SummaryMathematical formulae to calculate body surface area from measurements of height, weight and other parameters date from the late 19th century. Drug doses, fluid therapy, caloric requirements and physiological parameters such as cardiac output, glomerular filtration rate and a variety of respiratory function parameters are all frequently expressed in terms of a body surface area. Body surface area is often used in preference to body mass (weight). However, the original rationale for using body surface area as an estimate for metabolic rate has never been tested and the algorithms used to approximate body surface area have little evidence to support their use in this role. Recent developments in technology using indirect calorimetry allow easy measurement of metabolic rate in the clinical setting. Such measurements should be used for standardisation when weight alone is considered inadequate.Keywords Body surface area. Metabolic rate. Calorimetry. Rubner's Law, published in 1883, crystallised a belief among physiologists in the mid to late 19th century that, regardless of species, the heat production (i.e. metabolic rate) of an individual was proportional to the body surface area (BSA) [1]. This law was very difficult to disprove because BSA could only be measured by very cumbersome means, such as skinning the subject. Measurement of metabolic rate via direct calorimetry was possible but not widely available. Being unable to measure the metabolic rate in a clinical setting, measuring BSA seemed to provide an acceptable alternative to metabolic rate. There was an impetus around the beginning of the 20th century to derive simpler ways of calculating BSA using mathematical manipulations of various body dimensions. Throughout the remainder of the century, investigators attempted to simplify the equations and expand the application of the formulae. Because of the importance and widespread use of BSA formulae in many areas of medicine, we undertook a literature review to determine the source of and evidence for these equations. MethodsComprehensive literature reviews of documents published around 100 years ago are difficult. The electronic database ÔMedlineÕ only includes publications from 1966 onwards, whilst its paper-based predecessor, Index Medicus, extends to only 1960. The Medline database was searched by combining a medical subject heading (MeSH) search for Ôbody surface areaÕ, which prior to 1970 was classified under ÔanthropometryÕ. The following search strategies were used: MeSH search for ÔmathematicsÕ, or keyword searches for Ôcalculat*Õ, ÔformulaÕ or ÔduBoisÕ (duBois being the author of the most widely used BSA formula). Index Medicus was searched using the ÔanthropometryÕ MeSH term. Documents prior to 1960 were found from the references in articles identified by Anaesthesia, 2003, 58, pages 50-83 Ó 2003 Blackwell Publishing LtdMedline and each relevant document prior to 1960 also had its references searched. The development of Ôheight)weightÕ formulaeThe first published equation for estimating B...
SummaryWe studied the success rates for tracheal intubation in 32 healthy, anaesthetised patients during simulated grade IIIa laryngoscopy, randomised to either the multiple-use or the single-use bougie. Success rates (primary end-point) and times taken (secondary end-point) to achieve tracheal intubation were recorded. The multiple-use bougie was more successful than the single-use one (15 ⁄ 16 successful intubations vs. 9 ⁄ 16; p ¼ 0.03). With either device, median [range] total tracheal intubation times for successful attempts were < 54 [24-84] s and there were no clinically important differences between these times. We conclude that the multiple-use bougie is a more reliable aid to tracheal intubation than the single-use introducer in grade IIIa laryngoscopy.
Diagnostic radiology residents in Canada report numerous barriers to research. Programs seeking to enhance radiology research should focus on providing appropriate training, protected time, and mentorship.
SummaryWe studied the success rates for tracheal intubation in 64 healthy patients during simulated grade III laryngoscopy after induction of anaesthesia, using either the single-use bougie or oral flexible intubating fibrescope, both in conjunction with conventional Macintosh laryngoscopy. Patients were randomly allocated to either simulated grade IIIa or grade IIIb laryngoscopy, and also to one of the two study devices. Success rates for tracheal intubation (primary outcome measure) and times taken to achieve intubation (secondary outcome measure) were recorded. For the simulated grade IIIa laryngoscopy group, the fibreoptic scope was more successful than the bougie (16 ⁄ 16 successful intubations vs. 8 ⁄ 16; p ¼ 0.02). For the simulated grade IIIb laryngoscopy group, the fibreoptic scope was also more successful than the bougie (8 ⁄ 16 successful intubations vs. 1 ⁄ 16; p ¼ 0.02), but clearly use of the fibreoptic scope was not as successful as it had been in simulated grade IIIa laryngoscopy (p ¼ 0.04). With either device, median (range) total tracheal intubation times for successful attempts with either grade of laryngoscopy were less than 60 s (19-109) and there were no clinically important differences. We conclude that the fibrescope used in conjunction with Macintosh laryngoscopy is a more reliable method of tracheal intubation than the single-use bougie in both types of grade III laryngoscopy. This finding has implications for the management of patients in whom grade III laryngoscopy is encountered unexpectedly after induction of anaesthesia, and also for the management of patients previously known to have grade III view at laryngoscopy.
Learning and practising cricothyroidotomy and similar procedures is an essential part of anaesthetic training, yet trainees are not obliged to attend courses that teach them. Furthermore, available cricothyrotomy trainers/manikins are expensive, preventing their widespread use. Our aim was to evaluate a simple, inexpensive 'homemade' model (from plastic breathing system tubing, sticky tape, cardboard/plastic drug tray, rubber glove and swabs) for teaching/practising surgical airway techniques. MethodsFollowing Ethics Committee approval, 20 anaesthetic trainees were recruited after informed consent. Each completed a questionnaire detailing previous experience in surgical airway training/procedures. They were individually shown a demonstration of transtracheal catheterisation and Minitracheotomy on the model, and allowed to practise them themselves. Participants evaluated aspects of the model according to their prior experience, from 1 (strongly disagree) to 5 (strongly agree). Results Six DiscussionWe have been using the model in our regular Simulator Centre courses for the past two years, and the above results confirm our impression of its usefulness. Adequate success rates in cricothyrotomy requires regular practice [1]. This easily constructed model provides a cheap alternative for regular practise and teaching.
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