The problem Worldwide, dehydration is probably the most common cause of death in childhood. In the UK, dehydration and iatrogenic overhydration are key

The problemWorldwide, dehydration is probably the most common

cause of death in childhood. In the UK, dehydration and iatrogenic overhydration are key issues in clinical practice.

A child suffering 10-15% dehydration will die or suffer permanent brain damage unless managed urgently and capably.

Why nurses?Nurses administer the fluidsNurses are responsible for ensuring that the fluids given

are safe in type and amountNurses must recognise an unsafe prescriptionUnder and over treatment with fluids (water and or

electrolytes) may cause severe morbidity or mortality

Fluid content as % of body weight

Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42

Water contributes to a higher percentage of body weight in child. Fluid balance is relatively more important and fluid imbalance

causes more morbidity and mortality

Body compartments


Fluid distribution according to age


Younger children have a higher proportion of extra-cellular fluid. In some forms of fluid loss, an important volume of fluid can be lost from the extra-cellular (mostly interstitial) compartment.

Isotonic fluid is given IV to reach this compartment.

Fluid distribution


Young children have a greater proportion of water

in their interstitial compartment

Osmotic pressureNormally the osmotic pressure in the different body

compartments is equal.Differentials in osmotic pressure between two body

compartments will cause fluid to move between compartments.

This can be a serious problem during the acute phase of treatment.

Therefore – electrolytes MUST be monitored during and (especially) after treatment.

What we put into the vascular compartment affects what is in the

other compartments

Blood VolumeNeonate 90 ml / kg

Infants and children 80 ml / kg

Adults 65 ml / kg


ElectrolytesLearn the plasma values for

these electrolytes

Water

What is acquired from:DrinkingIV fluids etc.Oxidation of nutrients

(carbohydrate)

Water is lost throughRenalsLungsSkinGI Tract

Note that we make our own water

Note the avenues of insensible loss

Insensible lossWater is normally lost via:

Renals (not insensible)LungsSkinGI Tract

Obligatory loss of fluid from the skin etc. Is influenced by: Surface area Environmental temperature Humidity Respiratory rate (lungs)

Non obligatory loss controlled by ADH (posterior pituitary).

ADH causes the reabsorption of water from the renal collecting ducts.

Insensible loss

To calculate Body Surface Area

Insensible loss is 300ml / M2 / day so use this formula (left)


Homeostasis

Normal Oral Fluid (Feed) Requirements

Normal oral fluid requirements(adapted from Behrman RE (1992)).

Age Av. Weight (kg) mL per kg per day

3/7 3.0 80-10010/7 3.2 125-1503/12 5.4 140-1606/12 7.3 130-1559/12 8.6 125-1451 yr 9.5 120-1352 yr 11.8 115-1254 yr 16.2 100-1106 yr 20.0 90-10010 yr 28.7 70-8514 yr 45.0 50-6018 yr 54.0 40-50

Subdivision of total fluidsFraction of Total Function Amount Type

1st fifth Insensible loss One fifth Insensible losses only

2nd fifth Essential urine output

Two fifths Severe fluid restriction

3rd to 5th fifths Maintenance of urine output

Three fifths Moderate fluid restriction

Four to five fifths Adequate fluids

Six to ten fifths Induced diuresis

Maintenance IV requirements

A 15kg child requires 1000ml plus 250ml =1250ml dailyNote that oral fluid requirements are higher than IV requirements.

Glasper , McEwing and Richardson (2007). Oxford handbook of children’s and young people’s nursing. Oxford University Press.

Types of IV Fluid

Fluid losses (children)


Dehydration a problem because children have: Higher proportion of water Higher metabolic rate (children exchange up to 50% of the body fluid daily (adult 17%) Higher metabolic rate (more water produced and excreted) Higher metabolic rate = greater propensity to dehydration Greater surface area in proportion to weight Greater proportion of extracellular fluid Neonates relative inability to concentrate urine on dehydration:

Neonatal Glomerular filtration Rate is 30ml/min/1.73 m2

At 9/12 GFR is 100ml / min / 1.73 m2

Note that circulatory failure (shock) can be highly compensated and so vital signs may mask underlying pathology. Consequently hypotension may be a late sign of hypovolaemia.

A child is a small vessel with a large spoutAn adult is a large vessel with a small spout

Therefore – children lose fluid FASTER

A child is a small vessel with a large spoutAn adult is a large vessel with a small spout

Therefore – children lose fluid FASTER

DehydrationClinical signs of dehydration

Clinical signs Mild (<5%) Moderate (5-10%)

Severe (>10%) Comments

Decreased weight Loss of fluid = loss of weight

Drowsiness ? the most important sign of severity

Decreased urine output Measure it from the beginning

Dry mouth Not as obvious in babies, feel inside their cheek

Decreased skin turgor Most obvious on abdomen

Sunken eyes Ask parents

Tachypnoea Late sign

Tachycardia Late sign

Hypotension Pre terminal sign

Sunken fontanelle Only for the experienced

Means of estimating clinical dehydration Capillary refill time (should be < 2 seconds) Central – peripheral temperature gap (should be

< 2 degrees centigrade) Tissue turgur (abdomen or inside of thigh)

3-5% weight (fluid) loss skin remains raised for seconds Severe malnutrition can cause reduced skin

turgur Obesity can cause skin turgur to appear normal Hypernatraemic dehydration associated with firm

‘thick-feeling’ skin Oedema Dry mucosa (inside cheek) Oligurea – Normal urine output is at least

1ml/kg/hour Weight change (1ml water weighs 1 gram).

Equation for dehydration

Treatment for fluid loss (dehydration)

Less than 5% dehydration – treat with Oral rehydration solution (ORS), e.g. dioralyte

Treatment of shock – initial RxAdmission to 2 hours post admission

Weigh childEstimate degree of dehydrationMeasure urine outputGive 20 ml / kg Normal saline or Colloid over 1-2 hoursRepeat if shock not reversedDo electrolyte levelsAllow IV potassium only in the presence of adequate renal

function.

Treatment of shock 2-24 hoursGive maintenance fluids plus 2/3 deficit and minus volume

already administered (20ml / kg)

ExampleWeight on admission 9kgDehydration estimated at 10% fluid deficit is 900ml (10% of 9kg)Deficit X 0.66 is 594mlMaintenance requirement 900ml (100ml/kg)Subtract fluid administered 180ml (20ml/kg)Volume required over 22 hours is 1314ml

Monitor – be vigilantMonitor electrolytes after infusion

and at intervalsCorrect major electrolyte

imbalances SLOWLYMonitor systemic perfusionMonitor urine outputMonitor neurological statusUnderhydration is SAFER than

overhydration

Lab Serum Values

Potassium 3.5-7mmol/l

Sodium 136-146mmol/l

Types of dehydration Normonatraemic

Isotonic pressure of intravascular compartment is the same as that in the extravascular compartment [normal]

Hypernatraemic The vascular compartment is

hypertonic

Hyponatraemic The vascular compartment is

hypotonicNa = sodium, aemia = blood, ‘Na’traemic

syn. ‘blood sodium’

Normonatraemic dehydrationNormonatraemic

Most common in UKNo significant shift of fluid between intra-cellular and extra-

cellular compartmentNormal serum sodium is 130-150mmol/L

Hypernatraemic dehydrationRelatively uncommon in the UKSerum sodium > 150mmol/LCan be caused by high levels of water loss with retention of sodium or

iatrogenicallyPossible causes include

High levels of insensible fluid lossDiabetes incipidus

Extra-cellular fluid is well maintained at the expense of intracellular fluidClinical features underestimate the actual level of dehydration

Hyponatraemic dehydrationCaused by the loss of fluid high in sodiumFluid passes into the cellsResults in convulsions and shock which is more severe

than the level of dehydration would indicate

Shock – the three stages

Compensated shockUncompensatedIrreversible

Compensated shockNormal BPOligureaPallor, coldness, clamminessTachycardiaIncreased capillary refill timeAnxious, agitated and confused

Uncompensated shockInsufficient oxygenation of tissuesInsufficient provision of glucose to tissuesFailure of normal metabolismBuild up of lactic acid and carbonic acid (acidosis)Reduced cardiac outputPlatelet aggregation is small blood vessels (bleeding)Increased capillary permeability ( fluid moves from

capillaries into interstitial space)

Irreversible shockDamage to the renals and brain is such that even if

dehydration (hypovolaemia) is corrected and fluid balance is restored, death will still take place

Oxygen free radicals are released (or have been released) and have cause irreversible major organ damage

Documents

The problem Worldwide, dehydration is probably the most common cause of death in childhood. In the UK, dehydration and iatrogenic overhydration are key