sodium Flashcards
(56 cards)
1
Q
how much body weight does water account for? How much is in ICF and ECF?
A
- 60% of body weight
- TBW = 40 L
- 2/3 is in ICF = 25 L
- 1/3 is in ECF = 15 L
2
Q
is body water less or more in obese individuals
A
- proportion of TBW per weight is less in obese adults
- body fat is essentially free of water
3
Q
of the body water that is in the extracellular fluid, how much is in interstitial fluid and plasma
A
- 3/4 = interstitial fluid
- 1/4 = plasma
4
Q
normal range of osmolality? when so symptoms occur
A
280-295 mOsm/kg
- symptoms occur if
- > 320
- < 265
5
Q
What is the equation to calculate osmolality
A
- osmolality = 2 Na + (glucose/18) + (BUN/2.8)
6
Q
where does fluid tend to shift in hyponatremic conditions? Hypernatremic?
A
- Hyponatremic: water movement from ECF -> ICF => cell swells
- hypernatremic: water movement from ICF -> ECF => cell shrinks
7
Q
isotonic changes in body fluids are largely confined to what
A
ECF
8
Q
these clinical features are consistent with what volume status
- increased thirst, decreased sweating
- decreased skin turgor and dry mucus membranes
- olifuria with increased urine concentration
- CNS depression
- weakness and muscle cramps
- decreased BP
- tachycardia
A
hypovolemia
9
Q
list causes of sequestration causing hypovolemia
A
- bowel obstruction
- peritonitis
- pancreatitis
- sepsis
10
Q
these clinical features are characteristics of what volume status
- edema
- SOB
- orthopnea, PND
- HTN, tachycardia
- ? crackles
- JVD
- hepatojugular reflux
A
hypervolemia
11
Q
what conditions can cause primary renal sodium retention
A
- ARF
- acute GN
- chronic RF
- nephrotic syndrome
- cushing’s syndrome
- liver disease
12
Q
what conditions can cause secondary renal sodium retention
A
- heart failure
- liver disease
- pregnancy
13
Q
where is ADH produced and stored
A
- produced in hypothalamus
- transported to and stored in posterior pituitary
14
Q
function of aldosterone
A
- increase renal sodium reabsorption
- increase renal potassium secretion
15
Q
homeostatic mechanisms respond to what rather than the total extracellular fluid volume
A
- effective circulating volume (intravascular volume)
- therefore conditions in which there is total ECF excess but decreased ECV continue to stimulate volume sensors to promote further salt and water retention
- ex: heart failure and liver failure
- therefore conditions in which there is total ECF excess but decreased ECV continue to stimulate volume sensors to promote further salt and water retention
16
Q
water rentention is influenced by what two things
A
- thirst
- ADH
17
Q
salt retention is influenced by
A
- renin-angiotensin system**
- ANP and catecholamines
18
Q
What are some treatment options for volume overload
A
- dietary sodium restriction
- fluid restriction (hyponatremic)
- diuretics
- avoid offending medications
- promote sodium retention: NSAIDs, corticosteroids, estrogens/androgens
19
Q
danger zone of hyponatremia (level)
A
< 125
20
Q
symptoms of hyponatremia
A
- weakness, lethargy
- anorexia, N/V
- muscle cramps, sz, coma
- death
21
Q
what is the most common electrolyte abnormality in hospitalized patients
A
hyponatremia
22
Q
What are some causes of hypervolemic hyponatremia
A
- CHF
- cirrhosis
- renal failure
- nephrotic syndrome
23
Q
What are some causes of euvolemic hyponatremia
A
- SIADH ** (most common cause)
- diuretic use
- hypothyroidism
- adrenal insufficiency
24
Q
What are some causes of hypovolemic hyponatremia with urine sodium < 10; FENa < 1%
A
-
urine Na < 10: extrarenal
- vomiting
- diarrhea
- hemorrhage
- excessive sweating
25
What are some causes of hypovolemic hyponatremia with urine sodium \>10; FENa \> 1%
* renal causes
* adrenal insufficiency
* diuretics
* salt wasting nephropathy: interstitial nephritis, PCKD
* partial urinary tract obstruction
26
if patient presents with hyponatremia, need to r/o pseudohyponatremia. What is it
* serum Na \< 135 but normal osmolality
* due to hyperlipidemia or hyperproteinemia, with decrease in aqueous portion of plasma
27
if patient presents with hyponatremia, need to r/o hyponatremia due to hyperosmolar state. What can cause this
* increased glucose in ECF causes shift of water from ICF to ECF thus lowering serum Na
28
Na drops how much for every 100mg/dl rise of plasma glucose
1.5mmole/L
29
if hyponatremia with hypovolemia is a chronic process, rapid correction may cause what
* osmotic demylination
* neurologic morbidity or mortality
* no more than 10 mEq/L increase in 24 hours
30
small cell carcinoma of lung can cause what condition that can result in hyponatremia
SIADH
31
List the etiologies of SIADH
* neuropsychiatric disorders
* malignancies
* pulmonary disorders (small cell CA lung)
* drug induced:
* carbamezepine, tricyclic antidepressants, antineoplastic agents, narcotics
32
List the 4 characteristics of SIADH
* serum osmolarity below normal
* inappropriately concentrated urine
* euvolemia
* normal renal, adrenal, and thyroid function
33
treatment of SIADH induced hyponatremia
fluid restriction
34
treatment of hypervolemic hyponatremia
1. manage underlying disease
2. sodium and water restriction
3. diuretics
35
what sodium lab value should warrant hospitalization
Na \< 125
36
overall, if patient has hypervolemic or euvolemic hyponatremia, first line of tx is
restrict fluids
37
overall, if patient has hypovolemic hyponatremia, first line of tx is
replace fluid, usually with isotonic saline
38
what is the traditional treatment of chronic hyponatremia
* demeclocycline
* induces nephrogenic diabetes insipidus
39
clinical presentation is consistent with
* thirst
* restlessness
* irritability
* AMS
* sz
* muscle twitching
* hyperreflexia
* ataxia
hypernatremia
* clinical features due to brain shrinkage secondary to increased ECF osmolality
40
what are the big picture causes of hypernatremia
* too little dietary water
* too much dietary salt
* excessive water loss from body
41
name some conditions or situations that will cause **hypovolemic hypernatremia**
* loss of solute-free water
1. renal: loop diuretics, osmotic diuresis
2. extrarenal: osmotic diarrhea, sweat
42
in response to hypernatremia, the body's homeostatic mechanism would normally
1. create thirst and increase fluid intake
2. maximally concentrate the urine to prevent further water loss
43
list the body's homeostatic priorites in order
* volume
* pH
* electrolytes
44
what is central diabetes insipidus
* impaired secretion of ADH
* see nonosmotic urinary water loss in setting of elevated serum sodium (urine is dilute when it should be concentrated)
45
what is nephrogenic diabetes insipidus
* lack of kidney response to ADH causing continued water loss even though patient is low on water
* adequate ADH is present
46
list some causes of acquired nephrogenic diabetes insipidus
* chronic renal insufficiency
* tubulointerstitial renal disease
* amyloidosis
* lithium toxicity
* hypercalcemia, hypokalemia
47
in diabetes insipidus, a urine osmolarity of what indicated impaired release or action
\<500 mOsm/kg
48
Giving vasopressin will increase urine osmolality in which form of diabetes insipidus
central DI
49
tx options for nephrogenic Diabetes insipidus
* thiazide diuretics
* amiloride (potassium sparing diuretic)
* chlorpropamide
50
Why should a patient with hypernatremia present for several days not be given water too rapidly
* could result in rapid shift of water into brain cells causing seizures or brain damage
* **central pontine myelinolysis** (osmotic demyelination)
51
how do you calculate water deficit
* water deficit = normal TBW - current TBW
* normal TBW = 0.6 x body weight in Kg
* current TBW = (normal serum Na x normal TBW / measured serum Na)
52
name some conditions or situations that will cause **hypervolemic hypernatremia**
* excess sodium and extracellular volume expansion
1. excess saline or sodium bicarb
2. exteral or parenteral feeding without free water
53
name some conditions or situations that will cause **euvolemic hypernatremia**
* loss of fluid low in sodium and potassium
1. diabetes insipidus
1. central:
1. head trauma, inflammatory, neoplastic, infiltrative
2. nephrogenic
1. congential or acquired defect of vasopressin 2 receptors
54
treatment of hypovolemic hypernatremia
* rehydrate
* isotonic solution initially then hypotonic
55
treatment of euvolemic hypernatremia
* rehydration
* D5 or 1/2 normal saline
56
treatment of hypervolemic hypernatremia
loop diuretics
