Association of dexmedetomidine use with haemodynamics, postoperative recovery, and cost in paediatric anaesthesia: a hospital registry study

BACKGROUND

Dexmedetomidine utilisation in paediatric patients is increasing. We hypothesised that intraoperative use of dexmedetomidine in children is associated with longer postanaesthesia care unit length of stay, higher healthcare costs, and side-effects.

METHODS

We analysed data from paediatric patients (aged 0-12 yr) between 2016 and 2021 in the Bronx, NY, USA. We matched our cohort with the Healthcare Cost and Utilization Project-Kids' Inpatient Database (HCUP-KID).

RESULTS

Among 18 104 paediatric patients, intraoperative dexmedetomidine utilisation increased from 51.7% to 85.7% between 2016 and 2021 (P<0.001). Dexmedetomidine was dose-dependently associated with a longer postanaesthesia care unit length of stay (adjusted absolute difference [ADadj] 19.7 min; 95% confidence interval [CI]: 18.0-21.4 min; P<0.001, median length of stay of 122 vs 98 min). The association was magnified in children aged ≤2 yr undergoing short (≤60 min) ambulatory procedures (ADadj 33.3 min; 95% CI: 26.3-40.7 min; P<0.001; P-for-interaction <0.001). Dexmedetomidine was associated with higher total hospital costs of USD 1311 (95% CI: USD 835-1800), higher odds of intraoperative mean arterial blood pressure below 55 mm Hg (adjusted odds ratio [ORadj] 1.27; 95% CI: 1.16-1.39; P<0.001), and higher odds of heart rate below 100 beats min-1 (ORadj 1.32; 95% CI: 1.21-1.45; P<0.001), with no preventive effects on emergence delirium requiring postanaesthesia i.v. sedatives (ORadj 1.67; 95% CI: 1.04-2.68; P=0.034).

CONCLUSIONS

Intraoperative use of dexmedetomidine is associated with unwarranted haemodynamic effects, longer postanaesthesia care unit length of stay, and higher costs, without preventive effects on emergence delirium.

Sedation Research in Critically Ill Pediatric Patients: Proposals for Future Study Design From the Sedation Consortium on Endpoints and Procedures for Treatment, Education, and Research IV Workshop

OBJECTIVES

Sedation and analgesia for infants and children requiring mechanical ventilation in the PICU is uniquely challenging due to the wide spectrum of ages, developmental stages, and pathophysiological processes encountered. Studies evaluating the safety and efficacy of sedative and analgesic management in pediatric patients have used heterogeneous methodologies. The Sedation Consortium on Endpoints and Procedures for Treatment, Education, and Research (SCEPTER) IV hosted a series of multidisciplinary meetings to establish consensus statements for future clinical study design and implementation as a guide for investigators studying PICU sedation and analgesia.

DESIGN

Twenty-five key elements framed as consensus statements were developed in five domains: study design, enrollment, protocol, outcomes and measurement instruments, and future directions.

SETTING

A virtual meeting was held on March 2-3, 2022, followed by an in-person meeting in Washington, DC, on June 15-16, 2022. Subsequent iterative online meetings were held to achieve consensus.

SUBJECTS

Fifty-one multidisciplinary, international participants from academia, industry, the U.S. Food and Drug Administration, and family members of PICU patients attended the virtual and in-person meetings. Participants were invited based on their background and experience.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Common themes throughout the SCEPTER IV consensus statements included using coordinated multidisciplinary and interprofessional teams to ensure culturally appropriate study design and diverse patient enrollment, obtaining input from PICU survivors and their families, engaging community members, and using developmentally appropriate and validated instruments for assessments of sedation, pain, iatrogenic withdrawal, and ICU delirium.

CONCLUSIONS

These SCEPTER IV consensus statements are comprehensive and may assist investigators in the design, enrollment, implementation, and dissemination of studies involving sedation and analgesia of PICU patients requiring mechanical ventilation. Implementation may strengthen the rigor and reproducibility of research studies on PICU sedation and analgesia and facilitate the synthesis of evidence across studies to improve the safety and quality of care for PICU patients.

Children with Congenital Heart Disease Show Increased Behavioral Problems Compared to Healthy Peers: A Systematic Review and Meta-Analysis

Millions of children and adults are living with congenital heart disease (CHD). Their risk for behavioral problems has not been the subject of a meta-analysis. We performed a systematic review and meta-analysis of measures of behavioral problems in people born with CHD compared to peers without CHD. We searched Pubmed, CINAHL, Embase, PsycInfo, and the Cochrane Library from January 1, 1986 to November 15, 2021. We included studies that reported a measure of behavioral problems in patients with CHD in children and adults older than 3 years of age. We screened 26,343 search results, and 24 studies met inclusion criteria. The quality of evidence was generally low. Subjects with CHD had a small increase in internalizing problems [standardized mean difference (SMD): 0.198, p = 0.02] and total behavior problems (SMD: 0.287, p = 0.013), but no difference in externalizing behavioral problems. There was significant heterogeneity in all three domains of behavior problems analyzed, and it could not be explained by variables such as age, severity, assessor, or assessment tool. There are small increases in parent- and self-reported overall behavioral problems and internalizing problems in patients with CHD compared to healthy controls. Wide confidence intervals in the meta-analyses leave open the possibility that certain factors may increase the risk of behavioral problems in this group, and future studies with important attention paid to potential confounders may help identify risk factors.

Impact of Anesthetic Exposures on the Neurocognitive Profiles of Pediatric Brain Tumor Survivors: A New Direction for Research and Multidisciplinary Collaboration

Primary brain tumors are the most commonly diagnosed solid tumors in children, and pediatric brain tumor survivors experience lasting, pervasive deficits of neurocognitive functioning. Repeated exposure to anesthetic drugs is a necessary component not only of surgical resection but also of multimodal cancer care for the youngest patients with brain tumors. The potential for anesthetic neurotoxicity to worsen neurocognitive outcomes in this vulnerable group, therefore, warrants our attention and further study through multi-disciplinary collaboration. This review discusses neurocognitive functioning in pediatric brain tumor survivors, highlighting the findings of a recent study of children with tumors of the posterior fossa which identified treatment-related risk factors for neurocognitive difficulties, with those undergoing multimodal therapies (eg, chemotherapy and irradiation) experiencing the greatest deficits compared with healthy controls. The role of anesthetic neurotoxicity in long-term outcomes among pediatric brain tumor survivors is also reviewed.

Multireference configuration interaction study of the predissociation of C2 via its F 1Πu state

Photodissociation is one of the main destruction pathways for dicarbon (C2) in astronomical environments such as diffuse interstellar clouds, yet the accuracy of modern astrochemical models is limited by a lack of accurate photodissociation cross sections in the vacuum ultraviolet range. C2 features a strong predissociative F 1Πu-X 1Σg+ electronic transition near 130 nm originally measured in 1969; however, no experimental studies of this transition have been carried out since, and theoretical studies of the F 1Πu state are limited. In this work, potential energy curves of excited electronic states of C2 are calculated with the aim of describing the predissociative nature of the F 1Πu state and providing new ab initio photodissociation cross sections for astrochemical applications. Accurate electronic calculations of 56 singlet, triplet, and quintet states are carried out at the DW-SA-CASSCF/MRCI+Q level of theory with a CAS(8,12) active space and the aug-cc-pV5Z basis set augmented with additional diffuse functions. Photodissociation cross sections arising from the vibronic ground state to the F 1Πu state are calculated by a coupled-channel model. The total integrated cross section through the F 1Πu v=0 and v=1 bands is 1.198×10−13 cm2cm-1, giving rise to a photodissociation rate of 5.02×10−10 s−1 under the standard interstellar radiation field, much larger than the rate in the Leiden photodissociation database. In addition, we report a new 2 1Σu+ state that should be detectable via a strong 2 1Σu+-X 1Σg+ band around 116 nm.

Anesthetic Exposure During Childhood and Neurodevelopmental Outcomes: A Systematic Review and Meta-analysis

IMPORTANCE

Clinical studies of neurodevelopmental outcomes after anesthetic exposure have evaluated a range of outcomes with mixed results.

OBJECTIVE

To examine via meta-analyses the associations between exposure to general anesthesia and domain-specific neurodevelopmental outcomes in children.

DATA SOURCES

PubMed/MEDLINE, Embase, CINAHL, Web of Science and the Cochrane Library were searched from inception to August 31, 2021.

STUDY SELECTION

Inclusion criteria were exposures to procedures requiring general anesthesia at younger than 18 years and evaluation of long-term neurodevelopmental function after exposure. Studies lacking unexposed controls or focused on children with major underlying comorbidities were excluded.

DATA EXTRACTION AND SYNTHESIS

Extracted variables included effect size; hazard, risk, or odds ratio; number of exposures; procedure type; major comorbidities; age of exposure and assessment; presence of unexposed controls; and study design. Studies were independently reviewed by 2 coders, and review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Data were pooled using a random-effects model.

MAIN OUTCOMES AND MEASURES

The main outcomes were standardized mean differences (SMD) for scores in the neurodevelopmental domains of academics, behavioral problems, cognition, executive function, general development, language, motor function, nonverbal reasoning, social cognition, and hazard and risk of neurodevelopmental disorder diagnoses.

RESULTS

A total of 31 studies contributed data for meta-analysis. For each of the assessed neurodevelopmental domains, the numbers of children evaluated ranged from 571 to 63 315 exposed and 802 to 311 610 unexposed. Children with any exposure (single or multiple) had significantly worse behavioral problems scores, indicating more behavioral problems (SMD, -0.10; 95% CI, -0.18 to -0.02; P = .02), and worse scores in academics (SMD, -0.07; 95% CI -0.12 to -0.01; P = .02), cognition (SMD, -0.03; 95% CI, -0.05 to 0.00; P = .03), executive function (SMD, -0.20; 95% CI, -0.32 to -0.09; P < .001), general development (SMD, -0.08; 95% CI, -0.13 to -0.02; P = .01), language (SMD, -0.08; 95% CI, -0.14 to -0.02; P = .01), motor function (SMD, -0.11; 95% CI, -0.21 to -0.02; P = .02), and nonverbal reasoning (SMD, -0.15; 95% CI, -0.27 to -0.02; P = .02). Higher incidences of neurodevelopmental disorder diagnoses were also reported (hazard ratio, 1.19; 95% CI, 1.09 to 1.30; P < .001; risk ratio, 1.81; 95% CI, 1.25 to 2.61; P = .002).

CONCLUSIONS AND RELEVANCE

These findings support the hypothesis that associations between anesthetic exposure during childhood and subsequent neurodevelopmental deficits differ based on neurodevelopmental domain.

COVID-19 in Pediatric Patients: A Systematic Review

INTRODUCTION

The coronavirus disease (COVID)-19 pandemic has been an enormous global health burden, resulting in hundreds of millions of documented infections and more than 3 million deaths. Increasing reports characterizing the effects of COVID-19 in pediatric populations have been published during the course of the pandemic. We performed a systematic review to assess the scope of diagnosis, treatment, and management of COVID-19 in pediatric patients.

MATERIALS AND METHODS

We searched the Cochrane Database of Systematic Reviews, PubMed, CINAHL, and Embase for studies published between January 1, 2020, and May 1, 2021. Each result was screened by 2 authors independently, and discordant findings were adjudicated by a third party. Data extracted included demographic data, symptom data, and clinical data including mortality, severe illness, laboratory data, radiologic data, and treatment. Bias assessment was performed using the Newcastle-Ottawa Quality Assessment Scale for Cohort Studies.

RESULTS

We found a total of 16,266 search results, and we accepted 63 manuscripts into the review. The quality of evidence was low. It was difficult to estimate the risk of mortality in pediatric patients with COVID-19 given the quality of the evidence, but overall it is likely below 1%. The most common symptoms in symptomatic pediatric COVID-19 patients were fever (58%) and cough (50%). There was a high proportion of asymptomatic infection (65%).

DISCUSSION

Pediatric COVID-19 infection is mild and frequently asymptomatic. There is a low risk of severe illness or death in children who contract COVID-19. High-quality studies should be conducted to develop best practices for prevention, diagnosis, and management of symptomatic illness.

COVID-19: A Catalyst for Transforming Randomized Trials

The coronavirus disease 2019 (COVID-19) pandemic incited a global clinical trial research agenda of unprecedented speed and high volume. This expedited research activity in a time of crisis produced both successes and failures that offer valuable learning opportunities for the scientific community to consider. Successes include the implementation of large adaptive and pragmatic trials as well as burgeoning efforts toward rapid data synthesis and open science principles. Conversely, notable failures include: (1) inadequate study design and execution; (2) data reversal, fraud, and retraction; and (3) research duplication and waste. Other challenges that became highlighted were the need to find unbiased designs for investigating complex, nonpharmaceutical interventions and the use of routinely collected data for outcomes assessment. This article discusses these issues juxtaposing the COVID-19 trials experience against trials in anesthesiology and other fields. These lessons may serve as a positive catalyst for transforming future clinical trial research.

Prospectively assessed neurodevelopmental outcomes in studies of anaesthetic neurotoxicity in children: a systematic review and meta-analysis

BACKGROUND

Whether exposure to a single general anaesthetic (GA) in early childhood causes long-term neurodevelopmental problems remains unclear.

METHODS

PubMed/MEDLINE, Embase, CINAHL, Web of Science, and the Cochrane Library were searched from inception to October 2019. Studies evaluating neurodevelopmental outcomes and prospectively enrolling children exposed to a single GA procedure compared with unexposed children were identified. Outcomes common to at least three studies were evaluated using random-effects meta-analyses.

RESULTS

Full-scale intelligence quotient (FSIQ); the parentally reported Child Behavior Checklist (CBCL) total, externalising, and internalising problems scores; and Behavior Rating Inventory of Executive Function (BRIEF) scores were assessed. Of 1644 children identified, 841 who had a single exposure to GA were evaluated. The CBCL problem scores were significantly higher (i.e. worse) in exposed children: mean score difference (CBCL total: 2.3 [95% confidence interval {CI}: 1.0-3.7], P=0.001; CBCL externalising: 1.9 [95% CI: 0.7-3.1], P=0.003; and CBCL internalising problems: 2.2 [95% CI: 0.9-3.5], P=0.001). Differences in BRIEF were not significant after multiple comparison adjustment. Full-scale intelligence quotient was not affected by GA exposure. Secondary analyses evaluating the risk of these scores exceeding predetermined clinical thresholds found that GA exposure was associated with increased risk of CBCL internalising behavioural deficit (risk ratio [RR]: 1.47; 95% CI: 1.08-2.02; P=0.016) and impaired BRIEF executive function (RR: 1.68; 95% CI: 1.23-2.30; P=0.001).

CONCLUSIONS

Combining results of studies utilising prospectively collected outcomes showed that a single GA exposure was associated with statistically significant increases in parent reports of behavioural problems with no difference in general intelligence.

Branching Ratios of the N(2D03/2) and N(2D05/2) Spin-Orbit States Produced in the State-Selected Photodissociation of N2 Determined Using Time-Sliced Velocity-Mapped-Imaging Photoionization Mass Spectrometry (TS-VMI-PI-MS)

Branching ratios for N(²D⁰_3/2) and N(²D⁰_5/2) produced by predissociation of state selected excited nitrogen molecules in the vacuum ultraviolet region have been measured for the first time. The quantum numbers of the excited nitrogen molecule are defined by selective excitation of the nitrogen molecule in the Franck-Condon region from the ground electronic, ¹Σ_g⁺, vibrational, v″, and rotational, J″ state to an excited E_u', v', J' state with a tunable vacuum ultraviolet, VUV₁, laser. The neutral atoms produced by predissociation from this excited state are then selectively ionized with a second tunable VUV₂ laser. Measurement of the relative populations of these two atoms formed in their spin-orbit states defines the quantum states for the atomic products. This means that the wave functions of the initial state and knowledge of the relative yields define all the experimental parameters for this series of unimolecular reactions. The ions formed by VUV₂ are mass analyzed with a time-of-flight mass spectrometer and detected with a time slice velocity ion imaging mass spectrometer. In this manner, we can determine the recoil velocity associated with the predissociation process. Two different techniques are used to determine the spin-orbit ratios, namely, resonant VUV photoionization (RVUV-PI) spectroscopy and total kinetic energy release (TKER) spectroscopy determined from the image produced when the atoms are selectively ionized by VUV₂ in the interaction region. The TKER spectra obtained from the lines at 110 296.25 and 110 304.96 cm^-1 that couple to a newly discovered autoionization line at 129 529.4255 ± 0.0015 cm^-1 prove that the lines observed in this region originate from the N(²D⁰_3/2) and N(²D⁰_5/2) atoms. Two other lines in this region at 110 286.20 and 110 299.89 cm^-1 originate from the nitrogen N(⁴S⁰_3/2) that is photoionized in a 1+ 1 VUV-UV resonant multiphoton ionization process. The spin-orbit branching ratios have been evaluated for valence and Rydberg electronic excited states from 104 129.4 to 118 772.1 cm^-1, and it shows that they are independent of the rotational and vibrational quantum numbers. They are not appreciably affected by the symmetry properties of the wave function in the Franck-Condon region of the excited states. In the energy region below 117 153.8 cm^-1 the pathways at long internuclear distances appear to determine [N(²D⁰_3/2)]/[N(²D⁰_5/2)] branching ratios of ∼0.38, ∼0.62, and ∼1.04. At higher energies, TKER and RVUV-PI spectroscopy have been used to show that the average fraction of the N(²D⁰_3/2) and N(²D⁰_5/2) atoms produced in the spin-allowed channels that produce two N(²D⁰_J) is 0.85 versus 0.15 for spin-forbidden channels. The importance and need for this information for comparison with theory and applications in astrochemistry are briefly discussed.

Branching Ratio Measurements of the Predissociation of 12C16O by Time-Slice Velocity-Map Ion Imaging in the Energy Region from 106 250 to 107 800 cm-1

Photodissociation of CO is a fundamental chemical mechanism for mass-independent oxygen isotope fractionation in the early Solar System. Branching ratios of photodissociation channels for individual bands quantitatively yield the trapping efficiencies of atomic oxygen resulting into oxides. We measured the branching ratios for the spin-forbidden and spin-allowed photodissociation channels of ¹²C¹⁶O in the vacuum ultraviolet (VUV) photon energy region from 106 250 to 107 800 cm^-1 using the VUV laser time-slice velocity-map imaging photoion technique. The excitations to four ¹Π bands and three ¹Σ⁺ bands of ¹²C¹⁶O were identified and investigated. The branching ratios for the product channels C(³P) + O(³P), C(¹D) + O(³P), and C(³P) + O(¹D) of these predissociative states strongly depend on the electronic and vibrational states of CO being excited. By plotting the branching ratio of the spin-forbidden dissociation channels versus the excitation energy from 102 500 to 110 500 cm^-1 that has been measured so far, the global pattern of the ¹Π-³Π interaction that plays a key role in the predissociation of CO is revealed and discussed.

The failing medial compartment in the varus knee and its association with CAM deformity of the hip

BACKGROUND

Since 2011, the knee service at the Nuffield Orthopaedic Centre has been offering a neutralising medial opening wedge high tibial osteotomy (HTO) to a specific group of patients with genu varum and early knee osteoarthritis. An observation was made concerning this group of patients and the presence of CAM deformity at the hip. The aim of this study is to establish whether or not any association exists between the OA phenotype shared by our HTO group and the incidence of CAM deformity at the hip.

METHODS

A cross-sectional study was designed to estimate the prevalence of CAM-type lesions across different groups of individuals. Our HTO group (n=30) was compared to a pre-arthroplasty group (n=20) and control group (n=20). A total of 70 subjects were identified across the different groups all of whom had long-leg radiographs (LLRs) available for analysis. LLRs were analysed using an in house developed Matlab®-based (Matlab R2009b; MathWorks) software package for hip measurements and MediCAD® (Hectec GmbH, Germany) for lower limb alignment measurements.

RESULTS

The HTO group had a significantly higher prevalence of CAM lesions (57%) than both the pre-arthroplasty (40%) and control (30%) groups. This difference was maintained when results were adjusted for potential confounding factors (age, gender and laterality). Across the groups, individuals with tibia vara were more likely to have CAM-deformity of the hip (p=0.021).

CONCLUSION

Patients with symptomatic early knee OA and varus deformity of the knee have a high prevalence of CAM deformity in the hip.

Neurogenesis and developmental anesthetic neurotoxicity

The mechanism by which anesthetics might act on the developing brain in order to cause long term deficits remains incompletely understood. The hippocampus has been identified as a structure that is likely to be involved, as rodent models show numerous deficits in behavioral tasks of learning that are hippocampal-dependent. The hippocampus is an unusual structure in that it is the site of large amounts of neurogenesis postnatally, particularly in the first year of life in humans, and these newly generated neurons are critical to the function of this structure. Intriguingly, neurogenesis is a major developmental event that occurs during postulated windows of vulnerability to developmental anesthetic neurotoxicity across the different species in which it has been studied. In this review, we examine the evidence for anesthetic effects on neurogenesis in the early postnatal period and ask whether neurogenesis should be studied further as a putative mechanism of injury. Multiple anesthetics are considered, and both in vivo and in vitro work is presented. While there is abundant evidence that anesthetics act to suppress neurogenesis at several different phases, evidence of a causal link between these effects and any change in learning behavior remains elusive.

Photochemistry. Evidence for direct molecular oxygen production in CO₂ photodissociation

Photodissociation of carbon dioxide (CO2) has long been assumed to proceed exclusively to carbon monoxide (CO) and oxygen atom (O) primary products. However, recent theoretical calculations suggested that an exit channel to produce C + O2 should also be energetically accessible. Here we report the direct experimental evidence for the C + O2 channel in CO2 photodissociation near the energetic threshold of the C((3)P) + O2(X(3)Σ(g)(-)) channel with a yield of 5 ± 2% using vacuum ultraviolet laser pump-probe spectroscopy and velocity-map imaging detection of the C((3)PJ) product between 101.5 and 107.2 nanometers. Our results may have implications for nonbiological oxygen production in CO2-heavy atmospheres.

Communication: direct measurements of nascent O((3)P0,1,2) fine-structure distributions and branching ratios of correlated spin-orbit resolved product channels CO(ã(3)Π; v) + O((3)P0,1,2) and CO(X̃(1)Σ(+); v) + O((3)P0,1,2) in VUV photodissociation of CO2

We present a generally applicable experimental method for the direct measurement of nascent spin-orbit state distributions of atomic photofragments based on the detection of vacuum ultraviolet (VUV)-excited autoionizing-Rydberg (VUV-EAR) states. The incorporation of this VUV-EAR method in the application of the newly established VUV-VUV laser velocity-map-imaging-photoion (VMI-PI) apparatus has made possible the branching ratio measurement for correlated spin-orbit state resolved product channels, CO(ã(3)Π; v) + O((3)P0,1,2) and CO(X̃(1)Σ(+); v) + O((3)P0,1,2), formed by VUV photoexcitation of CO2 to the 4s(10 (1)) Rydberg state at 97,955.7 cm(-1). The total kinetic energy release (TKER) spectra obtained from the O(+) VMI-PI images of O((3)P0,1,2) reveal the formation of correlated CO(ã(3)Π; v = 0-2) with well-resolved v = 0-2 vibrational bands. This observation shows that the dissociation of CO2 to form the spin-allowed CO(ã(3)Π; v = 0-2) + O((3)P0,1,2) channel has no potential energy barrier. The TKER spectra for the spin-forbidden CO(X̃(1)Σ(+); v) + O((3)P0,1,2) channel were found to exhibit broad profiles, indicative of the formation of a broad range of rovibrational states of CO(X̃(1)Σ(+)) with significant vibrational populations for v = 18-26. While the VMI-PI images for the CO(ã(3)Π; v = 0-2) + O((3)P0,1,2) channel are anisotropic, indicating that the predissociation of CO2 4s(10 (1)) occurs via a near linear configuration in a time scale shorter than the rotational period, the angular distributions for the CO(X̃(1)Σ(+); v) + O((3)P0,1,2) channel are close to isotropic, revealing a slower predissociation process, which possibly occurs on a triplet surface via an intersystem crossing mechanism.

Branching ratio measurements for vacuum ultraviolet photodissociation of 12C16O

The branching ratios for the spin-forbidden photodissociation channels of (12)C(16)O in the vacuum ultraviolet (VUV) photon energy region from 102,500 (12.709 eV) to 106,300 cm(-1) (13.180 eV) have been investigated using the VUV laser time-slice velocity-map imaging photoion technique. The excitations to three (1)Σ(+) and six (1)Π Rydberg-type states, including the progression of W(3sσ) (1)Π(v' = 0, 1, and 2) vibrational levels of CO, have been identified and investigated. The branching ratios for the product channels C((3)P) + O((3)P), C((1)D) + O((3)P), and C((3)P) + O((1)D) of these predissociative states are found to depend on the electronic, vibrational, and rotational states of CO being excited. Rotation and e/f-symmetry dependences of the branching ratios into the spin-forbidden channels have been confirmed for several of the (1)Π states, which can be explained using the heterogeneous interaction with the repulsive D'(1)Σ(+) state. The percentage of the photodissociation into the spin-forbidden channels is found to increase with increasing the rotational quantum number for the K(4pσ) (1)Σ(+) (v' = 0) state. This has been rationalized using a (1)Σ(+) to (1)Π to (3)Π coupling scheme, where the final (3)Π state is a repulsive valence state correlating to the spin-forbidden channel.

Oxytocin and catechol-O-methyltransferase receptor genotype predict the length of the first stage of labor

OBJECTIVE

We aimed to identify genetic factors that influence the rate of the first stage of labor.

STUDY DESIGN

We prospectively enrolled 233 laboring nulliparous parturients. Demographic, clinical, and genetic data were collected. We evaluated the influence of population and individual variability using a nonlinear mixed effects model.

RESULTS

Parturients who were homozygous for "G" at oxytocin receptor gene rs53576 transitioned to active labor later and thus had slower labor. Catechol-O-methyltransferase rs4633 genotype TT was associated with slower latent phase labor. Labor induction with prostaglandin was associated with faster labor, and request for meperidine was associated with slower labor. Birthweight was related inversely to the rate of the active phase.

CONCLUSION

There are demographic, clinical, and genetic factors that influence an individual's rate of labor progress. This information could be used in automated form to improve the prediction of the length of the first stage of labor.

Branching ratio measurements of the predissociation of 12C16O by time-slice velocity-map ion imaging in the energy region from 108,000 to 110,500 cm(-1)

Direct branching ratio measurements of the three lowest dissociation channels of (12)C(16)O that produce C((3)P) + O((3)P), C((1)D) + O((3)P), and C((3)P) + O((1)D) are reported in the vacuum ultraviolet region from 108,000 cm(-1) (92.59 nm) to 110,500 cm(-1) (90.50 nm) using the time-slice velocity-map ion imaging and nonlinear resonant four-wave mixing techniques. Rotationally, resolved carbon ion yield spectra for both (1)Σ(+) and (1)Π bands of CO in this region have been obtained. Our measurements using this technique show that the branching ratio in this energy region, especially the relative percentages of the two spin-forbidden channels, is strongly dependent on the particular electronic and vibrational energy levels of CO that are excited.

Communication: branching ratio measurements in the predissociation of 12C16O by time-slice velocity-map ion imaging in the vacuum ultraviolet region

The first direct branching ratio measurement of the three lowest energy dissociation channels of CO that produce C((3)P) + O((3)P), C((1)D) + O((3)P), and C((3)P) + O((1)D) is reported. Rotational resolved carbon ion yield spectra for two Π bands (W(3sσ)(1)Π (v(') = 3) at 108,012.6 cm(-1) and (1)Π(v(') = 2) at 109,017 cm(-1)) and two Σ bands ((4sσ)(1)Σ(+)(v(') = 4) at 109,452 cm(-1) and (4pσ)(1)Σ(+)(v(') = 3) at 109,485 cm(-1)) of CO were obtained. Our measurements show that the branching ratio in this energy region is strongly dependent on the electronic and vibrational energy but it is independent or just weakly dependent on the parity and rotational energy levels. To our knowledge, this is the first time that the triplet channel producing O((1)D) has been experimentally observed and this is also the first time that a direct measurement of the branching ratio for the different channels in the predissociation of CO in this energy region has been made.

Time-sliced velocity-mapped imaging studies of the predissociation of single ro-vibronic energy levels of N2 in the extreme ultraviolet region using vacuum ultraviolet photoionization

The predissociation of N(2) from the rotational levels in the o(1)∏(u) (v(') = 2) and b(') (1)Σ(u) (v(') = 8) bands has been studied in the wavenumber (or energy) range from 109 350 cm(-1) (13.5577 eV) to 109 580 cm(-1) (13.5862 eV) by time-sliced velocity-mapped imaging technique with VUV photoionization detection of the fragments. These levels were excited from the ground state of N(2) (X(1)Σ(g) (+), v(") = 0) levels using an unfocused vacuum ultraviolet (VUV) laser via a one-photon process. The same VUV laser is used to ionize the metastable N ((2)D(o)) produced from the predissociation process and the time-sliced velocity-mapped imaging technique is used to determine their velocity and angular distributions. Two different theoretical methods developed, respectively, by Kim et al. [J. Chem. Phys. 125, 133316 (2006) and Zande [J. Chem. Phys. 107, 9447 (1997)] were used to calculate the anisotropic parameters for the predissociation to the channel N((4)S(o)) + N((2)D(o)) to compare with the observed value for each of the rotational levels. Very good agreement with the experimental results was obtained for both methods. Possible predissociation mechanisms were predicted from the measurements and calculations.

Mesenchymal progenitor cells derived from traumatized human muscle

Mesenchymal stem cells (MSCs) derived from adult tissues are an important candidate cell type for cell-based tissue engineering and regenerative medicine. Currently, clinical applications for MSCs require additional surgical procedures to harvest the autologous MSCs (i.e. from bone marrow) or commercial allogeneic alternatives. We have recently identified a population of mesenchymal progenitor cells (MPCs) in traumatized muscle tissue that has been surgically debrided from traumatic orthopaedic extremity wounds. The purpose of this study was to evaluate whether MPCs derived from traumatized muscle may provide a clinical alternative to bone-marrow MSCs, by comparing their morphology, proliferation capacity, cell surface epitope profile and differentiation capacity. After digesting the muscle tissue with collagenase, the MPCs were enriched by a direct plating technique. The morphology and proliferation rate of the muscle-derived MPCs was similar to bone-marrow derived MSCs. Both populations expressed cell surface markers characteristic for MSCs (CD 73, CD 90 and CD105), and did not express markers typically absent on MSCs (CD14, CD34 and CD45). After 21 days in specific differentiation media, the histological staining and gene expression of the MPCs and MSCs was characteristic for differentiation into osteoblasts, chondrocytes and adipocytes, but not into myoblasts. Our findings demonstrate that traumatized muscle-derived MPCs exhibit a similar phenotype and resemble MSCs derived from the bone marrow. MPCs harvested from traumatized muscle tissue may be considered for applications in tissue engineering and regenerative medicine following orthopaedic trauma requiring circumferential debridement.

Parameters contributing to efficient ion generation in aerosol MALDI mass spectrometry

The Bioaerosol Mass Spectrometry (BAMS) system was developed for the real-time detection and identification of biological aerosols using laser desorption ionization. Greater differentiation of particle types is desired; consequently MALDI techniques are being investigated. The small sample size ( approximately 1 microm3), lack of substrate, and ability to simultaneously monitor both positive and negative ions provide a unique opportunity to gain new insight into the MALDI process. Several parameters known to influence MALDI molecular ion yield and formation are investigated here in the single particle phase. A comparative study of five matrices (2,6-dihydroxyacetophenone, 2,5-dihydroxybenzoic acid, alpha-cyano-4-hydroxycinnamic acid, ferulic acid, and sinapinic acid) with a single analyte (angiotensin I) is presented and reveals effects of matrix selection, matrix-to-analyte molar ratio, and aerosol particle diameter. The strongest analyte ion signal is found at a matrix-to-analyte molar ratio of 100:1. At this ratio, the matrices yielding the least and greatest analyte molecular ion formation are ferulic acid and alpha-cyano-4-hydroxycinnamic acid, respectively. Additionally, a significant positive correlation is found between aerodynamic particle diameter and analyte molecular ion yield for all matrices. SEM imaging of select aerosol particle types reveals interesting surface morphology and structure.

Photodissociation dynamics of CBr4 at 267 nm by means of ion velocity imaging

The photodissociation dynamics of CBr4 at 267 nm has been studied using time of flight (TOF) mass spectrometry and ion velocity imaging techniques. The photochemical products are detected with resonance enhanced multiphoton ionization (REMPI) as well as single-photon vacuum ultraviolet ionization at 118 nm. REMPI at 266.65 and 266.71 nm was used to detect the ground Br(2P32) and spin-orbit excited Br(2P12) atoms, respectively. The translational energy and angular distributions are consistent with direct dissociation from an excited triplet state and indirect dissociation from high vibrational levels on the singlet ground state surface. Br2+ ions are also observed in the TOF spectra with a focused 267 nm laser. The counter fragment, CBr2+, is observed when this photolysis laser is unfocused, and photons at 118 nm are used to ionize the radical products. The translational energy distributions of the CBr2+ and Br2+ products can be momentum matched, which indicates that molecular Br2 elimination is one of the primary dissociation channels.

Single-photon spectroscopy of singlet sulfur atoms and the autoionization lifetime measurements of the superexcited singlet states

Single-photon excitation spectra from the lowest singlet (1)D(2) level of sulfur atoms were recorded with a tunable vacuum ultraviolet (VUV) radiation source generated by frequency tripling in noble gases. The photolysis of CS(2) at 193 nm was used to produce the singlet S((1)D(2)) sulfur atoms that were then excited to neutral superexcited states with the tunable VUV radiation. These superexcited states undergo autoionization into the first ionization continuum state of S(+)((4)S(3/2) (o))+e(-), which is not directly accessible from the S((1)D(2)) state via an allowed transition. The excitation spectra were recorded by monitoring the S(+) signal in a velocity imaging apparatus while scanning the VUV excitation wavelength. Three new lines were observed in the spectra which have not been previously reported. The full widths at half maximum (FWHM) of each of the observed transitions were determined by fitting the profiles of each absorption resonances with the Fano formula. Autoionization lifetimes tau of these singlet superexcited states were obtained from FWHM using the Uncertainty Principle. Abnormal autoionization lifetimes were found for the 3s(2)3p(3)((2)D(o))nd((1)D(2)) and the 3s(2)3p(3)((2)D(o))ns((1)D(2)) Rydberg series, in which tau(5d) and tau(7s) are shorter than tau(4d) and tau(6s), respectively. This is contrary to the well-known scaling law of tau(n*) proportional, variantn(*3), which should be followed within a series unless there exist perturbations from other series or new channels open up to which some members of the series can decay. Possible perturbations from the nearby triplet series are suspected for causing the broadening of the 5d and 7s levels.

Photodissociation of CCH: Classical trajectory calculations involving seven electronic states

The photodissociation dynamics of ethynyl radical, C(2)H, involving seven electronic states is studied by classical trajectory calculations. Initial values of the trajectories are selected based on relative absorption intensities calculated by Mebel et al. The energies and the derivatives are interpolated by three-dimensional cubic spline interpolator using an extended data pool. Mean square errors and standard deviations in interpolation of energies for 450 data points are found to be in the range 3.1 x 10(-6)-1.4 x 10(-5) and 1.7 x 10(-3)-3.8 x 10(-3) hartrees, respectively. The photofragments of C(2) and H are produced mainly in the X (1)Sigma(g) (+), a (3)Pi(u), b (3)Sigma(g) (-), c (3)Sigma(u) (+), A (1)Pi(u), B (1)Delta(g) electronic states of C(2) as product. The avoided crossings do not appear to be in the main dissociation pathways. The internal distributions are in good accord with the experimental results where comparison is possible, suggesting that the fragmentation mechanism of C(2)H(2) into C(2) and H is a two step process involving C(2)H radical as an intermediate with a life time long enough to allow complete collection of the phase space in the experiments.

Photodissociation studies of CBr4+ and CBr3+ at 267 nm using ion velocity imaging

Time-of-flight (TOF) mass spectroscopy and ion velocity imaging were employed to study the formation and photodissociation of CBr(4) (+) and CBr(3) (+) ions that were observed in the TOF spectrum when a CBr(4) beam was irradiated with 118 nm and 355 nm lasers. Energy dependence measurements show that both CBr(4) (+) and CBr(3) (+) ions depend on the fourth power of the 355 nm laser energy, which indicates that direct ionization and dissociative ionization of CBr(4) have low probabilities from the state initially excited at 118 nm. This is likely due to the large geometry change in the CBr(4) (+) ion. Two ionic fragments Br(+) and CBr(2) (+) were observed from the dissociation of CBr(4) (+) and CBr(3) (+) ions when another laser at 267 nm was introduced to the interaction region at a delayed time. The possible dissociation pathways and the angular and translational distributions are discussed in the paper.

Measurement of the autoionization lifetime of the superexcited atomic sulfur S(3s23p3(2Do)4d) state using tunable vacuum ultraviolet (VUV) radiation

A new method is described that combines a tunable coherent vacuum ultraviolet (VUV) radiation source and an ion velocity imaging apparatus to study the autoionization of superexcited sulfur atoms. The photolysis of CS2 at 193 nm is used to produce metastable sulfur atoms in the 1D2 state. The S(1D2) atom is then directly excited to the neutral superexcited state 3s23p3(2Do)4d (1Do2) at 11.317 eV with a tunable VUV photon at ~121.896 nm. This excited state then undergoes autoionization into the first ionization continuum state of S+(4So3/2) + e–, which is not directly accessible from the S(1D2) state through optical transition. By monitoring the S+ signal in the time-of-flight mass spectrometer while scanning the excitation wavelength, the line profile of the 3s23p34d 1Do2 ← 3s23p4 1D2 transition is recorded and found to have a full width at half maximum (FWHM) of 0.9 cm–1. This has been used to determine an autoionization lifetime of the neutral superexcited 3s23p34d 1Do2 state of 5.9 ps. The accurate measurement of the autoionization lifetime provides a benchmark for testing fundamental theoretical models of processes occurring in excited states of atoms. Key words: autoionization, atomic sulfur, vacuum ultraviolet (VUV), full width at half maximum (FWHM).

Reinvestigation of CS2 dissociation at 193 nm by means of product state-selective vacuum ultraviolet laser ionization and velocity imaging

A branching ratio of 1.6 +/- 0.3 for S(3P)/S(1D) is obtained for the dissociation of CS2 with very low fluence 193 nm laser (less than 2 mJ/cm2), in which the S(3P) and S(1D) have been state-selectively ionized using VUV lasers at different wavelengths. The anisotropy parameters betamax(3P) = 0.8 and betamax(1D) = 1.9 indicate that these channels are preferentially populated at different geometries and the lifetime is very short.