Pediatric Firearm Trauma on the Rise: A Retrospective Review of Over 1,100 Cases in 12 Years at One Center.

BACKGROUND: Gunshot injuries are the leading cause of death among children in the United States. The goal of this study was to better understand if certain age groups, mechanisms of injury, and type of firearms were associated with the increasing rates of pediatric gun-related trauma. We hypothesized that the extremities were disproportionately targeted when compared with the random likelihood of striking specific body-surface areas. METHODS: This study includes pediatric firearm-related injury (FRI) patients who presented to a single free-standing level 1 pediatric hospital or died at the scene from 2010 to 2021. The hospital data was collected prospectively as part of a level 1 trauma system electronic database. Death data was collected from the local coroner's office. RESULTS: Between 2010 and 2021, 1,126 pediatric FRI occurred in the geographic region studied. Demographic information available for 1,118 patients showed that 897 (80.23%) were male, and that black individuals had a statistically significant increased rate of FRI compared with white or Hispanic individuals. Mean age was 13.69 years. Most injuries were caused by handguns. CONCLUSIONS: This data could help leaders design strategies to combat the violence, such as legislation that limits handgun access to all, especially children, and mandates safe storage of handguns. Gun-lock programs, universal background checks, and firearm-ownership education also might help stem this tide of violence. LEVEL OF EVIDENCE: Level II Prognosis study.

Call to Action: The Rise of Pediatric Gun Violence During the COVID-19 Pandemic.

This study examines and describes circumstances involving non-fatal firearm injuries in a pediatric population from a Level I Pediatric Trauma Center in the southeastern U.S. Researchers analyzed Firearm Injury Questionnaire (FIQ) data collected from 144 children and adolescents, aged 2-17 years, who were treated in the emergency department and/or admitted to the hospital for non-fatal firearm injuries. Descriptive statistics are presented regarding participant demographics and FIQ responses, such as caregiver information, mental health history, adverse childhood experience (ACE) exposure, firearm access, injury intent, relationship to shooter, type of firearm used, and context of injury. Most patients identified as Black (82%) and male (75%), with most injuries categorized as intentional (72%) versus unintentional (24%) assaults. The average ACEs score was .60, with only 37% of patients' reporting any ACE experience; however, nearly half (47%) of patients reported experiencing a traumatic event beyond an identified ACE. Community violence was the most common context that attributed to patients' assaults (56%). As U.S. pediatric gun injury and fatality trends are increasing, this study provides timely data regarding pediatric firearm injuries and exposure to community violence. These findings highlight the need to provide integrated health services to pediatric patients experiencing non-fatal firearm injuries. Researchers discuss public health implications for integrated mental health care services, hospital- and school-based violence intervention programs, policy recommendations, and directions for future research. Supplementary Information: The online version contains supplementary material available at 10.1007/s40653-023-00568-4.

Management of Pediatric Solid Organ Injuries.

Solid organ injury (SOI) is common in children who experience abdominal trauma, and the management of such injuries has evolved significantly over the past several decades. In 2000, the American Pediatric Surgical Association (APSA) published the first societal guidelines for the management of blunt spleen and/or liver injury (BLSI), advocating for optimized resource utilization while maintaining patient safety. Nonoperative management (NOM) has become the mainstay of treatment for SOI, and since the publication of the APSA guidelines, numerous groups have evaluated how invasive procedures, hospitalization, and activity restrictions may be safely minimized in children with SOI. Here, we review the current evidence-based management guidelines in place for the treatment of injuries to the spleen, liver, kidney, and pancreas in children, including initial evaluation, inpatient management, and long-term care, as well as gaps that exist in the current literature that may be targeted for further optimization of protocols for pediatric SOI.

Prevalence and Outcomes of High versus Low Ratio Plasma to Red Blood Cell Resuscitation in a Multi-Institutional Cohort of Severely Injured Children.

BACKGROUND: The benefit of targeting high ratio fresh frozen plasma (FFP):red blood cell (RBC) transfusion in pediatric trauma resuscitation is unclear as existing studies are limited to patients who retrospectively met criteria for massive transfusion. The purpose of this study is to evaluate the use of high ratio FFP:RBC transfusion and the association with outcomes in children presenting in shock. METHODS: A post-hoc analysis of a 24-institution prospective observational study (4/2018-9/2019) of injured children <18 years with elevated age-adjusted shock index was performed. Patients transfused within 24 hours were stratified into cohorts of low (<1:2) or high (>1:2) ratio FFP:RBC. Nonparametric Kruskal-Wallis and chi-square were used to compare characteristics and mortality. Competing risks analysis was used to compare extended (≥75th percentile) ventilator, intensive care, and hospital days while accounting for early deaths. RESULTS: Of 135 children with median (IQR) age 10 (5,14) years and weight 40 (20,64) kg, 85 (63%) received low ratio transfusion and 50 (37%) high ratio despite similar activation of institutional massive transfusion protocols (MTP; low-38%, high-46%, p = .34). Most patients sustained blunt injuries (70%). Median injury severity score was greater in high ratio patients (low-25, high-33, p = .01); however, hospital mortality was similar (low-24%, high-20%, p = .65) as was the risk of extended ventilator, ICU, and hospital days (all p > .05). CONCLUSION: Despite increased injury severity, patients who received a high ratio of FFP:RBC had comparable rates of mortality. These data suggest high ratio FFP:RBC resuscitation is not associated with worst outcomes in children who present in shock. MTP activation was not associated with receipt of high ratio transfusion, suggesting variability in MTP between centers. LEVEL OF EVIDENCE: Prospective cohort study, Level II.

Delphi Process for Validation of Fluid Treatment Algorithm for Critically Ill Pediatric Trauma Patients.

INTRODUCTION: While intravenous fluid therapy is essential to re-establishing volume status in children who have experienced trauma, aggressive resuscitation can lead to various complications. There remains a lack of consensus on whether pediatric trauma patients will benefit from a liberal or restrictive crystalloid resuscitation approach and how to optimally identify and transition between fluid phases. METHODS: A panel was comprised of physicians with expertise in pediatric trauma, critical care, and emergency medicine. A three-round Delphi process was conducted via an online survey, with each round being followed by a live video conference. Experts agreed or disagreed with each aspect of the proposed fluid management algorithm on a five-level Likert scale. The group opinion level defined an algorithm parameter's acceptance or rejection with greater than 75% agreement resulting in acceptance and greater than 50% disagreement resulting in rejection. The remaining were discussed and re-presented in the next round. RESULTS: Fourteen experts from five Level 1 pediatric trauma centers representing three subspecialties were included. Responses were received from 13/14 participants (93%). In round 1, 64% of the parameters were accepted, while the remaining 36% were discussed and re-presented. In round 2, 90% of the parameters were accepted. Following round 3, there was 100% acceptance by all the experts on the revised and final version of the algorithm. CONCLUSIONS: We present a validated algorithm for intavenous fluid management in pediatric trauma patients that focuses on the de-escalation of fluids. Focusing on this time point of fluid therapy will help minimize iatrogenic complications of crystalloid fluids within this patient population.

Pediatric Surgery Firearm Injury Collaborative Symposium.

Injury from a firearm is now the leading cause of death of children and youth under age 19 in the United States (U.S.) [1] and the incidence of these deaths continues to increase each year [2]. For every death from firearm violence, there are several young people who have been injured by a bullet but not killed. As pediatric surgeons, we are on the front lines of treating these young patients. We have the unforgettable memories of delivering the horrible news to parents in "quiet rooms." [3]. As these injuries fall within our scope of practice, it is incumbent on us as professionals to work to prevent these injuries, apply best practices and work for the best pathways to recovery for our patients who do survive. There is a diverse community of pediatric surgeons tackling this public health problem in a variety of ways [4]. In a pre-meeting symposium at the APSA 2023 Annual meeting, we brought together a community of pediatric surgeons working on this critical area. The following summarizes the presentations of the symposium, with topics including Risk Factors, Injury Prevention, Treatment, Public Initiatives, and National Collaborative Efforts. TYPE OF STUDY: Review Article, Proceedings of a Symposium. LEVEL OF EVIDENCE: 1 through 4 all presented.

Utility of continuous pulse CO-oximetry for hemoglobin monitoring in pediatric patients with solid organ injuries at level 1 trauma centers: A pilot study.

INTRODUCTION: Hemorrhage is a major cause of preventable death in injured children. Monitoring after admission often requires multiple blood draws, which have been shown to be stressful in pediatric patients. The Rainbow-7 device is a continuous pulse CO-oximeter that measures multiple wavelengths of light, permitting continuous estimation of the total hemoglobin (Hb) level. The purpose of this study was to evaluate the utility of the noninvasive Hb measurement for monitoring pediatric trauma patients admitted with solid organ injury. METHODS: This is a prospective, dual-center, observational trial for patients younger than age 18 years admitted to a Level I pediatric trauma center. Following admission, blood was routinely measured as per current solid organ injury protocols. Noninvasive Hb monitoring was initiated after admission. Time-synced data for Hb levels were compared with that taken using blood draws. Data were evaluated using bivariate correlation, linear regression, and Bland-Altman analysis. RESULTS: Over a 1-year period, 39 patients were enrolled. The mean ± SD age was 11 ± 3.8 years. Forty-six percent (n = 18) of patients were male. The mean ± SD Injury Severity Score was 19 ± 13. The average change in Hb levels between laboratory measurements was -0.34 ± 0.95 g/dL, and the average change in noninvasive Hb was -0.12 ± 1.0 g/dL per measurement. Noninvasive Hb values were significantly correlated with laboratory measurements ( p < 0.001). Trends in laboratory Hb measurements were highly correlated with changes in noninvasive levels ( p < 0.001). Bland-Altman analysis demonstrated similar deviation from the mean throughout the range of Hb values, but the differences between measurements were increased by anemia, African American race, and elevated shock index, pediatric age-adjusted score and Injury Severity Score. CONCLUSION: Noninvasive Hb values demonstrated correlation with measured Hb concentration as isolated measurements and trends, although results were affected by skin pigmentation, shock, and injury severity. Given the rapid availability of results and the lack of requirement of venipuncture, noninvasive Hb monitoring may be a valuable adjunct for pediatric solid organ injury protocols. Further study is required to determine its role in management. LEVEL OF EVIDENCE: Dianostic Test or Criteria; Level III.

Updated APSA Guidelines for the Management of Blunt Liver and Spleen Injuries.

BACKGROUND: Non-operative management of blunt liver and spleen injuries was championed initially in children with the first management guideline published in 2000 by the American Pediatric Surgical Association (APSA). Multiple articles have expanded on the original guidelines and additional therapy has been investigated to improve care for these patients. Based on a literature review and current consensus, the management guidelines for the treatment of blunt liver and spleen injuries are presented. METHODS: A recent literature review by the APSA Outcomes committee [2] was utilized as the basis for the guideline recommendations. A task force was assembled from the APSA Committee on Trauma to review the original guidelines, the literature reported by the Outcomes Committee and then to develop an easy to implement guideline. RESULTS: The updated guidelines for the management of blunt liver and spleen injuries are divided into 4 sections: Admission, Procedures, Set Free and Aftercare. Admission to the intensive care unit is based on abnormal vital signs after resuscitation with stable patients admitted to the ward with minimal restrictions. Procedure recommendations include transfusions for low hemoglobin (<7 mg/dL) or signs of ongoing bleeding. Angioembolization and operative exploration is limited to those patients with clinical signs of continued bleeding after resuscitation. Discharge is based on clinical condition and not grade of injury. Activity restrictions remain the same while follow-up imaging is only indicated for symptomatic patients. CONCLUSION: The updated APSA guidelines for the management of blunt liver and spleen injuries present an easy-to-follow management strategy for children. LEVEL OF EVIDENCE: Level 5.

Crystalloid volume is associated with short-term morbidity in children with severe traumatic brain injury: An Eastern Association for the Surgery of Trauma multicenter trial post hoc analysis.

OBJECTIVE: This study examined differences in clinical and resuscitation characteristics between injured children with and without severe traumatic brain injury (sTBI) and aimed to identify resuscitation characteristics associated with improved outcomes following sTBI. METHODS: This is a post hoc analysis of a prospective observational study of injured children younger than 18 years (2018-2019) transported from the scene, with elevated shock index pediatric-adjusted on arrival and head Abbreviated Injury Scale score of ≥3. Timing and volume of resuscitation products were assessed using χ 2t test, Fisher's exact t test, Kruskal-Wallis, and multivariable logistic regression analyses. RESULTS: There were 142 patients with sTBI and 547 with non-sTBI injuries. Severe traumatic brain injury patients had lower initial hemoglobin (11.3 vs. 12.4, p < 0.001), greater initial international normalized ratio (1.4 vs. 1.1, p < 0.001), greater Injury Severity Score (25 vs. 5, p < 0.001), greater rates of ventilator (59% vs. 11%, p < 0.001) and intensive care unit (ICU) requirement (79% vs. 27%, p < 0.001), and more inpatient complications (18% vs. 3.3%, p < 0.001). Severe traumatic brain injury patients received more prehospital crystalloid (25% vs. 15%, p = 0.008), ≥1 crystalloid boluses (52% vs. 24%, p < 0.001), and blood transfusion (44% vs. 12%, p < 0.001) than non-sTBI patients. Among sTBI patients, receipt of ≥1 crystalloid bolus (n = 75) was associated with greater ICU need (92% vs. 64%, p < 0.001), longer median ICU (6 vs. 4 days, p = 0.027) and hospital stay (9 vs. 4 days, p < 0.001), and more in-hospital complications (31% vs. 7.5%, p = 0.003) than those who received <1 bolus (n = 67). These findings persisted after adjustment for Injury Severity Score (odds ratio, 3.4-4.4; all p < 0.010). CONCLUSION: Pediatric trauma patients with sTBI received more crystalloid than those without sTBI despite having a greater international normalized ratio at presentation and more frequently requiring blood products. Excessive crystalloid may be associated with worsened outcomes, including in-hospital mortality, seen among pediatric sTBI patients who received ≥1 crystalloid bolus. Further attention to a crystalloid sparing, early transfusion approach to resuscitation of children with sTBI is needed. LEVEL OF EVIDENCE: Therapeutic/Care Management; Level IV.

Centers of Excellence: If We Build It, Will They Come?

Pediatric surgeons have been pursuing high quality, affordable care or value-based care for over 50 years. One approach to streamlining the clinical care for a complex problem was the development of a center of excellence (COE). The concept of COE focuses on a shared vision of providing high quality care through a multidisciplinary approach. The goal is to improve diagnostic accuracy as well as therapeutic outcomes using focused expertise within a group. COEs are often resource intensive before becoming fiscally viable and therefore require initial support from hospital leadership. This review discusses the key steps to consider before building a COE, strategies to help build one, and how to keep one successful as defined by quality, accessibility, equity, training, and maintaining teams within the group.

TQIP mortality reporting system case reports: Unanticipated mortality due to communication and handoff failures.

ABSTRACT: The TQIP Mortality Reporting System is an online anonymous case reporting system designed to share experiences from rare events that may have contributed to unanticipated mortality at contributing trauma centers. The TQIP Mortality Reporting System Working group monitors submitted cases and organizes them into emblematic themes. This report summarizes unanticipated mortality from two cases of failure of communication and handoff, and presents strategies to mitigate these events locally with the hope of decreasing unanticipated mortality nationwide.

TQIP mortality reporting system case reports: Unanticipated mortality due to failures in clinical performance.

ABSTRACT: The Trauma Quality Improvement Program Mortality Reporting System is an online anonymous case reporting system designed to share experiences from rare events that may have contributed to unanticipated mortality at contributing trauma centers. The Trauma Quality Improvement Program Mortality Reporting System Working group monitors submitted cases and organizes them into emblematic themes. This report summarizes unanticipated mortality from two cases of failure of clinical performance and presents strategies to mitigate these events locally with the hope of decreasing unanticipated mortality nationwide.

Impact of insertion site on complications in central venous access devices.

PURPOSE: There is still debate over the safest route for the placement of long-term central venous access devices. The aim of this study was to review a large, single-institution experience to determine the impact of access location on peri-operative complications. METHODS: The records of patients undergoing subcutaneous port (SQP) and tunneled catheter insertion over a seven-year period were reviewed. Vein cannulated (subclavian (SCV) versus internal jugular (IJ) vein), and 30-day complications were assessed. Surgical complications included pneumothorax, hemothorax, infections, arrhythmia or malpositioning requiring intervention. RESULTS: A total of 1,309 patients were included (618 SQP, 691 tunneled catheters). The location for insertion was SCV (909, 69.4%) and IJ (400, 30.6%). There were 69 complications (5.2%) (41, 4.5% SCV, 28, 7.0% IJV) including: malpositioning/malfunctioning (SCV 13, 1.4% and IJV 14, 3.0%), pneumothorax (SCV 4, 0.4% and IJV 1, 0.3%), hemothorax (SCV 0 and IJV 1, 0.3%), arrhythmia (SCV 1, 0.1%, and IJV 0), and infection within 30 days of placement (SCV 20, 2.2% and IJ 11, 2.8%). The complication rates were not significantly different based on site (p = 0.080). CONCLUSION: There was no significant difference in complication rates when using the subclavian versus the internal jugular vein as the site for long-term central venous access. LEVEL OF EVIDENCE: III, retrospective comparative study.

Indocyanine green near infrared-guided surgery in children, adolescents, and young adults with otolaryngologic malignancies.

OBJECTIVE: Head and neck cancers represent critical challenges due to the restricted anatomical space in children and the proximity of critical neurovascular structures which can compromise complete tumor resection. Applications of Indocyanine green (ICG) near infrared (NIR) fluorescent image-guided surgery (FGS) have recently expanded into the pediatric population, emphasizing its relevance for tumor delineation and evaluation of tissue perfusion. The objectives of the present study are twofold. First, we aim to assess the role of ICG NIR imagery in identifying neoplastic disease and second, to evaluate its role as an adjunct to identify metastatic deposits in cervical lymph node in children, adolescents, and young adults with head and neck cancers. METHODS: Eight patients with head and neck malignancies underwent ICG NIR FGS, between January 2019 and November 2021. ICG NIR findings were compared with preoperative cross-sectional imaging and results of operative tissue pathology analyses. RESULTS: All primary tumors were identified on preoperative imaging and intraoperatively with ICG NIR; however, for one case, extension of tumor was revealed with ICG NIR and confirmed by histopathological examination but was not otherwise visible on preoperative imaging or with naked eye visual and tactile assessment. ICG NIR assisted the decision process in a difficult case for which curative resection, without significant functional morbidity and potential mortality, was unrealistic. Although ICG NIR evaluation of the surgical bed did not display residual tumor, margins were found positive in two cases. ICG NIR evaluation for local metastases changed the surgical strategy in one patient by prompting conversion to bilateral neck dissections. The sensitivity of preoperative multimodality imaging to identify cervical levels of invasion was 75% with a specificity of 70%, a PPV of 33%, a NPV of 78% and an accuracy of 72%. The ICG NIR sensitivity was 83%, its specificity was 88% with a PPV of 91%, a NPV of 80% and an accuracy of 86%. The combination of preoperative multimodality imaging with ICG NIR findings led to a sensitivity of 83%, specificity of 88% and accuracy of 86%. CONCLUSION: This case series provides a proof of concept of the feasibility of ICG NIR, as an adjunct in tumor and local metastases identification in young patients with head and neck tumors. It revealed to be feasible and safe for intra-operative tumor identification, thus guiding and facilitating resection. However, it showed some limitations in precise tumor margin assessment. The combination of preoperative multimodality imaging with ICG NIR findings improved local metastases localization.

Examining the incidence of acute stress in pediatric trauma patients.

Objective: Pediatric patients can be significantly impacted emotionally by exposure to acute trauma which may negatively impact long-term functioning and lead to an increase in overall distress. This study reports on the incidence of acute stress disorder among pediatric trauma patients in a hospital setting in the southeastern region of the USA. Methods: Pediatric patient mental health assessments were conducted using the Childhood Stress Disorders Checklist- Short Form (CSDC-SF) as part of a new integrated behavioral health standard of care within the Trauma Services Division of a level 1 pediatric hospital. Mental health consultations occurred at bedside on inpatient hospital admission into trauma services, or at the outpatient hospital clinic after discharge for injuries treated in the emergency department. Results: Associations among type of trauma, child age, and sex were explored in a sample of 617 children (58.9% male) aged 2-18 years (M age=10.27). The sample was primarily ethnic minorities (56.1% black/African-American, 5% Hispanic/Latinx). Fifteen per cent or more of trauma reports were for burns (26%), motor vehicle accident (22.7%), and recreational sports or leisure activity-related injury (17.5%). Sixty-four per cent of children scored ≥1 on the CSDC-SF, indicating symptoms consistent with acute stress disorder. Higher scores were associated with female sex, age, and injury type. Level of evidence: Level IV study provides evidence of the link between traumatic injury and mental health symptoms in a pediatric population. Findings highlight the critical need for mental health screening and provision of integrated mental health counseling services at time of acute pediatric trauma.

Guidance for Structuring a Pediatric Intermediate Care Unit.

The purpose of this policy statement is to update the 2004 American Academy of Pediatrics clinical report and provide enhanced guidance for institutions, administrators, and providers in the development and operation of a pediatric intermediate care unit (IMCU). Since 2004, there have been significant advances in pediatric medical, surgical, and critical care that have resulted in an evolution in the acuity and complexity of children potentially requiring IMCU admission. A group of 9 clinical experts in pediatric critical care, hospital medicine, intermediate care, and surgery developed a consensus on priority topics requiring updates, reviewed the relevant evidence, and, through a series of virtual meetings, developed the document. The intended audience of this policy statement is broad and includes pediatric critical care professionals, pediatric hospitalists, pediatric surgeons, other pediatric medical and surgical subspecialists, general pediatricians, nurses, social workers, care coordinators, hospital administrators, health care funders, and policymakers, primarily in resource-rich settings. Key priority topics were delineation of core principles for an IMCU, clarification of target populations, staffing recommendations, and payment.

Ultrasound is safe and highly specific for confirmation of proper gastrostomy tube replacement in pediatric patients.

BACKGROUND: Gastrostomy tube (GT) dislodgement is a common cause of Pediatric Emergency Department (PED) visits. Postoperative patients and those who require stoma dilation are more likely to have complications during emergent replacement. Although incorrect replacement can cause significant morbidity overall, the occurrence is infrequent. Contrast injection of the GT is considered the standard for confirming proper placement. Case reports in both pediatric and adult patients suggest that ultrasound can be used to confirm proper replacement. The objective of the present study was to assess the utility of ultrasound to confirm GT placement in pediatric patients most at risk for complications from incorrect replacement. METHODS: This is a non-randomized cohort pilot trial to determine the sensitivity and specificity of ultrasound to confirm proper replacement of a GT in a Pediatric Emergency Department. RESULTS: We enrolled 55 pediatric subjects, of which 50 had ultrasound imaging after GT replacement in the PED prior to contrast injection. Ultrasound was found to have 96% sensitivity and 100% specificity for confirming GT placement. CONCLUSIONS: Ultrasound is a safe and reliable confirmatory study to confirm GT placement in pediatric patients, especially those at highest risk of complications from incorrect placement. LEVEL OF EVIDENCE: II.

Hospital-based intervention is rarely needed for children with low-grade blunt abdominal solid organ injury: An analysis of the Trauma Quality Improvement Program registry.

BACKGROUND: Children with low-grade blunt solid organ injury (SOI) have historically been admitted to an inpatient setting for monitoring, but the evidence supporting the necessity of this practice is lacking. The purpose of this study was to quantify the frequency and timing of intervention for hemorrhage and to describe hospital-based resource utilization for low-grade SOI in the absence of other major injuries (OMIs). METHODS: A cohort of children (aged <16 years) with blunt American Association for the Surgery of Trauma grade 1 or 2 SOI from the American College of Surgeons Trauma Quality Improvement Program registry (2007-2017) was analyzed. Children were excluded if they had confounding factors associated with intervention for hemorrhage (comorbidities, OMIs, or extra-abdominal surgical procedures). Outcomes included frequency and timing of intervention (laparotomy, angiography, or transfusion) for hemorrhage, as well as hospital-based resource utilization. RESULTS: A total of 1,019 children were identified with low-grade blunt SOI and no OMIs. Nine hundred eighty-six (96.8%) of these children were admitted to an inpatient unit. Admitted children with low-grade SOI had a median length-of-stay of 2 days and a 23.9% intensive care unit admission rate. Only 1.7% (n = 17) of patients with low-grade SOI underwent an intervention, with the median time to intervention being the first hospital day. No child who underwent angiography was transfused or had an abnormal initial ED shock index. CONCLUSION: Children with low-grade SOI are routinely admitted to the hospital and often to the intensive care unit but rarely undergo hospital-based intervention. The most common intervention was angiography, with questionable indications in this cohort. These data question the need for inpatient admission for low-grade SOI and suggest that discharge from the emergency room may be safe. Prospective investigation into granular risk factors to identify the rare patient needing hospital-based intervention is needed, as is validation of the safety of ambulatory management. LEVEL OF EVIDENCE: Prognostic and epidemiological, level III.

Mandibular muscle troponin of the Florida carpenter ant Camponotus floridanus: extending our insights into invertebrate Ca2+ regulation.

Ants use their mandibles for a variety of functions and behaviors. We investigated mandibular muscle structure and function from major workers of the Florida carpenter ant Camponotus floridanus: force-pCa relation and velocity of unloaded shortening of single, permeabilized fibres, primary sequences of troponin subunits (TnC, TnI and TnT) from a mandibular muscle cDNA library, and muscle fibre ultrastructure. From the mechanical measurements, we found Ca2+-sensitivity of isometric force was markedly shifted rightward compared with vertebrate striated muscle. From the troponin sequence results, we identified features that could explain the rightward shift of Ca2+-activation: the N-helix of TnC is effectively absent and three of the four EF-hands of TnC (sites I, II and III) do not adhere to canonical sequence rules for divalent cation binding; two alternatively spliced isoforms of TnI were identified with the alternatively spliced exon occurring in the region of the IT-arm α-helical coiled-coil, and the N-terminal extension of TnI may be involved in modulation of regulation, as in mammalian cardiac muscle; and TnT has a Glu-rich C-terminus. In addition, a structural homology model was built of C. floridanus troponin on the thin filament. From analysis of electron micrographs, we found thick filaments are almost as long as the 6.8 µm sarcomeres, have diameter of ~ 16 nm, and typical center-to-center spacing of ~ 46 nm. These results have implications for the mechanisms by which mandibular muscle fibres perform such a variety of functions, and how the structure of the troponin complex aids in these tasks.