dr mark luscombe consultant anaesthetics/critical care doncaster royal infirmary

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