The document discusses the importance of fluid and electrolyte balance in maintaining homeostasis, detailing the composition and distribution of body fluids. It categorizes fluids into intracellular and extracellular compartments, explaining types of solutions (isotonic, hypertonic, hypotonic) and their clinical applications in surgery. Additionally, it covers fluid types such as crystalloids and colloids, including their osmolarity and electrolyte composition.

1. Normal Body Fluids and
Electrolytes
with fluids used in surgery
Dr. Sunil K S Gaur (MS)
Senior Resident, Surgery,
HIMS, Varanasi

2. Introduction
Fluid and electrolyte balance is a dynamic
process that is crucial for life.
It plays an important role in homeostasis.
Imbalance may result from manyfactors,
and it is associated with the illness

3. Bodyfluids/Water
• Provide transportation of nutrients to cells
• Carry waste products away from cells
• Provide the environment for electrolyte
chemical reactions to occur
• Aids in regulation of body temperature
• Maintain blood volume
• Solvent for minerals, vitamins and glucose

4. Fluid compartment of thebody
Total body fluid
60% of total body weight
Extracellular fluid
Total 20% of body weight
Intracellular fluid
Total 40% of total body
weight
Interstitial fluid
15% of total body weight
Plasma
5% of total body weight
Transcellular
fluid
Fluid in
potential
spaces
Fluid in GIT
and
respiratory
tract
Intraocula
r fluid
CSF
Pleural cavity
Pericardial
cavity

6. Total body water varies with…
a) Age
b) Gender
c) Bodyfat

7. Intracellular fluid
 60% of bodyfluid
 Rich in :
 Potassium
 Magnesium
 proteins

8. Extracellular fluid
 40 %of bodyfluid
 Rich in :
 Sodium
 Chloride
 Bicarbonate
 Consists of:
o Interstitial fluid :between cells,low in protein
o Intravascularfluid(Plasma) : High in protein
o Transcellular fluids: CSF,intraocularfluids, serous
membranes (thirdspace)

9.  Fluid compartments are separated by
membranes that are freely permeable to water
but not to solutes (semi-permeable).
 Movement of fluids due to:
Hydrostatic pressure
Osmotic pressure
Movement of particles due to:
Diffusion – movement of particles
down a concentration gradient.
Active transport – movement of
particles up a concentration gradient ;
requires energy

10. 9

11. Fluid
balance

12. Balance
12
 Neutral balance: input =output
 Positive balance: input>output
 Negative balance: input<output

13. Solutes – dissolved
particles
15
 Electrolytes –chargedparticles
 Cations –positivelycharged ions
Na+, K+, Ca++,H+
 Anions –negativelycharged ions
Cl-, HCO3
-,PO4
3-
 Non-electrolytes -Uncharged
Proteins, urea, glucose,O2,CO2

14. Definitions
• Solute: a particle, usually a salt
• Solvent: liquid, usually water
• Solution: solute and solvent mixed
together

15. 16
Definitions
 MW (Molecular Weight) =sum of theweights
of atoms in a molecule
 mEq(milliequivalents) =MW (in mg)/ valence
 mOsm (milliosmoles) =number of particles in
asolution

16. Definitions
• Osmolarity: the concentration of a
solution expressed as the total
number of solute particles per litre.
• Osmolality: the concentration of a
solution expressed as the total
number of solute particles per
kilogram
• Tonicity: is a measure of the effective
osmotic pressure gradient, as defined
by the water potential of two solutions
separated by a semipermeable
membrane

17. Solutes determine the tonicity of a solution.
Solution canbe:
• Hypotonic: low solute, high solvent; osmolality is
<275mmol/kg
• Isotonic: equal solute and solvent ratio; osmolality
275-295mmol/kg
• Hypertonic: high solute, low solvent; osmolality is
>295mmol/kg

18. Isotonic
• Iso: same/equal
• Tonic: concentration of a solution
• The cell has the same concentration on the
inside and outside.
• Isotonic solutions are used to increase
the extracellular fluid volume in
oblood loss
osurgery
odehydration

19. Isotonicfluids
1) 0.9% NaCl (Normal Saline)
2) 5% dextrose in water (D5W) (In the bag)
also used as a hypotonic solution after it is administered
because the body absorbs the dextrose BUT it is
considered isotonic
3) 5% Dextrose in 0.225% saline (D5W1/4NS)
4) Lactated Ringer’s

21. Hypertonic
• Hyper: excessive
• Tonic: concentration of a solution
• The cell has an excessive amount of solute extra-
cellularly and osmosis is causing water to rush out
of the cell which will cause the cell to shrink.
• Hypertonic solutions are used very cautiously.
(most likely to be given in the ICU due to quickly
arising side effects of pulmonary edema/fluid over
load).
• In addition, it is preferred to give hypertonic
solutions
via a central line due to the hypertonic solution
being vesicant on the veins and the risk of

22. Hypertonicsolutions
1) 3% Saline
2) 5% Saline
3) 10% Dextrose in Water
(D10W)
4) 5% Dextrose in 0.9% Saline
5) 5% Dextrose in 0.45% saline
6) 5% Dextrose in Lactated
Ringer’s

23. Cell in a
hypertonic
solution

24. Hypotonic
• Hypo: ”under/beneath”
• Tonic: concentration of a solution
• The cell has a low amount of solute extracellularly
and fluid shifts inside the cell to get everything
back to normal via osmosis. This will cause cell
swelling which can cause the cell to burst or lyses.
• Hypotonic solutions are used when the
cell is dehydrated and fluids need to be
put back intracellularly.
o diabetic ketoacidosis (DKA)
o hyperosmolar hyperglycemia

25. Hypotonicsolutions
1) D5W (in the body)
2) 0.25% NaCl
3) 0.45% NaCl (half normal
saline)
4) 2.5% Dextrose

26. Cell in a
hypotonic
solution

27. Fluidtypes: Crystalloids andcolloids
3ml of crystalloids = 1ml of colloid
Crystalloids
1. Molecular wt<8000 daltons
2.Replaces mainly extracellularvolume
E.g.
a. Normal saline.
b. 5%dextrose
c. Ringer’s lactate
3.Shorter intravascular half-life
4. In trauma it stabilizes the haemodynamics in 3hrs

28. Colloids
1. Molecular wt>8000 daltons
2. Replace intravascular volume
E.g.
a. Serumalbumin.
b. Humanplasma.
c. Synthetic plasmaexpanders.i.
ii. Gelatin solution
Dextrans
3.Longer intravascular halflife
4. In trauma it stabilizes the haemodynamics in 2 hrs

29. Electrolyte composition &
osmolarity of common crystalloids
Intravenous
fluid
(crystalloids)
Osmolari
ty
(mOsm/L
)
Na+
(mmol/L
)
Cl-
(mmol/L
)
Components
Normal saline (0.9% NaCl) 306 154 154 NaCl
5% dextrose in aqua 278 - - Glucose
5% dextrose in NS 560 154 154 Glucose., NaCl
0.45% NaCl 153 77 77 NaCl
%5 dextrose in 0.45%
NaCl
406 77 77 Glucose, NaCl
5% dextrose in 0.25%
NaCl
320 34 34 Glucose, NaCl
3% NaCl 1026 513 513 NaCl
Ringer’s lactate 273 130 130 NaCl, K+,
Ca++,
lactate

30. Composition of Common
Colloids

31. 0.9% NaCl (normalsaline)
0.25%NaCl
0.45%NaCl
2.5%dextrose
Lactated Ringer'ssolution
D5W(acts asahypotonic
solution inbody)
D5NaCl
D5in LactatedRinger's
D50.45%NaCl
isotonic
hypotonic
hypotonic
hypotonic
isotonic
isotonic
hypertonic
hypertonic
hypertonic

34. • Calculating volume of fluid
Maintenance fluid for each hour:
4/2/1 rule
Maintenance fluids for each day:
100/50/20 rule
Replace the loss
Look for end-points of resuscitation
(HW)

36. What I hear, I forget;
What I see, I
remember. What I do,
I understand.
- Confusius, 451
BC