Laboratory evaluation of a novel anaesthesia delivery device.

Here, we describe proof of concept of a novel method for delivering volatile anaesthetics, where the liquid anaesthetic (sevoflurane or isoflurane) is formulated into an emulsion that is contained in a compact, lightweight device through which carrier gas flows. Release of anaesthetic is achieved by stirring of the formulation, allowing controlled and responsive release of anaesthetic at a variety of fixed flow rates between 0.5 l.min-1 and 5 l.min-1 , with ventilated, non-ventilated and draw-over breathing systems. Anaesthetic release was evaluated using target anaesthetic concentrations ranging from 0.5% v/v to 8% v/v to mimic those typically required for induction and maintenance of anaesthesia, and lower concentrations suitable for sedation. Under all conditions, output could be maintained within 0.1% v/v of the intended setting, and the device could deliver a controlled level of anaesthetic for at least 60 min, with compensation for different ambient temperatures (10-30 °C) and carrier gas flow rates. This device offers a simple, inexpensive method of delivering safe concentrations of volatile anaesthetics for a wide range of applications.

Vision Amniotic Leak Detector (ALD) to Eliminate Amniotic Fluid Leakage as a Cause of Vaginal Wetness in Pregnancy: A NICE Medical Technology Guidance.

In prelabour rupture of membranes (PROM) or preterm PROM the amniotic membranes rupture prior to labour. Where this is not overt a speculum examination is undertaken to confirm diagnosis. The Vision Amniotic Leak Detector (ALD) is a panty liner that can diagnose amniotic fluid as a cause of vaginal wetness. It was evaluated by the UK National Institute for Health and Care Excellence (NICE) as part of the Medical Technologies Evaluation Programme. The sponsor (CommonSense Ltd) identified five studies, of which three were deemed within scope by the External Assessment Centre (EAC). Two of these three used an inappropriate comparator. The EAC recalculated the diagnostic accuracy of Vision ALD using speculum examination as the comparator: sensitivity of 97% (95% CI 93-99%), negative predictive value of 96% (95% CI 92-98%). A negative result would therefore allow patients to be discharged with confidence. In the sponsor's cost-consequence model only patients with a positive Vision ALD result would have a speculum examination, producing a cost saving of around £10 per patient. The EAC felt that some costs were unjustified and the model did not include infection outcomes or use in a community setting. The EAC revised the sponsor's model and found the results were most sensitive to clinician costs. Vision ALD was associated with savings of around £15-£25 per patient when administration in lower-cost community healthcare avoided a referral to a higher-cost secondary-care centre. NICE published guidance MTG15 in July 2013 recommending that the case for adopting Vision ALD was supported by the evidence.

A comparison of fibreoptic-guided tracheal intubation through the Ambu ® Aura-i ™, the intubating laryngeal mask airway and the i-gel ™: a manikin study.

We compared the Aura-i(™) , intubating laryngeal mask airway and i-gel(™) as conduits for fibreoptic-guided tracheal intubation in a manikin. Thirty anaesthetists each performed two tracheal intubations through each device, a total of 180 intubations. The median (IQR [range]) time to complete the first intubation was 40 (31-50 [15-162]) s, 37 (34-48 [25-75]) s and 28 (22-35 [14-59]) s for the Aura-i, intubating laryngeal mask airway and i-gel, respectively. Tracheal intubation through the i-gel was the quickest (p < 0.01). Resistance to railroading of the tracheal tube over the fibrescope was significantly greater through the Aura-i compared with the intubating laryngeal mask airway and the i-gel (p = 0.001). There were no failures to intubate through the intubating laryngeal mask airway or the i-gel but six intubation attempts through the Aura-i were unsuccessful, in five owing to a railroading failure and in one owing to accidental oesophageal intubation. We conclude that the Aura-i does not perform as well as the intubating laryngeal mask airway or the i-gel as an adjunct for performing fibreoptic-guided tracheal intubation.

Effect of early tracheostomy on resource utilization and clinical outcomes in critically ill patients: meta-analysis of randomized controlled trials.

BACKGROUND: Early tracheostomy may decrease the duration of mechanical ventilation, sedation exposure, and intensive care stay, possibly resulting in improved clinical outcomes, but the evidence is conflicting. METHODS: Systematic review and meta-analysis of randomized trials in patients allocated to tracheostomy within 10 days of start of mechanical ventilation was compared with placement of tracheostomy after 10 days if still required. Medline, EMBASE, the Cochrane Controlled Clinical Trials Register, and Google Scholar were searched for eligible trials. The co-primary outcomes were mortality within 60 days, and duration of mechanical ventilation, sedation, and intensive care unit stay. Secondary outcomes were the number of tracheostomy procedures performed, and incidence of ventilator-associated pneumonia (VAP). Outcomes are described as relative risk or weighted mean difference with 95% confidence intervals. RESULTS: Of note, 4482 publications were identified and 14 trials enrolling 2406 patients were included. Tracheostomy within 10 days was not associated with any difference in mortality [risk ratio (RR): 0.93 (0.83-1.05)]. There were no differences in duration of mechanical ventilation [-0.19 days (-1.13-0.75)], intensive care stay [-0.83 days (-2.05-0.40)], or incidence of VAP. However, duration of sedation was reduced in the early tracheostomy groups [-2.78 days (-3.68 to -1.88)]. More tracheostomies were performed in patients randomly assigned to receive early tracheostomy [RR: 2.53 (1.18-5.40)]. CONCLUSION: We found no evidence that early (within 10 days) tracheostomy reduced mortality, duration of mechanical ventilation, intensive care stay, or VAP. Early tracheostomy leads to more procedures and a shorter duration of sedation.

Bougie-related airway trauma: dangers of the hold-up sign.

The bougie is a popular tool in difficult intubations. The hold-up sign is used to confirm tracheal placement of a bougie. This study aimed to establish the potential for airway trauma when using this sign with an Eschmann re-usable bougie or a Frova single-use bougie. Airways were simulated using a manikin (hold-up force) and porcine lung model (airway perforation force). Mean (SD) hold-up force (for airway lengths over the range 25-45 cm) of 1.0 (0.4) and 5.2 (1.1) N were recorded with the Eschmann and Frova bougies, respectively (p < 0.001). The mean (SD) force required to produce airway perforation was 0.9 (0.2) N with the Eschmann bougie and 1.1 (0.3) N with the Frova bougie (p = 0.11). It is possible to apply a force at least five times greater than the force required to produce significant trauma with a Frova single-use bougie. We recommend that the hold-up sign should no longer be used with single-use bougies. Clinicians should be cautious when eliciting this sign using the Eschmann re-usable bougie.

Investigation of phthalate release from tracheal tubes.

Phthalates are chemicals used extensively in the manufacture of plastics for their desirable physical characteristics. In addition to enhancing the performance of plastics, phthalates have a number of undesirable effects, principally endocrine disruptor effects, that may have adverse effects on reproductive development and functioning. As a result, they have been banned from the manufacture of children's toys. Despite this, they continue to be used in the manufacture of medical devices, including anaesthetic equipment. This study aimed to assess phthalate release from five brands of tracheal tube. Using gas chromatography-mass spectrometry, we analysed phthalate concentrations from samples of ultra pure water in which tracheal tubes had been submerged. Phthalate concentration increased from 6.7 to 149 µg.l(-1) over a period of 4.8 days. Phthalate release from anaesthetic equipment has not previously been documented over short time periods and raises the possibility of iatrogenic endocrine disruption with routine anaesthesia.

A randomised crossover trial comparing a single-use polyvinyl chloride laryngeal mask airway with a single-use silicone laryngeal mask airway.

We compared insertion rates of single-use polyvinyl chloride laryngeal mask airways (LMAs) vs single-use silicone LMAs in 72 anaesthetised patients. Both airways were produced by Flexicare Medical. Laryngeal mask airway insertion was successful on the first attempt in 68/72 (94%) polyvinyl chloride LMAs vs 64/72 (89%) silicone LMAs (p = 0.39). Overall insertion rates were 72/72 (100%) for the polyvinyl chloride LMAs and 71/72 (99%) for the silicone LMAs (p = 1.0). Mean (SD) insertion times were similar for polyvinyl chloride and silicone LMAs: 24.3 (5.1)s vs 24.8 (7.8)s (p = 0.64). Laryngeal mask airway position, as assessed using a fibrescope, was not different (p = 0.077). The median (IQR [range]) leak pressure was 16 (12-20 [6-30]) cmH(2) O for the polyvinyl LMA and 18 (13-22 [6-30]) cmH(2) O or the silicone LMA (p = 0.037). In conclusion, we did not find any important differences between polyvinyl chloride and silicone laryngeal mask airways.

Epidural catheter connectors: a laboratory-based comparison of the Portex Tuohy-Borst and EpiFuse™ designs.

Disconnection of an epidural catheter from its connector may result in patient harm and commonly requires resiting of the epidural. Clamp-connector designs such as the novel Portex EpiFuse™ potentially offer an improved safety profile over screw-cap designs such as the Tuohy-Borst, but comparative studies are limited. We therefore compared the tensile strength of EpiFuse and Tuohy-Borst connectors in a laboratory setting. We further sought to establish whether operator modification of the EpiFuse increased its vulnerability to disconnection. The median (IQR [range]) force to induce disconnection was 8.0 (4.1-12.8 [0.0-22.6]) N for Tuohy-Borst connectors and 16.4 (15.2-17.7 [5.7-18.9]) and 15.9 (15.0-16.9 [5.8-18.1]) N for standard and modified EpiFuse connectors, respectively (p<0.0001). The Tuohy-Borst was also less likely to meet British Standard requirements (13/20 sets vs 19/20 and 20/20, p=0.002). Modification of the EpiFuse did not affect lumen patency or connection strength. We conclude that under controlled conditions, EpiFuse connectors are superior to Tuohy-Borst connectors.

The history of anaesthetic equipment evaluation in the United Kingdom: lessons for developing future strategy.

Recent guidance published by the Association of Anaesthetists of Great Britain and Ireland encourages the purchase of equipment based on evidence of safety and performance. For many years, evidence of the safety and performance of anaesthetic equipment was published by various government departments and agencies. However, these schemes were gradually eroded over time such that many devices entered the market with little or no clinical evidence of their efficacy. This recently led to the Difficult Airway Society's issuing guidance to its members on how best to select new airway devices; guidance that was based on the available evidence. This article provides a short history of the evaluation of anaesthetic equipment in the United Kingdom.

Comparison of the manoeuvrability and ease of use of the Ambu aScope and Olympus re-usable fibrescope in a manikin.

In this study, we compared the manoeuvrability and ease of use of the single-use Ambu aScope and Olympus re-usable fibrescope in a manikin set to simulate difficult fibrescope placement. A total of 75 anaesthetists took part in this randomised crossover non-inferiority study. We recorded the time to task completion, tip surface collision count and participants' impression of ease of use. For the Ambu aScope and Olympus fibrescope, the mean (SD) first attempt time to task completion was 63 (31) s and 53 (23) s, respectively (95% CI of the difference 3-17 s), p = 0.008. This rejected the null hypothesis of a difference of > 30 s. The mean (SD) number of tip surface collisions was 2.7 (1.9) and 2.5 (1.8), respectively, (95% CI of the difference -0.4 to 0.7) p = 0.56. However, the participants found the Olympus easier to use (p < 0.001). Mean (SD) visual analogue scores for the perceived ease of use (0 mm = extremely difficult and 100 mm = extremely easy) were 65 (18) mm and 77 (14) mm for the Ambu aScope and Olympus scopes, respectively. This study found that the single-use Ambu aScope is as easy to manoeuvre as the Olympus re-usable fibrescope. This single-use device appears to be an acceptable alternative to the re-usable fibrescope.

The Difficult Airway Society 'ADEPT' guidance on selecting airway devices: the basis of a strategy for equipment evaluation.

Faced with the concern that an increasing number of airway management devices were being introduced into clinical practice with little or no prior evidence of their clinical efficacy or safety, the Difficult Airway Society formed a working party (Airway Device Evaluation Project Team) to establish a process by which the airway management community within the profession could itself lead a process of formal device/equipment evaluation. Although there are several national and international regulations governing which products can come on to the market and be legitimately sold, there has hitherto been no formal professional guidance relating to how products should be selected (i.e. purchased). The Airway Device Evaluation Project Team's first task was to formulate such advice, emphasising evidence-based principles. Team discussions led to a definition of the minimum level of evidence needed to make a pragmatic decision about the purchase or selection of an airway device. The Team concluded that this definition should form the basis of a professional standard, guiding those with responsibility for selecting airway devices. We describe how widespread adoption of this professional standard can act as a driver to create an infrastructure in which the required evidence can be obtained. Essential elements are that: (i) the Difficult Airway Society facilitates a coherent national network of research-active units; and (ii) individual anaesthetists in hospital trusts play a more active role in local purchasing decisions, applying the relevant evidence and communicating their purchasing decisions to the Difficult Airway Society.

Assessment of thrombin generation measured before and after cardiopulmonary bypass surgery and its association with postoperative bleeding.

BACKGROUND: Bleeding after cardiopulmonary bypass (CPB) is a major cause of morbidity and mortality and consumes large amounts of blood. Identifying patients at increased risk of bleeding secondary to hemostatic impairment may improve clinical outcomes by allowing early intervention. METHODS: This present study recruited 77 patients undergoing CPB and measured coagulation screens, coagulation factors, TEG(®), Rotem(®) and thrombin generation (TG) before surgery and 30 min after heparin reversal. The tests were analyzed to investigate whether they identified patients at increased risk of excess bleeding (defined as > 1000 mL) in the first 24 h postoperatively. RESULTS: Patients who bled > 1000 mL had a lower: platelet count (P < 0.02), factors (F)IX, X and XI (P < 0.005), endogenous thrombin potential (ETP) and an initial rate of TG (P < 0.02) and higher activated partial thromboplastin time (aPTT) (P < 0.001) than patients who bled < 1000 mL. Receiver operating characteristic (ROC) analysis was significant for post-operative TG and aPTT (P < 0.001). Furthermore, reduced pre-operative TG was associated with increased postoperative bleeding (P < 0.02). Pre- and postoperative TG were correlated (ρ = 0.7, P < 0.001). TEG(®), Rotem(®) and prothrombin time (PT) at either time point were not associated with increased bleeding. CONCLUSION: These data suggest that pre-operative defects in the propagation phase of hemostasis are exacerbated during CPB, contributing to bleeding post-CPB. TG taken both pre- and postoperatively could potentially be used to identify patients at an increased risk of bleeding post-CPB.

Heat and moisture exchangers and breathing system filters: their use in anaesthesia and intensive care. Part 1 - history, principles and efficiency.

Heat and moisture exchangers and breathing system filters are intended to replace the normal warming, humidifying and filtering functions of the upper airways when these structures are bypassed during anaesthesia and intensive care. Guidance on their use continues to evolve. The aim of this part of the review is to describe the principles of their action and efficiency and to summarise the findings from clinical and laboratory studies. Based on previous studies, an appropriate minimum target for moisture output is 30 and 20 g.m⁻³ for long-duration use in intensive care and short-duration use in anaesthesia, respectively. The practice of reusing a breathing system in anaesthesia, provided it is protected by a filter, assumes that the filter is effective. However, there is wide variation in the gas-borne filtration performance, and contaminated condensate can potentially pass through some filters under typical pressures encountered during mechanical ventilation.

Heat and moisture exchangers and breathing system filters: their use in anaesthesia and intensive care. Part 2 - practical use, including problems, and their use with paediatric patients.

Heat and moisture exchangers and breathing system filters are intended to replace the normal warming, humidifying and filtering functions of the upper airways. The first part of this review considered the history, principles of operation and efficiency of these devices. The aim of this part of the review is to summarise recent guidelines on the use of these devices and outline the problems that can occur. In particular, the effect of these devices on gas analysis, dead space, resistance to gas flow and blockage of the breathing system is considered. In children, it is important to consider the addition of dead space and resistance to gas flow. A body weight of 2.5 kg is probably the lower weight limit for use with heat and moisture exchangers, and 3 kg for filters. The resistance to gas flow of a heat- and moisture-exchanging filter added to a Mapleson F breathing system can cause a delay in the induction of anaesthesia.

[Prevention of infections under anesthetic breathing with breathing filters: concerted recommendations of the Deutsche Gesellschaft für Krankenhaushygiene e.V. (DGKH) and the Deutsche Gesellschaft für Anästhesiologie und Intensivmedizin e.V. (DGAI)]. / Infektionsprävention bei der Narkosebeatmung durch Einsatz von Atemsystemfiltern: Gemeinsame Empfehlung der Deutschen Gesellschaft für Krankenhaushygiene e.V. (DGKH) und der Deutschen Gesellschaft für Anästhesiologie und Intensivmedizin e.V. (DGAI).

An interdisciplinary working group from the German Society of Hospital Hygiene (DGKH) and the German Society for Anesthesiology and Intensive Care (DGAI) worked out the following recommendations for infection prevention during anesthesia by using breathing system filters (BSF). The BSF shall be changed after each patient. The filter retention efficiency for airborne particles is recommended to be >99% (II). The retention performance of BSF for liquids is recommended to be at pressures of at least 60 hPa (=60 mbar) or 20 hPa above the selected maximum ventilation pressure in the anesthetic system.The anesthesia breathing system may be used for a period of up to 7 days provided that the functional requirements of the system remain unchanged and the manufacturer states this in the instructions for use. The breathing system and the manual ventilation bag are changed immediately after the respective anesthesia if the following situation has occurred or it is suspected to have occurred: Notifiable infectious disease involving the risk of transmission via the breathing system and the manual bag, e.g. tuberculosis, acute viral hepatitis, measles, influenza virus, infection and/or colonization with a multi-resistant pathogen or upper or lower respiratory tract infections. In case of visible contamination e.g. by blood or in case of defect, it is required that the BSF and also the anesthesia breathing system is changed and the breathing gas conducting parts of the anesthesia ventilator are hygienically reprocessed.Observing of the appropriate hand disinfection is very important. All surfaces of the anesthesia equipment exposed to hand contact must be disinfected after each case.