Important in
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pts in ICU
Fluids/elec can make/break a patient
If give wrong fluids, pt will go down
Have to be very aware of what pt has so you give him/her what they
really need
 Thorough understanding of electrolyte metabolism
Total Body Water
o 50-70% of Total body weight
o Male 60%; female 50% of body wt
 Males have more muscle --more water
 Females more fat; hydrophobic -- no water
o
Decreases with age; elderly are stooped down due to lack of water in
the bones
 Elderly --skin not elastic anymore
 Elasticity comes from total amount of water
 In elderly, skin stays stretched or pulled
o
Highest proportion of tbw to body weight is found in infants
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Interstitial Fluid (tissues) - 15% of body wt
 Aldosterone - increases Na inside the intervascular
space; acts as magnet to attract water from interstitial
space
 Non functional component
 1-2 % of body wt
 Connective tissue water -- tendons, bones, CSF
 CSF
 Joint fluid
 Doesn't participate in fluid exchange
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Na - principal extracellular cation
Cl - anion
o
Gibbs-Donnan Equilibrium Equation
 Have semipermeable membrane (cell membrane); lots of
movement btw intra and extra cell compartment (of ions)
 To have equilibrium (homeostasis), the amt of water and
electrolytes on one side should always equal that of the other
side; body tries to maintain that balance by movement of water
and electrolytes
 Big molecules can't pass thru; selective membrane
 Hence, the majority of movement will be mostly water;
some of the electrolytes will require energy to pass
membrane; water diffuses freely to maintain number of
ions on one side and the other
 If extra cell, filled with Na, water will go out to dilute
amt of sodium outside
o
Osmotic Pressure
 Like a magnet
 The ability to attract water from one side to the other
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If pressure is greater in intra dept, it will attract water inside
the cell
If extra greater, attract water outside the cell
Depends on # particles, charges,
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290-310 in both compartments (intra/extra)
 If one becomes higher (intra), then 310 mOsm,
then water comes in from outside
 Na acts like a magnet to the water
 Anything more inside/out will attract the
water
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Total osmotic pressure
 Not only Na; it's Na and Cl plus magnesium, bicarbonate
etc
 Sum of all particles found on one side of semipermeable
membrane
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Effective Osmotic pressure
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Colloid oncotic pressure
 Pressure that attracts water from one side to the other
 Like osmotic pressure
Normal Exchange of Fluid and Electrolytes
o Know how exchange takes place
o Organs
 Kidneys; if lots of water extracellularly, you put it out (urine
output)
 Brain tells kidneys there's a lot of water
 Lungs have capacity to bring out water
 Skin --perspiration
 GIT tract or stools
Water Exchange
 2000-2500 ml consumed per day
Daily Water Losses
o Stool - 250 ml
o Urine
 800-1500 ml
 Obligatory urine loss; even if dehydrated, body will try to
create urine to try to release metabolites; if don't you go into
uremia ---problems to GI tract, to brain
o Insensible losses -- 600 ml
 Losses that you can't control
 Obligatory loss
 Not lost in the form of something that you can see (water,
liquid)
 In the form of gas --water vapor
 Comes from the skin and lungs
 Skin - 75 % (not perspiration)
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 Lungs - 25 %
Increased by hyperventilation, hypermetabolism and fever
 For every degree of fever above 38 degrees, add
200 ml to fluid daily losses
 If hyperventilating, you add another 200 ml a day
(additional losses)
Salt Gain and Loss
o Intake -- 50-90 meq/day (3-5 g) ---one teaspoon a day only
 We consume much more as people
 Main cause of hypertension in young pts (< 35) is due to salt
o Limit salt losses to < 1 meq/day
 In kidneys
 Salt-wasting- can't control amt of Na being excreted
 More than 200 meq maybe lost in urine; almost
double your intake
Sweat
o
o
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Hypotonic loss
Doesn't contain a lot of salt -- 15 meq/L
If you play sports, you sweat more; drink water to prevent cramps
 Water has little salt; you still have cramps because you lost all
the salt that water doesn't have
Body fluid changes
o Volume
 Most common problem (fluid/elec) in surgery
 Hypovolemia -- stab wound, bleeding, gun shot wound
 Volume loss -- if you have blood loss, then it's isotonic solution
compared to serum --same amt of salt, Cl, Mg as other body
fluids (isotonic loss); all you have is hypovolemia
 No exchange of water because it's volume loss
 Still same amt of particles in both compartments; just
less volume
 Exchange loss with isotonic solution
 High sodium fluid - NSS (normal saline solution)
 Normal serum Na - 135-145 meq
 Above it --hypertonic
 Below -hypotonic
 Within- isotonic
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NSS - 154 meq of Na solution
 No potassium
 hypertonic
Lactated Reiner's Solution
 130 meq of Na (135 normal); close
enough
 Potassium --4.5-5.5
 LR -- potassium is 4
 Or D5 water (no salt)
 No potassium
MN -- normal maintenance (40 meq of Na)
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14 meq of potassium
Use it on special occassions
Concentration
 If water added to fluid, concentration will change
 Example
 Person plays ball; loses water and salt; drinks purified water
(no salt); reason why he gets cramp; conc of Na goes down
and you don't replace it;
 Clinical
 Pt who is vomiting;
 Losses - potassium, Na and Cl
 Left at home; parents give him water
 Will get weaker despite water given due to loss of
electrolytes
 Brought to hospital, check for serum electrolytes;
check what's low ---usually potassium
 So you give MN -- it is high in potassium
 If low in Na, give NSS (one with highest Na)
 Case to case basis
o
Composition
 Can be altered without change
 Example
 Pt vomitting due to obstruction in the pylorus of
stomach (has a mass); ulcer; what will he be vomitting?
(water, HCl --patients lose H and Cl); initially, give pt a
replacement for hydrogen which is potassium (H is
cation and potassium is cation); H replaced by
potassium; treat what's obstructing the stomach -- inter
cell H will go out ---extracell K will go in to replace
vomitus coming out; don't give IV with acid; give
solution that contains 2 other cations --Na and K (both
cations); only be a compostitional change; instead of H
as cation, it's replaced by Na and K initially; later body
will compensate for H that was lost
 Then you treat obstruction in the stomach
o
Vol changes
 Vol deficit - loss of fluid is not water alone
 Fluid replacement - LR given
 NGT saction
 diarrhea
 Fistula drainage
 Abnormal communication btw 2 epithelial lines
 Btw small bowel and skin
 Example
 Intestinal obstruction, TB, typhoid
 There's a connection btw bowel and skin
 What comes in, goes out
 Lots of effluent coming out
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Problematic situation not only for patient, but for
surgeon
Hard to treat
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Infections
Perionitis
Intestinal obstruction
Burns
 Formula --massive losses
CNS and CVS signs
 Tachycardia --- heart rate faster due to NE resp trying to
maintain tissue perfusion (blood pressure = CO times
peripheral resistance)
 CO = heart rate x stroke volume
Tissue signs
 Sunken eyeballs, loss of skin turgor (elasticity lost)
Oliguria -- 2ndry to renal hypoperfusion --all other organs will
be sacrificied
 Vasoconstriction in renal artery due to angiotensin 2,
endothelins
Volume excess
Iatrogenic
 One situation common; nurses try to fix fluids of pt.
from 40 to 20 drops per minute; pt's will increase the
fluids by themselves
 Extended operations (6-12 hour operations)
 Anastesiologist --overestimate the losses; next
day you find crackles (water) in the lungs --congestive heart failure
Renal
 Aldosterone attracts more water
Liver cirrhosis
Congestive heart failure
 Inability for heart to pump blood effectively;
accumulates in the lungs
Concentration Changes
o Na responsible for osmolarity of the ECF comp
 Na -- main electrolyte that determines ECF osmolarity
o Serum --tonicity
o Hyponatremia
 Na < 130 meq (not significant)
 If pt who fall from 2nd floor hits his head, and serum sodium
only 130; movement of water is from extra cell dept going in;
little sodium; take out water -- amt of Na relative to water will
increase ---- water goes into brain cell ----cells will swell and
you now have edema in the brain increase in intracranial
pressure
 To get water out of cell, give NSS -- make intracell
hypertonic --now from intracell going out to extra ---to
dilute excess salt you give patient ---cells will now
o
shrink ---avoid increase intracranial pressure --avoid
brain edema
 Chronic hyponatremic state
 Asymptomatic - exhibiting/producing no symptoms until
serum falls below 120 meq/L
 Done very slowly; if done rapidly, pt goes into seizures
 After surgery, due to excessive free water from breakdown of
proteins, Na and fat
 If Na falls below 120 mEq, then you perform dialysis
Hypernatremia
 Dry sticky mucous membrane
 Body temp generally elevated (almost fatal in many pts)
 40-42 degree
Mixed Volume Concentration
o Dialysis
 Not done at a point when pt goes into seizures
 Done when you see a persistant rise in serum Na; or downfall
 Act before pt becomes asymptomatic
High Output Renal Failure
o Surgeons worry if urine output goes down (below 30 ml per hour)
 If happens, give more fluids, meds
 If you have pt who shows only signs and symp of metab
 Called high output renal failure
 Uremia occurs without…
 There's a rise in creatinine --metabolites not being
excreted
o Renal response
 Milder form of renal insufficiency
o Seen in a state of diabetes insipitus
 Lots of renal output; accumulation of metabolites (not flushed
out)
o Treatment is dialysis
Formula to compute for sodium deficit of 70 kg male with 110 meq/L Na level
o 0.6 x BW (Body weight) (140 - Na)
o 0.6 x 70 kg (140 -110)
 = 42 (.30)
 1260 meq
Formula to compute for potassium deficit for 60 kg female with 2 meq/l K level
o 0.5 x Bw (4 - K)
= 0.5 x 60 kg (4-2)
= 30 (2)