MAINTENANCE ,REPLACEMENT AND DEFICIT THERAPY

Dr.rajesh.K

INTRODUCTION

Maintenance iv fluids are used in a child who cannot be fed enterally.

Along with maintenance fluids, children may require concurrent replacement fluids if they have continued excessive losses,such as may occur with drainage from a nasogastric(NG) tube or with high urine output due to nephrogenic diabetes insipidus.

If dehydration is present, the patient also needs to receive deficit therapy.

A child awaiting surgery may need only maintenance fluids, whereas a child with diarrheal dehydration needs maintenance and deficit therapy

MAINTENANCE THERAPY

Children normally have large variations in their daily intake of water and electrolytes.

The only exceptions are patients who receive fixed dietary regimens orally, via a gastric tube, or as intravenous total parenteral nutrition.

Maintenance fluids do not provide adequate calories, protein, fat, minerals, or vitamins.

A patient receiving maintenance intravenous fl uids is receiving inadequate calories and will lose 0.5-1% of weight each day

total parental nutrition should be used for children who cannot be fed enterally for more than a few days especially patients with underlying malnutrition.

Prototypical maintenance fluid therapy does not provide electrolytes such as calcium, phosphorus, magnesium, and bicarbonate.

Intravenous fluids Normal saline (NS) and Ringer lactate (LR) are isotonic

solutions; they have approximately the same tonicity as plasma. Isotonic fluids are generally used for the acute correction of intravascular volume depletion The usual choices for maintenance fluid therapy in children are half-normal saline( 1/2NS ) and 0.2NS.

These solutions are available with 5% dextrose(D5). In addition, they are available with 20 mEq/L of potassium chloride, 10 mEq/L of potassium chloride, or no potassium.

A hospital pharmacy can also prepare custom-made solutions with different concentrations of glucose, sodium, or potassium. In addition, other electrolytes, such as calcium, magnesium, phosphate, acetate, and bicarbonate, can be added to intravenous solutions. Custom-made solutions take time to prepare and are much more expensive than commercial solutions.

The use of custom-made solutions is necessary only for patients who have underlying disorders that cause significant electrolyte imbalances. The use of commercial solutions saves both time and expense.

Holliday segar method

for calculating maintenance fluid requirement

Body weight Fluid per day

0-10kg 100ml per kg

10-20kg 1000ml+50ml per kg

>20kg 1500ml+20ml per kg

Selection of maintenance fliuds

A normal plasma osmolality is 285-295 mOsm/kg.

Infusing an intravenous solution peripherally with a much lower osmolality can cause water to move into red blood cells, leading to hemolysis.

Thus, intravenous fluids are generally designed to have an osmolality that is either close to 285 or greater (fluids with moderately higher osmolality do not cause problems).

Thus,0.2NS (osmolality = 68) should not be administered peripherally,but D5 0.2NS (osmolality = 346) or D5 1/2NS + 20 mEq/L KCl(osmolality = 472) can be administered.

Children weighing less than approximately 10 kg do best with the solution containing 0.2NS because of their high waterneeds per kilogram. Larger children and adults may receive the solution with 1/2NS .

In all children, it is critical to carefully monitor weight, urine output, and electrolytes to identify overhydration or underhydration,hyponatremia, and other electrolyte disturbances, and to then adjust the rate or composition of the intravenous solution accordingly.

Maintenance fluids and hyponatremia

Hyponatremia is seen in the postoperative patient who is intravascularly volume-depleted from surgical losses, third space losses, and venous pooling .

Surgical patients typically receive isotonic fluids (NS, LR) during surgery and in the recovery room for 6-8 hr postoperatively; the rate is typically approximately 2/3 of the calculated maintenance rate.

Subsequent maintenance fluids should contain 1/2NS , even in smaller patients,unless there is a specific indication to use 0.2NS. Electrolytes should be measured at least daily.

Variations in maintenanace water and electrolytes

Sources of water loss

Urine 60%Insensible 35% (skin ,lungs)Stool 5%

• Urine is the most important contributor to normal water loss.•Insensible losses represent approximately 1/3 of total maintenance water (40% in infants and closer to 25% in adolescents and adults).• Insensible losses are composed of evaporative losses from the skin and lungs that cannot be quantitated. •The evaporative losses from the skin do not include sweat, which would be considered an additional (sensible) source of water loss.• Stool normally represents a minor source of water loss.

Maintenance water and electrolyte needs may be increased or decreased, depending on the clinical situation.

This may be obvious, in the case of the infant with profuse diarrhea, or subtle, in the case of the patient who has decreased insensible losses while receiving mechanical ventilation.

It is helpful to consider the sources of normal water and electrolyte losses and to determine whether any of these sources is being modified in a specific patient.

It is then necessary to adjust maintenance water and electrolyte calculations.

• The skin can be a source of very signifi cant water loss, particularly in neonates, especially premature infants, who are under radiant warmers or are receiving phototherapy.• Very low birthweight infants can have insensible losses of 100-200 mL/kg/24 hr. • Burns can result in massive losses of water and electrolytes, and there are specific guidelines for fluid management in children with burns . • Sweat losses of water and electrolytes, especially in a warm climate, can also be significant. • Children with cystic fibrosis have increased sodiumlosses from the skin. Some children with pseudohypoaldosteronismalso have increased cutaneous salt losses.

Adjustments in Maintenance water

Fever increases evaporative losses from the skin. These losses are somewhat predictable, leading to a 10-15% increase in maintenance water needs for each 1 ° C increase in temperature above 38 ° C.

These guidelines are for a patient with a persistent fever;a 1-hr fever spike does not cause an appreciable increase in water needs.

Tachypnea or a tracheostomy increases evaporative losses from the lungs.

A humidified ventilator causes a decrease in insensible losses from the lungs and can even lead to water absorption via the lungs; a ventilated patient has a decrease in maintenance water requirements.

Thus,It may be difficult to quantify the changes that takeplace in the individual patient in these situations.

Replacement fluids

The gastrointestinal (GI) tract is potentially a source of considerable water loss.

GI water losses are accompanied by electrolytes and thus may cause disturbances in intravascular volume and electrolyte concentrations.

GI losses are often associated with loss of potassium, leading to hypokalemia.

Because of the high bicarbonate concentration in stool, children with diarrhea usually have a metabolic acidosis, which may be accentuated if volume depletion causes hypoperfusion and a concurrent lactic acidosis.

Emesis or losses from an NG tube can cause a metabolic alkalosis

It is impossible to predict the losses for the next 24 hr; it is better to replace excessive GI losses as they occur.

The child should receive an appropriate maintenance fluid that does not consider the GI losses.

The losses should then be replaced after they occur, with use of a solution with the same approximate electrolyte concentration as the GI fluid. The losses are usually replaced every 1-6 hr, depending on the rate of loss, with very rapid losses being replaced more frequently.

Diarrhea is a common cause of fluid loss in children. It can cause dehydration and electrolyte disorders.

In the unusual patient with significant diarrhea and a limited ability to take oral fluid, it is important to have a plan for replacing excessive stool losses.

The volume of stool should be measured, and an equal volume of replacement solution should be given.

Data are available on the average electrolyte composition of diarrhea in children in the next slide.

With use of this information, it is possible to design an appropriate replacement solution.

Replacement fluid for diarrhea

Each 1 mL of stool should be replaced by 1 mLof this solution.

Loss of gastric fluid, via either emesis or NG suction, is also likely to cause dehydration, in that most patients with either condition have impaired oral intake of fluids.

Electrolyte disturbances,particularly hypokalemia and metabolic alkalosis, are also common.

Patients with gastric losses frequently have hypokalemia,although the potassium concentration of gastric fluid is relatively low.

The associated urinary loss of potassium is an important cause of hypokalemia in this situation.

These patients may need additional potassium either in their maintenance fluids or in their replacement fluids to compensate for prior or ongoing urinary losses.

Restoration of the patient’s intravascular volume, by decreasing aldosterone synthesis, lessens the urinary potassium losses.

Adjusting fluid therapy for altered renal output

Surgical drains and chest tubes can produce measurable fluid output.

These fluid losses should be replaced when they are significant.

Third space losses, which manifest as edema and ascites, are due to a shift of fluid from the intravascular space into the interstitial space.

Although these losses cannot be quantitated easily, third space losses can be large and may lead to intravascular volume depletion, despite the patient’s weight gain.

Replacement of third space fluid is empirical but should be anticipated in patients who are at risk, such as children who have burns or abdominal surgery.

Deficit therapy

Dehydration, most often due to gastroenteritis, is a common problem in children. Most cases can be managed with oral rehydration.

Even children with mild to moderate hyponatremic or hypernatremic dehydration can be managed with oral rehydration.

The first step in caring for the child with dehydration is to assess the degree of dehydration

Assessment of severity of dehydration

no dehydration Alert,no thirst,normal skinturgor,normal eyes,moist oral mucosa,no signs of dehydration,wt loss <3%,normal heart rate,warm extrimitiesTreatment :plan A

Some dehydration Irritable,thirsty drinks eagerly,skin turgor goes back slowly,sunken eyes,tears absent,dry oral mucosa,signs of dehydration,3-9% wt loss,increased HR,decreased pulse volume,cold extremities treatment:planB

Severe dehydration lethargic/unconscious,drinks poorly,skin turgir goes back very slowly, very sunken eyes,very dry oral mucosa,two or more above signs,>9% wt loss,tachy or bradycardia, weak or thready /impalpable pulse,cold mottled and cyanotic extremities.treatment:plan C

Plan Aage Amount of ors to be

given after every stool

Amout of ors to provide for use at home

<24months 50-100ml per loose stool

500ml /day

2-10yrs 100-200ml per loose stool

1000ml/day

10yrs or above As much as child wants

2000ml/day

Amount of ORS to be used in first 4hrs for children with some dehydration(PLAN-B)

age <4months

4-11mon

12-23mon

2-4yrs 5-14yrs >14yrs

Wt (kg) <5 5-8 8-11 11-16 16-30 >30

ORS(ml) 200-400 400-600 600-800 800-1200

1200-2200

>2200

The Child is reassessed at the end of 4hrs and managed accordingly.

For replacement of ongoing losses,also give ors 10-20ml/kg for each loose stool.

Plan -C

The child with severe dehydration should initially receive intravenous therapy.

These children require immediate IVfluids as 100ml/kg of the solution,either RL (preferably) or NS.

In case of unavailability of IV line,the NG tube can be used for rehydration by ORS.

ORS can be given at 20ml/kg/hr(total 120ml/kg) by NG tube.

Clinical assessment of dehydration is only an estimate; thus,the patient must be continually reevaluated during therapy.

The degree of dehydration is underestimated in hypernatremic dehydration because the movement of water from the intracellular space to the extracellular space helps preserve the intravascular volume.

Plan C

age 30ml/kg 70ml/kg

<12months 1hour 5hours

Older child 30 minutes 2 hrs30min

According to the age and clinical condition of the child100ml/kg of RL is given intravenously over 3-6hrs.

In severly malnourished or in infants ,this amount is given slowly over 6hrs.

The first 30ml/kg infused rapidly in first 1hr.the remaining 70ml/kg is infused in the next 5hrs.

Once the intracellular dehydration is corrected,isolyte P can be used.

The child should be continuously assessed for urinary output,electrolytes,blood urea,serum creatinine and glucose levels.

monitor the vital signs and observe forcomplications(metabolic acidosis,etc.) and behavioural changes.

The history usually suggests the etiology of the dehydration and may predict whether the patient will have a normal sodium concentration (isotonic dehydration), hyponatremic dehydration,

or hypernatremic dehydration. The neonate with dehydration due to poor intake of breast

milk often has hypernatremic dehydration. Hypernatremic dehydration is likely in any child with losses

of hypotonic fluid and poor water intake, such as may occur with diarrhea, and poor oral intake due to anorexia or emesis.

Hyponatremic dehydration occurs in the child with diarrhea who is taking in large quantities of low-salt fluid, such as

water or diluted formula

Laboratory Findings

The serum sodium concentration determines the type of dehydration. Metabolic acidosis may be due to stool bicarbonate losses in children with diarrhea, secondary renal insufficiency, or lactic acidosis from shock. The anion gap is useful for differentiating among the various causes of a metabolic acidosis .

Emesis or nasogastric losses usually cause a metabolic alkalosis.

The serum potassium concentration may be low as a result of diarrheal losses.

In children with dehydration due to emesis, gastric potassium losses, metabolic alkalosis, and urinary potassium losses all contribute to hypokalemia.

Metabolic acidosis, which causes a shift of potassium out of cells, and renal insuffi ciency may lead to hyperkalemia.

The blood urea nitrogen (BUN) value and serum creatinine concentration are useful in assessing the child with dehydration.

A normal hemoglobin concentration during acute dehydration may mask an underlying anemia.

A decreased albumin level in a dehydrated patient suggests a chronic disease, such as malnutrition, nephrotic syndrome, or liver disease, or an acute process, such as capillary leak.

An acute or chronic protein-losing enteropathy may also cause a low serum albumin concentration.

Types of dehydration

Dehydration is of 3 specific types Isotonic Hyponatremic hypernatremic

Isotonic dehydration

Incidence is70-80% Most common causes are diarrhea with

vomitings,simple enteritis. Serum osmolality is 281-297mEq/L. Sodium conc.133-145mEq/L Decreased skin turgor. Pulse Increased.

Treatment: ½ isotonic solution for 24 hrs followed by

isotonic solution. Complications: Metabolic acidosis ,prerenal failure

Hyponatremic dehydration

Incidence is 10-15% Causes:cholera ,sweating,viral diarrhea. Serum osmolality:<281mEq/L Serum sodium:<133mEq/L Symptoms:altered sensorium Decreased skin turgor Pulse:very highly increased Treatment: 0.9%Nacl solution Complications:Cerebral edema

Hypernatremic dehydration

Incidence:<5% Causes:diabetes insipidus,administration of

faulty prepared ORS Serum osmolality:>297mEq/L Serumsodium:>145mEq/L Symptoms:irritability Normal skin turgor Pulse:decreased Treatment:hypotonic solution 0.2%nacl with

5%D for 24 hrs followed by ½ isotonic solution Complications:intracranial hemorrhage

The End