2 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.
3 Why nurses? Nurses administer the fluids Nurses 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
4 Fluid content as % of body weight Water contributes to a higher percentage of body weight in child. Fluid balance is relatively more important and fluid imbalance causes more morbidity and mortalityWillock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
5 Body compartmentsWillock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
6 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.Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
7 Fluid distributionYoung children have a greater proportion of water in their interstitial compartmentWillock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
8 What we put into the vascular compartment affects what is in the other compartments 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.
9 Blood Volume Neonate 90 ml / kg Infants and children 80 ml / kg Adults Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
11 Water Water is lost through What is acquired from: Renals Drinking LungsSkinGI TractWhat is acquired from:DrinkingIV fluids etc.Oxidation of nutrients (carbohydrate)Note that we make our own waterNote the avenues of insensible loss
12 Insensible loss Water is normally lost via: Renals (not insensible) Non obligatory loss controlled by ADH (posterior pituitary).ADH causes the reabsorption of water from the renal collecting ducts.Water is normally lost via:Renals (not insensible)LungsSkinGI TractObligatory loss of fluid from the skin etc. Is influenced by:Surface areaEnvironmental temperatureHumidityRespiratory rate (lungs)
13 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
14 Homeostasis Homeostasis Osmo-receptors in the hypothalamus and elsewhereHypothalamus and posterior pituitary responsible for sensation of thirst (mid hypothalamus) and releases of antidiuretic hormoneThe absorption of fluid from the gut is a passive response to the active transport of sodium (failure results in diarrhoea)The renal collective ducts re-absorb waterVolume receptors (baroreceptors) in the atria and elswhere
15 Normal Oral Fluid (Feed) Requirements Pre-TermPre-term baby needs approximately 200ml / kg / dayTermTerm babies need approximately 150ml / kg / dayAdultAdults need approximately 70ml / kg / dayNormal oral fluid requirements (adapted from Behrman RE (1992)). AgeAv. Weight (kg)mL per kg per day3/73.080-10010/73.23/125.46/127.39/128.61 yr9.52 yr11.84 yr16.26 yr20.090-10010 yr28.770-8514 yr45.050-6018 yr54.040-50
16 Subdivision of total fluids Fraction of TotalFunctionAmountType1st fifthInsensible lossOne fifthInsensible losses only2nd fifthEssential urine outputTwo fifthsSevere fluid restriction3rd to 5th fifthsMaintenance of urine outputThree fifthsModerate fluid restrictionFour to five fifthsAdequate fluidsSix to ten fifthsInduced diuresis
17 Maintenance IV requirements First 10kg100 ml / kg / day for the first 10kg body weight (4ml / kg / hour)Second 10kg50ml / kg / day for the second 10kg body weight (2ml / kg / hour)Each additional kg20ml / kg / day for each additional kg body weight (1ml / kg / hour)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.
19 Fluid losses (children) Willock J, Jewkes F (). Making sense of fluid balance in children. Paediatric Nursing. 12 (7) 37-42
20 Dehydration a problem because children have: Higher proportion of waterHigher 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 dehydrationGreater surface area in proportion to weightGreater proportion of extracellular fluidNeonates relative inability to concentrate urine on dehydration:Neonatal Glomerular filtration Rate is 30ml/min/1.73 m2At 9/12 GFR is 100ml / min / 1.73 m2Note 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 spoutTherefore – children lose fluid FASTER
21 Clinical signs of dehydration Clinical signsMild (<5%)Moderate (5-10%)Severe (>10%)CommentsDecreased weightLoss of fluid = loss of weightDrowsiness? the most important sign of severityDecreased urine outputMeasure it from the beginningDry mouthNot as obvious in babies, feel inside their cheekDecreased skin turgorMost obvious on abdomenSunken eyesAsk parentsTachypnoeaLate signTachycardiaHypotensionPre terminal signSunken fontanelleOnly for the experienced
22 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 secondsSevere malnutrition can cause reduced skin turgurObesity can cause skin turgur to appear normalHypernatraemic dehydration associated with firm ‘thick-feeling’ skinOedemaDry mucosa (inside cheek)Oligurea – Normal urine output is at least 1ml/kg/hourWeight change (1ml water weighs 1 gram).
24 Treatment for fluid loss (dehydration) Less than 5% dehydration – treat with Oral rehydration solution (ORS), e.g. dioralyte
25 Treatment of shock – initial Rx Admission to 2 hours post admissionWeigh 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.
26 Treatment of shock 2-24 hours Give maintenance fluids plus 2/3 deficit and minus volume already administered (20ml / kg)ExampleWeight on admission 9kgDehydration estimated at 10% fluid deficit is ml (10% of 9kg)Deficit X 0.66 is mlMaintenance requirement 900ml (100ml/kg)Subtract fluid administered 180ml (20ml/kg)Volume required over 22 hours is 1314ml
27 Monitor – be vigilantMonitor electrolytes after infusion and at intervalsCorrect major electrolyte imbalances SLOWLYMonitor systemic perfusionMonitor urine outputMonitor neurological statusUnderhydration is SAFER than overhydrationLab Serum ValuesPotassium3.5-7mmol/lSodiummmol/l
28 Na = sodium, aemia = blood, ‘Na’traemic syn. ‘blood sodium’ Types of dehydrationNormonatraemicIsotonic pressure of intravascular compartment is the same as that in the extravascular compartment [normal]HypernatraemicThe vascular compartment is hypertonicHyponatraemicThe vascular compartment is hypotonicNa = sodium, aemia = blood, ‘Na’traemic syn. ‘blood sodium’
29 Normonatraemic dehydration Most common in UKNo significant shift of fluid between intra-cellular and extra-cellular compartmentNormal serum sodium is mmol/L
30 Hypernatraemic dehydration Relatively uncommon in the UKSerum sodium > 150mmol/LCan be caused by high levels of water loss with retention of sodium or iatrogenicallyPossible causes includeHigh levels of insensible fluid lossDiabetes incipidusExtra-cellular fluid is well maintained at the expense of intracellular fluidClinical features underestimate the actual level of dehydration
31 Hyponatraemic dehydration Caused 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
32 Shock – the three stages Compensated shockUncompensatedIrreversible
33 Compensated shock Normal BP Oligurea Pallor, coldness, clamminess TachycardiaIncreased capillary refill timeAnxious, agitated and confused
34 Uncompensated shock Insufficient oxygenation of tissues Insufficient 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)
35 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 placeOxygen free radicals are released (or have been released) and have cause irreversible major organ damage
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