An observational study of gastric contents in pediatric patients with long bone fracture using gastric ultrasound.

BACKGROUND: The retention of gastric contents at surgery presentation is a risk factor for perioperative aspiration. A preoperative fasting (nil per os; NPO) interval is widely used to reduce this risk, but this approach is based on assumptions about the prevalence of typical gastric emptying rates. We assessed NPO guidelines' reliability with ultrasound (US) imaging and suction in pediatric patients presenting for single long-bone fracture repair after appropriate NPO intervals, when nearly all should have had empty stomachs. AIMS AND METHODS: This prospective cross-sectional observational study comprised 200 pediatric surgical patients. As their NPO times varied by food/drink type, we defined "weighted NPO units" as the lowest multiple of elapsed recommended NPO times between consumption and surgery for each type of food or drink. We used US to image the stomach and its contents before anesthesia induction, followed by gastric suction. We evaluated the relationships between weighted NPO units, US gastric contents grade, opioid analgesic dosage and timing, and suctioned volume. RESULTS: Despite meeting typical NPO standards (median 14 h fasting), many patients retained nontrivial quantities of gastric contents at surgery. Weighted NPO units did not exhibit statistically-significant relationships with either suctioned volume or US grade. However, suctioned volume did correspond well to US grade. CONCLUSION: NPO status may be a less reliable predictor of gastric contents at anesthesia induction in this patient population than has been assumed. Bedside US screening appears to provide more useful information for the planning of airway management.

Use of Transparent Film Dressing to Facilitate Mask Ventilation in Bearded Patients.

BACKGROUND: Mask ventilation is a critical airway procedure made more difficult in the bearded patient. OBJECTIVE: We sought to objectively investigate whether application of transparent cling film (TegadermTM; 3M Healthcare, Maplewood, MN) over a beard in the operating room improves the quality of mask ventilation. METHODS: This was a randomized crossover trial of bearded adult patients undergoing surgery. Exclusions included emergency procedures, American Society of Anesthesiologists physical status classification > 3, a documented history of difficult mask ventilation, and body mass index (BMI) > 50. Transparent cling film was applied snuggly over the lower face with a 2- to 3-cm slit cut over the mouth after anesthesia induction. Mask ventilation performed by an anesthesiology resident, anesthesiology assistant, or anesthesiology assistant student and standardized to a thenar-eminence grip without use of airway adjuncts in a sniffing position. Standardized pressure-controlled ventilations were delivered via an anesthesia machine. A calibrated external pneumotachograph was used to measure delivered and returned tidal volumes from which raw and percent air leak were calculated. A clinically significant difference was determined a priori to be 15%, necessitating the enrollment of 25 patients. RESULTS: Of 25 subjects, 96% were men with a mean ± SD BMI of 29.3 ± 6. Seventeen (68%) had a full beard and 8 (32%) had a partial beard. The mean ± SD leakage was 48% ± 26% for transparent cling film vs. 46% ± 20% without its application, which was not significantly different (p = 0.67). CONCLUSIONS: The use of transparent cling film to cover the lower half of the bearded face did not have an impact on the ability or efficacy to perform mask ventilation in the operating room setting. CLINICALTRIALS: gov, Number NCT04274686.

Chargemaster Pricing Variation for Commonly Billed Procedures in Interventional Cardiology.

OBJECTIVES: A chargemaster is a database of all of the billable items offered by a hospital with their base price listings. A 2018 executive order required all American hospitals to publish their chargemasters to increase price transparency and reduce healthcare expenditures. Chargemaster listings, however, demonstrate marked variability and inconsistency and have not been associated with consumer benefit. The objective of this study was to analyze chargemasters for commonly billed interventional cardiology procedures across five diverse states to explore relationships between price listings and hospital characteristics, ownership, location, and hospital quality. METHODS: Chargemasters were downloaded from hospitals in five states selected to represent the nation's healthcare diversity. Price listings for five interventional cardiology procedures (percutaneous coronary angiography, coronary angiography, single-vessel angioplasty, single-vessel stent, and percutaneous coronary intervention of acute myocardial infarction) were extracted. Statistical analyses such as the Kruskal-Wallis test were performed to explore relationships between mean chargemaster price listings for each procedure and hospital characteristics, ownership, location, and quality ratings. RESULTS: The median mean chargemaster price of four of the five interventional cardiology procedures significantly differed across all states. Price listings were significantly higher in urban versus rural areas and in general acute care hospitals and state government-owned facilities. The highest prices were found with the highest hospital quality rating. CONCLUSIONS: Chargemaster price listings for common interventional cardiology procedures varied significantly across these five states. Urban and metropolitan hospital location, hospital type, and hospital ownership could be factors driving increased chargemaster procedure prices. Prices were highest at hospitals with the highest quality rating.

Chlorhexidine gluconate vs povidone-iodine vaginal antisepsis for urogynecologic surgery: a randomized controlled noninferiority trial.

BACKGROUND: Although povidone-iodine (iodine) is the only Food and Drug Administration-approved vaginal antiseptic solution, there is a lack of comparative data evaluating alternatives. Chlorhexidine gluconate is readily accessible, recommended by multiple societies as an alternative for patients with iodine allergy, and preliminary data indicate that it may provide superior antisepsis. OBJECTIVE: This study aimed to compare the effectiveness of chlorhexidine and iodine as presurgical vaginal antiseptic solutions in preventing the most common surgery-associated infection after gynecologic surgery, urinary tract infections. STUDY DESIGN: We conducted a randomized controlled noninferiority trial among women undergoing urogynecologic surgery. The primary outcome measure was symptomatic urinary tract infection within 2 weeks after surgery. The secondary outcomes included culture-proven urinary tract infection at 2 and 6 weeks after surgery, symptomatic urinary tract infections at 6 weeks after surgery, any surgical site infection at 2 weeks after surgery, and patient-reported vaginal irritation after surgery. We required 58 participants per arm to demonstrate noninferiority of chlorhexidine vs iodine (margin of relative risk of <1.5 for the upper limit of 95% confidence interval) between groups for the primary outcome. RESULTS: A total of 119 participants (61 in the chlorhexidine group and 58 in the iodine group) completed the primary outcome and were included in the analyses. There was no difference in the groups' demographic characteristics, medical history, operations performed, or perioperative factors. Chlorhexidine was not inferior to iodine concerning the primary outcome, symptomatic urinary tract infection at 2 weeks after surgery (10% vs 17%; relative risk, 0.6; 95% confidence interval [-∞, 1.3]). Furthermore, chlorhexidine was not inferior to iodine for the secondary urinary tract infection outcomes (culture-proven urinary tract infection at 2 and 6 weeks after surgery and symptomatic urinary tract infection at 6 weeks after surgery). Groups were similar in terms of surgical site infection (overall 3/119 [2.5%]) and presence of any vaginal irritation (4/54 [7.4%], for both groups). CONCLUSION: Chlorhexidine was not inferior to iodine for vaginal antisepsis before urogynecologic surgery concerning urinary tract infection. Given the similar postoperative urinary tract infection rates demonstrated in this study and the lack of difference in vaginal irritation, chlorhexidine seemed to be a safe and reasonable option for vaginal antisepsis before surgical procedures. Additional studies are needed to further examine surgical site infection.

Use of Erector Spinae Fascial Plane Blocks in Enhanced Recovery for Open Abdominal Surgery.

BACKGROUND: Bilateral erector spinae fascial plane blocks (ESPB) offers a novel, alternative method of regional post-operative pain control to thoracic epidural analgesia (TEA). The aim of this study was to compare rates of postoperative hypotension, and other standard enhanced recovery after surgery (ERAS) endpoints, in patients receiving ESPB versus TEA for open hepatopancreaticobiliary (HPB) surgery. MATERIALS AND METHODS: This retrospective analysis compared historical controls of ERAS patients undergoing open HPB surgery with TEA versus ESPB. The incidence of postoperative hypotension and clinical outcomes, including opioid requirements, were compared. RESULTS: Forty patients receiving TEA were compared to 27 ESPB patients. Return of bowel function and length of stay (mean 7.2 versus7.4 days; P = 0.83) were similar. ESPB patients received less intraoperative colloid (142cc versus 340cc; P = 0.01) and had less postoperative hypotension versus TEA (22% versus 55%; P = 0.03). No ESPB patient required patient-controlled analgesia (versus 32.5% TEA; P< 0.001). ESPB MME requirements decreased over time, while TEA MME requirements increased over 72 hours (P = 0.019). CONCLUSIONS: ESPB is a novel method that shows promising outcomes in improving enhanced recovery parameters and minimizing opioid administration in open HPB surgery.

Detection of Ring and Adatom Defects in Activated Disordered Carbon via Fluctuation Nanobeam Electron Diffraction.

How the structure of disordered porous carbons evolves during their activation is particularly poorly understood. This problem endures primarily because of a lack of high-resolution 3D techniques for the characterization of amorphous and highly disordered structure. To address this, the measurement of the 3D pair-angle distribution function using nanodiffraction patterns from high-energy electrons is demonstrated. These rich multiatom correlations are measured for a disordered carbon and they clearly show the structural evolution during activation. They provide previously inaccessible bond-angle information and direct evidence for the presence of ring and adatom defects. An increase in the short-range order and the number of fivefold ring defects with activation are observed, indicating stress relaxation by increasing curvature. These observations support models of disordered porous carbons based on curved graphene networks and explain how large amounts of free volume can be created with surprisingly small changes in the average ratios of tetrahedral to graphitic bonding.

Anesthetic concerns for pediatric patients in the era of COVID-19.

After a novel human coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was reported in China in December 2019, the disease quickly reached pandemic level. On January 30, 2020, the World Health Organization (WHO) declared that the SARS-CoV-2 outbreak constituted a Public Health Emergency of International Concern. The caseload has increased exponentially, with WHO reporting 182 000 global cases by March 17, 2020, and over 2.6 million by 23 April. The clinical situation is complex, with children presenting different clinical features compared to adults. Several articles with recommendations on the anesthetic management of adult patients with COVID-19 have been published, but no specific recommendations for pediatric anesthesiologists have been made yet. This article addresses specific concerns for the anesthetic management of the pediatric population with COVID-19.

Favored local structures in amorphous colloidal packings measured by microbeam X-ray diffraction.

Local structure and symmetry are keys to understanding how a material is formed and the properties it subsequently exhibits. This applies to both crystals and amorphous and glassy materials. In the case of amorphous materials, strong links between processing and history, structure and properties have yet to be made because measuring amorphous structure remains a significant challenge. Here, we demonstrate a method to quantify proportions of the bond-orientational order of nearest neighbor clusters [Steinhardt, et al. (1983) Phys Rev B 28:784-805] in colloidal packings by statistically analyzing the angular correlations in an ensemble of scanning transmission microbeam small-angle X-ray scattering (µSAXS) patterns. We show that local order can be modulated by tuning the potential between monodisperse, spherical colloidal silica particles using salt and surfactant additives and that more pronounced order is obtained by centrifugation than sedimentation. The order in the centrifuged glasses reflects the ground state order in the dispersion at lower packing fractions. This diffraction-based method can be applied to amorphous systems across decades in length scale to connect structure to behavior in disordered systems with a range of particle interactions.

A Genome-Wide Helicobacter pylori Morphology Screen Uncovers a Membrane-Spanning Helical Cell Shape Complex.

Evident in its name, the gastric pathogen Helicobacter pylori has a helical cell morphology which facilitates efficient colonization of the human stomach. An improved light-focusing strategy allowed us to robustly distinguish even subtle perturbations of H. pylori cell morphology by deviations in light-scattering properties measured by flow cytometry. Profiling of an arrayed genome-wide deletion library identified 28 genes that influence different aspects of cell shape, including properties of the helix, cell length or width, cell filament formation, cell shape heterogeneity, and cell branching. Included in this mutant collection were two that failed to form any helical cells, a soluble lytic transglycosylase and a previously uncharacterized putative multipass inner membrane protein HPG27_0728, renamed Csd7. A combination of cell fractionation, mutational, and immunoprecipitation experiments show that Csd7 and Csd2 collaborate to stabilize the Csd1 peptidoglycan (PG) endopeptidase. Thus, both csd2 and csd7 mutants show the same enhancement of PG tetra-pentapeptide cross-linking as csd1 mutants. Csd7 also links Csd1 with the bactofilin CcmA via protein-protein interactions. Although Csd1 is stable in ccmA mutants, these mutants show altered PG tetra-pentapeptide cross-linking, suggesting that Csd7 may directly or indirectly activate as well as stabilize Csd1. These data begin to illuminate a highly orchestrated program to regulate PG modifications that promote helical shape, which includes nine nonessential nonredundant genes required for helical shape and 26 additional genes that further modify H. pylori's cell morphology.IMPORTANCE The stomach ulcer and cancer-causing pathogen Helicobacter pylori has a helical cell shape which facilitates stomach infection. Using light scattering to measure perturbations of cell morphology, we identified 28 genes that influence different aspects of cell shape. A mutant in a previously uncharacterized protein renamed Csd7 failed to form any helical cells. Biochemical analyses showed that Csd7 collaborates with other proteins to stabilize the cell wall-degrading enzyme Csd1. Csd7 also links Csd1 with a putative filament-forming protein via protein-protein interactions. These data suggest that helical cell shape arises from a highly orchestrated program to regulate cell wall modifications. Targeting of this helical cell shape-promoting program could offer new ways to block infectivity of this important human pathogen.

Impact of Isolyte Versus 0.9% Saline on Postoperative Event of Acute Kidney Injury Assayed by Urinary [TIMP-2] × [IGFBP7] in Patients Undergoing Cardiac Surgery.

OBJECTIVE: Administration of excess chloride in 0.9% normal saline (NS) decreases renal perfusion and glomerular filtration rate, thereby increasing the risk for acute kidney injury (AKI). In this study, the effect of NS versus Isolyte use during cardiac surgery on urinary levels of tissue inhibitor of metalloproteinase 2 and insulin-like growth factor-binding protein 7 [TIMP-2] × [IGFBP7] and postoperative risk of AKI were examined. DESIGN: Prospective, randomized, and single-blinded trial. SETTING: Single university medical center. PARTICIPANTS: Thirty patients over 18 years without chronic renal insufficiency or recent AKI undergoing elective cardiac surgery. INTERVENTIONS: Subjects were randomized to receive either NS or Isolyte during the intraoperative period. MEASUREMENTS AND MAIN RESULTS: The primary outcome was the change in urinary levels of [TIMP2] × [IGFBP7] from before surgery to 24 hours postoperatively. Secondary outcomes included serum creatinine pre- and postoperatively at 24 and 48 hours, serum chloride pre- and postoperatively at 24 and 48 hours, need for dialysis prior to discharge, and arterial pH measured 24 hours postoperatively. Sixteen patients received NS and 14 patients received Isolyte. Three patients developed AKI within the first 3 postoperative days, all in the NS group. The authors found increases in [TIMP-2] × [IGFBP7] in both groups. However, the difference in this increase between study arms was not significant (p = 0.92; -0.097 to 0.107). CONCLUSION: The authors observed no change in urinary [TIMP-] × [IGFBP7] levels in patients receiving NS versus Isolyte during cardiac surgery. Future larger studies in patients at higher risk for AKI are recommended to evaluate the impact of high- versus lower-chloride solutions on the risk of postoperative AKI after cardiac surgery.

Apneic nasal oxygenation and safe apnea time during pediatric intubations by learners.

BACKGROUND: Apneic nasal oxygenation (ApOx) prolongs the time to desaturation during intubation of adult patients, but there is limited prospective evidence for apneic oxygenation in pediatric patients. AIMS: We hypothesized that ApOx during operating room intubation of pediatric patients by inexperienced learners would prolong the interval before desaturation. METHODS: This prospective observational study compared intubation data for 196 pediatric surgical patients intubated by learners under baseline practice (no nasal cannula), to 160 patients enrolled after adoption of routine apneic nasal cannula oxygenation at 5 L/min. The primary outcome was elapsed time between anesthetic induction and pulse oximetry (SpO2 ) falling to 95, if ever. RESULTS: Nasal cannula oxygenation during intubation by learners delayed desaturation to SpO2 95 (risk ratio for this event before intubation 0.05, 95% CI 0.03-0.09; P < 0.0001). CONCLUSIONS: Apneic oxygenation via nasal cannula during intubation of pediatric surgical patients prolongs time before desaturation, thus extending the safe interval for airway management by learners.

Nodal-line dynamics via exact polynomial solutions for coherent waves traversing aberrated imaging systems.

We obtain exact polynomial solutions for two-dimensional coherent complex scalar fields propagating through arbitrary aberrated shift-invariant linear imaging systems. These solutions are used to model nodal-line dynamics of coherent fields output by such systems.

Complications in Pediatric Regional Anesthesia: An Analysis of More than 100,000 Blocks from the Pediatric Regional Anesthesia Network.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Complications in pediatric regional anesthesia are rare, so a large sample size is necessary to quantify risk. The Pediatric Regional Anesthesia Network contains data on more than 100,000 blocks administered at more than 20 children's hospitals. This study analyzed the risk of major complications associated with regional anesthesia in children. METHODS: This is a prospective, observational study of routine clinical practice. Data were collected on every regional block placed by an anesthesiologist at participating institutions and were uploaded to a secure database. The data were audited at multiple points for accuracy. RESULTS: There were no permanent neurologic deficits reported (95% CI, 0 to 0.4:10,000). The risk of transient neurologic deficit was 2.4:10,000 (95% CI, 1.6 to 3.6:10,000) and was not different between peripheral and neuraxial blocks. The risk of severe local anesthetic systemic toxicity was 0.76:10,000 (95% CI, 0.3 to 1.6:10,000); the majority of cases occurred in infants. There was one epidural abscess reported (0.76:10,000, 95% CI, 0 to 4.8:10,000). The incidence of cutaneous infections was 0.5% (53:10,000, 95% CI, 43 to 64:10,000). There were no hematomas associated with neuraxial catheters (95% CI, 0 to 3.5:10,000), but one epidural hematoma occurred with a paravertebral catheter. No additional risk was observed with placing blocks under general anesthesia. The most common adverse events were benign catheter-related failures (4%). CONCLUSIONS: The data from this study demonstrate a level of safety in pediatric regional anesthesia that is comparable to adult practice and confirms the safety of placing blocks under general anesthesia in children.

Preliminary Report: Comparing Aspiration Rates between Prehospital Patients Managed with Extraglottic Airway Devices and Endotracheal Intubation.

INTRODUCTION: There has been a shift from endotracheal intubation (ETI) toward extraglottic devices (EGDs) for prehospital airway management. A concern exists that this may lead to more frequent cases of aspiration. METHODS: This was a retrospective study using a prehospital quality assurance database. Patients were assigned to groups based on the method that ultimately managed their airways (EGD or ETI). Cases with documented blood/emesis obscuring the airway were considered inevitable aspiration cases and excluded. Aspiration was defined by the radiology report within 48 hours. RESULTS: A total of 104 EGD and 152 ETI patients were identified. Aspiration data were available for 67 EGD and 94 ETI cases. Of those, 8 EGD and 3 ETI cases had blood/emesis obscuring the airway and were excluded as planned. After exclusions, there were 5 EGD and 11 ETI cases in which aspiration was later diagnosed (EGD aspiration rate = 8%, ETI aspiration rate = 12%; χ2: P = .359; relative risk = .841; 95% confidence interval, .329-2.152). CONCLUSION: In this small quality assurance database, aspiration rates were not significantly different for prehospital patients managed with an EGD versus ETI.

On reverse Monte Carlo constraints and model reproduction.

Reverse Monte Carlo (RMC) simulations were performed to investigate the effectiveness of any combination of five experimentally motivated constraints on the reproduction of a test case, a ternary ab initio model. It was found that low energy structures fitting a variety of constraints commonly used in the RMC methodology could still provide an incorrect description of the chemical structural unit populations in multi-elemental systems. It is shown that the use of an elemental bond type constraint is an effective way to avoid this. © 2017 Wiley Periodicals, Inc.

Axicon Lens for Electrons Using a Magnetic Vortex: The Efficient Generation of a Bessel Beam.

We demonstrate experimentally an efficient electron axicon lens using a magnetic vortex. We show that naturally occurring magnetic vortices with circular magnetic moment distributions in a soft-magnetic thin film create conical phase shifts for fast electrons. Such radially symmetric linear phase ramps are equivalent to ideal light optical axicons. We apply this lens to generate efficient nondiffracting electron Bessel beams, which we observe experimentally in through-focus Lorentz images as well as in propagated off-axis electron holograms. This highlights the potential for using magnetic nanostructures as highly efficient and flexible phase plates for crafting desired electron beam shapes.

Prenatal alcohol exposure potentiates chronic neuropathic pain, spinal glial and immune cell activation and alters sciatic nerve and DRG cytokine levels.

A growing body of evidence indicates that prenatal alcohol exposure (PAE) may predispose individuals to secondary medical disabilities later in life. Animal models of PAE reveal neuroimmune sequelae such as elevated brain astrocyte and microglial activation with corresponding region-specific changes in immune signaling molecules such as cytokines and chemokines. The aim of this study was to evaluate the effects of moderate PAE on the development and maintenance of allodynia induced by chronic constriction injury (CCI) of the sciatic nerve in adult male rat offspring. Because CCI allodynia requires the actions of glial cytokines, we analyzed lumbar spinal cord glial and immune cell surface markers indicative of their activation levels, as well as sciatic nerve and dorsal root ganglia (DRG) cytokines in PAE offspring in adulthood. While PAE did not alter basal sensory thresholds before or after sham manipulations, PAE significantly potentiated adult onset and maintenance of allodynia. Microscopic analysis revealed exaggerated astrocyte and microglial activation, while flow cytometry data demonstrated increased proportions of immune cells with cell surface major histocompatibility complex II (MHCII) and ß-integrin adhesion molecules, which are indicative of PAE-induced immune cell activation. Sciatic nerves from CCI rats revealed that PAE potentiated the proinflammatory cytokines interleukin (IL)-1ß, IL-6 and tumor necrosis factor-alpha (TNFα) protein levels with a simultaneous robust suppression of the anti-inflammatory cytokine, IL-10. A profound reduction in IL-10 expression in the DRG of PAE neuropathic rats was also observed. Taken together, our results provide novel insights into the vulnerability that PAE produces for adult-onset central nervous system (CNS) pathological conditions from peripheral nerve injury.

Perioperative Outcomes and Management in Pediatric Complex Cranial Vault Reconstruction: A Multicenter Study from the Pediatric Craniofacial Collaborative Group.

BACKGROUND: The Pediatric Craniofacial Collaborative Group established the Pediatric Craniofacial Surgery Perioperative Registry to elucidate practices and outcomes in children with craniosynostosis undergoing complex cranial vault reconstruction and inform quality improvement efforts. The aim of this study is to determine perioperative management, outcomes, and complications in children undergoing complex cranial vault reconstruction across North America and to delineate salient features of current practices. METHODS: Thirty-one institutions contributed data from June 2012 to September 2015. Data extracted included demographics, perioperative management, length of stay, laboratory results, and blood management techniques employed. Complications and outlier events were described. Outcomes analyzed included total blood donor exposures, intraoperative and perioperative transfusion volumes, and length of stay outcomes. RESULTS: One thousand two hundred twenty-three cases were analyzed: 935 children aged less than or equal to 24 months and 288 children aged more than 24 months. Ninety-five percent of children aged less than or equal to 24 months and 79% of children aged more than 24 months received at least one transfusion. There were no deaths. Notable complications included cardiac arrest, postoperative seizures, unplanned postoperative mechanical ventilation, large-volume transfusion, and unplanned second surgeries. Utilization of blood conservation techniques was highly variable. CONCLUSIONS: The authors present a comprehensive description of perioperative management, outcomes, and complications from a large group of North American children undergoing complex cranial vault reconstruction. Transfusion remains the rule for the vast majority of patients. The occurrence of numerous significant complications together with large variability in perioperative management and outcomes suggest targets for improvement.

Chronic Sciatic Neuropathy in Rat Reduces Voluntary Wheel-Running Activity With Concurrent Chronic Mechanical Allodynia.

BACKGROUND: Animal models of peripheral neuropathy produced by a number of manipulations are assessed for the presence of pathologic pain states such as allodynia. Although stimulus-induced behavioral assays are frequently used and important to examine allodynia (ie, sensitivity to light mechanical touch; von Frey fiber test), other measures of behavior that reflect overall function are not only complementary to stimulus-induced responsive measures, but are also critical to gain a complete understanding of the effects of the pain model on quality of life, a clinically relevant aspect of pain on general function. Voluntary wheel-running activity in rodent models of inflammatory and muscle pain is emerging as a reliable index of general function that extends beyond stimulus-induced behavioral assays. Clinically, reports of increased pain intensity occur at night, a period typically characterized with reduced activity during the diurnal cycle. We therefore examined in rats whether alterations in wheel-running activity were more robust during the inactive phase compared with the active phase of their diurnal cycle in a widely used rodent model of chronic peripheral neuropathic pain, the sciatic nerve chronic constriction injury (CCI) model. METHODS: In adult male Sprague Dawley rats, baseline (BL) hindpaw threshold responses to light mechanical touch were assessed using the von Frey test before measuring BL activity levels using freely accessible running wheels (1 hour/day for 7 sequential days) to quantify the distance traveled. Running wheel activity BL values are expressed as total distance traveled (m). The overall experimental design was after BL measures, rats underwent either sham or CCI surgery followed by repeated behavioral reassessment of hindpaw thresholds and wheel-running activity levels for up to 18 days after surgery. Specifically, separate groups of rats were assessed for wheel-running activity levels (1 hour total/trial) during the onset (within first 2 hours) of either the (1) inactive (n = 8/group) or (2) active (n = 8/group) phase of the diurnal cycle. An additional group of CCI-treated rats (n = 8/group) was exposed to a locked running wheel to control for the potential effects of wheel-running exercise on allodynia. The 1-hour running wheel trial period was further examined at discrete 20-minute intervals to identify possible pattern differences in activity during the first, middle, and last portions of the 1-hour trial. The effect of neuropathy on activity levels was assessed by measuring the change from their respective BLs to distance traveled in the running wheels. RESULTS: Although wheel-running distances between groups were not different at BL from rats examined during either the inactive phase of the diurnal cycle or active phase of the diurnal cycle, sciatic nerve CCI reduced running wheel activity levels compared with sham-operated controls during the inactive phase. In addition, compared with sham controls, bilateral low-threshold mechanical allodynia was observed at all time points after surgical induction of neuropathy in rats with free-wheel and locked-wheel access. Allodynia in CCI compared with shams was replicated in rats whose running wheel activity was examined during the active phase of the diurnal cycle. Conversely, no significant reduction in wheel-running activity was observed in CCI-treated rats compared with sham controls at any time point when activity levels were examined during the active diurnal phase. Finally, running wheel activity patterns within the 1-hour trial period during the inactive phase of the diurnal cycle were relatively consistent throughout each 20-minute phase. CONCLUSIONS: Compared with nonneuropathic sham controls, a profound and stable reduction of running wheel activity was observed in CCI rats during the inactive phase of the diurnal cycle. A concurrent robust allodynia persisted in all rats regardless of when wheel-running activity was examined or whether they ran on wheels, suggesting that acute wheel-running activity does not alter chronic low-intensity mechanical allodynia as measured using the von Frey fiber test. Overall, these data support that acute wheel-running exercise with limited repeated exposures does not itself alter allodynia and offers a behavioral assay complementary to stimulus-induced measures of neuropathic pain.