Alanine response to low energy synchrotron x-ray radiation.

Objective. The radiation response of alanine is very well characterized in the MV photon energy range where it can be used to determine the dose delivered with an accuracy better than 1%, making it suitable as a secondary standard detector in cancer radiation therapy. This is not the case in the very low energy keV x-ray range where the alanine response is affected by large uncertainties and is strongly dependent on the x-ray beam energy. This motivated the study undertaken here.Approach. Alanine pellets with a nominal thickness of 0.5 mm and diameter of 5 mm were irradiated with monoenergetic x-rays at the Diamond Light Source synchrotron, to quantify their response in the 8-20 keV range relative to60Co radiation. The absorbed dose to graphite was measured with a small portable graphite calorimeter, and the DOSRZnrc code in the EGSnrc Monte Carlo package was used to calculate conversion factors between the measured dose to graphite and the absorbed dose to water delivered to the alanine pellets. GafChromic EBT3 films were used to measure the beam profile for modelling in the MC simulations.Main results. The relative responses measured in this energy range were found to range from 0.616 to 0.643, with a combined relative expanded uncertainty of 3.4%-3.5% (k= 2), where the majority of the uncertainty originated from the uncertainty in the alanine readout, due to the small size of the pellets used.Significance. The measured values were in good agreement with previously published data in the overlapping region of x-ray energies, while this work extended the dataset to lower energies. By measuring the response to monoenergetic x-rays, the response to a more complex broad-spectrum x-ray source can be inferred if the spectrum is known, meaning that this work supports the establishment of alanine as a secondary standard dosimeter for low-energy x-ray sources.

Deep phenotyping of cardiac function in heart transplant patients using cardiovascular system models.

KEY POINTS: Right heart catheterization data from clinical records of heart transplant patients are used to identify patient-specific models of the cardiovascular system. These patient-specific cardiovascular models represent a snapshot of cardiovascular function at a given post-transplant recovery time point. This approach is used to describe cardiac function in 10 heart transplant patients, five of which had multiple right heart catheterizations allowing an assessment of cardiac function over time. These patient-specific models are used to predict cardiovascular function in the form of right and left ventricular pressure-volume loops and ventricular power, an important metric in the clinical assessment of cardiac function. Outcomes for the longitudinally tracked patients show that our approach was able to identify the one patient from the group of five that exhibited post-transplant cardiovascular complications. ABSTRACT: Heart transplant patients are followed with periodic right heart catheterizations (RHCs) to identify post-transplant complications and guide treatment. Post-transplant positive outcomes are associated with a steady reduction of right ventricular and pulmonary arterial pressures, toward normal levels of right-side pressure (about 20 mmHg) measured by RHC. This study shows that more information about patient progression is obtained by combining standard RHC measures with mechanistic computational cardiovascular system models. The purpose of this study is twofold: to understand how cardiovascular system models can be used to represent a patient's cardiovascular state, and to use these models to track post-transplant recovery and outcome. To obtain reliable parameter estimates comparable within and across datasets, we use sensitivity analysis, parameter subset selection, and optimization to determine patient-specific mechanistic parameters that can be reliably extracted from the RHC data. Patient-specific models are identified for 10 patients from their first post-transplant RHC, and longitudinal analysis is carried out for five patients. Results of the sensitivity analysis and subset selection show that we can reliably estimate seven non-measurable quantities; namely, ventricular diastolic relaxation, systemic resistance, pulmonary venous elastance, pulmonary resistance, pulmonary arterial elastance, pulmonary valve resistance and systemic arterial elastance. Changes in parameters and predicted cardiovascular function post-transplant are used to evaluate the cardiovascular state during recovery of five patients. Of these five patients, only one showed inconsistent trends during recovery in ventricular pressure-volume relationships and power output. At the four-year post-transplant time point this patient exhibited biventricular failure along with graft dysfunction while the remaining four exhibited no cardiovascular complications.

A national survey of the impact of NAP4 on airway management practice in United Kingdom hospitals: closing the safety gap in anaesthesia, intensive care and the emergency department.

BACKGROUND: The 4th National Audit Project of the Royal College of Anaesthetists' and Difficult Airway Society (NAP4) made recommendations to improve reliability and safety of airway management in hospitals. This survey examines its impact. METHODS: A survey was sent to all UK National Health Service hospitals to examine changes in practice in response to NAP4. We performed a 'gap analysis' to determine whether NAP4 had reduced the 'safety gap' between actual and ideal practice. RESULTS: The response rate was 62% (192 of 307 hospitals), and 78% answered all questions. Most (97%) respondents reported changes in practice in response to NAP4 but these differed by specialty: 95% in anaesthesia; 80% in intensive care (ICU) and 59% in the emergency department (ED). Approximately 25% reported changes in organizational aspects of airway and human factors teaching. Practice changes led to a median closure of the 'safety gap' in anaesthesia of 39% (IQR 14-66%, range 11-83%), 59% in ICU (IQR 54-73%, range 31-81%) and 48% in ED (IQR 39-53%, range 35-53%). CONCLUSIONS: Publication of NAP4 was followed by changes in practice in the majority of responding departments within two yr. Improvements included improved provision of difficult airway equipment and more widespread routine use of capnography. The biggest change occurred in ICU; the impact on training nursing and junior staff was modest and here, significant safety gaps remain.

Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults.

These guidelines provide a strategy to manage unanticipated difficulty with tracheal intubation. They are founded on published evidence. Where evidence is lacking, they have been directed by feedback from members of the Difficult Airway Society and based on expert opinion. These guidelines have been informed by advances in the understanding of crisis management; they emphasize the recognition and declaration of difficulty during airway management. A simplified, single algorithm now covers unanticipated difficulties in both routine intubation and rapid sequence induction. Planning for failed intubation should form part of the pre-induction briefing, particularly for urgent surgery. Emphasis is placed on assessment, preparation, positioning, preoxygenation, maintenance of oxygenation, and minimizing trauma from airway interventions. It is recommended that the number of airway interventions are limited, and blind techniques using a bougie or through supraglottic airway devices have been superseded by video- or fibre-optically guided intubation. If tracheal intubation fails, supraglottic airway devices are recommended to provide a route for oxygenation while reviewing how to proceed. Second-generation devices have advantages and are recommended. When both tracheal intubation and supraglottic airway device insertion have failed, waking the patient is the default option. If at this stage, face-mask oxygenation is impossible in the presence of muscle relaxation, cricothyroidotomy should follow immediately. Scalpel cricothyroidotomy is recommended as the preferred rescue technique and should be practised by all anaesthetists. The plans outlined are designed to be simple and easy to follow. They should be regularly rehearsed and made familiar to the whole theatre team.

Can we make airway management (even) safer?--lessons from national audit.

The Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society (NAP4) has published an extensive report examining both current practices in the United Kingdom regarding airway management during anaesthesia and the complications of airway management during anaesthesia and in intensive care units and emergency departments. The report makes more than 160 recommendations designed to improve care of patients. These recommendations have implications for individuals, departments, organisations and potentially for national policy in terms of training, standards of practice and the need for guidelines. The report also indicates several specific areas where future research might be directed. This article focuses on the implementation phase of NAP4, emphasising the importance of taking the lessons derived from NAP4 and turning them into actions to improve the safety of airway care delivered to patients, wherever in hospital this takes place.

Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia.

BACKGROUND: This project was devised to estimate the incidence of major complications of airway management during anaesthesia in the UK and to study these events. METHODS: Reports of major airway management complications during anaesthesia (death, brain damage, emergency surgical airway, unanticipated intensive care unit admission) were collected from all National Health Service hospitals for 1 yr. An expert panel assessed inclusion criteria, outcome, and airway management. A matched concurrent census estimated a denominator of 2.9 million general anaesthetics annually. RESULTS: Of 184 reports meeting inclusion criteria, 133 related to general anaesthesia: 46 events per million general anaesthetics [95% confidence interval (CI) 38-54] or one per 22,000 (95% CI 1 per 26-18,000). Anaesthesia events led to 16 deaths and three episodes of persistent brain damage: a mortality rate of 5.6 per million general anaesthetics (95% CI 2.8-8.3): one per 180,000 (95% CI 1 per 352-120,000). These estimates assume that all such cases were captured. Rates of death and brain damage for different airway devices (facemask, supraglottic airway, tracheal tube) varied little. Airway management was considered good in 19% of assessable anaesthesia cases. Elements of care were judged poor in three-quarters: in only three deaths was airway management considered exclusively good. CONCLUSIONS: Although these data suggest the incidence of death and brain damage from airway management during general anaesthesia is low, statistical analysis of the distribution of reports suggests as few as 25% of relevant incidents may have been reported. It therefore provides an indication of the lower limit for incidence of such complications. The review of airway management indicates that in a majority of cases, there is 'room for improvement'.

Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 2: intensive care and emergency departments.

BACKGROUND: The Fourth National Audit Project of the Royal College of Anaesthetists and Difficult Airway Society (NAP4) was designed to identify and study serious airway complications occurring during anaesthesia, in intensive care unit (ICU) and the emergency department (ED). METHODS: Reports of major complications of airway management (death, brain damage, emergency surgical airway, unanticipated ICU admission, prolonged ICU stay) were collected from all National Health Service hospitals over a period of 1 yr. An expert panel reviewed inclusion criteria, outcome, and airway management. RESULTS: A total of 184 events met inclusion criteria: 36 in ICU and 15 in the ED. In ICU, 61% of events led to death or persistent neurological injury, and 31% in the ED. Airway events in ICU and the ED were more likely than those during anaesthesia to occur out-of-hours, be managed by doctors with less anaesthetic experience and lead to permanent harm. Failure to use capnography contributed to 74% of cases of death or persistent neurological injury. CONCLUSIONS: At least one in four major airway events in a hospital are likely to occur in ICU or the ED. The outcome of these events is particularly adverse. Analysis of the cases has identified repeated gaps in care that include: poor identification of at-risk patients, poor or incomplete planning, inadequate provision of skilled staff and equipment to manage these events successfully, delayed recognition of events, and failed rescue due to lack of or failure of interpretation of capnography. The project findings suggest avoidable deaths due to airway complications occur in ICU and the ED.

National census of airway management techniques used for anaesthesia in the UK: first phase of the Fourth National Audit Project at the Royal College of Anaesthetists.

BACKGROUND: The first stage of the Royal College of Anaesthetists Fourth National Audit Project (NAP4) (to determine the incidence of major complications of airway management in the UK) required a national census of airway management techniques currently in use. METHODS: A network of local reporters (LRs) was established, with a link to each of the 309 National Health Service hospitals believed to undertake surgery. LRs were requested to report the primary airway management technique used for all general anaesthetics performed in their hospital during a specified 2 week period. Individual unit's data for the survey period were extrapolated using a multiplier of 25 to provide an estimated annual usage. RESULTS: Data were received from all 309 hospitals. The number of general anaesthetics reported in the 2 weeks was 114,904 giving an estimate of 2.9 million annually. Eighty-nine per cent of returns were reported by the LR to be 'accurate' or 'a close estimate' (an error of <10%). The primary airway management device for general anaesthesia was a supraglottic airway in 64,623 (56.2%), a tracheal tube in 44,114 (38.4%), and a facemask in 6167 (5.3%). CONCLUSIONS: The second stage of NAP4 is designed to register and collect details of each major airway complication from the same hospitals over a 12 month period. The individual case reports will produce the numerator to calculate the incidence of airway complications associated with general anaesthesia in the UK. The results of the census presented here will provide the denominator.

Complications of awake fibreoptic intubation without sedation in 200 healthy anaesthetists attending a training course.

BACKGROUND: Two hundred anaesthetists underwent airway endoscopy and attempted awake fibreoptic intubation (FOI) on a training course. Complications were recorded and each subject's response to the procedure was assessed. METHODS: Topical airway local anaesthesia was produced with up to 9 mg kg(-1) of lidocaine, sedation was not used. Complications during and after the procedure were noted. Later, the subjects completed an anonymous questionnaire about anxiety, pain, coughing, and side-effects of lidocaine. RESULTS: More than 1300 endoscopies were performed, 180 delegates were intubated, 175 by the nasal route and five orally. Intubation was abandoned in 20 (10%) subjects. Nasal bleeding occurred in 20 (10%) subjects. Symptoms that could be attributed to lidocaine were reported by 71 (36%) subjects. Afterwards, two (1%) subjects experienced rigors and one developed a lower respiratory tract infection. CONCLUSIONS: Nasendoscopy and FOI under local anaesthesia are associated with complications, notably those of infection and airway trauma. Side-effects potentially attributable to lidocaine administration were commonly reported.

Combined nebulization and spray-as-you-go topical local anaesthesia of the airway.

BACKGROUND: Twenty-five anaesthetists underwent awake fibreoptic intubation using a combination of nebulization and topical local anaesthesia. Plasma lidocaine concentrations were measured and the quality of the local anaesthesia was assessed. METHODS: After i.v. glycopyrrolate 3 microg kg(-1) and intranasal xylometolazone 0.1%, lidocaine 4% 200 mg was administered by nebulizer. Supplementary lidocaine to a maximum total of 9 mg kg(-1) was applied directly and via a fibreoptic endoscope. Nasotracheal intubation was performed once the vocal cords became unreactive. Heart rate, non-invasive blood pressure and oxygen saturation were recorded at 5-min intervals. Blood sampling commenced with a baseline sample and continued at 10 min intervals until 60 min after final administration of local anaesthetic. Subjects graded levels of anxiety, pain and coughing using written and visual analogue scales. RESULTS: Conditions for fibreoptic endoscopy and intubation were good. Seventeen received the maximum lidocaine dose of 9 mg kg(-1). The average dose used was 8.8 mg kg(-1). All plasma lidocaine concentrations assayed were below 5 mg litre(-1). Four volunteers reported feeling lightheaded after the procedure, despite normal blood pressure. Of these, two had the highest plasma lidocaine concentrations recorded: 3.5 and 4.5 mg litre(-1). Twenty-two of the 25 subjects found endoscopy and intubation acceptable, three found it enjoyable and no subject rated it as distressing. CONCLUSIONS: This method of airway anaesthesia was acceptable to this small group of unsedated subjects. It produced good conditions for fibreoptic intubation. A maximum calculated lidocaine dose of 9 mg kg(-1) did not produce toxic plasma concentrations of lidocaine.

Training course in local anaesthesia of the airway and fibreoptic intubation using course delegates as subjects.

BACKGROUND: We describe a practical method of training anaesthetists in the technique of awake fibreoptic intubation. This is performed on a training course using the delegates as subjects. METHODS: The first 15 subjects underwent cardiovascular monitoring during airway fibreoptic endoscopy performed by other course members. They were subsequently interrogated by use of a questionnaire. RESULTS: Evidence from questionnaires suggests this method of instruction is acceptable in this self-selected group of individuals. Gagging was the commonest unpleasant side-effect of airway endoscopy, although only one delegate rated this as uncomfortable. Fifty-four per cent of subjects found the procedure slightly painful; 46% reported no pain at all. Overall, the procedure was rated as acceptable by 85% of subjects and enjoyable by 15% of subjects. No delegate found endoscopy or intubation distressing. Cardiovascular monitoring revealed pulse rate and arterial pressure changes of less than 25% of baseline values. Paraesthesia developed in one individual and nasal bleeding in two cases, neither of which was clinically significant and did not interfere with endoscopy. CONCLUSIONS: The use of course delegates as subjects for training was acceptable to anaesthetists and is associated with a low level of discomfort and morbidity.