Fluid Replacement Flashcards
Body water compostition
Infants (75-85%), adult men (50-60%), adult females (45-55%)
Fluid type composition
intracellular (2/3), extracellular (1/3)- interstitial (3/4), Plasma (1/4)
Maintenance requirements
Holliday-segar calculation- 100 mL/kg first 10 kg, 50 ml/kg first 10 kg, 20 ml/kg after; or estimate ~30 mL/kg
Two major types of fluid
crystalloids- normal saline (.9%NaCl), half normal saline (.45% NaCl), lactated ringers, Dextrose 5% in H2O; Colloid- albumin, hetastarch, plasmanate
Crystalloids
provide water and sodium to maintain the osmotic gradient between extravascular and intravascular spaces
Normal saline
.9 % NaCl, isotonic, used most common for fluid replacement, resuscitation in septic pt, can be used to correct Na or Cl deficiencies
1/2 Normal saline
.45% NaCl hypotonic, use for maintenance fluids for hypernatremic pt
Lactate ringers
approximates human plasma regarding electrolyte concentration, used for replacement of blood loss, mainstay in laboring women
D5W
used for free water replacement, not a resuscitative fluid, various concentrations; 5g dextrose in 100 ml, given in liters so there is 50 g in dose
NaCl 3%
hypertonic saline, rarely used for hypernatremia, inc ICP, dangerous! if not used appropriately, monitor very closely, give small volumes
Never give what as IV fluids
sterile H2O, this is LETHAL
Colloids
used to increase plasma oncotic pressure and move fluid from interstitial compartment to plasma compartment, use selectively for volume expansion during extreme situations like hemorrhagic shock
Colloid options
albumin, blood, hetastarch
Sodium
normal 135-145 mEq/L, extracellular cation needed to maintain cellular integrity and osmolar gradient to maintain fluid homeostasis throughout the different fluid compartments
Hyponatremia
most commonly encountered electrolyte disturbance in hospitalized pts, associated w/ significant morbidity and mortality
pseudohyponatremia
extreme elevations of lipid or proteins, osmolality is number of particles per liter H2O, measured serum osmolality is not sig affected, calc osmalitlity will be low
hypertonic hyponatremia
RARE, serum [Na] falls by 1.6 mEq/l for each 100 mg/dL incremental increase in blood glucose; by correcting glucose you will correct hyponatremia
hypotonic hyponatremia
more than 90% of cases, access ECF volume; hypovolemic, euvolemic, hypervolemic
hypovolemic hyponatremia
dehydration, caused by diuretics and salt losing nephropathy, treat w/ IV fluids, hypertonic NaCl in symptomatic pts or isotonic NaCl in asymptomatic
SIADH
syndrome of inappropriate antidiuretic hormone, water intake exceeds the capacity of the kidneys to excrete water, inability to concentrate urine
Causes of SIADH
tumors, CNS disorders, head trauma, stroke, meningitis, pituitary surgery, DRUGS
Drugs that induce SIADH
Despressin, oxytocin, carbamazepine, antipsychotics, TCAs, cyclophosphamides, chemo, NSAIDs, Morphine
Isovolemic hyponatremia
will likely appear as euvolemic, slight increase in ECF, caused by glucocorticoid deficiency, hypothyroidism, psychogenic polydipsia, SIADH
Treatment of isovolemic hyponatremia
furosemide +3% NaCL in symptomatic pts, isotonic fluids in asymptomatic pts, fluid restrictions (if correction needed quickly)
Hypervolemic hyponatremia
total body water increased, seen in CHF, liver failure, renal failure, nephrotic syndromes
Treatment of hypervolemic hyponatremia
furosemide and judicious use of 3% NaCl in symptomatic pts, furosemide in asymptomatic
When treating hyponatremia, NEVER…
Correct faster than .5 mEq/L/hr or 12 mEq/L/day, it can cause osmotic demylenation
Vasopressin receptor antagonists
Tolvaptan (Samsca), Conivaptan (Vaprisol)
Tolvaptan (Samsca)
only available PO, given 10-60 mg daily, $$$
Conivaptan (Vaprisol)
only available IV, CI, 20 mg IV load, then 20 mg infused over 24 hrs, $$$
MOA of vasopressin receptor antagonists
promotes excretion of free water w/o loss of serum electrolytes resulting in net fluid loss, increased urine output, decreased urine osmoloality and restoration or normal serum Na levels
Safety concerns w/ vasopressin receptor antagonists
risk of correcting too fast, must be initiated in hospital, must lift fluid restriction, most places only allow nephrologist to use
Hypervolemic hypernatremia
caused by excessive hypertonic saline resuscitation, NaCHO3 administration, excessive table salt
Treating hypervolemic hypernatremia
stop hypertonic fluids and give diuretics
hypovolemic hypernatremia
treatment by restoring hemodynamic status first, can replace with NS even though the pt is hypernatremic
Potassium
hypo and hyperkalemia associated w/ fatal arrythmias, each 1 mEq/L decrease in K
factors affecting serum [K]
kidneys, arterial pH, insulin, B agonists, Na/K pumps
hypokalemia caused by
diuretics, vomiting, NG drainage, magnesium depletion
Goal for replacement in hypokalemia
4mEq/L, oral route preferred, less risk of overshoot; K= 3-3.9 mEq/L; 10 mEq K supplement will increase [K] by .1 mEq/L; K
It is impossible to correct K if
mag is low, so correct mag first, then address K
IV KCl
preferred if pt symptomatic or NPO, rate IV replacement limited if pt has only a peripheral IV (10 mEq/hr max), central IV can run at 20 mEq/hr, Dangerous!
Hypokalemia w/ 3.2 mEq/L, not symptomatic
add 30 mEq KCl to IVF, or give 40 mEq PO q6hrs x3
hypokalemia w/ 2.7 mEq/L and sympomatic
give KCl 40 mEq IV q4h x 3, and KCl liquid 40 mEQ PO x1 dose bolus
Hyperkalemia
more consequential and more rare than hypokalemia, mild 5.5-6 mEq/L. mod 6-6.9 mEq/L, severe >7; some may not have symptoms if really high, still treat!
Management of hyperkalemia
calcium gluconate (1 gm IVPx1 dose), Humulin R (10 units IVPx1), sodium bicarb 50 mEq IVPx1, albuterol (10 mg continuous neb), hemodialysis (4 hr session), sodium polystyrene (Kayexalate, 30 gm POx1); can do combo
which management of hyperkalemia only stabilizes pericardium, inc threshold
calcium gluconate
Which management of hyperkalemia has to be given w/ dextrose and works quickly?
Humulin R
which management of hyperkalemia works quickly by driving K back into the cells
sodium bicarb and albuterol
which management of hyperkalemia has fastest onset
hemodialysis
which management of hyperkalemia has slower onset, works by a resin exchange of Na for K
sodium polystyrene
Magnesium
needed for stabilizing macromolecule structures such as DNA/RNA and related to Ca and K metabolism; regulated by intake and kidney excretion
Hypomagnesemia
associated w/ disorders of the GI tract or kidneys, decreased intestinal absorption, can be caused by chronic EtOH, amphotericin, diuretics, aminoglycosides
Treatment of hypomagnesemia
asymptomatic- PO, milk of mag, or mag ox, will cause diarrhea; symptomatic- IV mag sulfate, 1 gram Mag sulfate= 8 gEq magnesium, infuse each gram over 1 hour, exceeding this results in renal excretion (level 1-2 give .5 mEq/kg, if
Calcium, organs involved w/ metabolism
bone, kidneys, intestines
hypocalcemia
correct for albumin, accounts for protein binding, if low albumin likely have norm Ca; if mag low fix that first
hypocalcemia treatment
100-300 mg Ca IV over 10 mins, 1 g CaCl or 2-3 g Calcium gluconate
Difference in CaCl and gluconate
CaCl contains more Ca, harder on veins; CaGL contains less Ca, easier on veins
Hypercalcemia
seen in CA pts and hyperparathyroidism, caused by dec renal elimination, inc bone resorption, inc GI absorption
Hypercalcemia tx
calcitonin, most common, loop diuretic, short term (lasix inc urinary excretion), bisphosphonates- pamidronate (Aredia-IV infusion over several hours, short term only, very effective)
Phosphorus
critical for protein, fat and carb metabolism, modulates O2 carrying capacity of hemoglobin
hypophoshatemia
1mmol=1.33 mEq sodium and 1.47 Eq potassium, replace orally or enteraly w/ neutra phos packet or Kphos tab q6-8h, also NaPhos/Kphos parenterally
Hypophoshatemia levels/treatment
mild (2.3-3 mg/dL)- .32 mM/kg q4-6h; mod (1.6-2.2 mg/dL)- .64 mM/kG q4-6h; severe (
