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Clin Lab Med > Electrolyte > Flashcards

Electrolyte Flashcards

1
Q

Normal Na range

A

135-145 mEq/L

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2
Q

normal K range

A

3.5-5 mEq/L

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3
Q

normal Cl

A

98-106 mEq/L

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4
Q

normal CO2 “bicarb”

A

22-32 mEq/L

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5
Q

electrolyte panel CPT code

A

80051

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6
Q

what percent of Body weight is body water

A

60%

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7
Q

describe body water ie ICF and ECF composition

A

ICF: 2/3 body water
ECF: 1/3 body water - divided into interstitial (3/4 of ECF) and plasma (1/4 ECF)

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8
Q

What cations/anions are in ICF

A
  • ICF 2/3 body water
    anion: Protein, Phosphate
    cation: Na+, Mg2+, K+
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9
Q

What cations/anions are in the interstitial fluid of ECF

A
  • ECF 1/3 body water, interstitial = 3/4 of ECF*
    anion: HCO3-, Cl-
    cation: Na+
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10
Q

What cation/anions are in the plasma of ECF (*plasma has)

A
  • ECF 1/3 body water, plasma 1/4 ECF*
    anions: Protein, HCO3-, Cl-
    cation: Na+
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11
Q

What is the association be body water and obesity

A

body fat is free of water, so less total body water per weight ratio in obese
*inflants have more TBW and more in ECF space

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12
Q

define osmolality, normal range? (*note osmolality = tonicity)

A

solute or particle concentration of a fluid
normal range = 280-295 mOsm/kg
sx if >320 or <265

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13
Q

How do you calculate osmolality

A

2NA +GLU/18 + BUN/2.8

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14
Q

what are other osmotically active substances besides Na, GLU, BUN

A

mannitol and various proteins

ethanol, methanol, ethylene glycol (aka antifreeze)

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15
Q

what happens in isotonic fluid excess

A

increase in ECF volume/space; no shift into ICF bc isotonic

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16
Q

what happens in isotonic fluid deficit

A

decrease in volume of water in ECF space; no shifting out of ICF bc isotonic

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17
Q

What is hyponatremia and what happens in cell

A

Na deficit in ECF less than 135mEq/L (due to loss of sodium or gain in water). Results in water movement from extracellular to intracellular thus CELL SWELLS

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18
Q

What is hypernatremia and what happens in cell

A

Na excess in ECF (>145 mEq/L) due to gain of sodium or loss of water. Results in water movement from intracellular to extracellular space. CELL SHRINKS

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19
Q

clinical features of normovolemia

A

well being and alert, normal for vital, skin turgor, thirst, sweating and urination

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20
Q

clinical features hypovolemia

A

increased thirst, decrease sweating and skin turgor, dry mucus membrane, oliguria, CNS depression, weakness, cramps, decreased BP, increase pulse

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21
Q

clinical features hypervolemia

A

edema, SOB, orthopnea, PND, HTN, tachycardia, possible crackles on pulm exam, JCD, hepatojugular reflux

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22
Q

causes of Hypervolemia (increased total ECF): primary renal sodium retention (increased ECV)

A

acute or chronic renal failure, glomerulonephritis, nephrotic syndrome, cushings syndrome, primary hyperaldosteronism, liver disease

general: Increased ECF and increased ECV

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23
Q

causes of volume excess (increased total ECF): secondary renal sodium retention (decreased ECV)

A

HF, liver dz, nephrotic syndrome, pregnancy

General: increased ECF BUT decreased ECV

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24
Q

significance of ECV

A

aka intravascular volume; this is what homeostatic mechanisms respond to, NOT total ECF volume… thus can have ECF excess but low ECV = volume sensors promote salt/water retention (as in HF, Liver failure)

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25
how to determine ECV
right heart cath to determine PCW (pulmonary capillar wedge) pressure aka CVP (central venous pressure) JVD estimate less accurate
26
Decreased ECV signals afferent sensors to...
* dec ANP (atrial natriuretic peptide) --> Na retention * increase catecholamines --> Na retention * increase renin -->inc angiotensin, aldosterone --> Na retention and incr thirst --> water retention * increase thirst and ADH --> water retention note: ADH = vasopressin
27
decreased ECV alters what physical factors in order to what..?
GFR, RBF, peritubular starling forces --> Na retention
28
What is more important to maintain.. blood volume or osmotic changes
loss of blood volume takes precedence over osmotic changes
29
where is ADH produced and where does it travel
decreased blood volume signals hypothalamus --> posterior pituitary --> blood --> reabsorption of water by kidney
30
what effect does aldosterone have (RAS)
increases renal Na REABSORPTION | increases renal K SECRETION
31
what is renal activity EXCRETION
sum of the processes of filtration, reabosrption and secretion in nephron
32
What is a normal saline solution
0.9% NaCL 308 mOsm/soln kg 154 Na, 154 Cl
33
What is serum sodium in regards to body distribution?
principle cation in ECF (90-95%) total body sodium located here
34
Hypernatremia lab indication and features
>145 mEq/L serum sodium clinical features due to brain shrinkage secondary to increased ECF osmolality - thirst, dehydration, alt mental status/weakness, tics/termors, focal neuro deficits, seizures or coma *condition gradual onset = less dramatic sx
35
etiology of Hypernatremia
* GI loss (common in elderly, infants w/ diarrhea) * skin loss: sweating, fever etc. * renal loss: OSMOTIC DIURESIS due to HYPERGLYCEMIA in DM pt --> obligatory water loss --> see glucosuria and hyperglycemia (can cause Hyperosmolar nonketotic coma) * drug related: diuretics, lithium (induces nephrogenic diabetes insipidus)
36
Hypernatremia can be... (volume)
Hypervolemic, euvolemic, hypovolemic
37
Hypervolemic hypernatremia causes
1. admin of hypertonic saline or sodium bicarb 2. Hypertonic dialysis 3. hypertonic feedings 4. primary hyperaldosteronism 5. cushing syndrome
38
Euvolemic Hypernatremia causes
1. Diabetes inspidus (central or nephrogenic) (may be hypovolemic) 2. hypodipsia 3. insensible dermal and skin losses (if hypodipsic)
39
causes of Hypovolemic Hypernatremia
1. GI losses 2. Renal losses (diuretics, osmotic diuresis,renal tubular acidosis, diabetes insipidus) 3. skin/respiratory losses 4. Sequestration without external fluid loss (intestinal obstrution, rhabdomyolysis)
40
Hypovolemia vs hypervolemia homeostatic response
hypovolemia sensed by baroreceptors --> increase ADH hypervolemia sensed by osmoreceptors --> decreased ADH secretion *overall ECV volume overrides osmolarity
41
how does the body normally respond to hypernatremia
1. create thirst and increase fluid intake | 2. Maximally concentrate urine to prevent further water loss
42
what is most important for body to maintain... volume, electrolyes or pH. Put in order most important to least
Volume, pH, then electrolytes
43
What is Diabetes Insipidus
nonosmotic urinary water loss despite elevated serum sodium: urine dilute when should be concentrated bc CD impermeable to water so water is not reabsorbed
44
Central vs nephrogenic diabetes insipidus
central is due to impaired ADH secretion | nephrogenic is a lack of kidney response to ADH.. water loss even lot pt low on water and adequate ADH is present
45
what tx for central diabetes insipidus
dAVP nasal spray (ADH analogue) bc central neurogenic DM is due to inadequate ADH secretion
46
Hx of Nephrogenic DIabetes Insipidus
* may be genetic or aquired * acquired = chronic renal insufficiency, tubulointerstitial dz, amyloidosis, lithium toxicity, hypercalcemia or hypokalemia
47
tx for nephrogenic DI
varied. . goal is to increase renal responsiveness to ADH - thiazide diuretics - amiloride (K sparing diuretic) - chlorpropamide (antidiabetic oral agent) - NSAIDS (incl indomethacin)
48
Tx Hypernatremia
- if severe, hospitalization - stop water loss - replace water deficit (orally, NG tube, or IV of hypotonic fluid) *do not replace too rapidly or rapid shift into brain causing seizure/brain damage/ central pontine myelinolysis with quadriplegia and coma it is OK to correct more rapidly if hypernatremia developed recently; otherwise correct over 48-72 hr
49
What is hyponatremia, what is the danger zone and what are sx?
disorder due to serum sodium below 135 mEq/L danger zone if Na below 125 sx: weakness, lethargy, somnolence, anorexia N/V, muscle cramp, seizures, coma, death
50
what is the most common electrolyte abnormality in hospitalized patients? BOARD Question!!!!
HYPONATREMIA is the most common electrolyte abnormality in hospitalized patients
51
what are the risks of chronic hyponatremia
serum sodium 120-132 | 9X higher risk of falls due to gait and balance problems (improves if hyponatremia corrected)
52
What are the 3 main categories of hyponatremia? subcategories?
1. hyponatremia hyperosmolar (hyperglycemia) 2. Hyponatremia hypoosmolar (then broken down by hypervolemic, Euvolemic, or Hypovolemic) 3. Hyponatremia with iso-osmolar (pseudohyponatremia due to hyperlipid or hyperpro)
53
What 2 situations do you need to r/o with hyponatremia (think hyperosmolar and iso-osmolar)
r/o pseudohyponatremia (serum Na <135 but normal osmolarity due to hyperlipidemia or hyperproteinemia) r/o hyponatremia due to hyperglycemia) - increaed glu in ECF causes shift of water from ICF to ECF. Na drops 1.5 mmole/L for every 100mg/dl rise in plasma glucose
54
What are causes of hyperosmolar hyponatremia?
hyperglycemia, hypertonic mannitol | *low in sodium but high in other osmolar substances
55
What conditions result in iso-osmolar Hyponatremia | *low Na but normal osmolality
1. pseudohyponatremia (hyperlipid or hyperproteinemia) | 2. Post transurethral hyster/prostatectomy
56
What are the different categories of hypoosmolar hyponatremia and their causes **think volume differences
1. Hypervolemia/^ECF: can be dec ECV (renal failure) OR incr ECV (HF, liver dz, sepsis, prenancy, anaphylaxis) 2. Euvolemic: (SIADH, drugs, hypothyroid, primary polydipsia, glucocorticoid def, poor osmolar intake, positive pressure ventilation) 3. Hypovolemic: (decreased ECF, decreased ECV) - diuretics, diabetes insipidus, osmotic diuresis, GI losses, sequestration ie rhabdo...)
57
what is Hyponatremia with Hypervolemia and what clinical findings are there
* fluid overload condition: CHF, nephrotic syndrome, renal failure, hepatic dz * clinical findings: pedal edema, pulmonary crackles, JVD; anemia; other signs heart/lever/renal disease
58
what findings are there for hyponatremia with euvolemia **BOARD... ddx?
NO evidence of fluid overload, volume depletion or dehydration ``` ddx: Hypothyroidism SIADH (most common cause euvolemic hyponatremia; impaired water excretion) Diuretic use (w/o vol depletion) Adrenal insufficiency ```
59
what are the etiologies and 4 characteristics of SIADH (most common cause of euvolemic hyponatremia)
Etiology: neuropsychiatric disorders, malignancy, pulm disorders (small cell lung CA), drug induced (carbamazepine, TCA, narcotic) Characteristics: 1. low serum osmolality below 275 2. Inappropriately concentrated urine 3. euvolemia (clinically) 4. normal renal, adrenal, thyroid function
60
How should you treat SIADH? (the most common cause of euvolemic hyponatremia)
determine underlying cause: CT/MRI heck to check CNS disorder and CXR to check lung tumor/infection tx dependent on cause
61
What can cause hyponatremia with hypovolemia and what clinical characteristic is manifest with hyponatremia with hypovolemia?
* Due to renal or nonrenal causes (get rid of water and salt) a) renal: diuretics; osmotic diuresis, addisons dz b) Nonrenal: external GI (vomiting, diarrhea, fistula); internal GI (Pancreatitis, peritonitis, internal fistula results in clinical characteristics of dehydration
62
What are the various txs of hyponatremia *** know this!
a) symptomatic or Na <125: hospitalize b) tx underlying cause * If hypervolemic or euvolemic: restrict fluid * if hypovolemic, replace fluid usually with NS (.9%) - cautiously to avoid CNS damage ie central pontine myelinolysis (demylination c) traditional tx CHRONIC hyponatremia: Declomycin which induces nephrogenic DI (decreases kidney response to ADH) d) new class: v2 receptor antagonists conivaptan or tolvaptan
63
Tx of hyponatremia continued (NEW Tx)
``` New class of drugs for chronic hyponatremia: vasopressin/ADH antagonists "aquaretics" or "V2 receptor antagonists" *conivaptan, tolvaptan ```

Clin Lab Med (6 decks)

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