Regulation and Disorders of Salt and Water - Gyamlani Flashcards Preview

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Flashcards in Regulation and Disorders of Salt and Water - Gyamlani Deck (43):
1

What percent of weight is TBW?

60% males
50% females

2

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

Plasma osmolality

3

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

Plasma volume

4

What is total body sodium proportional to?

TBW

5

What is an equation for plasma osmolarity?

2*Na + glucose / 18 + urea / 2.8

6

What is a normal plasma Na?

140 mEq / L

7

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

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

8

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

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

9

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

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

10

What are sensors of plasma osmolality?

Hypothalamic osmoreceptors?

11

What are effectors of plasma osmolality regulation?

ADH
Thirst

12

What is manipulated through osmoregulation?

Urine osmolality
Water intake

13

What are sensors of EABV?

Macula densa
Afferent arteriole
Atria
Carotid sinus

14

What are effectors of EABV regulation?

RAS
Aldosterone
ANP
Norepinephrine
ADH

15

What is manipulated through volume regulation

Urine Na
Thirst

16

What stimulates RAS?

Decreased sodium
Decreased ECFV
Decreased arterial pressure

17

What stimulates aldosterone?

Increased AT II
Increased plasma potassium

18

What are the actions of AT II?

Vasoconstriction
Increased Na absorption in PT

19

What are the actions of aldosterone?

Increased Na reabsorption in DT
Increased K secretion

20

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

Increased Na excretion
Afferent arteriolar vasodilation

21

What is the result of hypertonic stimulation of hypothalamic receptors?

Increased thirst
Increased AVP

22

Where is the thirst center located?

Third ventricle

23

What stimulates the thirst center?

Increased ECF osmolality
Volume depletion / Decreased EABV
Angiotensin II

24

What stimulates vasopressin / AVP / ADH?

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

25

Where is AVP formed and released?

Formed - Hypothalamus
Released - Posterior pituitary

26

Is sodium or water typically pathologic in hyponatremia?

Mostly water imbalance

27

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

Assess volume status

28

Describe the underlying mechanism of hypovolemic hyponatremia.

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

29

What are common mechanisms of sodium loss in hypovolemic hyponatremia?

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

30

What are signs of sodium depletion?

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

31

Describe the underlying mechanism of euvolemic hyponatremia.

Water retention due to altered regulation of vasopressin (SIADH)

32

What causes SIADH?

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

33

What are the diagnostic criteria for SIADH?

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

34

Describe the underlying mechanism of hypervolemic hyponatremia.

Retention of both sodium and water (greater water)

35

What are common causes of hypervolemic hyponatremia?

CHF
Hepatic cirrhosis
Nephrotic syndrome
Renal disease

36

What are symptoms of hyponatremia?

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

37

What can be caused by correcting hyponatremia too quickly?

Cerebral Demyelination Syndrome

38

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

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

39

What is the equation for water excess?

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

40

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

Dysfunction ADH
Diabetes insipidous

41

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

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

42

What are the symptoms of hypernatremia?

Lethargy
Weakness
Irritability
Seizure
Coma
Death

43

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

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