Weight formula for kids

The traditional ‘APLS formula’ for weight estimation in children based on age (wt in kg = [age+4] x 2) is recognised as underestimating weight in ‘developed’ countries, with the degree of underestimation increasing with increasing age.

Several authors have attempted to derive a more accurate formula.

In the UK, the measured weights of over 93 000 children aged 1-16 who attended a paediatric emergency department were used to compare a previously derived formula (wt=3[age]+7) with the APLS formula.
The formula ‘Weight=2(age+4)’ underestimated children’s weights by a mean of 33.4% (95% CI 33.2% to 33.6%) over the age range 1–16 years whereas the formula ‘Weight=3(age)+7’ provided a mean underestimate of 6.9% (95% CI 6.8% to 7.1%); this latter formula remained applicable from 1 to 13 years inclusive.

The authors state: ‘The APLS formula has clearly become a victim of better nourished children. With a mean underestimate of more than 20% (nearly 40% at age 10 years), its place as a weight estimation tool is questionable…. To continue with an inaccurate formula with no evidence base cannot be considered good medical practice.’

Weight estimation in paediatrics: a comparison of the APLS formula and the formula ‘Weight=3(age)+7’
Emerg Med J. 2010 Jul 20. [Epub ahead of print]

A previous retrospective Australian study on over 70 000 paediatric ED attendances derived formulae for three different age ranges:

  • For Infants < 12 months: Weight (kg) = (age in months + 9)/2
  • For Children aged 1-5 years: Weight (kg) = 2 x (age in years + 5)
  • For Children aged 5-14 years: Weight (kg) = 4 x age in years.

Make your Best Guess: An updated method for paediatric weight estimation in emergencies
Emerg Med Australas. 2007 Dec;19(6):528-34

T-piece SBT harder work

24 difficult to wean patients underwent three spontaneous breathing trials in random order, with PA catheter monitoring in place. T-piece spontaneous ventilation was compared with pressure support ventilation 7 cmH20 without PEEP, and with pressure support ventilation 7 cmH20 with 5 cmH20 PEEP. T-piece was associated with higher SBT failure rates and more patient effort, left ventricular failure, and smaller tidal volumes. The study suggests that in selected difficult-to-wean patients, clinical and physiological responses differ depending on the type of SBT used to ascertain whether or not a patient is ready for extubation. Of note, the authors did not extubate the patients who succeeded a PSV trial, because it has been shown that a spontaneous breathing trial using T-piece mimics the work of breathing performed after extubation, and an extubation failure is associated with high mortality.

Physiological comparison of three spontaneous breathing trials in difficult-to-wean patients
Intensive Care Med. 2010 Jul;36(7):1171-9

Dexmedetomidine meta-analysis

Results from 24 studies on dexmedetomidine were assessed in a meta-analysis to determine the effect on ICU length of stay. The authors concluded that the limited evidence suggests that dexmedetomidine might reduce length of ICU stay in some critically ill patients, but the risk of bradycardia was significantly higher when both a loading dose and high maintenance doses (>0.7 μg/kg/h) were used.

Use of dexmedetomidine as a sedative and analgesic agent in critically ill adult patients: a meta-analysis.
Intensive Care Med. 2010 Jun;36(6):926-39

Mallampati assessment in ED airways

In a series of approximately 300 patients intubated in the ED, operators were unable to complete a Mallampati assessment in three quarters of them, citing lack of patient cooperation and critical illness as the main reasons. This is in keeping with work by Richard Levitan, lending further support to the lack of applicability of routine pre-operative airway assessment methods in critical care.

Feasibility of the preoperative Mallampati airway assessment in emergency department patients
J Emerg Med. 2010 Jun;38(5):677-8


One for the ‘hardly surprising’ category….

A study of end-tidal CO2 during out-of-hospital adult and child cardiac arrest resuscitation showed a sudden rise in CO2 was associated with return of spontaneous circulation (ROSC), suggesting that witnessing this would be a good time for a pulse check. Data from the 59 patients who achieved ROSC are shown below, time zero being time of ROSC. There was no such observed rise in the 49 patients who did not achieve ROSC.

A Sudden Increase in Partial Pressure End-Tidal Carbon Dioxide (PETCO2) at the Moment of Return of Spontaneous Circulation
The Journal of Emergency Medicine, Vol. 38, No. 5, pp. 614–621, 2010

Stab wounds to the neck

An algorithm for the management of patients with stab wounds to the neck has been proposed by authors of a review of the topic.

‘Hard’ signs of vascular injury include severe active bleeding, unresponsive shock, evolving stroke, and large/expanding haematoma. ‘Soft’ signs include a non-expanding moderate haematoma, a bruit/thrill, or a radial pulse deficit (although some consider the latter two to be hard signs). Mentioned in the text, but omitted from the algorithm, is the option of placing a Foley catheter into the wound and inflating the balloon to blindly control bleeding in a crashing haemodynamically unstable patient in order to buy time to get to the operating room.

Review article: Emergency department assessment and management of stab wounds to the neck.
Emerg Med Australas. 2010 Jun;22(3):201-10

Saline can be used in place of US gel

A study comparing sterile saline as a conduction agent with ultrasound gel showed adequate visualization of anatomic structures for ultrasound-guided vascular access. The authors state that given sterile saline’s theoretical advantages over gel in terms of availability, cost, safety and ease of use in the procedural field, it should be considered as a viable alternative to gel as a conduction agent.

Saline - so many uses we hadn't thought of

Use of sterile saline as a conduction agent for ultrasound visualization of central venous structures
Emerg Med Australas. 2010 Jun;22(3):232-5

Etomidate in RSI – systematic review

A systematic review of 20 included studies comparing a bolus dose of etomidate for rapid sequence induction with other induction agents resulted in the following conclusion:

“The available evidence suggests that etomidate suppresses adrenal function transiently without demonstrating a significant effect on mortality. However, no studies to date have been powered to detect a difference in hospital, ventilator, or ICU length of stay or in mortality”

The Effect of a Bolus Dose of Etomidate on Cortisol Levels, Mortality, and Health Services Utilization: A Systematic Review
Ann Emerg Med. 2010 Aug;56(2):105-13

Tracheal tube cuff pressure in flight

Tracheal tube cuff pressures increased from a mean 28.7 cm H2O pre-flight to 62.6 cm H2O in flight (mean altitude increase 2260 feet) in a Swiss helicopter-based study.
At cruising altitude, 98% of patients had intracuff pressure >30 cm H2O, 72% had intracuff pressure>50 cm H2O, and 20% even had intracuff pressure>80 cm H2O.
Multiple different referring hospitals meant the type of tracheal tube was not controlled for.

Endotracheal Tube Intracuff Pressure During Helicopter Transport
Ann Emerg Med. 2010 Aug;56(2):89-93