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What is normal range for serum osmolarity?
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
What must you assess when looking at Na and fluid imbalances?
Na lab values and I&O
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.
What is ADH?
"water conserving hormone" manufactured in the hypothalamus and stored in the posterior pituitary
What is aldosterone?
hormone instrumental in F&E homeostasis, mainly Na and K balance. Secreted from adrenal cortex.
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.
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)
What are the 3 causes of isonatremic dehydration?
- 1) hemorrhage
- 2) profuse diaphoresis (sweating)
- 3) GI fluid loss
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)
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
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)
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
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
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)
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.
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.
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
- -wt. loss
- Nervous system dehydration:-mental status changes (with incr. or decr. IC space)
- -muscle weakness
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
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
What are the causes of isotonic overhydration/edema?
- 1) incr. in capillary fluid hydrostatic pressure (and oncotic pull can't compensate)
- 2) decr. in interstitial fluid hydrostatic pressure
- 1) decr. in capillary oncotic pressure
- 2) incr. in interstitial oncotic pressure
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)
What is the gold standard for checking H20 balance?
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
What is the treatment for isotonic overhydration?
- -elevation of dependant part
- -tx. of underlying condition
- -daily weights
- -strict I&O
- -fluid restriction
- -reduced salt intake (PMS foods)
- Moo (dairy)
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
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
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
- -lethargy and stupor
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