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What is normal range for serum osmolarity?
285-295 mOsm/L
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What are the 3 factors that constitute serum osmolarity and what are their normal ranges?
- 1) Na (has biggest effect on osmolarity) 135-145
- 2) glucose (= a big molecule, has a lot of pull) 70-100
- 3) BUN 10-20
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What must you assess when looking at Na and fluid imbalances?
Na lab values and I&O
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Define isotonic FVD/ isonatremic dehydration.
Proportionately = loss of water and Na. There is no osmotic pull from ICF to ECF. The plasma voulume is greatly reduced.
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What is ADH?
"water conserving hormone" manufactured in the hypothalamus and stored in the posterior pituitary
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What is aldosterone?
hormone instrumental in F&E homeostasis, mainly Na and K balance. Secreted from adrenal cortex.
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What are the 2 ways your body compensates for isotonic/isonatremic dehydration?
1) The decr. in intravascular pressure leads to an incr. in colloidal osmotic pressure which moves fluid from the intersititial to intravascular spaces.
- Hormones secreted:
- 2) The decr. in kidney flow (isotonic dehydration= reduced plasma volume) causes aldosterone release which causes Na retention and K loss. ADH is also released causing renal retention of water (helps bc you're dehydrated)
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What are the 3 causes of isonatremic dehydration?
- 1) hemorrhage
- 2) profuse diaphoresis (sweating)
- 3) GI fluid loss
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What are the early s/sx of isonatremic dehydration?
- -postural tachycardia (when HR incr. from laying flat to sitting or standing)
- -postural hypotension (when BP drops >20 mmHg systolic and >10 mmHg diastolic over a 2-3 min period)
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What are the late s/sx of isonatremic dehydration?
- -weak pulse
- -tachypnea (pt. breathing quickly bc FVD causs less plsma volume = less circulating O2)
- -flat neck veins supine
- -slow vein filing in hands
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What are the s/sx due to decr. renal perfusion as a result of isonatremic dehydration?
- - Urine <20-40 ml/hr
- - incr. BUN (dehydration causes incr. BUN bc it's reabsorbed
- - incr. Hct (if no hemorrhage, due to heme concentration)
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What are some other s/sx of isonatremic dehydration as a result of decr. interstitial fluid?
- -thirst at 1-2% loss
- - eyes sunken
- -soft eyeballs
- -dry mucous membranes
- -weight loss
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Whatis the treatment for isonatremic dehydration?
- Replace both fluids and electrolytes.1) oral intake of salty foods (e.g. Bullion)
- 2) Fluid expanders: IV fluids which stay in the vascular space and therefore incr. blood volume and restore circulation there
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What are examples of Fluid volume expanders used to treat isonatremic dehydration?
- 1) Normal Saline- NS (0.9% NaCl)
- 2) Ringers Lactate- RL (has buffers like K, HCO3, Ca...like gatoratde of IV fluids)
- 3) Albumin (used for oncotic pull properties to help pull fluid back into vascular space, incr. colloid osmotic pressure in edematous cases)
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Define hypertonic FVD/hypernatremic dehydration.
- Water loss greater than Na loss. Na greater than 145 mEq/L.
- ECF and ICF volumes are both decr.
- Incr. ECF osmolarity (soulutes) results in a shift of fluid from the ICF to the ECF causing severe cellular dehydration.
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What are the causes of hypernatremic dehydration?
- 1) soulte taken in w/o adequate water (tube feedings of high concentration) Kidney wants to remove high solutes via osmotic diuresis. (pt. on tube feedings may need a H2O bolus to make up for high concentration feedings)
- 2) Pts w/ decr. LOC and are unaware they are thirsty.
- 3) Diabetics w/ high blood sugar having osmotic diuresis.
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What are the s/sx of hypernatremic dehydration (in addition to the s/sx of isonatremic dehydration)?
- Skin and membrane dehydration:
- -dry skin (tenting skin)
- -tongue furrows
- -dysphagia
- -wt. loss
- -thirst
- Nervous system dehydration:-mental status changes (with incr. or decr. IC space)
- -muscle weakness
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What is the treatment for hypernatremic dehydration?
- 1) water taken in orally if possible
- 2) IV D5W or D5 w/ 0.2% NaCl (it's not standard to hang D5W, suspect that pt. is in hypernatremic state, check labs)
- 3) additional water w/ tube feedings
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Define Isotonic fluid volume excess.
- -aka hypervolemia
- -excessive fluid in the ECF compartment (plasma)
- -serum osmolarity remains normal despite overhydration
- -no shifting of fluids between ECF and ICF compartments
- -isotonic circulatory overload can lead to edema
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What are the causes of isotonic overhydration/edema?
- PUSH:
- 1) incr. in capillary fluid hydrostatic pressure (and oncotic pull can't compensate)
- 2) decr. in interstitial fluid hydrostatic pressure
- PULL:
- 1) decr. in capillary oncotic pressure
- 2) incr. in interstitial oncotic pressure
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What are the causes of isotonic overhydration/edema?
- 1) heart failure- leads to decr. excretion of H2O and Na (heart can't pump correctly, fluid backs up, can't excrete)
- 2) renal failure- leads to decr. excretion of H20 and Na
- 3) longterm cortiocosteroid therapy results in H20 and Na retention (i.e. prednisone is cousins w/ aldosterone and causes Na retention therefore H20 retention and pt. will gain wt.)
- 4) poorly controlled IV therapy
- 5) High aldosterone levels (stress response, adrenal dysfunction)
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What is the gold standard for checking H20 balance?
weights
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What are the s/sx of isonatremic overhydration?
- - wt. gain over 2.2 lbs/24 hr = 1Kg = 1L gain
- -diuresis (attempting to remove excess fluid, if kidneys are normal)
- -jugular vein distention (JVD)
- -tachycardia (bounding) to push more fluid
- -lung sounds = fine crackles (bc capillaries in lungs are overhydrated)
- late signs:
- -s/s of pulmonary edema
- -peripheral edema: pitting edema, approx. 8lbs wt. gain
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What is the treatment for isotonic overhydration?
- -elevation of dependant part
- -tx. of underlying condition
- -diuretics
- -daily weights
- -strict I&O
- -fluid restriction
- -reduced salt intake (PMS foods)
- Processed
- Moo (dairy)
- Salty
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Define hypotonic overhydration/water intoxication.
- -the excess fluid is hypotonic to normal body fluids (usually accompanied by hyponatremia, Na less than 135)
- -osmolarity of the ECF decr., and hydrostatic pressure incr. Fluid moves into the intracellular space bc of decr. vascular osmotic pressure, and all body fluid compartments expand
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What are the causes of hypotonic overhydration?
- 1) incr. water w/o incr. Na or other electrolytes leads to cellular swelling:
- -tap water enemas given repeatedly (pulls out Na)
- -Contiunous bladder irrigation w/ sterile water (careful w/ men w/ prostate cancer to flush blood clots)
- -high intake of Na free fluids IV or PO (if pt. is treated w/ D5 w/ water for hypernatremia and then bag keeps hung eventhough pt. is hyponatremic
- 2) syndrome of inappropriate antidiuretic hormone (SIADH)= excess release of ADH (water conserving hormone)
- 3) replacement of isotonic fluid loss with hypotonic fluids
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What are the s/sx of hypotonic overhydration?
- -weight gain-GI dysfunction -anorexia, cramping, N/V
- -neurological (brain swelling): cerebral cells absorb free water more readily that other cells, thus are very sensitive to hpotonic ECF state
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HA/depression/confusion - -lethargy and stupor
- -convulsions/coma
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What is the treatment for hypotonic overhydration?
- -treat underlying condition
- -diuretics (pt. will void H20 but be careful bc pt also voiding Na, we need to give Na supplements)
- -fluid restriction
- -Na supplements (IV)
- -daily wt/strict I&O
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