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.
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
The Britsh Thoracic Society has published its 2010 guidelines on the management of spontaneous pneumothorax. These are one of number of guidelines for the management of pleural disease. Management of spontaneous pneumothorax: British Thoracic Society pleural disease guideline 2010 Thorax 2010;65(Suppl 2):ii18-ii31 All pleural disease guidelines
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
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
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
Working out the expected compensatory response to an acid base disturbance often reveals a second acid-base problem that was otherwise hidden. I regularly use Winter’s formula when I see a metabolic acidosis, but I have trouble remembering the others, so here they are, from Harwood-Nuss’ Clinical Practice of Emergency Medicine (apologies if you ‘think’ in kilopascals): Formulas Describing Expected Compensatory Response to Primary Acid–Base Disturbances Simple Metabolic Acidosis
Predicted decreased PCO2 mm Hg = 1.2 × Δ(HCO3-) mEq/L
Predicted PCO2 mm Hg = 1.5(HCO3-) mEq/L + 8 ± 2
Anticipated PCO2 approximates last two digits of arterial pH
Bloods sampled from both femoral vein and SVC-sited catheters in critically ill patients showed good correlation in lactate levels but the oxygen saturation was not so reliable, with >5% variation in more than 50% and >15% variation in some patients. The authors suggest one reason is that the femoral catheter tip usually sits in the iliac vein and samples blood prior to the mixing of blood returning from intra-abdominal organs. They advise caution in using SfvO2 to guide resuscitation when narrow end points are used, as this may lead to inappropriate vasoactive drug or blood component therapy.
Femoral-Based Central Venous Oxygen Saturation Is Not a Reliable Substitute for Subclavian/Internal Jugular-Based Central Venous Oxygen Saturation in Patients Who Are Critically Ill Chest. 2010 Jul;138(1):76-83
A CME article in Critical Care Medicine summarises the literature on ARDS (including its limitations) and provides evidence based recommendations on what to do about severe hypoxaemia. They summarise:
For life-threatening hypoxaemia, initial management with a recruitment manoeuvre and/or high PEEP should be undertaken if plateau airway pressures and lack of barotrauma allow. If not, or if these are not effective, then proceed to the prone position or HFOV. If hypoxemia still persists, then consider the administration of inhaled NO. If NO fails, then glucocorticoids can then be administered. For elevated plateau airway pressures when tidal volumes are 4 mL/kg, consider prone positioning or HFOV. For life- threatening respiratory acidosis, consider the use of a buffer or continuous veno-venous hemofiltration. It is most important to assess for objective physiologic improvement in the appropriate time period for each intervention. If no benefit is evident, then the therapy should be discontinued to minimise harm and delay in the initiation of another therapy. If the patient continues to have life-threatening hypoxemia, acidosis, or elevated plateau airway pressures, then consider ECMO or extracorporeal carbon dioxide removal.
