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

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 weight In females – 55% of body weight e.g. In a 60kg male – TBW is 36L

TBW = 60% OF BODY WEIGHT ICF ECF 05% 40% 15% Plasma Interstitial Fluid Our intravascular compartment holds the smallest amount of water at around 3 litres ( a further 2 litres of red cells makes up our total blood volume ). 15% Interstitial Fluid

TYPES OF I.V. FLUIDS 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 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 Tonicity – osmolality of a solution relative to the osmolality of plasma

TYPES OF I.V. FLUIDS Balanced vs. unbalanced intravenous fluids UNBALANCED SOLUTIONS BALANCED SOLUTIONS 0.9% Saline Hartmann's' solution Dextrans have a number of additional components to normal saline in an attempt to approximate the composition of the solution to plasma. Balanced colloids are being developed.

TYPES OF I.V. FLUIDS 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: 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 In dengue patients as once hypovolaemia sets in there is circulatory collapse, Some points may apply for other crystalloids

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. Story about dengue deaths and alkaline diuresis used in Aspirin poisoning earlier, now abondoned due to risk of pul oedema

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.

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 !! Not used for fluid resuscitation. Wernicke’s encephalopathy. The brain is surrounded by a membrane separating it from the vascular space - the blood-brain barrier. This membrane will only allow water to pass through it. Therefore only fluid with the same concentration of sodium as plasma should be given intravenously. Otherwise, the plasma will become more dilute and water will pass from it into the brain, making the brain swell, and thus increase pressure further. Normal Saline (0.9%) has a similar concentration of sodium and therefore is the fluid of choice for the brain. Colloid can be given if required to treat hypovolaemia due by major blood loss. When Dextrose solutions in water (5% Dextrose, Dextrose 4%-Saline 0.18%) are given, the dextrose is metabolised leaving just the water or a very dilute saline solution. This "dilutes" the blood, reducing the concentration of sodium in the plasma. The water then passes into the brain where the concentration of sodium is higher. The brain then swells, and intracranial pressure will rise.

5% Dextrose Adverse effects: Causes red cell clumping (cannot be given with blood). May cause water intoxication 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 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 Usually both colloids and crystalloids used to expand both vascular and interstitial compartments in resuscitation.

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. Because of the significant calcium content of Haemaccel, blood should not be infused through a giving set that has been previously used for this product.

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 In patients whose haemostatic function is normal prior to infusion a maximum dose of 1.5 g/kg is often recommended to avoid risk of bleeding complications.

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 Even more than albumin

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. Even more than albumin

PHYSIOLOGY Water is transported paracellularly as a result of the osmotic gradient. - 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 unaffected It is estimated that in the 1990s, more than 1 million deaths related to diarrhoea may have been prevented each year, largely attributable to the promotion and use of ORT and ORS. unaffected

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

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 Cereal bases ORS better than glucose based ORS. Why? Continuous slow releasing source of glucose Colonic bacteria produce short chain fatty acids which further enhance colonic sodium and water absorption.