# Weight formula validation

Further validation of the UK-derived Luscombe weight formula has been made in the Australian setting. The nice simple formula for estimating the weight of a child based on age is:

Weight (kg) = 3 x age(years) + 7

It was compared with other formulae including the Best Guess formula, which is a bit more difficult to apply as the formula varies according to age range. This is reported in a previous post.

The authors provide the following cautionary advice:

“Whereas age-based formulae are, in the main, easy to calculate, the evidence suggests that ethnicity and body habitus pose serious challenges to their accuracy. In comparative studies, age-based formulae were found to be less accurate than the Broselow tape and parental estimate, with parental estimate being the most accurate weight estimation method. In light of this evidence, age-based formulae should only be used when these more accurate methods are not available.”

OBJECTIVE: Several paediatric weight estimation methods have been described for use when direct weight measurement is not possible. A new age-based weight estimation method has recently been proposed. The Luscombe formula, applicable to children aged 1-10 years, is calculated as (3 × age in years) + 7. Our objective was to externally validate this formula using an existing database.

METHOD: Secondary analysis of a prospective observational cohort study. Data collected included height, age, ethnicity and measured weight. The outcome of interest was agreement between estimated weight using the Luscombe formula and measured weight. Secondary outcome was comparison with performance of Argall, APLS and Best Guess formulae. Accuracy of weight estimation methods was compared using mean difference (bias), 95% limits of agreement, root mean square error and proportion with agreement within 10%.

RESULTS: Four hundred and ten children were studied. Median age was 4 years; 54.4% were boys. Mean body mass index was 17 kg/m(2) and mean measured weight was 21.2 kg. The Luscombe formula had a mean difference of 0.66 kg (95% limits of agreement -9.9 to +11.3 kg; root mean square error of 5.44 kg). 45.4% of estimates were within 10% of measured weight. The Best Guess and Luscombe formulae performed better than Argall or APLS formulae.

CONCLUSION: The Luscombe formula is among the more accurate age-based weight estimation formulae. When more accurate methods (e.g. parental estimation or the Broselow tape) are not available, it is an acceptable option for estimating children’s weight.

Validation of the Luscombe weight formula for estimating children’s weight
Emerg Med Australas 2011 Feb;23(1):59-62

# ILCOR neonatal cooling guideline

On the basis of the published data to date the Neonatal Task Force of the International Liaison Committee on Resuscitation (ILCOR) made the following recommendation on February 2010 with regard to therapeutic hypothermia:

• Newly born infants born at term or near-term with evolving moderate to severe hypoxic-ischemic encephalopathy should be offered therapeutic hypothermia.
• Whole-body cooling and selective head cooling are both appropriate strategies.
• Cooling should be initiated and conducted in neonatal intensive care facilities using protocols consistent with those used in the randomized clinical trials i.e. commence within 6 h, continue for 72 h and rewarm over at least 4 h.
• Carefully monitor for known adverse effects of cooling – thrombocytopenia and hypotension.
• All treated infants should be followed longitudinally.

Therapeutic hypothermia following intrapartum hypoxia-ischemia. An advisory statement from the Neonatal Task Force of the International Liaison Committee on Resuscitation
Resuscitation 2010;81(11):1459-1461

# 2J or 4J/kg in Paediatric Defibrillation?

Should we shock with 2J/kg or 4J/kg in Paediatric Defibrillation? The answer seems to be ‘we still don’t know’. Don’t worry – just follow the guidelines (reproduced for you at the bottom)

OBJECTIVE To examine the effectiveness of initial defibrillation attempts. We hypothesized that (1) an initial shock dose of 2 ± 10 J/kg would be less effective for terminating fibrillation than suggested in published historical data and (2) a 4 J/kg shock dose would be more effective.

PATIENTS AND METHODS This was a National Registry of Cardiopulmonary Resuscitation prospective, multisite, observational study of in-hospital pediatric (aged 18 years) ventricular fibrillation or pulseless ventricular tachycardia cardiac arrests from 2000–2008. Termination of ventricular fibrillation or pulseless ventricular tachycardia and event survival after initial shocks of 2 J/kg were compared with historic controls and a 4 J/kg shock dose.

RESULTS Of 266 children with 285 events, 173 of 285 (61%) survived the event and 61 of 266 (23%) survived to discharge. Termination of fibrillation after initial shock was achieved for 152 of 285 (53%) events. Termination of fibrillation with 2 ± 10 J/kg was much less frequent than that seen among historic control subjects (56% vs 91%; P < .001), but not different than 4 J/kg. Compared with 2 J/kg, an initial shock dose of 4 J/kg was associated with lower rates of return of spontaneous circulation (odds ratio: 0.41 [95% confidence interval: 0.21–0.81]) and event survival (odds ratio: 0.42 [95% confidence interval: 0.18–0.98]).

CONCLUSIONS The currently recommended 2 J/kg initial shock dose for in-hospital cardiac arrest was substantially less effective than previously published. A higher initial shock dose (4 J/kg) was not associated with superior termination of ventricular fibrillation or pulseless ventricular tachycardia or improved survival rates. The optimal pediatric defibrillation dose remains unknown.

Effect of defibrillation energy dose during in-hospital pediatric cardiac arrest
Pediatrics. 2011 Jan;127(1):e16-23

Here’s what the guidelines say:

Many AEDs have high specificity in recognizing pediatric shockable rhythms, and some are equipped to decrease (or attenuate) the delivered energy to make them suitable for infants and children <8 years of age. For infants a manual defibrillator is preferred when a shockable rhythm is identified by a trained healthcare provider (Class IIb, LOE C). The recommended first energy dose for defibrillation is 2 J/kg. If a second dose is required, it should be doubled to 4 J/kg. If a manual defibrillator is not available, an AED equipped with a pediatric attenuator is preferred for infants. An AED with a pediatric attenuator is also preferred for children <8 year of age. If neither is available, an AED without a dose attenuator may be used (Class IIb, LOE C). AEDs that deliver relatively high energy doses have been successfully used in infants with minimal myocardial damage and good neurological outcomes

Pediatric Basic Life Support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care
Full text document

# Estimating child weight in Hong Kong

We know that the ‘APLS formula’ is inaccurate as a tool for estimating weight in Western children, and British and Australian researchers have devised more fitting formulae for their local populations as described here.

The emergency medicine team at the Accident and Emergency Medicine Academic Unit, Chinese University of Hong Kong have now provided a solution for Chinese children:

weight (kg) = (3 x age) + 5.

This was most accurate and precise in children <7 years old.

Age-based formulae to estimate children’s weight in the emergency department
Emerg Med J. 2010 Oct 13. [Epub ahead of print]

# Paediatric airway gems

Dr Rich Levitan has made an enormous contribution to the science and practice of emergency airway management, as his bibliography demonstrates. In a new article in Emergency Physicians Monthly entitled ‘Demystifying Pediatric Laryngoscopy’, Rich covers some great tips for optimising laryngoscopic view in kids.

Check this excerpt out for an example:

During laryngoscopy in infants the epiglottis and uvula are often touching; the epiglottis may be located within an inch of the mouth. Often the epiglottis lies against the posterior pharynx, and it is critical to have a Yankauer to dab the posterior pharynx as the laryngoscope is advanced. Hyperextension of the head pushes the base of tongue and epiglottis backwards against the posterior pharyngeal wall, and makes epiglottis identification more difficult

Gems like this come thick and fast when you hear or read what Rich has to say. Seven years ago I was left reeling after finishing his ‘Airway Cam Guide to Intubation and Practical Emergency Airway Management‘ which profoundly influenced the way I practice and teach emergency airway skills, including on the Critical Care for Emergency Physicians course.

I’ve finally gotten round to booking a place on one of his courses in March in Baltimore. I’ll let you know how it goes. In the mean time, I’d like to point you toward his training videos as a great educational resource, like this one that demonstrates for novice laryngoscopists the difference between the appearances of trachea and oesophagus, the former having recognisable, defined posterior cartilagenous structures:

Demystifying Pediatric Laryngoscopy
Emergency Physicians Monthly January 19, 2011

Seventy doctors and nurses from neonatal units administered positive pressure ventilation to a term newborn manikin using a Neopuff T-piece device. Recordings were made (1) before training, (2) after training in mask handling and (3) 3 weeks later. Leak and obstruction were calculated.

Median (IQR) leak was 71% (32–95%) before training, 10% (5–37%) directly after training and 15% (4–33%) 3 weeks later (p<0.001). When leak was minimal, gas flow obstruction was observed before, directly after training and 3 weeks later in 46%, 42% and 37% of inflations, respectively.

The training provided included the following demonstrated mask technique:

1. Place the manikin’s head in a neutral position and gently roll the mask upwards onto the face from the tip of the chin.
2. Hold the mask with the two-point-top hold where the thumb and index finger apply balanced pressure to the top flat portion of the mask where the silicone is thickest.
3. The stem is not held and the fingers should not encroach onto the skirt of the mask.
4. The thumb and index finger apply an even pressure on top of the mask.
5. The third, fourth and fifth fingers perform a chin lift with the same pressure upwards as applied by the thumb and index finger downwards.

In this technique the mask is squeezed onto the face, between the downward thrust of the fingers and upward pull of the chin lift.

Leak and obstruction with mask ventilation during simulated neonatal resuscitation
Arch Dis Child Fetal Neonatal Ed 2010;95:F398-F402

Even with the right technique, adequacy of ventilation can be hard to assess. Principles to bear in mind are:

• International guidelines recommend that infants with inadequate breathing or bradycardia be given positive pressure ventilation (PPV) via a face mask with a self-inflating bag, flow-inflating bag or T-piece device.
• Adequacy of ventilation is then judged by assessing the heart rate.
• However, if the heart rate does not increase, chest wall movements should be assessed to gauge adequacy of ventilation.
• A human observational study reported a mean VT of 6.5 ml/kg in spontaneous breathing preterm infants in the first minutes of life.
• When assisted ventilation is required, a peak inflating pressure (PIP) is chosen with the assumption that this will deliver an appropriate VT.
• However, lung compliance and therefore the PIP required to deliver an appropriate VT vary in the minutes after birth.
• It is likely that there are even greater differences between infants as the mechanical properties of the lung vary with gestational age and disease states.
• In addition, many infants breathe during PPV adding to the inconsistency of VT delivered with a set PIP. Therefore, relying on a fixed PIP and subjective assessment of chest wall movement may result in either under- or over-ventilation.
• Animal studies have shown that PPV with VT >8 ml/kg or inflations with large VTs can damage the lungs.

In an observational study of actual newborn resuscitations in Melbourne, researchers measured inflating pressures and VT delivered using a respiratory function monitor, and calculated face mask leak. After 60 seconds of PPV, resuscitators were asked to estimate VT and face mask leak. These estimates were compared with measurements taken during the previous 30 s.

In 20 infants, the median (IQR) expired tidal volume (VTe) delivered was 8.7 ml/kg (5.3–11.3). VTe and mask leak varied widely during each resuscitation and between resuscitators, who were also poor at estimating VT and mask leak.

Assessment of tidal volume and gas leak during mask ventilation of preterm infants in the delivery room.
Arch Dis Child Fetal Neonatal Ed. 2010 Nov;95(6):F393-7

# Swimming the Channelopathy

Drowning is one of the leading causes of accidental death in children. Some apparent drownings may be related to sudden cardiac death, in particular to unidentified channelopathies, which are known to precipitate fatal arrhythmias during swimming-related events.

The majority of cases of sudden cardiac death in children and adolescents are secondary to either hypertrophic or right ventricular cardiomyopathy with coronary artery abnormalities also prevalent, and reports have demonstrated these cardiac abnormalities on autopsy following sudden swimming-related deaths.

However, the majority of autopsies in swimming-related sudden deaths are normal suggesting causation at molecular level, in particular ion channel defects such as type 1 long-QT syndrome (LQT1) and catecholaminergic polymorphic ventricular tachycardia (CPVT).

Some recommendations are made in an article in Archives of Disease in Childhood:

Proposed implementations to improve detection and appropriate management of apparent drownings secondary to cardiac channelopathies

1. Improving awareness in the coronial service of the possibility of a cardiac cause for poorly explained drownings.
2. Education of lifeguards and provision of automated defibrillators in swimming pools.
3. Molecular autopsy for non-survivors to look for potential channelopathies.
4. Screening for survivors and family members of non-survivors to identify those with a channelopathy.
5. Proper counselling for those identified to have a channelopathy on family screening.

Drowning and sudden cardiac death
Arch Dis Child 2011;96:5-8

# Brain chain

Therapeutic hypothermia (TH) has been associated with improved outcomes in term infants who present with moderate hypoxic-ischaemic encephalopathy (HIE). However, in the three major studies the time to initiate cooling was at approximately 4.5 postnatal hours. Many newborns are referred to specialist centres where cooling takes place from outlying hospitals (‘outborn’). It may be the case that earlier initiation of TH could improve outcomes, leading Takenouchi and colleagues to propose a ‘Chain of Brain Preservation’.

Given that most infants are outborn, a time sensitive education metaphor termed Chain of Brain Preservation may facilitate early recognition of high risk infants and thus earlier treatment.

Chain of Brain Preservation—A concept to facilitate early identification and initiation of hypothermia to infants at high risk for brain injury
Resuscitation. 2010 Dec;81(12):1637-41

# Paediatric arrest outcomes

A study of out-of-hospital paediatric arrests in Melbourne gives some useful outcome data: overall, paediatric victims of out-of-hospital cardiac arrest survived to leave hospital in 7.7% of cases, which is similar to adult survival in the same emergency system (8%). Survival was very rare (<1%) unless there was return of spontaneous circulation prior to hospital arrival. Sixteen of the 193 cases studied had trauma, but the survival in this subgroup was not specifically documented.

Epidemiology of paediatric out-of-hospital cardiac arrest in Melbourne, Australia
Resuscitation. 2010 Sep;81(9):1095-100