When two solutions are separated by a membrane that allows the passage of water butnot solutes, the water passes from the solution with the lower osmotic activity to thesolution with the higher osmotic activity. The relative osmotic activity in the two solutionsis called the effective osmolality, or tonicity. The solution with the higher osmolality isdescribed as hypertonic, and the solution with the lower osmolality is described ashypotonic. Thus, the tendency for water to move into and out of cells is determined by therelative osmolality (tonicity) of the intracellular and extracellular fluids.
Crystalloids are fluids that contain water and electrolytes. They are grouped as isotonic, hypertonic, and hypotonic salt solutions. Crystalloid solutions are used to provide maintenance water and electrolytes and to expand intravascular fluid. The replacement requirement is threefold or fourfold the volume of blood lost because administered crystalloid is distributed in a ratio 1 : 4 similar to ECF, which is composed of about 3 L intravascularly (plasma) and about 12 L extravascularl
100ml blood loss – need to give 400ml N. saline [only 25% remains intravascular
Hypertonic Salt Solutions Hypertonic salt solutions are less commonly used, and their sodium concentrations range from 250 to 1200 mEq/L. The greater the sodium concentration, the less the total volume is required for satisfactory resuscitation. This difference reflects the movement owing to osmotic forces of water from the intracellular space into the extracellular space. The reduced volume of water injected may reduce edema formation; this could be crucial in patients predisposed to tissue edema (e.g., prolonged bowel surgery, burns, brain injuries). Clinical studies have confirmed that a moderately hypertonic solution (250 mEq/L of sodium) can produce lower muscle interstitial pressure than lactated Ringer’s solution. Bowel function returned earlier, although the pulmonary shunt fraction was no different. Experimental studies have shown decreased intracranial pressures in animals receiving hypertonic solutions. The intravascular half-life of hypertonic solutions is no longer, however, than isotonic solutions of an equivalent sodium load. In most studies, sustained plasma volume expansion was achieved only when colloid was present in the resuscitation solution. The osmolality of these solutions can cause hemolysis at the point of injection.
– Think of it as ‘Sugar and Water’
Primarily used to maintain water balance in patients who are not able to take anything by mouth; Commonly used post-operatively in conjunction with salt retaining fluids ie saline
The colloid solutions contain particles which do not readily cross semi-permeable membranes such as the capillary membrane. Thus the volume infused stays (initially) almost entirely within the intravascular space . Stay intravascular for a prolonged period compared to crystalloids.
TETRASTARCH:3RD GEN. HES Newer starch based plasma expander Improved safety and pharmacological prop Minimal effect on coagulation process and platelet function Less accumulation and tissue storage No effects on renal function Positive effects on tissue oxygenation and microcirculation
Most gen and regional anaesthetics cause arteriolar and venous dilatation, expanding the vascular capacity, which reduces the peripheral venous pressure, venous return, and cardiac output
TOTAL BODY WATER
Approx. 60% Body weight
Varies with age, gender and body
50% BW in females
80% BW in infants
Less in obese : fat contain little water
Body Water Compartments
Intracellular volume : 2/3 of TBW
Extracellular volume : 1/3 of TBW
- Intravascular : Plasma volume (1/4)
- Extravascular: Interstitial fluid &
Preoperative Evaluation of Fluid
- Mental status
- H/O intake and output
- Blood pressure: supine and standing
- Heart rate
- Skin turgor
- Urinary output
• Systolic blood pressure decrease of greater than
20mmHg from supine to standing
• Indicates fluid deficit of 6-8% body weight
- Heart rate should increase as a compensatory
- If no increase in heart rate, may indicate
autonomic dysfunction or antihypertensive
Osmoles :unit for conc. Of osmotically
Osmolality: osmotic active solute per
volume of solution ( mOsm/L)
Osmolarity : mOsm/Kg
Plasma osmolarity : 290 mOsm/kg
Tonicity ( relative osmotic activity )
Intravenous fluid therapy may consist of infusions ofIntravenous fluid therapy may consist of infusions of
crystalloids, colloids, or a combination of both.crystalloids, colloids, or a combination of both.
Volume resuscitationVolume resuscitation
Vehicle for i/v drugsVehicle for i/v drugs
Clear fluids made up of water and electrolyte
solutions; Will cross a semi-permeable membrane
Grouped as isotonic, hypertonic, and hypotonic
Normal saline 0.9%,3 %
Dextrose solutions 5 %,10%,20%,25%
0.9% Normal Saline
Contains: Na+ 154 mmol/l, Cl-
- 154 mmol/l
Osm : 308mosm/l, pH 6.0
IsoOsmolar compared to normal plasma.
Intravascular resuscitation and replacement of salt loss
e.g. diarrhoea and vomiting.
Also for diluting packed RBCs prior to transfusion
Used for diluting Drugs
Stays almost entirely in the extracellular space.
Of 1 litre - 750ml extra vascular fluid; 250ml
When given in large volume can produces
Hyperchloremic metabolic acidosis because of
high Na+ and Cl- content.
3.0 % Saline = HYPERtonic saline
3% contain 513 mmol/l of Na+ and Cl-
osmol of 1026 mOsm/l; pH 5.0
Treatment of severe symptomatic
hyponatremia (coma, seizure)
To resuscitate hypovolemic shock
Must be administered slowly and
preferably with CV line because it
carries risk of causing phlebitis,
Precaution in pt. with CHF
severe renal insufficiency, edema with
5% Dextrose (often written D5W)
50g/l of glucose, 252mOsm/l, pH 4.5
Regarded as ‘electrolyte free’ – contains
NO Sodium, Potassium, Chloride or
To maintain water balance in patients
who are not able to take anything by
Used post-operatively in conjunction
with salt retaining fluids ie saline
Less than 10% stays in the intravascular space
therefore it is of limited use in fluid resuscitation.
Iatrogenic hyponatraemia in surgical patient
Not compatible with blood ,cause hemolysis
conc 5% 10% 20% 25% plasma
Osmolarity 252 505 1010 1262 290
Most physiological solution
Electrolyte composition similar to ECF
One litre of lactated Ringer's solution contains:
Sodium ion= 130 mmol/L.
Chloride ion = 109 mmol/L.
Lactate = 28 mmol/L.
Potassium ion = 4 mmol/L.
Calcium ion = 1.5 mmol/L
Osmolarity of 273 , pH of 6.5
Lactate is converted to bicarbonate in liver
Deficit ,Intraoperative fluid loss
Severe metabolic acidosis ( impaired lactate conversion)
Don’t give with blood product ( Ca bind with citrate
reduced anticoagulant activity )
0.9% saline & 5% dextrose
Na+ 154, Cl- 154, 5 gm. Glucose
Osm : 432 mosm/L
Correction of fluid deficit with supply of
Compatible with blood
Particles which do not readily cross semi-
Stays (initially) almost entirely within the
intravascular space .
Stay intravascular for a prolonged period
compared to crystalloids.
However they leak out of the intravascular space
when the capillary permeability significantly changes
e.g. Severe trauma or sepsis.
Because of their gelatinous properties they cause
platelet dysfunction and interfere with fibrinolysis and
coagulation factors (factor VIII) – thus they can cause
significant coagulopathy in large volumes.
Natural : Albumin
Artificial : Gelatin and Dextran , HES
Principal natural colloid comprising of 50-60% of all plasma
Synthesized only in liver and has a half life of app. 20 days.
5% soln is iso oncotic and leads to 80% initial vol expansion
25% soln leads to 200-400% increase in vol.
For emergency treatment of shock especially due to loss of
acute management of burns
Fluid resuscitation in ICU
Side effects :
pruritis, anaphylactoid reactions and coagulation
abnormalities as compared to synthetic colloids.
volume overload (in septic shock pt albumin add to
Highly branched polysaccharide molecules
Produced by synthesis using the bacterial enzyme
dextran sucrase from the bacterium Leuconostoc
Most widely used are 6%(dextran 70) and 10%
(dextran 40) soln.
Excreted via kidney primarily.
Used mainly to improve microcirculatory flow
in microsurgical re-implantation .
Also used in extracorporeal circulation during
Side effects: Anaphylactic reactions,
Coagulation abn, Interference with cross
match, Ppt of ARF.
Large mol. wt. proteins formed from
hydrolysis of collagen.
Produced by thermal degradation of cattle-
Gelatins lead to 70-80% of vol expansion
Rapid expansion of intravascular volume
and correction of hypotension
cost effectiveness and no effect of renal
impairment ,does not affect coagulation
Derivatives of amylopectin, which is a highly
branched compound of starch.
6% HES soln are isooncotic
10% soln are hyper oncotic , with a vol effect
exceeding the infused vol .(about 145%)
Duration of vol expansion is usually 8-12 H.
Cost effective: cheaper and comparable vol of
expansion to albumin.
Disadvantage: assoc. with 1st
- Coagulation abn
- Anaphylactoid reactions
- Renal impairment
- Increase in amylase level
Colloid or Crystalloid Resuscitation
Colloid should NOT be used as the sole fluid
replacement in resuscitation ,volumes infused
should be limited because of side effects and lack
of evidence for their continued use in the acutely
Colloid may be used in limited volume to reduce
volume of fluids required or until blood products
In elective surgical patients
Replace fluid loss with ‘physiological
Blood products and colloid may be
needed to replace intravascular volume
Peri- operative Fluid
• The following factors must be taken into
• C V E
• Maintenance fluid
• Third space losses
• Replacement of loss
COMPENSATORY INTRAVASCULAR VOLUME
Fluid must be adm. to expand the blood vol to
compensate for venodilation (GA,RA)
Expansion with 5-7ml/kg of crystalloid must
occur before or simultaneous with the onset of
Maintenance Fluid Requirements
• “4-2-1 Rule”
- 4 ml/kg/hr for the first 10 kg of body
- 2 ml/kg/hr for the second 10 kg body
- 1 ml/kg/hr subsequent kg body weight
Eg : 70 Kg pt
Maintenance fluid : 40+20+50= 110 ml/hr
• Deficit = number of hours NPO x maintenance
• Measurable fluid losses, e.g. NG suctioning,
vomiting, stoma output.
70 kg pt fasting for 8 hrs
Deficit : 8 X 110 = 880 ml
Half in first hr
One fourth each in next two hr .
Third Space Losses
• Isotonic transfer of ECF from functional body
fluid compartments to non-functional
• Depends on location and duration of surgical
procedure, amount of tissue trauma, ambient
temperature, room ventilation.
Replacing Third Space Losses
Minimal Surgical Trauma: 0-2 ml/kg/hr
- e.g. herniorrhaphy
Moderate Surgical Trauma: 2-4 ml/kg/hr
- e.g. cholecystectomy
Severe surgical trauma: 4-6 ml/kg/hr (or even
- e.g. major bowel resection
• Replace 4 cc of crystalloid solution per cc of blood
loss (crystalloid solutions leave the intravascular
• When using blood products or colloids replace blood
loss volume per volume.
Fluid management, starting with a hemoglobin level of 15 g/dL,
for a 70-kg patient undergoing gastrectomy who has been fasting
for 8 hours.
Maintenance rate is 110 mL/hr,
Deficit of 880 mL
First hr = CVE+ Half of deficit + maintenance + loss+ third space loss
350+440+110+50 + 420
Second hr = one fourth of deficit + maintenance + loss+ third space loss
220+ 110+ 250 + 420
Third hr = one fourth of deficit + maintenance + loss+ third space loss
220+ 110+ 250 + 420
Fourth hr = Maintenance + loss+ third space loss
110+ 50 + 420
Most physiological :RL
Rich in sodium : NS,DNS
Rich in potassium :ISo –p
Glucose free: ?RL,NS,3% saline
Sodium free: Dextrose
Potassium free: NS,DNS,Dextrose
Can correct acidosis directly : RL,ISo-p