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PRINCIPLES OF FLUID THERAPY ON THEBASIS OF SEVERITY OF LOSS OF BODY

FLUID AND NUTRITIONAL STATUS:RECOMMENDED TYPES OF IV FLUIDS AND ORAL FLUIDS

(ORS, RESOMAL).

Hendry Robert, MD

Group 7

Facilitator: Dr Ntogwisangu

_________________________________________________________________

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Introduction

Fluid therapy istherapy whose basicobjective isto restore the volume and composition of the bodyfluids to normal with respect to water-electrolytebalance.

Volume and composition derangement may be as aresult of inadequate fluid intake or abnormally rapid

losses of body fluids (example in haemorrhage,diarrhoea, vomiting, burn etc).

Fluidsmay be administered intravenously or orally.

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Intravenous fluid therapy

Is the giving of substances(IV fluids)directly into a vein (May also be giveintraosseous).

Types of IV Fluids

1. Isotonic fluids2. Hypotonic fluids

3. Hypertonic fluids

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Isotonic fluids

Osmolarity is similar to that of serum.

These fluids remain intravascularly mommentarily,thus expanding the volume.

Helpful with patients who are hypotensive orhypovolemic.

Risk of fluid overloading exists. Therefore, becareful in patients with left ventricular dysfunction,

history of CHF or hypertension. Avoid volume hyperexpansion in patients with

intracranial pathology or space occupying lesions.

Example: 0.9% Normal SalineBasically Salt and

Water

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Hypotonic fluids Less osmolarity than serum (meaning: in general less sodium ion

concentration than serum)

These fluids DILUTE serum thus decreasing osmolarity.

Water moves from the vascular compartment into the interstitial fluidcompartment interstitial fluid becomes diluted osmolarity descreases water is drawn into adjacent cells.

These are helpful when cells are dehydrated from conditions ortreatments such as dialysis or diuretics or patients with DKA (high serumglucose causes fluid to move out of the cells into the vascular andinterstitial compartments).

Caution with use because sudden fluid shifts from the intravascular spaceto cells can cause cardiovascular collapse and increased ICP in certainpatients.

Example:0.45% Normal saline = Half Normal Saline hypotonic saline

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Hypertonic fluids

These have a higher osmolarity than serum.

These fluids pull fluid and sometimes electrolytesfrom the intracellular/interstitial compartments

into the intravascular compartments. Useful for stabilizing blood pressure, increasing

urine output, correcting hypotonic hyponatremiaand decreasing edema.

These can be dangerous in the setting of celldehydration

Example:1.8, 3.0, 7.0, 7.5 and 10% Saline =hypertonic saline

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Main Groups of IV Fluids Crystalloids Colloids

Crystalloids Clear solutionsfluids- made up of water & electrolyte solutions; small molecules. These fluids are good for volume expansion. However, both water & electrolytes will cross a semi-permeable membrane into the

interstitial space and achieve equilibrium in 2-3 hours.

Remember: 3mL of isotonic crystalloid solution are needed to replace 1mL of patientblood.

This is because approximately 2/3rds of the solution will leave the vascular space inapprox. 1 hour.

In the management of hemorrhage, initial replacement should not exceed 3L beforeyou start using whole blood because of risk of edema, especially pulmonary edema

Some of the advantages of crystalloids are that they are inexpensive, easy to storewith long shelf life, readily available with a very low incidence of adverse reactions,and there are a variety of formulations that are available that are effective for use asreplacement fluids or maintenance fluids.

A major disadvantage is that it takes approximately 2-3 x volume of a crystalloid tocause the same intravascular expansion as a single volume of colloid.

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Composition of commonly usedcrystalloids

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Colloids Colloids are large molecular weight solutions (nominally MW >

30,000 daltons)> These solutes are macormolecular substancesmade of gelatinous solutions which have particles suspended in

solution and do NOT readily cross semi-permeable membranes orform sediments. Because of their high osmolarities, these are important in capillary

fluid dynamics because they are the only constituents which areeffective at exerting an osmotic force across the wall of thecapillaries.

These work well in reducing edema because they draw fluid from theinterstitial and intracellular compartments into the vascularcompartments.

Initially these fluids stay almost entirely in the intravascular space fora prolonged period of time compared to crystalloids.

These will leak out of the intravascular space when the capillary

permeability is deranged or leaky. Albumin solutions are available for use as colloids for volumeexpansion in the setting of CHF however albumin is in short supplyright now.

There are other solutions containing artificial colloids available.

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Principles of fluid therapyHypovolemia

True volume depletion, or hypovolemia, usuallyrefers to a state of combined salt and water lossexceeding intake which leads to ECF volumecontraction. The loss of sodium may be renal or

extrarenal. ECF volume contraction is manifested as adecreased plasma volume and hypotension.

Signs of intravascular volume contraction includedecreased jugular venous pressure, posturalhypotension, and postural tachycardia.

Larger and more acute fluid losses lead tohypovolemic shock and manifest as hypotension,tachycardia, peripheral vasoconstriction, &

hypoperfusion

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Hypovolemia Etiologies WithECF Volume Contraction

Extrarenal Na+ Losses:

GI: vomiting, NG suction, drainage, fistual, diarrhea

Skin/Respiratory: insensible losses, sweat, burns

Hemorrhage

Renal Na+ and H2O Losses:

Diuretics

Osmotic Diuresis

Hypoaldosteronism

Salt-wasting Nephropathies

Renal Water Loss

Diabetes Insipidus (central or nephrogenic)

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Hypovolemia Etiologies With ECFVolume Normal or Expanded

Decreased Cardiac Output

Myocardial, Valvular or Pericardial Disease

Redistribution

Hypoalbuminemia: hepatic, cirrhosis, nephroticsyndrome

Capillary Leak: acute pancreatitis, ischemic

bowl, rhabdomyolysis Increased Venous Capacitance

Sepsis

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Principles of Treatment ofHypovolemia

The goals of treatment is to restore normovolemia with fluid similarin composition to that lost and replace ongoing losses.

Mild volume losses can be corrected via oral rout. More severe hypovolemia requires IV therapy. Isotonic or Normal Saline (0.9%NaCl) is the solution of choice in

normonatremic and mildly hyponatremic patients and should beadministered initially in patients with hypotension or shock. Severe hyponatremia may require Hypertonic Saline (3.0% NaCl) In the Hypernatremic patient, there is a proportionately greater

deficit of water than sodium, therefore to correct this patient you willuse a Hypotonic solution like NS (0.45% NaCl) of D5W.

Patients with significant hemorrhage, anemia, or intravascularvolume depletion may require blood transfusions or colloids(albumin/dextran).

Hypokalemia can be simultaneously corrected by addingappropriate amounts of KCl to replacement solutions.

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Example of severe body fluid lossBURN

Burn injury results in loss of thecholesterol-filled cornified layer of the skin,which provides a barrier against excessive

loss by diffusion (the average water lossby diffusion through the skin is about 300to 400 ml/day), When the cornified layerbecomes denuded, as occurs with a result

of extensive burns, the rate of evaporationcan increase as much as 10-fold, to 3 to 5L/day

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Burn also results in the activation of thecompliment system and the release of large

number of inflammatory mediators such ashistamine, prostaglandins and leukotrienes.These mediators increase the permeability ofthe local and systemic vasculature, resulting in

extravastion of intracellular fluids and proteins ininto the interstitial space, contributing to fluiddepletion and soft tissue oedema. The leakageof plasma proteins during the first 3 to 5 hours

reduces the intravascular oncotic pressure andincreases the interstitial oncotic pressure, whichleads to an increase in oedema formation.

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Therapeutics must therefore be based onknow ledge of these changes in time. It isimportant to realize that many of the

problems are predictable and can andshould be prevented before they happen.One of the many aspects of the care of the

burn patient that must be monitored is theelectrolyte balance. The correct approachwill be considered with regard to three

periods of time in relation to the mainchanges in each period

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The correct approach will be considered withregard to three periods of time in relation to themain changes in each period:

the initial resuscitation period (between 0 and 36h). characterized by hyponatraernia andhyperkalaemia;

the early post-resuscitation period (between

days and 6). in which we considerhypernatraemia. hypokalaemia, hypocalcaemia,hypomagnesaemia. and hypophosphataetnia:

the inflammation-infection period (also known as

the hypermetabolic period). which is mostevident after the first week. when severalimbalances may coexist, depending whethercorrection was performed. and. if so, how.

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First period

In major burns. intravascular volume is lost in

burned and unburned tissues: this process isdue to an increase in vascular permeability,increased interstitial osmotic pressure in burntissue. and cellular oedema. with the mostsignificant shifts occurring in the first hours.Hyponatraemia is frequent, and the restorationof sodium losses in the burn tissue is thereforeessential hyperkalaemia is also characteristic ofthis period because of the massive tissue

necrosis.Hyponatraemia (Na) (< 135 mEq/L) is due toextracellular sodium depletion following changesin cellular permeability

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It is fundamental that sodium replacementshould be performed xvith resuscitation fluids(lactated Ringer's. normal saline); sometimestwo ampoules of sodium lactate are added toeach 1000 ml of normal saline in order toincrease osmolaritv;' volume replacement withblood and the reduction ofJ additional sodium

losses are other important factors If a hypertonic solution is used to restore serum

sodium. it should not be allowed to increaseabove 160 mEq/1 and the rate of increase

should not exceed 1.5 mEq/h.Hyperkalaemia (K+) (> 5.5 mEq/1) is mainlycaused by- cell lvsis and tissue necrosis

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Second period

The early post-resuscitation phase is a period of transition from the shock phase tothe hypermetabolic phase, and fluid strategies should change radically with a view torestoring losses due to water evaporation.The main changes in this period are:

A. Hypernatraemia(Na+) (> 115 mEq/1). This is caused by several mechanisms:intracellular sodium mobilization. reabsotption of cellular oedema, urinary retention ofsodium (because of the increase in renin, angiotensin. and ADH), and the use of iso-/hypertonic fluids in the resuscitation phase.Hypernatraemia presents in variousforms, depending on the amount of water retained: peripheral oedema, ascites,pleural effusion, and interstitial/a1-eolar oedema (with possible impaired ventilation)may dominate, or alternatively manifestations of dehydration may be more significant.Therapeutics is performed with hypotonic~fluids (low sodium content, with or without

glucose): NaCl 0.45% or DSc NaCI 0.-15%: in some cases it may be necessary toadd diuretics. The amount of water necessary to bring Na+ back to normal is given bythe formula: 0.6Jx weight (kg) x (Na+ initial/NaT desired -1).Correction should be performed in such a way that the decrease in Na` does notexceed 1.5 mEq/h (there is a danger of cerebral oedema if correction is too quick).

B. Hypcoalaemia. This is most prevalent in the period following the first -18 h post-burn and is characterized by K+ < 3.5 mEq/l. It may be due to increased potassiumlosses (urinary-, gastric. faecal) and the intracellular shift of potassium because of the

administration of carbohydrates; this imbalance is also increased by coexistinffhypomagnesaemia.

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ORAL REHYDRATION THERAPY(ORT)

Is a simple treatment for dehydration associated withdiarrhea, particularly gastroenteritis or gastroenteropathy,such as that caused by cholera or rotavirus.

ORT consists of a solution of salts and sugars which istaken by mouth. It is used around the world, but is mostimportant in the developing world, where it saves millionsof children a year from death due to diarrhea . Oral fluidtherapy is effective, safe, convenient, and inexpensive

compared with IV therapy. It should be used for childrenwith mild to moderate dehydration who are acceptingfluids orally unless prohibited by copious vomiting orunderlying disorders (eg, surgical abdomen, intestinalobstruction).

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ORS Composition

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ReSoMal

Diarrhoea is a serious and often fatal event in children with severe malnutrition.Although treatment and prevention of dehydration are essential, care of these childrenmust also focus on careful management of their malnutrition and treatment of otherinfection

Full-strength ORS solution should not be used for oral or NG rehydration. It providestoo much sodium and too little potassium. Two approaches to develop a suitable oralsolution are possible.

(i) When using the previous standard ORS solution containing 90 mEq/l of sodium: dissolve one ORS packet into two litres of clean water (to make two litres instead of

one litre); add 45 ml of potassium chloride solution (from stock solution containing 100g KCl/l);

and add and dissolve 50g sucrose. (ii) When using the new reduced (low) osmolarity ORS solution containing 75 mEq/l of

sodium: Dissolve one ORS packet into 1.5 litre of clean water (to make one and a half litresinstead of one litre)

add 33 ml of potassium chloride solution (from stock solution containing 100g KCl/l);and

add and dissolve 38g sucrose.

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EXAMPLE: Severe Diarrhea

During diarrhoea there is an increasedloss of water and electrolytes (sodium,chloride, potassium, and bicarbonate) in

the liquid stool. Water and electrolytes arealso lost through vomit, sweat, urine andbreathing. Dehydration occurs when these

losses are not replaced adequately and adeficit of water and electrolytes develops.

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The volume of fluid lost through the stoolsin 24 hours can vary from 5 ml/kg (nearnormal) to 200 ml/kg, or more. Theconcentrations and amounts ofelectrolytes lost also vary. The total body

sodium deficit in young children withsevere dehydration due to diarrhoea isusually about 70-110 millimoles per litre of

water deficit. Potassium and chloridelosses are in a similar range

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Electrolyte disturbances

Hypernatraemia Some children with diarrhoea develop hypernatraemic dehydration,

especially when given drinks that are hypertonic owing to theircontent of sugar (e.g. soft drinks, commercial fruit drinks) or salt.These draw water from the child's tissues and blood into the bowel,causing the concentration of sodium in extra-cellular fluid to rise. If

the solute in the drink is not fully absorbed, the water remains in thebowel, causing osmotic diarrhoea.

Children with hypernatraemic dehydration (serum Na >150 mmol/l)have thirst that is out of proportion to other signs of dehydration.Their most serious problem is convulsions, which usually occurwhen the serum sodium concentration exceeds 165 mmol/l, and

especially when IV therapy is given. Seizures are much less likelywhen hypernatraemia is treated with ORS solution, which usuallycauses the serum sodium concentration to become normal within 24hours.

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Hyponatraemia

Children with diarrhoea who drink mostly water,or watery drinks that contain little salt, maydevelop hyponatraemia (serum Na

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Hypokalaemia

Inadequate replacement of potassium losses during

diarrhoea can lead to potassium depletion andhypokalaemia (serum K+

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Conclusion

In Determining the administration of fluid therapyclinically one has always got to know

What is the volume status of my

patient(Hypovolemic, Hypervolemic, NPOPatient, surgical patient, euvolemic,Eating/drinking normally)?

Do they have ongoing losses?

Can my patient take PO safely?

Are the NPO for a reason?