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Dr Mark LuscombeConsultant Anaesthetics/Critical Care Doncaster Royal Infirmary
Today’s Talk
Aim to look at two questions:Does the current APLS weight estimation formula remain valid?
Is there a better alternative?
Increasing WeightConcern over
obesity in childrenIs it just extremes
or are children in general heavier?
Is there a real weight change or just a perceived change?
North & South Magazine
Medical Literature
Population Characteristics
Pilot StudiesFirst Study in Whangarei Hospital NZ
(n=103) Predicted weight is = 2(Age+4)Children aged between 1 and 10 yo Acute or day-case surgery in a 3 month
periodCompared recorded weights with
predicted weight
Results 90% children greater than estimated
weightsNZ mean weight difference =
24.75% (95% CI = +19.25% to +30.25%)
Pilot StudiesSecond Study
in Doncaster Royal Infirmary UK (n=134)
Method and Inclusion criteria as previous study
Results 86%(UK) children greater than estimated
weightsUK mean Weight Difference = +18.46%
95% CI = +14.87% to +22.05%Compared with NZ +24.75%
Problems & SolutionsCurrent estimation formula significantly
underestimates weightMore accurate formula required
Use Data to derive new formula
Importance of Weight EstimationOften needed for critically illRelied upon for:
Drug DosagesFluid Bolus (& Maintenance)DC Shock settingsVentilator settingsUrine output
Decision to ventilate based upon fluid given
New FormulaInclude 2 Standard deviationsDraw straight line of best fitResult is: Weight = 2.37 x Age + 9.63 (NZ)
Weight = 2.52 x Age + 7.56 (UK)
New Formula - Criteria1) Simple to use
2) More accurate than previous
3) In general should avoid over-estimation of weight
Two Options consideredWeight = 2 x (Age + 5) andWeight = 2.5x (Age + 4)
Early ConclusionsChildren are heavier than
predicted by current formula
The current formula is a poor estimate of the modern child’s weight.
Both new formulae tried were more accurate
Pilot studies recommendation - Which New Formula?
Weight = 2x(age+5) Whilst not as accurate on average as
the other formula tried, it is:
1) More accurate than Weight = 2x(age+4)
2) Likely to avoid drug over-dosage3) Simple to calculate
PublicationLuscombe M D, “Kids aren’t like what they
used to be”: a study of paediatric patient’s weights and their relationship to current weight estimation formulae. British Journal of Anaesthesia 2005; 95(4): 578
Next StepLarger scale study – need minimum n=400Checklist
ProposalProtocolCo-researchersEthical ApprovalFinance FormResearch and development approval at research
centreCollect data and analyseStatisticianWrite it!Publish
Next StepLuscombe MD & Owens BDData from Queens Medical centre,
Nottingham UK, ED database6 months data n= 17244 test sets of data.Age/Weight/Ethnicity/A&E Category
Differences from pilot studiesMany more formulae testedCheck made on weights by
A&E category.Individual ages consideredGraphical representation Ethnicity considered
Formulae tried :Weight =
2age+9 2age+11 2(age+5) 2(age+6) 2.5(age+3) 2.5(age+4) 3(age+2) 3(age+3) 3age+7 3age+8
Necessary?Weights of Category 1 patients (Acute-Life
Threatening) recorded = 41.5%
Weights of Category 5 patients (Minor injury to Emergency Nurse Practitioner) = 94.1%
Overall weight recording = 81.7%
Necessary?Weight estimate is still neededPrevious reasons for accurate weight
assessment remain valid i.e.Drug DosagesFluid Bolus (& Maintenance)DC Shock settingsVentilator settingsUrine outputDecision to ventilate based upon fluid givenWeight estimate may persist into ICU stay
Additional InformationNo evidence base for Weight=2(age+4)
foundFanconi, Wallgren & Collis “Textbook of
Paediatrics” 1952 – Weights listed for age groups
Small “audit” type projects had also found more accurate formulae.
ResultsAll formulae tried were more accurate overall3 formulae matching criteria
Weight = 3(age)+7 Weight = 2.5(age+3) Weight = 2(age+5)
Weight = 2(age+4) remains poor estimate
Graphical Representation
Which Formula?
DisseminationLuscombe MD & Owens BD. Weight
estimation in resuscitation: is the current formula still valid? Archives of Disease in Childhood 2007;92:412-415
Numerous presentations
Any problems?Formula is an estimateOverestimate in 4-5-6yrs old groupOnly from 1 – 10yrs oldEthnicity not recordedData from one area and in the UK only
Further WorkSheffield Children’s Hospital Validation Study
Luscombe MD, Owens BD, Burke D.Ages up to 16yrs
Sheffield n= 41792Interim Results:
FormulaFormula Mean Mean Weight Diff Weight Diff
1-10yrs1-10yrs
Mean Mean Weight Diff Weight Diff
11-16yrs11-16yrs
Mean Mean Weight Diff Weight Diff 11-12yrs11-12yrs
Mean Mean Weight Weight Diff (all)Diff (all)
2(age+4)2(age+4) 22.45%22.45% 59.43%59.43% 51.02%51.02% 34.14%34.14%
3(age) + 73(age) + 7 2.62%2.62% 17.93%17.93% 12.81%12.81% 7.45%7.45%
Further work
Interim ConclusionsResults validate previous study in new
populationWeight = 3(age)+7 more accurate 1-10yrsWeight = 3(age)+7 more accurate 1-16yrs“Acceptable” accuracy 1-12yrsPuberty
Males approx 11.5yrsFemales approx 10.5yrs
Formula works from 1 yrs to puberty
Thank youTo ALSG for inviting me.For your interest. To Ben Owens and the many who have
helped.
Any Questions? References Fanconi G, Wallgren A, Collis WRF. Textbook of Paediatrics. William Heinemann
Medical Books Ltd, London 1952 Luscombe M D, “Kids aren’t like what they used to be”: a study of paediatric
patient’s weights and their relationship to current weight estimation formulae. British Journal of Anaesthesia 2005; 95(4): 578
Luscombe MD & Owens BD. Weight estimation in resuscitation: is the current formula still valid? Archives of Disease in Childhood 2007;92:412-415
A M Fredriks, S van Buuren, et al, Arch Dis Child 2000;82:107–112 Jain, A Fighting Obesity, BMJ 2004;328;1327-1328 The advanced life support group, Advanced Paediatric Life Support, Fourth
Edition, BMJ Publishing Group 2004 The Dominion Post NZ December 2004 North & South Magazine NZ May 2004
Weight = 3(age) + 7