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.

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.

Weight gain and triceps skinfolds fat mass after gastrostomy placement in children with developmental disabilities

OBJECTIVE

To determine appropriate outcome indicators of nutritional status that are measurable over time after gastrostomy placement in children with severe neurologic impairments.

DESIGN

Twenty-two nonambulatory children met the selection criteria: feeding by gastrostomy of at least 50% of total energy, age between 1 and 12 years, diagnosis of neurologic impairments, and presurgical recommendation for weight gain. Each child served as his or her own control; three assessments were made after gastrostomy placement.

SETTING

Children were seen in specialty outpatient clinics.

STATISTICAL ANALYSES

Scores and Pearson product moment correlations.

RESULTS

Outcomes of gastrostomy placement were (a) increase in actual weight, (b) increase in weight-age equivalent, (c) rate of weight accretion as expected by National Center for Health Statistics growth charts and improved z scores for half of the children, and (d) improvement in triceps skinfolds percentiles for nearly half (n = 10) of the children. The results reflect the heterogeneity of children with severe disabilities. Pearson correlations showed a significant relationship between chronologic age and weight-age equivalent (r = .96), but not for weight for age and weight-age equivalent, or triceps skinfolds fat mass and weight-age equivalent.

CONCLUSIONS/APPLICATIONS

Weight and triceps skinfolds fat mass were appropriate outcome indicators of nutritional status measurable over time. Weight-age equivalent and z scores were more helpful than standard growth plots for interpreting weight gain over time. Our data also support findings that undernutrition limits growth before gastrostomy placement in patients with disabilities. Nutritionists are encouraged to track improvement in nutritional status after gastrostomy placement with measurements of triceps skinfolds fat mass and to use the information to support families facing decisions about the need for this surgery.

Postoperative paraplegia in a patient with an unsuspected dural arterio-venous malformation

We report a case in which laminectomy was performed in a patient with symptoms attributed to lumbar canal stenosis. The patient developed paraplegia in the early postoperative period. Further investigation revealed a dural arterio-venous malformation. This was treated surgically, producing some neurological recovery. The possible mechanisms for the perioperative deterioration and their implications for anaesthesia are discussed.