Dr Ruwan ParakramawanshaMBBS, MD, MRCP(UK),MRCPE, DMT(UK)

(2013/01/30)

INTRAVENOUS FLUIDS &

ORAL REHYDRATION SOLUTION

LEARNING OUTCOMES..

By the end of this lecture you will be able to,

– List different types of IV fluids

– Identify different methods of classifying i.v. fluids

– Understand differences in fluids in relation to their distribution in

different fluid compartments of the body

– Describe indications for IV therapy

– Outline complications of IV therapy

– List constituents of ORS

FLUID DISTRIBUTION IN THE BODY

Total body water (TBW)

In males – 60% of body weightIn females – 55% of body weight

e.g. In a 60kg male – TBW is 36L

TBW = 60% OF BODY WEIGHT

ICF ECF

40%

05%

15%

Plasma

Interstitial Fluid

TYPES OF I.V. FLUIDS

1. Crystalloids vs. Colloids

CRYSTALLOIDS COLLOIDS

Normal (0.9%) saline Human Albumin

Ringer's lactate solution (Hartmann's' solution)

Gelatin solutions (Haemaccel,Gelafundin )

5% Dextrose Dextran

Hydroxyethyl starches(Hetastarch)

TYPES OF I.V. FLUIDS

2. Hypotonic, Isotonic and Hypertonic solutions

HYPOTONIC SOLUTIONS

ISOTONIC SOLUTIONS

HYPERTONIC SOLUTIONS

0.45% (N/2) Saline Normal (0.9%) saline

3% Saline

0.18% (N/5) Saline Hartmann's' solution Mannitol

5% Albumin 20% Albumin

TYPES OF I.V. FLUIDS

3. Balanced vs. unbalanced intravenous fluids

UNBALANCED SOLUTIONS BALANCED SOLUTIONS

0.9% Saline Hartmann's' solution

Dextrans

TYPES OF I.V. FLUIDS

4. Natural vs. Synthetic

NATURAL SOLUTIONS SYNTHETIC SOLUTIONS

Human Albumin Gelatin solutions (Haemaccel,Gelafundin )

Fresh Frozen Plasma Hartmann’s solution

Dextran

CRYSTALLOIDS

Consist of inorganic ions and small organic molecules

dissolved in water

Either glucose or sodium chloride (saline) based.

May be isotonic, hypotonic or hypertonic

Both water and the electrolytes in the crystalloid solution

can freely cross the semi permeable membranes of the

vessel walls into the interstitial space

Normal Saline (0.9% NaCl)

Contains sodium and chloride ions in water and it is isotonic with extracellular fluid

Cell membrane is impermeable to Na+ and Cl- ions owing to the presence of the energy dependant

Na+ /K+ - ATPase

Intravenous infusion of an isotonic solution of sodium chloride will expand only the extracellular compartment

Normal Saline (0.9% NaCl)

Na+ is the main solute in ECF saline is well suited to

replace ECF fluid losses

e.g. dehydration due to nausea/vomiting

Na+ and Cl- freely moves across vascular membrane

into the interstitium.

Normal Saline (0.9% NaCl)

Remain in the intravascular space for only a short period before diffusing across the capillary wall into the interstitial space.

1 liter infusion of normal (0.9%) saline will result in ~ 250 ml expansion of the circulating volume.

Achieve equilibrium in 2-3 hours.

Normal Saline (0.9% NaCl)

Indications: 1. Replacement of fluids in hypovolaemic or

dehydrated patients ( Needs 3 blood loss)

2. A small amount of saline as a special adjunct can be used to keep the veins open for medication administration

3. As the initial plasma expander in blood loss while blood is typed and matched

Normal Saline (0.9% NaCl)

Adverse Effects

1. Fluid overload (peripheral and pulmonary

oedema)

2. With high volume administration,• Dilutional reduction of normal plasma components such

as calcium and potassium

• Dilutional coagulopathy

• Hyperchloraemic acidosis

3. Diuresis.

5% Dextrose

– Initially behave as an isotonic solution.

– Glucose is soon metabolized, leaving behind

water making the solution hypotonic.

– Water freely moves between intravascular,

interstitial and intracellular fluid compartments till

the osmolalities become the same.

Indications: 1. To maintain water balance ( In pure water deficit and

for patients on sodium restriction)

2. To supply calories ( ~ 200kcal/l)

An adult require ~2500 kcal/day

Hence, glucose alone can’t meet the need.

Would need >10 liters of 5% glucose to supply

all calories !!

5% Dextrose

5% Dextrose

Adverse effects:

1. Causes red cell clumping (cannot be given with

blood).

2. May cause water intoxication

3. Can cause hyponatraemia

Ringer’s Lactate

A balanced isotonic electrolyte solution. Similar to 0.9% saline in all aspects except,

– Contains sodium, chloride, potassium, calcium and lactate in water. ( “physiological”)

– Prevents dilutional reduction of normal plasma components such as calcium and potassium

– Avoids hyperchloraemic acidosis ( Lactate converted to bicarbonate in liver.)

– Preferred to normal saline when large quantities of volume infused rapidly

COLLOIDS

– Colloids contain large molecules such as proteins that do not readily pass through the capillary membrane

– Remain in the intravascular space for extended periods

– These large molecules also increase the osmotic pressure in the intravascular space

Cause fluid to move from the interstitial and intracellular space to the intravascular space

– Often referred to as volume expanders

COLLOIDS

– Colloids stay in the vascular compartment for a longer time compared to crystalloids

– Administered in a volume equal to the volume of blood lost.

COLLOIDS NORMAL SALINE

HALF LIFE IN INTRAVASCULAR COMPARTMENT

3-6 hrs 20-30 min

INDICATIONS

1. When rapid expansion of plasma volume is

desirable

e.g. in haemorrhage prior to blood

transfusion

2. For fluid resuscitation in the presence of

hypoalbuminaemia

3. In large protein losses e.g. in burns

Gelatins Prepared by hydrolysis of bovine collagen.

a). Gelafusine - succinylated gelatin in isotonic saline

b). Haemaccel - urea-linked gelatin and polygelinein an isotonic solution of sodium chloride withpotassium and calcium.

Theoretical risk of transmitting bovine spongiform encephalopathy. (new-variant Creutzfeldt-Jakob disease)

Volume expanding effect lasts 2-3 hrs.

Dextrans

High molecular weight D-glucose polymers prepared from the juice of sugar beets.

Preparations of different molecular weights

e.g. Dextran 40 (MW 40,000)

Dextran 70 (MW 70,000)

Volume expanding effect lasts 5-6 hrs.

Dextrans

Causes haemostatic derangements– Factor VIII activity is reduced– plasminogen activation and fibrinolysis is increased– platelet function impaired

Interfere with blood cross matching Alter laboratory tests

e.g. Plasma glucose, plasma proteins

Hydroxyethyl starches

Synthesized from amylopectin(a D-glucose polymer with a branching structure) derived from maize or sorghum.

The larger molecular size leads to prolonged intravascular retention compared to other colloids.

e.g. Hetastarch, Pentastarch

Human Albumin

Two preparations 5% albumin (isotonic) and 25% albumin (Hypertonic)

20% albumin expands the plasma volume up to five times the volume infused.

Heat treated - no risk of transmitting viral infections.

Reduce ionized calcium level.

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PHYSIOLOGY

- Water is absorbed along the osmotic gradient created by shift of electrolytes mainly Na+ and Cl-

- One form of sodium absorption occurs coupled to glucose.

In Diarrhoea……..

Imbalance between absorption and secretion of fluid

and electrolytes.

Prompt fluid replacement can prevent dehydration

and mortality( esp. in children)

Na+ - K+ ATPase

Na+ - Glucose co-transport unaffectedunaffected

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THE “NEW” WHO/UNICEF ORS FORMULA

A reduced osmolarity formula.

Contains reduced amounts of glucose and sodium.

Further reduces….

- stool out put

- vomiting

- unscheduled supplemental intravenous

therapy

Associated with increased risk of hyponatraemia

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WHO/UNICEF LOW OSMOLARITY ORS FORMULA

Anhydrous Glucose

13.5 g/l

Sodium chloride 2.6 g/l

Potassium chloride

1.5 g/l

Sodium citrate 2.9 g/l