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