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Background: Impact of social distancing on pediatric injuries is unknown., Methods: We retrospectively compared injury visits to a pediatric emergency department by individuals ≤21 years during "Stay at Home" (SHO) period to the same period in 2019 (non-SHO). Demographics, types, and outcomes of injuries were noted., Results: Although, there was a 35.6% reduction in trauma-related emergency department visits during SHO period (1226 vs 1904), the proportion of injury visits increased (15.5% vs 8.1%, P < .001) and mean age was lower (5.8 yrs ±4.5 vs 8.4 yrs ± 5.2, P < .001). There were significant increases in visits related to child physical abuse (CPA), firearms, and dog bites. Further, significant increases in trauma alerts ( P < .01), injury severity ( P < .01), critical care admissions ( P < .001), and deaths ( P < .01) occurred during the SHO period., Conclusions: Although overall trauma-related visits decreased during SHO, the proportion of these visits and their severity increased. Trauma visits related to child physical abuse, dog bites, and firearms increased. Further studies are required to assess the long-term impact of pandemic on pediatric trauma epidemiology., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: Pediatric trauma epidemiology altered during early COVID-19 pandemic period but the impact of the ongoing pandemic is unknown., Objectives: To compare pediatric trauma epidemiology between the pre, early and late pandemic periods and to evaluate the association of race and ethnicity on injury severity during the pandemic., Methods: We performed a retrospective study of trauma consults for an injury/burn in children ≤16 years between January 1, 2019 and December 31, 2021. Study period was categorized into pre (January 1, 2019-February 28, 2020), early (March 1, 2020-December 31, 2020), and late (January 1, 2021-December 31, 2021) pandemic. Demographics, etiology, injury/burn severity, interventions and outcomes were noted., Results: A total of 4940 patients underwent trauma evaluation. Compared to pre-pandemic, trauma evaluations for injuries and burns increased during both the early (RR: 2.13, 95% CI: 1.6-2.82 and RR: 2.24, 95% CI: 1.39-3.63, respectively) and late pandemic periods (RR: 1.42, 95% CI: 1.09-1.86 and RR: 2.44, 95% CI: 1.55-3.83, respectively). Severe injuries, hospital admissions, operations and death were higher in the early pandemic but reverted to pre-pandemic levels during late pandemic. Non-Hispanic Blacks had an approximately 40% increase in mean ISS during both pandemic periods though they had lower odds of severe injury during both pandemic periods., Conclusions: Trauma evaluations for injuries and burns increased during the pandemic periods. There was a significant association of race and ethnicity with injury severity which varied with pandemic periods., Level of Evidence: Retrospective comparative study, Level III., Competing Interests: Conflicts of interest The authors have no conflicts of interest to disclose., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Background: Dog bite injuries are a source of significant morbidity and expense in the USA, and rates of hospitalization have been rising. Children are at increased risk of dog bites compared with adults, yet there is a lack of published material on factors affecting hospital course. The objective of this study is to explore factors associated with increased length of stay (LOS), more complex course of care and post-discharge return rates in this population., Methods: A retrospective review was conducted of all patients presenting to our urban, academic children's hospital for dog bite injuries between January 2016 and May 2021. Only those patients admitted for inpatient care were included, as identified through our institution's trauma registry, and variables were examined prior to, during, and after hospital stay., Results: 739 pediatric patients in total were treated for dog bites during the study period, of which 349 were admitted. Analysis revealed two pre-admission predictors of increased LOS: bone fracture (mean LOS=5.3 days vs. 2.5 days, p=0.013) and prior medical comorbidity (4.3 days vs. 2.8 days, p=0.042). After admission, fractures were associated with a higher rate of postoperative complications (16% vs. 5.6%, p=0.014) and return (13% vs. 2.0%, p<0.001), primarily due to wound infection. Although the facial region represented the largest proportion of fractures, long bone fractures of the arm and leg were noted to have comparatively higher LOS and complication rates. Postoperative complications were not associated with any documented infection at admission., Conclusions: Our findings suggest that long bone fractures in pediatric dog bites can be an underappreciated source of latent wound infection associated with late-presenting negative outcomes. Increased awareness of these relationships could lead to earlier detection of infection in this vulnerable population., Level of Evidence: Level III, Prognostic / Epidemiological., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Nonsurgical bleeding occurs in a significant proportion of patients implanted with continuous-flow ventricular assist devices (CF-VADs) and is associated with nonphysiologic flow with diminished pulsatility. An in vitro vascular pulse perfusion model seeded with adult human aortic endothelial cells (HAECs) was used to identify biomarkers sensitive to changes in pulsatility. Diminished pulsatility resulted in an ~45% decrease in von Willebrand factor (vWF) levels from 9.80 to 5.32 ng/ml (n = 5, p < 0.05) and a threefold increase in angiopoietin-2 (ANGPT-2) levels from 775.29 to 2471.93 pg/ml (n = 5, p < 0.05) in cultured HAECs. These changes are in agreement with evaluation of patient blood samples obtained pre-CF-VAD implant and 30-day postimplant: a decrease in plasma vWF level by 50% from ~45.59 to ~22.49 μg/ml (n = 15, p < 0.01) and a 64% increase in plasma ANGPT-2 level from 7,073 to 11,615 pg/ml (n = 8, p < 0.05). This study identified vWF and ANGPT-2 as highly sensitive to changes in pulsatility, in addition to interleukin-6 (IL-6), IL-8, and tumor necrosis-α (TNF-α). These biomarkers may help determine the optimal level of pulsatility and help identify patients at high risk of nonsurgical bleeding., Competing Interests: Disclosure: G.A.G. has served as a consultant for NuPulseCV, but this manuscript does not directly pertain to the device of NuPulseCV. The other authors have no conflicts of interest to report., (Copyright © ASAIO 2023.)

The heart is a dynamic organ, and the cardiac tissue experiences changes in pressure and stretch during the cardiac cycle. Existing cell culture and animal models are limited in their capacity to decouple and tune specific hemodynamic stresses implicated in the development of physiological and pathophysiological cardiac tissue remodeling. This study focused on creating a system to subject engineered cardiac tissue to either pressure or stretch stimuli in isolation and the subsequent evaluation of acute tissue remodeling. We developed a cardiac tissue chip containing three-dimensional (3-D) cell-laden hydrogel constructs and cultured them within systems where we could expose them to either pressure changes or volume changes as seen in the left ventricle. Acute cellular remodeling with each condition was qualitatively and quantitatively assessed using histology, immunohistochemistry, gene expression studies, and soluble factor analysis. Using our unique model system, we isolated the effects of pressure and stretch on engineered cardiac tissue. Our results confirm that both pressure and stretch mediate acute stress responses in the engineered cardiac tissue. However, both experimental conditions elicited a similar acute phase injury response within this timeframe. This study demonstrates our ability to subject engineered cardiac tissue to either pressure or stretch stimuli in isolation, both of which elicited acute tissue remodeling responses., (© 2022 S. Karger AG, Basel.)

Introduction: This study sought to identify social determinants of health (SDH) patterns associated with severe pediatric injuries., Method: We used cross-sectional data from children (≤18 years) admitted to a pediatric trauma center between March and November 2021 (n = 360). We used association rule mining (ARM) to explore SDH patterns associated with severe injury. We then used ARM-identified SDH patterns in multivariable logistic regressions of severe injury, controlling for patient and caregiver demographics. Finally, we compared results to naive hierarchical logistic regressions that considered SDH types as primary exposures rather than SDH patterns., Results: We identified three SDH patterns associated with severe injury: (1) having child care needs in combination with neighborhood violence, (2) caregiver lacking health insurance, and (3) caregiver lacking social support. In the ARM-informed logistic regression models, the presence of a child care need in combination with neighborhood violence was associated with an increased odds of severe injury (aOR, 2.77; 95% CI, 1.01-7.62), as was caregiver lacking health insurance (aOR, 2.29; 95% CI, 1.02-5.16). In the naive hierarchical logistic regressions, no SDH type in isolation was associated with severe injury., Discussion: Our exploratory analyses suggest that considering the co-occurrence of negative SDH that families experience rather than isolated SDH may provide greater insights into prevention strategies for severe pediatric injury., (Copyright © 2022 National Association of Pediatric Nurse Practitioners. Published by Elsevier Inc. All rights reserved.)

Background: Patients with continuous flow ventricular assist devices (CF-VADs) are at high risk for non-surgical bleeding, speculated to associate with the loss of pulsatility following CF-VAD placement. It has been hypothesized that continuous shear stress causes elongation and increased enzymatic degradation of von Willebrand Factor (vWF), a key player in thrombus formation at sites of vascular damage. However, the role of loss of pulsatility on the unravelling behavior of vWF has not been widely explored., Methods: vWF molecules were immobilized on the surface of microfluidic devices and subjected to various pulsatile flow profiles, including continuous flow and pulsatile flow of different magnitudes, dQ/dt (i.e., first derivative of flow rate) of pulsatility and pulse frequencies to mimic in vivo shear flow environments with and without CF-VAD support. VWF elongation was observed using total internal reflection fluorescence (TIRF) microscopy. Besides, the vWF level is measured from the patients' blood sample before and after CF-VAD implantation from a clinical perspective. To our knowledge, this work is the first in providing direct, visual observation of single vWF molecule extension under controlled-pulsatile shear flow., Results: Unravelling of vWF (total sample size n ~ 200 molecules) is significantly reduced under pulsatile flow (p < 0.01) compared to continuous flow. An increase in the magnitude of pulsatility further reduces unravelling lengths, while lower frequency of pulsatility (20 vs. 60 pulses per min) does not have a major effect on the maximum or minimum unravelling lengths. Evaluation of CF-VAD patient blood samples (n = 13) demonstrates that vWF levels decreased by ~40% following CF-VAD placement (p < 0.01), which correlates to single-molecule observations from a clinical point of view., Conclusions: Pulsatile flow reduces unfolding of vWF compared to continuous flow and a lower pulse frequency of 20 pulses/minute yielded comparable vWF unfolding to 60 pulses/minute. These findings could shed light on non-surgical bleeding associated with the loss of pulsatility following CF-VAD placement., (© 2021 International Center for Artificial Organs and Transplantation and Wiley Periodicals LLC.)

Introduction: We hypothesized that imaging is overused in the initial workup of dog bite patients. To reduce radiation exposure, we aim to determine which circumstances surrounding dog bites, patient population, and injury patterns would necessitate imaging studies for management., Methods: A retrospective review was performed on all patients presenting with dog bites to our level I pediatric trauma center between 2013 and 2015. Data collected included: circumstances surrounding the injury, patient demographics, injuries, and imaging studies performed. Our analysis focused on maxillofacial and head CT scans, and plain radiographic studies of the limbs, hands, and feet. Imaging studies were considered positive if there was evidence of bony injury., Results: We identified 615 patients with dog bites, with 114 patients having had at least one imaging study performed (a total of 145 imaging studies to analyze). Only 13 (11%) patients had a positive study. In the CT scan group, 6 (22.2%) of 27 studies were positive. In the plain radiographic group, 7 (5.9%) of 118 studies were positive., Conclusions: Our review indicates that imaging studies are overused in the initial workup of these patients, and the majority of these studies are negative. This study confirms that it is feasible to institute guidelines for ordering imaging studies in dog bite patients. This will ultimately reduce radiation exposure and the cost of care for these injuries., Competing Interests: Disclosure: The authors declare no conflict of interest., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Cardiopulmonary bypass (CPB) results in short-term (3-5 h) exposure to flow with diminished pulsatility often referred to as "continuous flow". It is unclear if short-term exposure to continuous flow influences endothelial function, particularly, changes in levels of pro-inflammatory and pro-angiogenic cytokines. In this study, we used the endothelial cell culture model (ECCM) to evaluate if short-term (≤5 h) reduction in pulsatility alters levels of pro-inflammatory/pro-angiogenic cytokine levels. Human aortic endothelial cells (HAECs) cultured within the ECCM provide a simple model to evaluate endothelial cell function in the absence of confounding factors. HAECs were maintained under normal pulsatile flow for 24 h and then subjected to continuous flow (diminished pulsatile pressure and flow) as observed during CPB for 5 h. The ECCM replicated pulsatility and flow morphologies associated with normal hemodynamic status and CPB as seen with clinically used roller pumps. Levels of angiopoietin-2 (ANG-2), vascular endothelial growth factor-A (VEGF-A), and hepatocyte growth factor were lower in the continuous flow group in comparison to the pulsatile flow group whereas the levels of endothelin-1 (ET-1), granulocyte colony stimulating factor, interleukin-8 (IL-8) and placental growth factor were higher in the continuous flow group in comparison to the pulsatile flow group. Immunolabelling of HAECs subjected to continuous flow showed a decrease in expression of ANG-2 and VEGF-A surface receptors, tyrosine protein kinase-2 and Fms-related receptor tyrosine kinase-1, respectively. Given that the 5 h exposure to continuous flow is insufficient for transcriptional regulation, it is likely that pro-inflammatory/pro-angiogenic signaling observed was due to signaling molecules stored in Weible-Palade bodies (ET-1, IL-8, ANG-2) and via HAEC binding/uptake of soluble factors in media. These results suggest that even short-term exposure to continuous flow can potentially activate pro-inflammatory/pro-angiogenic signaling in cultured HAECs and pulsatile flow may be a successful strategy in reducing the undesirable sequalae following continuous flow CPB., (© 2021 S. Karger AG, Basel.)

Tissue chips (TCs) and microphysiological systems (MPSs) that incorporate human cells are novel platforms to model disease and screen drugs and provide an alternative to traditional animal studies. This review highlights the basic definitions of TCs and MPSs, examines four major organs/tissues, identifies critical parameters for organization and function (tissue organization, blood flow, and physical stresses), reviews current microfluidic approaches to recreate tissues, and discusses current shortcomings and future directions for the development and application of these technologies. The organs emphasized are those involved in the metabolism or excretion of drugs (hepatic and renal systems) and organs sensitive to drug toxicity (cardiovascular system). This article examines the microfluidic/microfabrication approaches for each organ individually and identifies specific examples of TCs. This review will provide an excellent starting point for understanding, designing, and constructing novel TCs for possible integration within MPS.

Background: Our pediatric trauma center has noted an increase in the occurrence of gunshot wounds in children. We aimed to understand the circumstances surrounding these injuries in order to provide targeted injury prevention methodologies., Methods: A retrospective review was performed on patients who presented with a gunshot wound to our Level I Pediatric Trauma Center and two neighboring Adult Trauma Centers between 2013 and 2017., Results: Three hundred twenty-six patients (6 months to 18 years) were treated for gunshot wounds. Patients were African American (86%), Caucasian (9%), and other races (5%). Eight zip-codes were identified as high-risk, accounting for 52% of patients. Most injuries (86%) were from powder firearms. Known circumstances (n = 275) included drive-by shootings (47%), unlocked guns (19%), crime related (13%), altercation between adolescents (7%), cross-fire from adult altercation (6%), home invasion (6%), and suicide attempts (2%). There was a progressive increase of 50% over the last 4 years. The increase in incidence was predominantly from an increase in drive-by shootings; however, the incidence of injuries from unlocked guns has remained relatively constant per year. Mortality was 6%., Conclusion: Identifying high-risk zones for drive-by shootings and other crimes is critical for developing system-focused interventions. Zip-code data stratified by age and circumstances, will allow for targeted community outreach on gun safety education, in an effort to reduce the incidence of injuries from unlocked guns., Level of Evidence: Prognostic and Epidemiologic study, Level III., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: There is little consensus on the management of dog bite victims. Few studies have examined long-term patient outcomes. This study was designed to evaluate two outcomes: infection and unfavorable scar formation., Methods: A retrospective study of dog bite cases from January 2013 to May 2016 was conducted at our level I pediatric trauma center. Forty-five patients were identified who received definitive repair and had long-term follow-up for reasons other than rabies vaccination. Variables recorded were wound characteristics including presence of tissue loss, location in the hospital of the wound repair procedure, personnel performing the repair, postrepair infection, and a binary assessment of unfavorable scar formation., Results: Unfavorable scarring was not significantly related to either repair location or personnel. Rate of infection was not significantly related to repair location. However, infection rate was significantly related to personnel performing the repair (p=0.002), with 8 of 11 (73%) infections after repair by emergency physicians compared with surgeons., Discussion: The presence of infection was significantly related to bedside repair by emergency physicians. The data are suggestive of differences in wound preparation and repair technique between emergency department and surgical personnel. Standardizing technique could reduce infectious complications and long-term morbidity associated with repairing dog bites and other contaminated wounds. A robust and practical classification system for dog bite wounds would be helpful in stratifying these wounds for research comparison and healthcare triage., Level of Evidence: The level of evidence for this retrospective study is level III., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background and Aims: The Months Backwards Test (MBT) is a commonly used bedside test of cognitive function, but there is uncertainty as to optimal testing procedures. We examined performance among hospitalised elderly patients and cognitively intact young persons with verbal and computerised versions of the test., Participants and Methods: Fifty acute elderly medical inpatients and fifty final year medical students completed verbal (MBTv) and computerised (MBTc) versions of the MBT and the Montreal Cognitive Assessment (MoCA). Completion time and errors were compared., Results: Thirty four participants scored <26 on the MoCA indicating significant cognitive impairment. The mean MoCA scores in the elderly medical group (23.6±3.4; range 13-28) were significantly lower than for the medical students (29.2±0.6; range 28-30: p<0.01). For the verbal months backwards test (MBTv), there were significantly more errors and longer completion times in the elderly medical patients (25.1±20.9 vs. 10.5±4.5; p<0.05). Completion times were 2-3 times longer for the MBTc compared to the MBTv (patients: 63.5±43.9 vs. students 20.3±4.4; p<0.05). There was high correlation between the two versions of the MBT (r=0.84) and also between the MBTc and the MoCA (r=0.85). The MBTc had higher correlation with visuospatial function (MBTc r=0.70, MBTv r=0.57). An MBTc cut-off time of 30s for distinguishing performance (pass/fail) had excellent sensitivity (100%) with modest specificity (44%) for cognitive impairment in elderly medical patients., Conclusion: The computerised MBT allows accurate and efficient testing of attention and general cognition in clinical populations., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Aim: To review the use of the Months Backwards Test (MBT) in clinical and research contexts., Methods: We conducted a systematic review of reports relating to the MBT based upon a search of PsychINFO and MEDLINE between January 1980 and December 2014. Only reports that specifically described findings pertaining to the MBT were included. Findings were considered in terms of rating procedures, testing performance, psychometric properties, neuropsychological studies and use in clinical populations., Results: We identified 22 data reports. The MBT is administered and rated in a variety of ways with very little consistency across studies. It has been used to assess various cognitive functions including focused and sustained attention as well as central processing speed. Performance can be assessed in terms of the ability to accurately complete the test without errors ("MB accuracy"), and time taken to complete the test ("MB duration"). Completion time in cognitively intact subjects is usually < 20 s with upper limits of 60-90 s typically applied in studies. The majority of cognitively intact adults can complete the test without error such that any errors of omission are strongly suggestive of cognitive dysfunction. Coverage of clinical populations, including those with significant cognitive difficulties is high with the majority of subjects able to engage with MBT procedures. Performance correlates highly with other cognitive tests, especially of attention, including the digit span backwards, trailmaking test B, serial threes and sevens, tests of simple and complex choice reaction time, delayed story recall and standardized list learning measures. Test-retest and inter-rater reliability are high (both > 0.90). Functional magnetic resonance imaging studies comparing the months forward test and MBT indicate greater involvement of more complex networks (bilateral middle and inferior frontal gyri, the posterior parietal cortex and the left anterior cingulate gyrus) for backwards cognitive processing. The MBT has been usefully applied to the study of a variety of clinical presentations, for both cognitive and functional assessment. In addition to the assessment of major neuropsychiatric conditions such as delirium, dementia and Mild Cognitive Impairment, the MBT has been used in the assessment of concussion, profiling of neurocognitive impairments in organic brain disorders and Parkinson's disease, prediction of delirium risk in surgical patients and medication compliance in diabetes. The reported sensitivity for acute neurocognitive disturbance/delirium in hospitalised patients is estimated at 83%-93%. Repeated testing can be used to identify deteriorating cognitive function over time., Conclusion: The MBT is a simple, versatile tool that is sensitive to significant cognitive impairment. Performance can be assessed according to accuracy and speed of performance. However, greater consistency in administration and rating is needed. We suggest two approaches to assessing performance - a simple (pass/fail) method as well as a ten point scale for rating test performance (467).

Purpose: Firearm injuries are the second most common cause of trauma deaths in American children. We reviewed gunshot wounds treated at an urban children's hospital to determine the most likely time for injuries to occur over 10 years., Methods: A retrospective chart review was completed for patients with a firearm injury from January 2003 to December 2012. Patients were excluded if over 17 years or readmitted. Demographics, injury circumstances, interventions, and outcomes were reviewed for 289 patients. Chi square and ANOVA analyses were completed. Alpha was chosen as p<0.05., Results: Mean age was 12 years, 74% were male and 80% African American. Unintentional injuries occurred in 26% and violence related in 72%. The most common months of injury were August and June, the least common November and October. Unintentional injuries were more likely to occur during the day and violence related injuries were more likely at night (p=0.01). The incidence was lowest 2008-2010 and highest in 2006 and 2011. Mortality was 3.5%., Conclusions: We noted an increasing incidence of pediatric firearm related injuries in the last two years of the study with over half requiring operative intervention. Most injuries were violence related and occurred in a large city during summer months., (Copyright © 2015. Published by Elsevier Inc.)

Background: We hypothesize that nonpowder firearms cause significant injuries in children, often requiring intervention. We have noted a difference in demographics of children presenting with injuries from nonpowder firearms compared with patients injured by powder firearms. We reviewed our institution's experience with patients with nonpowder firearm injuries to evaluate these aspects., Methods: A retrospective chart review was completed for all patients with a firearm injury from 2003 through February 2013 to a pediatric urban Level I trauma center. Patients were excluded if they were 18 years of age or older or readmitted. Demographics, injury circumstances, interventions, and outcomes were reviewed for 303 patients. The χ test and analysis of variance were completed with a statistical significance of p < 0.05., Results: There were 57 nonpowder firearm injuries and 246 injuries from other firearms. Injuries occurred from BB, pellet, and paintball guns. Treatment included computed tomography scan in 39 patients, three bedside procedures, one angiography, and operative intervention in 25 patients. The most common injury locations were the eye (n = 37), head (n = 7), and neck (n = 6). Children injured by nonpowder firearms were less likely to be female (p = 0.04), more likely to be white (p < 0.01), and less likely to be injured in a violence-related event (p < 0.01)., Conclusion: Nonpowder firearms can cause severe pediatric injuries requiring operative intervention and significant radiographic exposure from computed tomography scans. Prevention and education are important in decreasing this risk in the pediatric population and should be targeted to a different population than powder firearm prevention., Level of Evidence: Epidemiologic study, level V.

Some physicians feel gastric injury is not a significant contributing factor to the adverse outcome of trauma patients, but rather a marker of epigastric injury. We hypothesized the addition of a gastric injury to multiple injured trauma patients would increase infection rate. We conducted a retrospective study comparing 450 consecutive patients with full-thickness gastric injury with 983 patients without gastric injury during the same time period. Infection rate in patients with gastric injury was 44 per cent (200 of 455) and significantly higher than 36 per cent (357 of 983) seen without gastric injury (P = 0.006). Logistic regression revealed gastric injury was an independent risk factor for infection controlling for age, Injury Severity Scale, gender, mechanism of injury, shock, and associated injuries (P = 0.047). Requiring a transfusion, Injury Severity Scale, colon injury, age, pancreas injury, and emergency department shock were also independent risk factors for developing an infection. The addition of a gastric injury to a trauma patient appears to increase the risk for infection.

Background: Pericytes are capillary support cells that may play a role in regulating permeability by their contractile responses. Vascular endothelial growth factor (VEGF) may play a role in the increased permeability found in sepsis and other inflammatory conditions. The purpose of this study was to evaluate the role of VEGF in regulating pericyte contraction., Methods: Rat microvascular lung pericytes were isolated according to previously described methods and cultured on collagen gel matrices. Cells were exposed to VEGF (10, 100, and 1000 pg/mL) for varying time periods (0, 10, 30, 60, and 120 minutes). The gels were released and their contractile responses digitally quantified., Results: At all doses, VEGF induced initial pericyte relaxation (contraction 85% to 90% of controls; P < .001). This was followed-up by increased and sustained contraction (107% to 120% of controls; P < .01)., Conclusions: VEGF modifies the contractile response of microvascular lung pericytes. This mechanism may play a role in the increased permeability demonstrated in inflammatory states.