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The humble bougie…forty years and still counting?

2014; Wiley; Volume: 69; Issue: 3 Linguagem: Inglês

10.1111/anae.12600

1365-2044

M. R.,

Foreign Body Medical Cases

The history and development of the gum-elastic bougie are as fascinating as the controversies that have developed around its use over almost half a century later. In 1949, Macintosh described the use of a gum-elastic urinary catheter as an introducer to facilitate a difficult tracheal intubation 1. In 1973, Dr P. Hex Venn, an anaesthetic adviser to Eschmann Brothers & Walsh Ltd, designed an tracheal tube introducer 2, 3. Originally known as the 'Eschmann endotracheal tube introducer', Venn's revolutionary new design differed from all other introducers at the time in three major aspects and these probably contributed to its continued success over the years. It has a 35° curved or coudé tip, is longer in length (60 cm) and is constructed in two layers: a core of tube woven from polyester threads and an outer resin layer. This provides stiffness yet maintains flexibility, allowing it to enter the trachea with minimal trauma to the soft tissues. Forty years after it was first introduced into clinical practice, the gum-elastic bougie is the most widely used device to overcome intubation difficulties and is available on more than 90% of the difficult airway trolleys in the UK 4-6. It is a key component of the 'Plan A' of the Difficult Airway Society (DAS) guidelines for management of the unanticipated difficult intubation 7. Several large series and reviews of intubation practice and airway management algorithms from Australia 8, 9, the USA 10, 11, Singapore 12 and France 13-15 also describe the bougie as the 'most successful', 'effective' and 'commonly used' device for management of the difficult airway. The reasons for its widespread and continued success over the years are easy to understand. It is portable, inexpensive, easy to use and has high reported success rates, even in the hands of novice users and non-anaesthetists 9, 15, 16. Studies describe its successful use in 80–90% of the difficult airway situations encountered, with reported success rates of around 89% at the first attempt increasing to 94–100% at the second attempt 13-19. There have been very few reported complications over the years, and the few case reports describing trauma during its use have occurred in association with either unusual patient circumstances or incorrect use 20-26. The use of the bougie has expanded over the years, and studies and case reports have described its use to aid difficult extubation 27, accurate placement of a second-generation laryngeal mask airways such as the Proseal LMA 28, 29 and more recently, cricothyrotomy 30. There is evidence to suggest that use of the bougie in conjunction with a laryngoscope improves success rates and may be safer when performing intubation in patients with cervical spine injuries, as it reduces the forces exerted on the cervical spine 31. It may be argued that the rising popularity and success of videolaryngosopy is partly attributable to the bougie. Success rates and intubation time in up to one third of videolaryngoscope-assisted intubations are enhanced by the concurrent use of the bougie 32-34. This is not surprising when one considers that the challenge in videolaryngosopy lies primarily in the ability to manoeuvre the tube into the trachea. Having established that the bougie is here to stay, let us explore the main controversies that have developed around its use. Since the late nineties, there has been an increasing awareness of the risks of cross-infection associated with the use of re-usable anaesthetic equipment and the risk of transmission of variant Creutzfeldt-Jakob disease (vCJD) 35-38. Studies investigating the potential for contamination of the bougie have found significant bacterial and fungal pathogens and proteinaceous matter 39-42, as well as highlighting wide variation in the methods used for cleaning and sterilising bougies and the non-adherence of most hospitals to manufacturers' recommendations. In some hospitals, the bougies were just washed with soap and water between uses; only a few hospitals had effective system checks in place and most had no record of how many times the bougie had been re-used. The Association of Anaesthetists of Great Britain and Ireland (AAGBI) responded in 2002 with guidelines on infection control in anaesthesia, which were updated in 2008 43, 44. It risk-stratified devices and methods of decontamination into high, intermediate and low, based on the risk of penetration of skin and mucous membranes. The bougie is designated as an intermediate-risk device as it is highly likely to contact mucous membranes and become contaminated, and will require high-level disinfection to prevent transmission of bacteria/viruses and fungi. This does not prevent the transmission of prion proteins and the risk of vCJD. The AAGBI recommended that "single-use equipment should be utilised where appropriate" but a "sterile supplies department (SSD) should process re-usable items". This in turn led the move towards use of single-use airway devices. However, the AAGBI guideline also recommended that the "balance between single-use items as against re-usable equipment will require local determination based on risk assessment of patient safety, available facilities and cost". It appears that in the rush to adopt single-use devices, the balance recommended by AAGBI has been forgotten. The single-use bougies available at the time were the Portex Tracheal Tube Introducer (Smiths Medical, Hythe, UK) and the Frova Intubating Introducer (Cook UK Ltd, Letchworth, UK). The Portex single-use bougie was found to be more rigid and had lower success rates for intubation than the re-usable bougie 45. The Frova single-use bougie had a design similar to the original gum-elastic bougie and several manikin studies suggested that its success rate was similar, making it a more suitable replacement 46-48. However, there are risks in extrapolating data obtained from manikin studies directly to humans 49. The Frova and Portex single-use bougies found their way into clinical practice with little or no evidence of clinical efficacy or safety in patients. This method of introduction of airway devices into clinical practice is a cause for concern to many anaesthetists, leading to development of DAS's Airway Device Evaluation Project Team (ADEPT) process to establish a formal process of evaluation of devices 50. The rush to embrace the single-use bougie has not been without problems. Success rates of the single-use bougies are lower than that of the gum-elastic bougie, with a reported first time success rate with the Frova of ~84% at the first attempt and 96% at the second attempt 4, 18, 51. There are concerns regarding the increase in incidence of tracheobronchial trauma and bleeding associated with the use of single-use bougies 51-60. A study of the use of the Frova single-use bougie in 200 patients reported an incidence of airway trauma of ~5% 51. A suggested hypothesis is that the Frova catheter is much more rigid than the gum-elastic bougie, and attempts to elicit the hold-up sign may result in excessive force and resulting trauma. A postal survey in 2007 revealed 20 cases of airway trauma, of which 12 were from departments that only stocked single-use introducers; seven patients required ICU admission and there were two fatalities 53. The same survey showed that 31% of anaesthetic departments only had single-use bougies, 24% had the gum-elastic bougie and 45% had both. The Frova (which is considered the gold standard single-use bougie) was available in 31% and the Portex in 38% of anaesthetic departments. To add to the confusion, the lack of any kind of regulation has led to a further proliferation of available single-use bougies that vary in design, tip angulations, material and stiffness. We have data suggesting that the performance of the single-use bougie is different from that of the gum-elastic bougie, yet we continue to use the same techniques for both devices. The widely accepted and taught technique of confirming tracheal placement when the gum-elastic bougie is inserted blindly is by the clicks produced as the bougie runs over the tracheal cartilages and the hold-up sign, when the tip of the bougie reaches the small bronchi. Kidd et al. looked into the reliability of the two signs in 1988: clicks were recorded in 90% of the cases and hold-up generally occurs at 24–40 cm 17. The authors recommended that the two signs be taught as a part of difficult intubation drill when the gum-elastic bougie is used. This recommendation was adapted into the DAS guidelines for unexpected difficult intubation 7 and there has not been much reason to question this practice till now. There are no published data to support which of these signs is actually used by anaesthetists in their current clinical practice. A survey on the use of the gum-elastic bougie, published in 2002, revealed that clicks were elicited in only 65% cases and hold-up in 13% 19. I find the presence of clicks reassuring but have never tried to elicit the hold-up sign because of concerns over trauma and risk of bronchospasm, as recently highlighted by other clinicians 56, 61, 62. A recent report described two cases of distal bronchial lacerations caused by introducers, of which one was a gum-elastic bougie 58. In both cases, a CT scan showed bronchial laceration associated with alveolar haemorrhage. The patients were asymptomatic and the bronchial lesions resolved spontaneously, raising the possibility that tracheobronchial injuries may be under-reported and go undetected. In light of the increasing number of airway injuries associated with single-use devices, it may be time to rethink traditional teaching and practices. The studies by Paul et al. 63 and Marson et al. 64, in this issue of Anaesthesia, seek to address this issue and challenge the traditional wisdom of using the hold-up sign. The traffic light bougie described by Paul et al. 63 is an excellent concept, aimed at making anaesthetists aware of the depth of insertion of the bougie without needing to use hold-up as a sign of tracheal placement of a bougie. Marson et al. have attempted to measure the forces generated while attempting to elicit the hold-up sign with the bougie and the forces that would be required to cause airway perforation 64. Although the forces generated in a manikin and a porcine model may not be directly translated to the human lung, their study raises pertinent questions regarding the potential for airway trauma with the hold-up sign. While challenging the need to elicit the hold-up sign, there are other important questions regarding the use of the bougie that need to be answered. Does there need to be a balance between the risk of infection and the risk of injury with the bougie, and is there sufficient evidence to suggest that the single-use bougie is ready to replace the re-usable gum-elastic bougie? 65-67. Is it time to have national guidelines on how we use, clean and sterilise the bougie, as there are for fibreoptic endoscopes? 68 There is no reason why something as important and as commonly used in anaesthetic practise as the humble bougie should not follow suit. No external funding and no competing interests declared.