Efficacy of oral corticosteroids for acute preschool wheeze: a systematic review and individual participant data meta-analysis of randomised clinical trials

BACKGROUND

Oral corticosteroids are commonly used for acute preschool wheeze, although there is conflicting evidence of their benefit. We assessed the clinical efficacy of oral corticosteroids by means of a systematic review and individual participant data (IPD) meta-analysis.

METHODS

In this systematic review with IPD meta-analysis, we systematically searched eight databases (PubMed, Ovid Embase, CINAHLplus, CENTRAL, ClinicalTrials.gov, EudraCT, EU Clinical Trials Register, WHO Clinical Trials Registry) for randomised clinical trials published from Jan 1, 1994, to June 30, 2020, comparing oral corticosteroids with placebo in children aged 12 to 71 months with acute preschool wheeze in any setting based on the Population, Intervention, Comparison, Outcomes framework. We contacted principal investigators of eligible studies to obtain deidentified individual patient data. The primary outcome was change in wheezing severity score (WSS). A key secondary outcome length of hospital stay. We also calculated a pooled estimate of six commonly reported adverse events in the follow-up period of IPD datasets. One-stage and two-stage meta-analyses employing a random-effects model were used. This study is registered with PROSPERO, CRD42020193958.

FINDINGS

We identified 16 102 studies published between Jan 1, 1994, and June 30, 2020, from which there were 12 eligible trials after deduplication and screening. We obtained individual data from seven trials comprising 2172 children, with 1728 children in the eligible IPD age range; 853 (49·4%) received oral corticosteroids (544 [63·8%] male and 309 [36·2%] female) and 875 (50·6%) received placebo (583 [66·6%] male and 292 [33·4%] female). Compared with placebo, a greater change in WSS at 4 h was seen in the oral corticosteroids group (mean difference -0·31 [95% CI -0·38 to -0·24]; p=0·011) but not 12 h (-0·02 [-0·17 to 0·14]; p=0·68), with low heterogeneity between studies (I2=0%; τ2<0·001). Length of hospital stay was significantly reduced in the oral corticosteroids group (-3·18 h [-4·43 to -1·93]; p=0·0021; I2=0%; τ2<0·001). Subgroup analyses showed that this reduction was greatest in those with a history of wheezing or asthma (-4·54 h [-5·57 to -3·52]; pinteraction=0·0007). Adverse events were infrequently reported (four of seven datasets), but oral corticosteroids were associated with an increased risk of vomiting (odds ratio 2·27 [95% CI 0·87 to 5·88]; τ2<0·001). Most datasets (six of seven) had a low risk of bias.

INTERPRETATION

Oral corticosteroids reduce WSS at 4 h and length of hospital stay in children with acute preschool wheeze. In those with a history of previous wheeze or asthma, oral corticosteroids provide a potentially clinically relevant effect on length of hospital stay.

FUNDING

Asthma UK Centre for Applied Research.

Cost-effectiveness of Prednisolone to Treat Bell Palsy in Children: An Economic Evaluation Alongside a Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

Bell's palsy is the third most frequent diagnosis in children with sudden onset neurological dysfunction. The cost-effectiveness of treating Bell's palsy with prednisolone in children is unknown. We aimed to assess the cost-effectiveness of prednisolone in treating Bell's Palsy in children compared with placebo.

METHODS

This economic evaluation was a prospectively planned secondary analysis of a double-blinded, randomized, placebo-controlled superiority trial (BellPIC) conducted from 2015 to 2020. Time horizon was 6 months since randomization. Children aged 6 months to <18 years who presented within 72 hours of onset of clinician diagnosed Bell's palsy and who completed the trial were included (N=180). Interventions were oral prednisolone, or taste matched placebo administered for 10 days. Incremental cost-effectiveness ratio comparing prednisolone with placebo was estimated. Costs were considered from a healthcare sector perspective and included Bell's palsy related medication cost, doctor visits and medical tests. Effectiveness was measured using quality-adjusted life-years (QALYs) based on Child Health Utility 9D. Nonparametric bootstrapping was performed to capture uncertainties. Pre-specified sub-group analysis by age 12-18 years versus <12 years was conducted.

RESULTS

The mean cost per patient was A$760 in the prednisolone group and A$693 in the placebo group over the 6-month period (difference A$66, 95% confidence interval [CI]: -A$47, A$179). QALYs over 6-months was 0.45 in the prednisolone group and 0.44 in the placebo group (difference 0.01, 95%CI: -0.01, 0.03). The incremental cost to achieve one additional recovery was estimated to be A$1577 using prednisolone compared with placebo, and cost per additional QALY gained was A$6625 using prednisolone compared with placebo. Given a conventional willingness-to-pay threshold of A$50,000 per QALY gained (equivalent to US$35,000 or £28,000), prednisolone is very likely cost-effective (probability is 83%), . Sub-group analysis suggests that this was primarily driven by the high probability of prednisolone being cost-effective in children aged 12-18 years (probability is 98%) and much less so for those <12 years (probability is 51%).

DISCUSSION

This provides new evidence to stakeholders and policy makers when considering whether to make prednisolone available in treating Bell's palsy in children aged 12-18 years.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12615000563561.

Qualitative study of emergency clinicians to inform a national guideline on the management of children with mild-to-moderate head injuries

BACKGROUND

Head injury is a common reason children present to EDs. Guideline development to improve care for paediatric head injuries should target the information needs of ED clinicians and factors influencing its uptake.

METHODS

We conducted semi-structured qualitative interviews (November 2017-November 2018) with a stratified purposive sample of ED clinicians from across Australia and New Zealand. We identified clinician information needs, used the Theoretical Domains Framework (TDF) to explore factors influencing the use of head CT and clinical decision rules/guidelines in CT decision-making, and explored ways to improve guideline uptake. Two researchers coded the interview transcripts using thematic content analysis.

RESULTS

A total of 43 clinicians (28 doctors, 15 nurses), from 19 hospitals (5 tertiary, 8 suburban, 6 regional/rural) were interviewed. Clinicians sought guidance for scenarios including ED management of infants, children with underlying medical issues, delayed or representations and potential non-accidental injuries. Improvements to the quality and content of discharge communication and parental discussion materials were suggested. Known risks of radiation from head CTs has led to a culture of observation over use of CT in Australasia (TDF domain: beliefs about consequences). Formal and informal policies have resulted in senior clinicians making most head CT decisions in children (TDF domain: behavioural regulation). Senior clinicians consider their gestalt to be more accurate and outperform existing guidance (TDF domain: beliefs about capabilities), although they perceive guidelines as useful for training and supporting junior staff. Summaries, flow charts, publication in ED-specific journals and scripted training materials were suggestions to improve uptake.

CONCLUSION

Information needs of ED clinicians, factors influencing use of head CT in children with head injuries and the role of guidelines were identified. These findings informed the scope and implementation strategies for an Australasian guideline for mild-to-moderate head injuries in children.

1396 Prednisolone for Bell’s Palsy in children: A randomised, double-blind, placebo-controlled, Multicentre Trial

Aims, Objectives and Background

Corticosteroids can be used to treat idiopathic facial paralysis (Bell’s palsy) in children, but their effectiveness is uncertain.

Aims

To determine if prednisolone improves recovery of children with Bell’s palsy at one month.

Method and Design

Double-blind, placebo-controlled, randomised, trial of prednisolone in children presenting to ED with Bell’s palsy.1Patients 6 months to <18 years, recruited <72 hours after symptom onset, were randomly assigned to receive 10 days of treatment with oral prednisolone (1 mg/kg) or placebo. The primary outcome: complete recovery of facial function at 1 month on the House-Brackmann scale.2Secondary outcomes: facial function, adverse events and pain to 6 months.

Results and Conclusion

Between October 2015 to August 2020, 187 children were randomised (94 to prednisolone and 93 to placebo) and included in the intention-to-treat analysis. At 1 month, the proportions of patients who had recovered facial function were 49% (n=43/87) in the prednisolone group compared with 57% (n=50/87) in the placebo group (risk difference -8.1%, 95% CI -22.8 to 6.7; adjusted odds ratio [aOR] 0.7, 95% CI 0.4 to 1.3). At 6 months these proportion were 99% (n=77/78) for prednisolone and 93% (n=76/82) for placebo respectively (risk difference 6.0%, 95% CI -0.1 to 12.2; aOR 3.0 95% CI 0.5 to 17.7) (figure 1). There were no serious adverse events and little evidence for group differences in secondary outcomes.

Abstract 1396 Figure 1

In children with Bell’s palsy the vast majority recover without treatment. The study does not provide evidence that early treatment with prednisolone improves complete recovery.

References

Sullivan F, Swan I, Donna P, Morrison J, Smith B, McKinstry B,et al. Early treatment with prednisolone or acyclovir in bell’s palsy.N Eng J Med2007;357(16):1598–607.

House JW, Brackmann DE. Facial nerve grading system.Otolaryngol Head Neck Surg. 1985;93(2):146–7.

Cost-effectiveness of patient observation on cranial CT use with minor head trauma

OBJECTIVE

To evaluate the cost-effectiveness of planned observation on cranial CT use in children with minor head trauma.

DESIGN

Planned secondary analysis of a multicentre prospective observation study.

SETTING

Australia and New Zealand.

PATIENTS

An analytic cohort of 18 471 children aged <18 years with Glasgow Coma Scale scores 14-15 presenting <24 hours after blunt head trauma stratified by the Pediatric Emergency Care Applied Research Network (PECARN) traumatic brain injury (TBI) risk categories.

INTERVENTION

A plan for observation and immediate CT scan were documented after the initial assessment. The planned observation group included those with planned observation and no immediate plan for CT.

MAIN OUTCOME MEASURES

Taking an Australian public-funded healthcare perspective, we estimated the cost-effectiveness of planned observation on the adjusted mean costs per child and CT use reduction by net benefit regression analysis using ordinary least squares with robust SEs and bootstrapping. All costs presented in 2018 euros.

RESULTS

Planned observation in 4945 (27%) children was cost-saving of €85 (95% CI -120 to -51) with 10.4% lower CT use (95% CI 9.6 to 11.2). This strategy was cost-saving for the PECARN high-risk (-€757 (95% CI -961 to -554)) and intermediate-risk (-€52 (95% CI -99 to -4.3)) categories, with 43% (95% CI 39 to 47) and 11% (95% CI 9.6 to 12.4) lower CT use, respectively. The very low-risk category incurred more cost of €86 (95% CI 67 to 104) with planned observation and 0.05% lower CT use (95% CI -0.61 to 0.71).

CONCLUSION

Planned ED observation in selected children with minor head trauma is cost-effective for reducing CT use for the PECARN intermediate-risk and high-risk categories.

TRIAL REGISTRATION NUMBER

ACTRN12614000463673.

1324Clinical Registry for Acute Respiratory Infections in Children in Western Australia

Background

Acute respiratory infections (ARIs) are the leading cause for emergency presentation and a major driver for antibiotic use in children. In 2020, we established an ARI clinical registry to: evaluate clinical care for ARI to inform clinical guidelines; and as a platform for clinical trials assessing antimicrobial interventions.

Methods

Any child &lt;16 years presenting to Perth Children’s Hospital Emergency Department (ED) with cough, fever, sore throat and/or difficulty breathing was eligible for enrolment. Using an automated survey sent to parents’ mobile phones, each enrolled child was followed weekly until 28 days or disease recovery (whichever occurred first). Data collected included clinical symptoms, antibiotic prescription, adherence, and duration to return to regular activity (recovery).

Results

From Feb 2020-April 2021, 448 participants were enrolled (84% &lt;5 years). Fever and cough were the most frequently reported symptoms. Of 448, 274 (61%) ARI cases completed all surveys until recovered. The median recovery length was 9 days (IQR:6-12). The recovery days were longer, although not statistically significant (p &gt; 0.05), in: children who received antibiotics versus those who did not (9.5 days vs. 8); children &lt;5 years versus those over (9 days vs. 7); and children with chronic illnesses versus those without (9 days vs. 8).

Conclusions

Most children presenting to ED with ARI recover within 10 days. The length of recovery does not vary significantly by age, chronic illnesses, or antibiotic usage.

Key messages

Registry data provides baseline data to inform clinical trials assessing the role and duration of antibiotics for ARI.

Medical Disimpaction for Children With Organic Esophageal Foreign Body in the Era of Eosinophilic Esophagitis

OBJECTIVE

Esophageal foreign body impaction (EFBI) is a common presentation in pediatric emergency medicine. Interventions (medical or endoscopic) are often required because of the severity of symptoms and risk of complications. Use of medical disimpaction (MD) such as glucagon injections and effervescent agents (eg, carbonated beverages) has been well described in adults; however, there are limited data in the pediatric literature. Eosinophilic esophagitis (EoE) is a relatively "new" clinicopathological entity that may present with EFBI mostly due to food with histological findings of EoE. Our study aim was to determine the efficacy of MD for organic EFBI in the pediatric population especially in children with EoE.

METHODS

A retrospective chart review was performed using the International Classification of Diseases codes and the emergency department database of patients presenting with EFBI from January 2010 to December 2014. Response to MD was defined as symptomatic relief of obstruction. Age, object ingested, medical agent used, EoE status, complications, and outcome were recorded.

RESULTS

A total of 317 presentations of EFBI were identified during the study period, of which organic EFBI accounted for 101 impactions (31.9%). Medical disimpaction was attempted for 42 (41.6%) with organic EFBI, resulting in resolution of symptoms for 16 (38.1%). One child with EoE responded to MD compared with 15 without EoE (4.8% vs 71.4%, P < 0.0001).

CONCLUSIONS

Medical disimpaction was ineffective in children with EoE but may be of help with symptom resolution in approximately 70% of children without EoE.

Randomised controlled trial comparing immobilisation in above-knee plaster of Paris to controlled ankle motion boots in undisplaced paediatric spiral tibial fractures

BACKGROUND

Management of common childhood spiral tibial fractures, known as toddler's fractures, has not significantly changed in recent times despite the availability of immobilisation devices known as controlled ankle motion (CAM) boots. We compared standard therapy with these devices on quality-of-life measures.

METHODS

A prospective randomised controlled trial, comparing immobilisation with an above-knee plaster of Paris cast (AK-POP) with a CAM boot in children aged 1-5 years with proven or suspected toddler's fractures presenting to a tertiary paediatric ED in Perth, Western Australia, between March 2018 and February 2020. The primary outcome measure was ease of personal care, as assessed by a Care and Comfort Questionnaire (eight questions scored from 0, very easy, to 8, impossible) completed by the caregiver and assessed during three treatment time-points and preintervention and postintervention. Secondary outcome measures included weight-bearing status as well as complications of fracture healing and number of pressure injuries.

RESULTS

87 patients were randomised (44 CAM boot, median age 2 (IQR 1.5-2.3), 71% male; 43 AK-POP, median age 2 (IQR 1.7-2.8), 80% male), a significant difference in the care and comfort score was demonstrated at all treatment time-points; with the AK-POP group reporting greater personal care needs on assessment on day 2, day 7-10 and 4-week review (all p≤0.001). Weight-bearing status was significantly different at day 7-10 (77.5% CAM vs 53.8% AK-POP, p=0.027). There was no difference in fracture healing or pressure areas between the two treatment groups.

CONCLUSIONS

Immobilisation of toddler's fractures in a CAM boot allows faster return to activities of daily living and weight-bearing without any effect on fracture healing.

TRIAL REGISTRATION NUMBER

Australian New Zealand Clinical Trials Registry (ACTRN12618001311246).

Nasopharyngeal density of respiratory viruses in childhood pneumonia in a highly vaccinated setting: findings from a case-control study

Background

Detection of pneumonia-causing respiratory viruses in the nasopharynx of asymptomatic children has made their actual contribution to pneumonia unclear. We compared nasopharyngeal viral density between children with and without pneumonia to understand if viral density could be used to diagnose pneumonia.

Methods

Nasopharyngeal swabs (NPS) were collected from hospitalised pneumonia cases at Princess Margaret Hospital (PMH) and contemporaneous age-matched controls at PMH outpatient clinics and a local immunisation clinic in Perth, Australia. The density (copies/mL) of respiratory syncytial virus (RSV), influenza A virus (InfA), human metapneumovirus (HMPV) and rhinovirus in NPS was determined using quantitative PCR. Linear regression analysis was done to assess the trend between viral density and age in months. The association between viral density and disease status was examined using logistic regression. Area under receiver operating characteristic (AUROC) curves were assessed to determine optimal discriminatory viral density cut-offs.

Results

Through May 2015 to October 2017, 230 pneumonia cases and 230 controls were enrolled. Median nasopharyngeal density for any respiratory virus was not substantially higher in cases than controls (p>0.05 for each). A decreasing density trend with increasing age was observed—the trend was statistically significant for RSV (regression coefficient −0.04, p=0.004) but not for other viruses. After adjusting for demographics and other viral densities, for every log₁₀ copies/mL density increase, the odds of being a case increased by six times for RSV, three times for HMPV and two times for InfA. The AUROC curves were <0.70 for each virus, suggesting poor case–control discrimination based on viral density.

Conclusion

The nasopharyngeal density of respiratory viruses was not significantly higher in children with pneumonia than those without; however, the odds of being a case increased with increased density for some viruses. The utility of viral density, alone, in defining pneumonia was limited.

Thermionic microwave gun for terahertz and synchrotron light sources

Conventional thermionic microwave and radio frequency (RF) guns can offer high average beam current, which is important for synchrotron light and terahertz (THz) radiation source facilities, as well as for industrial applications. For example, the Advanced Photon Source at Argonne National Laboratory is a national synchrotron-radiation light source research facility that utilizes thermionic RF guns. However, these existing thermionic guns are bulky, difficult to handle and install, easily detuned, very sensitive to thermal expansion, and due for a major upgrade and replacement. In this paper, we present the design of a new, more stable, and reliable gun with optimized electromagnetic performance, improved thermal engineering, and a more robust cathode mounting technique, which is a critical step to improve the performance of existing and future light sources, industrial accelerators, and electron beam-driven THz sources. We will also present a fabricated gun prototype and show results of high-power and beam tests.

Traumatic brain injury in young children with isolated scalp haematoma

OBJECTIVE

Despite high-quality paediatric head trauma clinical prediction rules, the management of otherwise asymptomatic young children with scalp haematomas (SH) can be difficult. We determined the risk of intracranial injury when SH is the only predictor variable using definitions from the Pediatric Emergency Care Applied Research Network (PECARN) and Children's Head Injury Algorithm for the Prediction of Important Clinical Events (CHALICE) head trauma rules.

DESIGN

Planned secondary analysis of a multicentre prospective observational study.

SETTING

Ten emergency departments in Australia and New Zealand.

PATIENTS

Children <2 years with head trauma (n=5237).

INTERVENTIONS

We used the PECARN (any non-frontal haematoma) and CHALICE (>5 cm haematoma in any region of the head) rule-based definition of isolated SH in both children <1 year and <2 years.

MAIN OUTCOME MEASURES

Clinically important traumatic brain injury (ciTBI; ie, death, neurosurgery, intubation >24 hours or positive CT scan in association with hospitalisation ≥2 nights for traumatic brain injury).

RESULTS

In children <1 year with isolated SH as per PECARN rule, the risk of ciTBI was 0.0% (0/109; 95% CI 0.0% to 3.3%); in those with isolated SH as defined by the CHALICE, it was 20.0% (7/35; 95% CI 8.4% to 36.9%) with one patient requiring neurosurgery. Results for children <2 years and when using rule specific outcomes were similar.

CONCLUSIONS

In young children with SH as an isolated finding after head trauma, use of the definitions of both rules will aid clinicians in determining the level of risk of ciTBI and therefore in deciding whether to do a CT scan.

TRIAL REGISTRATION NUMBER

ACTRN12614000463673.

Medication use in infants admitted with bronchiolitis

BACKGROUND

There are no medications known that improve the outcome of infants with bronchiolitis. Studies have shown the management of bronchiolitis to be varied.

OBJECTIVES

To describe medication use at the seven study hospitals from a recent multi-centre randomised controlled trial on hydration in bronchiolitis (comparative rehydration in bronchiolitis [CRIB]).

METHODS

A retrospective analysis of extant data of infants between 2 months (corrected for prematurity) and 12 months of age admitted with bronchiolitis identified through the CRIB trial. CRIB study records, medical records, pathology and radiology databases were used to collect data using a standardised form and entered in a single site database. Medications investigated included salbutamol, adrenaline, steroids, ipratropium bromide, normal saline, hypertonic saline, steroids and antibiotics.

RESULTS

There were 3456 infants available for analysis, of which 42.0% received at least one medication during hospitalisation. Medication use varied by site between 27.0 and 48.7%. The most frequently used medication was salbutamol (25.5%). Medication use in general, and salbutamol use in particular, increased by 8.2 and 9.3%, respectively, per month after 4 months of age; from 22.9 and 3.6% at 4 months to 81.4 and 68.8% at 11 months. In infants admitted to the intensive care unit (ICU) compared with those not admitted to ICU 81.6 and 39.5%, respectively, received medication at one point during the hospital stay.

CONCLUSIONS

Medication was used for infants with bronchiolitis frequently and variably in Australia and New Zealand. Medication use increased with age. Better strategies for translating evidence into practice are needed.

Influence of weather on incidence of bronchiolitis in Australia and New Zealand

AIM

We aimed to examine the impact of weather on hospital admissions with bronchiolitis in Australia and New Zealand.

METHODS

We collected data for inpatient admissions of infants aged 2-12 months to seven hospitals in four cities in Australia and New Zealand from 2009 until 2011. Correlation of hospital admissions with minimum daily temperature, wind speed, relative humidity and rainfall was examined using linear, Poisson and negative binomial regression analyses as well as general estimated equation models. To account for possible lag between exposure to weather and admission to hospital, analyses were conducted for time lags of 0-4 weeks.

RESULTS

During the study period, 3876 patients were admitted to the study hospitals. Hospital admissions showed strong seasonality with peaks in wintertime, onset in autumn and offset in spring. The onset of peak incidence was preceded by a drop in temperature. Minimum temperature was inversely correlated with hospital admissions, whereas wind speed was directly correlated. These correlations were sustained for time lags of up to 4 weeks. Standardised correlation coefficients ranged from -0.14 to -0.54 for minimum temperature and from 0.18 to 0.39 for wind speed. Relative humidity and rainfall showed no correlation with hospital admissions in our study.

CONCLUSION

A decrease in temperature and increasing wind speed are associated with increasing incidence of bronchiolitis hospital admissions in Australia and New Zealand.

PREDICT prioritisation study: establishing the research priorities of paediatric emergency medicine physicians in Australia and New Zealand

BACKGROUND

The Paediatric Research in Emergency Departments International Collaborative (PREDICT) performs multicentre research in Australia and New Zealand. Research priorities are difficult to determine, often relying on individual interests or prior work.

OBJECTIVE

To identify the research priorities of paediatric emergency medicine (PEM) specialists working in Australia and New Zealand.

METHODS

Online surveys were administered in a two-stage, modified Delphi study. Eligible participants were PEM specialists (consultants and senior advanced trainees in PEM from 14 PREDICT sites). Participants submitted up to 3 of their most important research questions (survey 1). Responses were collated and refined, then a shortlist of refined questions was returned to participants for prioritisation (survey 2). A further prioritisation exercise was carried out at a PREDICT meeting using the Hanlon Process of Prioritisation. This determined the priorities of active researchers in PEM including an emphasis on the feasibility of a research question.

RESULTS

One hundred and six of 254 (42%) eligible participants responded to survey 1 and 142/245 (58%) to survey 2. One hundred and sixty-eight (66%) took part in either or both surveys. Two hundred forty-six individual research questions were submitted in survey 1. Survey 2 established a prioritised list of 35 research questions. Priority topics from both the Delphi and Hanlon process included high flow oxygenation in intubation, fluid volume resuscitation in sepsis, imaging in cervical spine injury, intravenous therapy for asthma and vasopressor use in sepsis.

CONCLUSION

This prioritisation process has established a list of research questions, which will inform multicentre PEM research in Australia and New Zealand. It has also emphasised the importance of the translation of new knowledge.

A multicentre randomised controlled trial of levetiracetam versus phenytoin for convulsive status epilepticus in children (protocol): Convulsive Status Epilepticus Paediatric Trial (ConSEPT) - a PREDICT study

Background

Convulsive status epilepticus (CSE) is the most common life-threatening childhood neurological emergency. Despite this, there is a lack of high quality evidence supporting medication use after first line benzodiazepines, with current treatment protocols based solely on non-experimental evidence and expert opinion. The current standard of care, phenytoin, is only 60% effective, and associated with considerable adverse effects. A newer anti-convulsant, levetiracetam, can be given faster, is potentially more efficacious, with a more tolerable side effect profile. The primary aim of the study presented in this protocol is to determine whether intravenous (IV) levetiracetam or IV phenytoin is the better second line treatment for the emergency management of CSE in children.

Methods/Design

200 children aged between 3 months and 16 years presenting to 13 emergency departments in Australia and New Zealand with CSE, that has failed to stop with first line benzodiazepines, will be enrolled into this multicentre open randomised controlled trial. Participants will be randomised to 40 mg/kg IV levetiracetam infusion over 5 min or 20 mg/kg IV phenytoin infusion over 20 min. The primary outcome for the study is clinical cessation of seizure activity five minutes following the completion of the infusion of the study medication. Blinded confirmation of the primary outcome will occur with the primary outcome assessment being video recorded and assessed by a primary outcome assessment team blinded to treatment allocation. Secondary outcomes include: Clinical cessation of seizure activity at two hours; Time to clinical seizure cessation; Need for rapid sequence induction; Intensive care unit (ICU) admission; Serious adverse events; Length of Hospital/ICU stay; Health care costs; Seizure status/death at one-month post discharge.

Discussion

This paper presents the background, rationale, and design for a randomised controlled trial comparing levetiracetam to phenytoin in children presenting with CSE in whom benzodiazepines have failed. This study will provide the first high quality evidence for management of paediatric CSE post first-line benzodiazepines.

Trial registration

Prospectively registered with the Australian and New Zealand Clinical Trial Registry (ANZCTR): ACTRN12615000129583 (11/2/2015). UTN U1111–1144-5272. ConSEPT protocol version 4 (12/12/2014).

Intensive care unit admissions and ventilation support in infants with bronchiolitis

OBJECTIVES

To describe the rate of intensive care unit (ICU) admission, type of ventilation support provided and risk factors for ICU admission in infants with bronchiolitis.

DESIGN

Retrospective review of hospital records and Australia and New Zealand Paediatric Intensive Care (ANZPIC) registry data for infants 2-12 months old admitted with bronchiolitis.

SETTING

Seven Australian and New Zealand hospitals. These infants were prospectively identified through the comparative rehydration in bronchiolitis (CRIB) study between 2009 and 2011.

RESULTS

Of 3884 infants identified, 3589 charts were available for analysis. Of 204 (5.7%) infants with bronchiolitis admitted to ICU, 162 (79.4%) received ventilation support. Of those 133 (82.1%) received non-invasive ventilation (high flow nasal cannula [HFNC] or continuous positive airway pressure [CPAP]) 7 (4.3%) received invasive ventilation alone and 21 (13.6%) received a combination of ventilation modes. Infants with comorbidities such as chronic lung disease (OR 1.6 [95% CI 1.0-2.6]), congenital heart disease (OR 2.3 [1.5-3.5]), neurological disease (OR 2.2 [1.2-4.1]) or prematurity (OR 1.5 [1.0-2.1]), and infants 2-6 months of age (OR 1.5 [1.1-2.0]) were more likely to be admitted to ICU. Respiratory syncitial virus positivity did not increase the likelihood of being admitted to ICU (OR 1.1 [95% CI 0.8-1.4]). HFNC use changed from 13/53 (24.5% [95% CI 13.7-38.3]) patient episodes in 2009 to 39/91 (42.9% [95% CI 32.5-53.7]) patient episodes in 2011.

CONCLUSION

Admission to ICU is an uncommon occurrence in infants admitted with bronchiolitis, but more common in infants with comorbidities and prematurity. The majority are managed with non-invasive ventilation, with increasing use of HFNC.

Economic evaluation of nasogastric versus intravenous hydration in infants with bronchiolitis

OBJECTIVE

Bronchiolitis is the most common lower respiratory tract infection in infants and the leading cause of hospitalisation. We aimed to assess whether intravenous hydration (IVH) was more cost-effective than nasogastric hydration (NGH) as a planned secondary economic analysis of a randomised trial involving 759 infants (aged 2-12 months) admitted to hospital with a clinical diagnosis of bronchiolitis and requiring non-oral hydration. No Australian cost data exist to aid clinicians in decision-making around interventions in bronchiolitis.

METHODS

Cost data collections included hospital and intervention-specific costs. The economic analysis was reduced to a cost-minimisation study, focusing on intervention-specific costs of IVH versus NGH, as length of stay was equal between groups. All analyses are reported as intention to treat.

RESULTS

Intervention costs were greater for IVH than NGH ($113 vs $74; cost difference of $39 per child). The intervention-specific cost advantage to NGH was robust to inter-site variation in unit prices and treatment activity.

CONCLUSION

Intervention-specific costs account for <10% of total costs of bronchiolitis admissions, with NGH having a small cost saving across all sites.

An observational study of febrile seizures: the importance of viral infection and immunization

Background

Febrile seizures are common in young children. Annual peaks in incidence mirror increased respiratory virus activity during winter. Limited virological data are available using modern diagnostic techniques for children with febrile seizures. We aimed to determine the frequency of detection of specific viral pathogens in children with febrile seizures, to describe risk factors including recent vaccination and clinical features associated with specific etiologies.

Methods

An observational study was performed. Children aged 6 months to 5 years presenting to the Emergency Department of a tertiary children’s hospital in Western Australia with febrile seizures were enrolled between March 2012 and October 2013. Demographic, clinical data and vaccination history were collected, and virological testing was performed on per-nasal and per-rectal samples.

Results

One hundred fifty one patients (72 female; median age 1.7y; range 6 m-4y9m) were enrolled. Virological testing was completed for 143/151 (95%). At least one virus was detected in 102/143 patients (71%). The most commonly identified were rhinoviruses (31/143, 22%), adenovirus (30/151, 21%), enteroviruses, (28/143, 20%), influenza (19/143, 13%) and HHV6 (17/143, 12%). More than one virus was found in 48/143 (34%). No significant clinical differences were observed when children with a pathogen identified were compared with those with no pathogen detected. Febrile seizures occurred within 14 days of vaccine administration in 16/151 (11%).

Conclusion

At least one virus was detected in over two thirds of cases tested (commonly picornaviruses, adenovirus and influenza). Viral co-infections were frequently identified. Febrile seizures occurred infrequently following immunization.

Predicting patient disposition in a paediatric emergency department

AIM

The aim of this study is to directly compare published prediction tools with triage nurse (TN) predictions within a defined paediatric population.

METHOD

A prospective observational study carried out over a week in May 2010 in the Emergency Department (ED) at Princess Margaret Hospital for Children in Perth, Western Australia. TN predicted which patients would be admitted to hospital at the time of ED presentation. Data required for the other prediction tools (paediatric early warning score (PEWS); triage category and the Pediatric Risk of Admission Score (PRISA) and PRISA II were obtained from the notes following the patient's ED attendance.

RESULTS

A total of 1223 patients presented during the study week, 91 patients were excluded and a total of 946 patients (83.6%) had TN predictions and were included in the analysis. TN predictions were compared against a PEWS ≥ 4, triage category 1, 2 and 3, PRISA ≥ 9 and PRISA II ≥ 2. TNs had the highest prediction accuracy (87.7%), followed by an elevated PEWS (82.9%), triage category of 1, 2, or 3 (82.9%). The PRISA and PRISA II score had an accuracy of 80.1% and 79.7%, respectively.

CONCLUSION

When compared with validated prediction tools, the TN is the most accurate predictor of need to admit. This study provides valuable information in planning efficient flow of patients through the ED.

A short-pulse X-ray beamline for spectroscopy and scattering

Experimental facilities for picosecond X-ray spectroscopy and scattering based on RF deflection of stored electron beams face a series of optical design challenges. Beamlines designed around such a source enable time-resolved diffraction, spectroscopy and imaging studies in chemical, condensed matter and nanoscale materials science using few-picosecond-duration pulses possessing the stability, high repetition rate and spectral range of synchrotron light sources. The RF-deflected chirped electron beam produces a vertical fan of undulator radiation with a correlation between angle and time. The duration of the X-ray pulses delivered to experiments is selected by a vertical aperture. In addition to the radiation at the fundamental photon energy in the central cone, the undulator also emits the same photon energy in concentric rings around the central cone, which can potentially compromise the time resolution of experiments. A detailed analysis of this issue is presented for the proposed SPXSS beamline for the Advanced Photon Source. An optical design that minimizes the effects of off-axis radiation in lengthening the duration of pulses and provides variable X-ray pulse duration between 2.4 and 16 ps is presented.

A prospective observational study to assess the diagnostic accuracy of clinical decision rules for children presenting to emergency departments after head injuries (protocol): the Australasian Paediatric Head Injury Rules Study (APHIRST)

Background

Head injuries in children are responsible for a large number of emergency department visits. Failure to identify a clinically significant intracranial injury in a timely fashion may result in long term neurodisability and death. Whilst cranial computed tomography (CT) provides rapid and definitive identification of intracranial injuries, it is resource intensive and associated with radiation induced cancer. Evidence based head injury clinical decision rules have been derived to aid physicians in identifying patients at risk of having a clinically significant intracranial injury. Three rules have been identified as being of high quality and accuracy: the Canadian Assessment of Tomography for Childhood Head Injury (CATCH) from Canada, the Children’s Head Injury Algorithm for the Prediction of Important Clinical Events (CHALICE) from the UK, and the prediction rule for the identification of children at very low risk of clinically important traumatic brain injury developed by the Pediatric Emergency Care Applied Research Network (PECARN) from the USA. This study aims to prospectively validate and compare the performance accuracy of these three clinical decision rules when applied outside the derivation setting.

Methods/design

This study is a prospective observational study of children aged 0 to less than 18 years presenting to 10 emergency departments within the Paediatric Research in Emergency Departments International Collaborative (PREDICT) research network in Australia and New Zealand after head injuries of any severity. Predictor variables identified in CATCH, CHALICE and PECARN clinical decision rules will be collected. Patients will be managed as per the treating clinicians at the participating hospitals. All patients not undergoing cranial CT will receive a follow up call 14 to 90 days after the injury. Outcome data collected will include results of cranial CTs (if performed) and details of admission, intubation, neurosurgery and death. The performance accuracy of each of the rules will be assessed using rule specific outcomes and inclusion and exclusion criteria.

Discussion

This study will allow the simultaneous comparative application and validation of three major paediatric head injury clinical decision rules outside their derivation setting.

Trial registration

The study is registered with the Australian New Zealand Clinical Trials Registry (ANZCTR)- ACTRN12614000463673 (registered 2 May 2014).

Optical design of the Short Pulse Soft X-ray Spectroscopy beamline at the Advanced Photon Source

The Short Pulse X-ray facility planned for the Advanced Photon Source (APS) upgrade will provide two sectors with photon beams having picosecond pulse duration. The Short Pulse Soft X-ray Spectroscopy (SPSXS) beamline will cover the 150-2000 eV energy range using an APS bending magnet. SPSXS is designed to take full advantage of this new timing capability in addition to providing circular polarized radiation. Since the correlation between time and electron momentum is in the vertical plane, the monochromator disperses in the horizontal plane. The beamline is designed to maximize flux and preserve the time resolution by minimizing the number of optical components. The optical design allows the pulse duration to be varied from 1.5 to 100 ps full width at half-maximum (FWHM) without affecting the energy resolution, and the resolution to be changed with minimal effect on the pulse duration. More than 10(9) photons s(-1) will reach the sample with a resolving power of 2000 and a pulse duration of ∼2 ps for photon energies between 150 and 1750 eV. The spot size expected at the sample position will vary with pulse duration and exit slit opening. At 900 eV and at a resolving power of 2000 the spot will be ∼10 µm × 10 µm with a pulse duration of 2.3 ps FWHM.

Optical design of the short pulse x-ray imaging and microscopy time-angle correlated diffraction beamline at the Advanced Photon Source

The short pulse x-ray imaging and microscopy beamline is one of the two x-ray beamlines that will take full advantage of the short pulse x-ray source in the Advanced Photon Source (APS) upgrade. A horizontally diffracting double crystal monochromator which includes a sagittally focusing second crystal will collect most of the photons generated when the chirped electron beam traverses the undulator. A Kirkpatrick-Baez mirror system after the monochromator will deliver to the sample a beam which has an approximately linear correlation between time and vertical beam angle. The correlation at the sample position has a slope of 0.052 ps/μrad extending over an angular range of 800 μrad for a cavity deflection voltage of 2 MV. The expected time resolution of the whole system is 2.6 ps. The total flux expected at the sample position at 10 keV with a 0.9 eV energy resolution is 5.7 × 10(12) photons/s at a spot having horizontal and vertical full width at half maximum of 33 μm horizontal by 14 μm vertical. This new beamline will enable novel time-dispersed diffraction experiments on small samples using the full repetition rate of the APS.

A prospective randomised trial comparing nasogastric with intravenous hydration in children with bronchiolitis (protocol): the comparative rehydration in bronchiolitis study (CRIB)

BACKGROUND

Bronchiolitis is the most common reason for admission of infants to hospital in developed countries. Fluid replacement therapy is required in about 30% of children admitted with bronchiolitis. There are currently two techniques of fluid replacement therapy that are used with the same frequency-intravenous (IV) or nasogastric (NG).The evidence to determine the optimum route of hydration therapy for infants with bronchiolitis is inadequate. This randomised trial will be the first to provide good quality evidence of whether nasogastric rehydration (NGR) offers benefits over intravenous rehydration (IVR) using the clinically relevant continuous outcome measure of duration of hospital admission.

METHODS/DESIGN

A prospective randomised multi-centre trial in Australia and New Zealand where children between 2 and 12 months of age with bronchiolitis, needing non oral fluid replacement, are randomised to receive either intravenous (IV) or nasogastric (NG) rehydration.750 patients admitted to participating hospitals will be recruited, and will be followed daily during the admission and by telephone 1 week after discharge. Patients with chronic respiratory, cardiac, or neurological disease; choanal atresia; needing IV fluid resuscitation; needing an IV for other reasons, and those requiring CPAP or ventilation are excluded.The primary endpoint is duration of hospital admission. Secondary outcomes are complications, need for ICU admission, parental satisfaction, and an economic evaluation. Results will be analysed using t-test for continuous data, and chi squared for categorical data. Non parametric data will be log transformed.

DISCUSSION

This trial will define the role of NGR and IVR in bronchiolitis

TRIAL REGISTRATION

The trial is registered with the Australian and New Zealand Clinical Trials Registry--ACTRN12605000033640.

Patterns of presentation to the Australian and New Zealand Paediatric Emergency Research Network

OBJECTIVE

To describe epidemiological data concerning paediatric ED visits to an Australian and New Zealand research network.

METHODS

We conducted a cross-sectional study of paediatric ED visits to all Paediatric Research in Emergency Departments International Collaborative (PREDICT) sites in 2004. Epidemiological data, including demographics, admission rates and diagnostic grouping, were examined and analysed using descriptive and comparative statistical methods. We compared the data, if possible, with published data from a US paediatric emergency research network (Pediatric Emergency Care Applied Research Network).

RESULTS

A total of 351 440 ED presentations were analysed from 11 PREDICT sites. Mean patient age was 4.6 years and 55% were boys. Presentations were identified as 3% Aboriginal at Australian sites and 44% Maori/Pacific in New Zealand locations. According to Australasian Triage Scale (ATS), 5% were ATS 1 or 2 (to be seen immediately or within 10 min), 27% ATS 3 (to be seen within 30 min) and 67% ATS 4 or 5. Although ED visits peaked in late winter and early spring, admission rates remained unchanged throughout the year with an overall admission rate of 24%. Most frequent diagnoses were acute gastroenteritis, acute viral illness and upper respiratory tract infection. Asthma was the next most common. Pediatric Emergency Care Applied Research Network and PREDICT data showed differences in terms of ethnicity descriptions/distribution and admission rates.

CONCLUSIONS

This is the first description of the epidemiology of patient presentations to major paediatric ED in Australia and New Zealand. It details baseline data important to future collaborative studies and for planning health services for children.

Emergency management of paediatric status epilepticus in Australia and New Zealand: practice patterns in the context of clinical practice guidelines

AIMS

To establish current acute seizure management through a review of clinical practice guidelines (CPGs) and reported physician management in the 11 largest paediatric emergency departments in Australia (n= 9) and New Zealand (n= 2) within the Paediatric Research in Emergency Departments International Collaborative (PREDICT) network, and to compare this with Advanced Paediatric Life Support (APLS) guidelines and existing evidence.

METHODS

(i) Review of CPGs for acute seizure management at PREDICT sites. (ii) A standardised anonymous survey of senior emergency doctors at PREDICT sites investigating management of status epilepticus (SE).

RESULTS

Ten sites used seven different seizure CPGs. One site had no seizure CPG. First line management was with benzodiazepines (10 sites). Second line and subsequent management included phenytoin (10), phenobarbitone (10), thiopentone (9), paraldehyde (6) and midazolam infusion (5). Of 83 available consultants, 78 (94%) responded. First line management of SE without intravenous (IV) access included diazepam per rectum (PR) (49%), and midazolam intramuscular (41%) and via the buccal route (9%). First line management of SE with IV access included midazolam IV (50%) and diazepam IV (44%). The second line agent was phenytoin (88%); third line agents were phenobarbitone (33%), thiopentone and intubation (32%), paraldehyde PR (22%) and midazolam infusion (6%). Fourth line agents were thiopentone and intubation (60%), phenobarbitone (16%), midazolam infusion (13%) and paraldehyde (9%).

CONCLUSIONS

Initial seizure management by CPG recommendations and reported physician practice was broadly similar across PREDICT sites and consistent with APLS guidelines. Practice was variable for second/third line SE management. Areas of controversy would benefit from multi-centred trials.

Emergency department management of gastro-enteritis in Australia and New Zealand

OBJECTIVE

Comparison of clinical practice guideline (CPG) recommendations and reported physician management of gastro-enteritis at Paediatric Research in Emergency Departments International Collaborative (PREDICT) network sites as a baseline for further randomised controlled trials.

METHODS

Two part survey comprising: (i) review of CPGs from PREDICT sites for gastro-enteritis; and (ii) survey of senior emergency department physicians regarding the management of gastro-enteritis.

RESULTS

All 11 PREDICT sites participated. Nine CPGs were available with three sites using a common CPG. For moderate dehydration, eight CPGs advocated nasogastric (NG) rehydration in preference to intravenous (IV) rehydration. The IV route was reserved for severe dehydration or failed NG rehydration. In the second component of the survey, 78 of 83 (94%) physicians responded. In moderate dehydration, 82% of respondents used NG rehydration. In severe dehydration, 86% used IV fluids; 12% used NG and 3% an initial IV bolus followed by NG fluid. Serum electrolytes were measured universally with IV fluid use and by 22% using NG rehydration. The IV fluid bolus was with normal saline (86%). Fifty-four per cent used anti-emetics 'rarely' or 'sometimes'. The commonest agents were ondansetron (60%) and metoclopramide (29%).

CONCLUSIONS

CPG recommendations and physician practice for the management of gastro-enteritis were similar across PREDICT sites with a focus on NG for moderate dehydration and IV for severe dehydration. A variety of fluids and administration rates were used. Anti-emetics were used infrequently. The efficacy and safety of newer anti-emetics should be explored in collaborative studies. Collaborative development of new CPGs should be considered to simplify fluid regimens.

Paediatric acute asthma management in Australia and New Zealand: practice patterns in the context of clinical practice guidelines

OBJECTIVES

To compare clinical practice guideline (CPG) recommendations and reported physician management of acute paediatric asthma in the 11 largest paediatric emergency departments, all of which have CPGs, in Australia (n = 9) and New Zealand (n = 2). All 11 sites participate in the Paediatric Research in Emergency Departments International Collaborative (PREDICT) research network.

METHODS

(a) A review of CPGs for acute childhood asthma from all PREDICT sites. (b) A standardised anonymous survey of senior emergency doctors at PREDICT sites investigating management of acute childhood asthma.

RESULTS

CPGs for mild to moderate asthma were similar across sites and based on salbutamol delivery by metered dose inhaler with spacer and oral prednisolone. In severe to critical asthma, differences between sites were common and related to recommendations for: ipratropium use; metered-dose inhaler versus nebulised delivery of salbutamol in severe asthma; use of intravenous aminophylline, intravenous magnesium and dosing of intravenous salbutamol in critical asthma. The questionnaire (78 of 83 doctors responded) also revealed significant differences between doctors in the treatment of moderate to severe asthma. Ipratropium was used for moderate asthma by 42%. For severe to critical asthma, nebulised delivery of salbutamol was preferred by 79% of doctors over metered dose inhalers. For critical asthma, doctors reported using intravenous aminophylline in 45%, intravenous magnesium in 55%, and intravenous salbutamol in 87% of cases. Thirty-nine different dosing regimens for intravenous salbutamol were reported.

CONCLUSIONS

CPG recommendations and reported physician practice for mild to moderate paediatric asthma management were broadly similar across PREDICT sites and consistent with national guidelines. Practice was highly variable for severe to critical asthma and probably reflects limitations of available evidence. Areas of controversy, in particular the comparative efficacy of intravenous bronchodilators, would benefit from multi-centre trials. Collaborative development of CPGs should be considered.

A randomized controlled trial comparing intranasal fentanyl to intravenous morphine for managing acute pain in children in the emergency department

STUDY OBJECTIVE

We compare the efficacy of intranasal fentanyl versus intravenous morphine in a pediatric population presenting to an emergency department (ED) with acute long-bone fractures.

METHODS

We conducted a prospective, randomized, double-blind, placebo-controlled, clinical trial in a tertiary pediatric ED between September 2001 and January 2005. A convenience sample of children aged 7 to 15 years with clinically deformed closed long-bone fractures was included to receive either active intravenous morphine (10 mg/mL) and intranasal placebo or active intranasal concentrated fentanyl (150 microg/mL) and intravenous placebo. Exclusion criteria were narcotic analgesia within 4 hours of arrival, significant head injury, allergy to opiates, nasal blockage, or inability to perform pain scoring. Pain scores were rated by using a 100-mm visual analog scale at 0, 5, 10, 20, and 30 minutes. Routine clinical observations and adverse events were recorded.

RESULTS

Sixty-seven children were enrolled (mean age 10.9 years [SD 2.4]). Fractures were radius or ulna 53 (79.1%), humerus 9 (13.4%), tibia or fibula 4 (6.0%), and femur 1 (1.5%). Thirty-four children received intravenous (i.v.) morphine and 33 received intranasal fentanyl. Statistically significant differences in visual analog scale scores were not observed between the 2 treatment arms either preanalgesia or at 5, 10, 20, or 30 minutes postanalgesia (P=.333). At 10 minutes, the difference in mean visual analog scale between the morphine and fentanyl groups was -5 mm (95% confidence interval -16 to 7 mm). Reductions in combined pain scores occurred at 5 minutes (20 mm; P=.000), 10 minutes (4 mm; P=.012), and 20 minutes (8 mm; P=.000) postanalgesia. The mean total INF dose was 1.7 microg/kg, and the mean total i.v. morphine dose was 0.11 mg/kg. There were no serious adverse events.

CONCLUSION

Intranasal fentanyl delivered as 150 microg/mL at a dose of 1.7 microg/kg was shown to be an effective analgesic in children aged 7 to 15 years presenting to an ED with an acute fracture when compared to intravenous morphine at 0.1 mg/kg.

Paediatric Research in Emergency Departments International Collaborative (PREDICT): first steps towards the development of an Australian and New Zealand research network

Paediatric emergency research is hampered by a number of barriers that can be overcome by a multicentre approach. In 2004, an Australia and New Zealand-based paediatric emergency research network was formed, the Paediatric Research in Emergency Departments International Collaborative (PREDICT). The founding sites include all major tertiary children's hospital EDs in Australia and New Zealand and a major mixed ED in Australia. PREDICT aims to provide leadership and infrastructure for multicentre research at the highest standard, facilitate collaboration between institutions, health-care providers and researchers and ultimately improve patient outcome. Initial network-wide projects have been determined. The present article describes the development of the network, its structure and future goals.

Evidence for microbunching "sidebands" in a saturated free-electron laser using coherent optical transition radiation

We report the first measurements of z-dependent coherent optical transition radiation (COTR) due to electron-beam microbunching at high gains ( >10(4)) including saturation of a self-amplified spontaneous emission free-electron laser (FEL). In these experiments the fundamental wavelength was near 530 nm, and the COTR spectra exhibit the transition from simple spectra to complex spectra ( 5% spectral width) after saturation. The COTR intensity growth and angular distribution data are reported as well as the evidence for transverse spectral dependencies and an "effective" core of the beam being involved in microbunching.

Exponential Gain and Saturation of a Self-Amplified Spontaneous Emission Free-Electron Laser

Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational x-ray free-electron laser.

First Observation of z-Dependent Electron-Beam Microbunching Using Coherent Transition Radiation

We report the first measurements of the electron-beam microbunching z dependence in a self-amplified spontaneous-emission (SASE) free-electron laser (FEL) experiment by the observation of visible wavelength coherent transition radiation (CTR). In this case the fundamental SASE wavelength was at 537 nm, and the CTR exhibited an exponential intensity growth similar to the SASE radiation. In addition, we observed for the first time structure in the CTR angular distribution patterns that may be useful for optimizing SASE FEL performance.