INTRAVENOUS FLUIDS & ORAL REHYDRATION SOLUTION

1. INTRAVENOUS FLUIDS & ORAL REHYDRATION SOLUTION Dr Ruwan Parakramawansha MBBS, MD, MRCP(UK),MRCPE, DMT(UK) (2013/01/30)

2. 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

3. FLUID DISTRIBUTION IN THE BODY • Total body water (TBW) • In males – 60% of body weight • In females – 55% of body weight e.g. In a 60kg male – TBW is 36L

4. TBW = 60% OF BODY WEIGHT ICF ECF 05% Plasma 40% 15% Interstitial Fluid

5. TYPES OF I.V. FLUIDS • Crystalloids vs. Colloids

6. TYPES OF I.V. FLUIDS • Hypotonic, Isotonic and Hypertonic solutions

7. TYPES OF I.V. FLUIDS • Balanced vs. unbalanced intravenous fluids

8. TYPES OF I.V. FLUIDS • Natural vs. Synthetic

9. 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

10. 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

11. 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+ andCl- freely moves across vascular membrane into the interstitium.

12. 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.

13. Normal Saline (0.9% NaCl) Indications: • Replacement of fluids in hypovolaemic or dehydrated patients ( Needs 3  blood loss) • A small amount of saline as a special adjunct can be used to keep the veins open for medication administration • As the initial plasma expander in blood loss while blood is typed and matched

14. Normal Saline (0.9% NaCl) Adverse Effects • Fluid overload (peripheral and pulmonary oedema) • With high volume administration, • Dilutional reduction of normal plasma components such as calcium and potassium • Dilutional coagulopathy • Hyperchloraemic acidosis • Diuresis.

15. 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.

16. 5% Dextrose Indications: • To maintain water balance ( In pure water deficit and for patients on sodium restriction) • 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 !!

17. 5% Dextrose Adverse effects: • Causes red cell clumping (cannot be given with blood). • May cause water intoxication • Can cause hyponatraemia

18. 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

19. 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

20. 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.

21. INDICATIONS • When rapid expansion of plasma volume is desirable e.g. in haemorrhage prior to blood transfusion • For fluid resuscitation in the presence of hypoalbuminaemia • In large protein losses e.g. in burns

22. Gelatins • Prepared by hydrolysis of bovine collagen. a). Gelafusine  - succinylated gelatin in isotonic saline b). Haemaccel - urea-linked gelatin and polygeline in an isotonic solution of sodium chloride with potassium and calcium. • Theoretical risk of transmitting bovine spongiform encephalopathy. (new-variant Creutzfeldt-Jakob disease) • Volume expanding effect lasts 2-3 hrs.

23. 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.

24. 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

25. 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

26. 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.

27. 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.

28. unaffected 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 unaffected

29. 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

30. WHO/UNICEF LOW OSMOLARITY ORS FORMULA