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Intravenous fluids: crystalloids and colloids

TYPES OF FLUID
 
Intravenous fluids may broadly be classified into colloid and crystalloid solutions. They have very different physical, chemical and physiological characteristics.
 
CRYSTALLOID SOLUTIONS
 
Solutions of inorganic ions and small organic molecules dissolved in water are referred to as crystalloids. The main solute is either glucose or sodium chloride (saline) and the solutions may be isotonic, hypotonic or hypertonic with respect to plasma. Isotonic saline has a concentration of 0.9% w/v (containing 0.9g NaCl in each liter of water). Potassium, calcium, and lactate may be added to more closely replicate the ionic makeup of plasma. Crystalloids with an ionic composition close to that of plasma may be referred to as “balanced” or “physiological
 
COLLOID SOLUTIONS
 
A colloid is a homogeneous non-crystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance - the particles do not settle and cannot be separated out by ordinary filtering or centrifuging like those of a suspension such as blood. Colloid solutions used in clinical practice for fluid therapy are divided into the semisynthetic colloids (gelatins, dextrans and hydroxyethyl starches) and the naturally occurring human plasma derivatives (human albumin solutions, plasma protein fraction, fresh frozen plasma, and immunoglobulin solution). Most colloid solutions are presented with the colloid molecules dissolved in isotonic saline but isotonic glucose, hypertonic saline and isotonic balanced or “physiological” electrolyte solutions are also used.
 
CRYSTALLOIDS VS COLLOID
 
Crystalloids freely distribute across the vascular barrier. Only one fifth of the intravenously infused amount remains intravascularly. A fourfold amount of crystalloid infusion is needed to reach comparable volume effects as achieved with colloid administration. A colloid is defined as a high molecular weight (MW) substance that largely remains in the intravascular compartment, thereby generating an oncotic pressure. Colloids are considered to have a greater intravascular persistence when compared to crystalloids

Table: Variations in Colloids and Crystalloids Formulations
 

Solution

pH

Na+

Cl-

K+

Ca++

Lactate

Glucose

Osmo
lality

Other

.9% normal saline

5.0

154

154

0

0

0

0

308

0

LR

6.5

130

109

4

3

28

0

275

0

5% dextrose in water (D5W)

4.0

0

0

0

0

0

50 g/L

252

0

.45% normal saline with dextrose (D51/2 NS)

4.5

77

77

0

0

0

50 g/L

406

0

Albumin (5%)

6.4-7.4

130-160

130-160

< 1

0

0

0

309

50 g/L albumin

Albumin (25%)

6.4-7.4

130-160

130-160

< 1

0

0

0

312

250 g/L albumin

Hetastarch 6%

5.5

154

154

0

0

0

0

310

60 g/L starch

Pentastarch 10%

5.0

154

154

0

0

0

0

326

100 g/L starch

Dextran-40
(10% solution)

3.5-7.0

154

154

0

0

0

0

311

100 g/L dextran

Dextran-70
(6% solution)

3.0-7.0

154

154

0

0

0

0

310

60 g/L dextran

Haemaccel 3.5%

7.4

145

145

5

6.25

0

0

293

35 g/L gelatin

Gelofusine

7.4

154

125

0

0

0

0

308

40 g/L gelatin

 
LR = lactated Ringer's
 
All electrolyte ions are expressed in meq/L.

Intraoperative fluid supplementation

Requirement of maintainance fluid/hour (holliday n segar rule)
 
“4-2-1 Rule”
  1. 4 ml/kg/hr for the first 10 kg of body weight
  2. 2 ml/kg/hr for the second 10 kg body weight
  3. 1 ml/kg/hr subsequent kg body weight
  4. Extra fluid for fever, tracheotomy, denuded surfaces
  1. Crystalloids
    1. Ringer lactate
    2. Normal saline
    3. 5% Dextrase
    4. DNS
    5. Hypertonic saline
    6. For 1 ml loss of blood 3 ml of crystalloid is required (1:3 ratio)
  1. Colloids: Required 1:1 ratio (Ratio of replacement with blood)
  2. Albumin
     
    Used for - peritonitis
    1. extensive burn
    2. cirrhosis
    3. protein losing nephropathies
  3. Dextran
    1. Dextran 70 (Lomodex)
    2. Dextran 150
    3. Dextran 40
      1. Interferes with blood grouping & cross matching
      2. Interferes with platelet functions
      3. High incidence of immunologic reactions
  4. Degraded gelatin (Haemcael) - most commonly used
    1. Used as 3.5% solution
    2. Expand plasma for 12 hrs.
  5. Hydroxyethyl starch (haessteril)
     
    * Improves microcirculation & improves O2 delivery (added advantage)
     
    S/E: Anaphylaxis are common
     
    C/I: Renal failure, CHF, coagulopathies
  6. Blood
  1. Fluids of choice for different clinical situations for
    1. Intestinal obstruction --> CRYSTALLOID --> Ringer lactate
    2. Liver failure --> colloid (esp. Albumin)
    3. Renal failure --> colloids preferred (start with 30% of calculated fluids)
    4. ARDS --> crystalloids (colloid can be given after 48 hrs.)




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