# Paediatric Weight Estimation: Small change – Big Difference?

## Presentation on theme: "Paediatric Weight Estimation: Small change – Big Difference?"— Presentation transcript:

Paediatric Weight Estimation: Small change – Big Difference?
Dr Mark Luscombe Consultant 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 Weight Concern over obesity in children
Is 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 Studies First 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 period Compared recorded weights with predicted weight

Results 90% children greater than estimated weights
NZ mean weight difference = % (95% CI = % to %)

Pilot Studies Second Study in Doncaster Royal Infirmary UK (n=134)
Method and Inclusion criteria as previous study

Results 86%(UK) children greater than estimated weights
UK mean Weight Difference = % 95% CI = % to % Compared with NZ %

Problems & Solutions Current estimation formula significantly underestimates weight More accurate formula required  Use Data to derive new formula

Importance of Weight Estimation
Often needed for critically ill Relied upon for: Drug Dosages Fluid Bolus (& Maintenance) DC Shock settings Ventilator settings Urine output Decision to ventilate based upon fluid given

New Formula Include 2 Standard deviations
Draw straight line of best fit Result is: Weight = 2.37 x Age (NZ) Weight = 2.52 x Age (UK)

New Formula - Criteria 1) Simple to use 2) More accurate than previous
3) In general should avoid over-estimation of weight Two Options considered Weight = 2 x (Age + 5) and Weight = 2.5x (Age + 4)

Early Conclusions Children 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-dosage 3) Simple to calculate

Publication 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

Next Step Larger scale study – need minimum n=400 Checklist Proposal
Protocol Co-researchers Ethical Approval Finance Form Research and development approval at research centre Collect data and analyse Statistician Write it! Publish

Next Step Luscombe MD & Owens BD
Data from Queens Medical centre, Nottingham UK, ED database 6 months data n= test sets of data. Age/Weight/Ethnicity/A&E Category

Differences from pilot studies
Many more formulae tested Check made on weights by A&E category. Individual ages considered Graphical 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 needed
Previous reasons for accurate weight assessment remain valid i.e. Drug Dosages Fluid Bolus (& Maintenance) DC Shock settings Ventilator settings Urine output Decision to ventilate based upon fluid given Weight estimate may persist into ICU stay

No evidence base for Weight=2(age+4) found Fanconi, Wallgren & Collis “Textbook of Paediatrics” 1952 – Weights listed for age groups Small “audit” type projects had also found more accurate formulae.

Results All formulae tried were more accurate overall
3 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? Mean Weight Difference = 2.48%
Weight = 3(age) + 7 Mean Weight Difference = 2.48% (95%CI = 2.17% to 2.79%) Same at age 1 then more accurate at all other ages than current formula. It is more accurate than all the other formulae from age 6 and older. Mean weight difference 2(age+4)= 18.8% (95% CI = 18.42% to 19.18%).

Dissemination Luscombe MD & Owens BD. Weight estimation in resuscitation: is the current formula still valid? Archives of Disease in Childhood 2007;92: Numerous presentations

Any problems? Formula is an estimate
Overestimate in 4-5-6yrs old group Only from 1 – 10yrs old Ethnicity not recorded Data from one area and in the UK only

Further Work Sheffield Children’s Hospital Validation Study Luscombe MD, Owens BD, Burke D. Ages up to 16yrs Sheffield n= Interim Results: Formula Mean Weight Diff 1-10yrs 11-16yrs Mean Weight Diff 11-12yrs Mean Weight Diff (all) 2(age+4) 22.45% 59.43% 51.02% 34.14% 3(age) + 7 2.62% 17.93% 12.81% 7.45%

Further work

Interim Conclusions Results validate previous study in new population
Weight = 3(age)+7 more accurate 1-10yrs Weight = 3(age)+7 more accurate 1-16yrs “Acceptable” accuracy 1-12yrs Puberty Males approx 11.5yrs Females approx 10.5yrs Formula works from 1 yrs to puberty

Thank you To 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: A M Fredriks, S van Buuren, et al, Arch Dis Child 2000;82:107–112 Jain, A Fighting Obesity, BMJ 2004;328; 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