

Increased Na excretion

Afferent arteriolar vasodilation

Question 21

What is the result of hypertonic stimulation of hypothalamic receptors?

Answer 21

Increased thirst

Increased AVP

Question 22

Where is the thirst center located?

Answer 22

Third ventricle

Question 23

What stimulates the thirst center?

Answer 23

Increased ECF osmolality
Volume depletion / Decreased EABV
Angiotensin II

Question 24

What stimulates vasopressin / AVP / ADH?

Answer 24

Increased ECF osmolality
Volume depletion / Decreased EABV
Angiotensin II
Pain
Nausea / Vomiting
Medications

Question 25

Where is AVP formed and released?

Answer 25

Formed - Hypothalamus | Released - Posterior pituitary

Question 26

Is sodium or water typically pathologic in hyponatremia?

Answer 26

Mostly water imbalance

Question 27

What is the first thing you should do when working up a hyponatremic patient?

Answer 27

Assess volume status

Question 28

Describe the underlying mechanism of hypovolemic hyponatremia.

Answer 28

Sodium depletion with reduction in ECFV and secondary water retention due to non-osmotic stimulation of vasopressin.

Question 29

What are common mechanisms of sodium loss in hypovolemic hyponatremia?

Answer 29

``` Renal (U Na > 20 mEq / L) Parenchymal disease affecting tubular handling of sodium Mineralocorticoid deficiency Persistent solute diuresis (glucosuria) Diuretic therapy ``` Extrarenal Vomiting / Diarrhea Burns Hemorrhage

Question 30

What are signs of sodium depletion?

Answer 30

Orthostatic BP Poor skin turgor Disproportionate increase in BUN:creatinine (prerenal azotemia) Reduced urine sodium excretion

Question 31

Describe the underlying mechanism of euvolemic hyponatremia.

Answer 31

Water retention due to altered regulation of vasopressin (SIADH)

Question 32

What causes SIADH?

Answer 32

Pulmonary / CNS disorders Malignancy Pain / nausea Drug-induced water retention (anti-psychotics)

Question 33

What are the diagnostic criteria for SIADH?

Answer 33

Decreased serum osmolarity (100 mosm/kg) Euvolemia Elevated U Na

Question 34

Describe the underlying mechanism of hypervolemic hyponatremia.

Answer 34

Retention of both sodium and water (greater water)

Question 35

What are common causes of hypervolemic hyponatremia?

Answer 35

CHF Hepatic cirrhosis Nephrotic syndrome Renal disease

Question 36

What are symptoms of hyponatremia?

Answer 36

Nausea / malaise Headache, lethargy, obtundation Seizures, coma *Chronic - few symptoms

Question 37

What can be caused by correcting hyponatremia too quickly?

Answer 37

Cerebral Demyelination Syndrome

Question 38

How do you treat hypo-, eu-, and hyper- volemic hyponatremia?

Answer 38

Hypo - Isotonic saline Eu - water restrict / 3% NS / Diuretic Hyper - Na restrict / Diuretic

Question 39

What is the equation for water excess?

Answer 39

.6 ( Wt ) * ( 1 - SNa / 140 )

Question 40

What does U osm < 300 mOsm/kg signify in hypernatremia?

Answer 40

Dysfunction ADH | Diabetes insipidous

Question 41

What does U osm > 500 mOsm/kg signify in hypernatremia?

Answer 41

Extra-renal water loss Sodium ingestion/infusion Decreased osmotic diuresis

Question 42

What are the symptoms of hypernatremia?

Answer 42

``` Lethargy Weakness Irritability Seizure Coma Death ```

Question 43

How do you treat hypo-, eu-, and hyper- volemic hypernatremia?

Answer 43

Hypo - Isotonic saline until hypovolemia resolved Eu - Replace water (and ADH if dysfunctional) Hyper - Remove Na