Male dingo urinary scents code for age class and wild dingoes respond to this information.

Chemical information in canid urine has been implicated in territoriality and influences the spacing of individuals. We identified the key volatile organic compound (VOC) components in dingo (Canis lupus dingo) urine and investigated the potential role of scents in territorial spacing. VOC analysis, using headspace gas chromatography-mass spectrometry (GC-MS), demonstrated that the information in fresh urine from adult male dingoes was sufficient to allow statistical classification into age categories. Discriminant function analyses demonstrated that the relative amounts or combinations of key VOCs from pre-prime (3-4 years), prime (5-9 years), and post-prime (≥10 years) males varied between these age categories, and that scents exposed to the environment for 4 (but not 33) days could still be classified to age categories. Further, a field experiment showed that dingoes spent less time in the vicinity of prime male dingo scents than other scents. Collectively, these results indicate that age-related scent differences may be discriminable by dingoes. Previous authors have suggested the potential to use scent as a management tool for wild canids by creating an artificial territorial boundary/barrier. Our results suggest that identifying the specific signals in prime-age male scents could facilitate the development of scent-based tools for non-lethal management.

Optimal face-to-face coupling for fast self-folding kirigami.

Kirigami-inspired designs can enable self-folding three-dimensional materials from flat, two-dimensional sheets. Hierarchical designs of connected levels increase the diversity of possible target structures, yet they can lead to longer folding times in the presence of fluctuations. Here, we study the effect of rotational coupling between levels on the self-folding of two-level kirigami designs driven by thermal noise in a fluid. Naturally present due to hydrodynamic resistance, we find that this coupling parameter can significantly impact a structure's self-folding pathway, thus enabling us to assess the quality of a kirigami design and the possibility for its optimization in terms of its folding rate and yield.

Turing Instabilities are Not Enough to Ensure Pattern Formation.

Symmetry-breaking instabilities play an important role in understanding the mechanisms underlying the diversity of patterns observed in nature, such as in Turing's reaction-diffusion theory, which connects cellular signalling and transport with the development of growth and form. Extensive literature focuses on the linear stability analysis of homogeneous equilibria in these systems, culminating in a set of conditions for transport-driven instabilities that are commonly presumed to initiate self-organisation. We demonstrate that a selection of simple, canonical transport models with only mild multistable non-linearities can satisfy the Turing instability conditions while also robustly exhibiting only transient patterns. Hence, a Turing-like instability is insufficient for the existence of a patterned state. While it is known that linear theory can fail to predict the formation of patterns, we demonstrate that such failures can appear robustly in systems with multiple stable homogeneous equilibria. Given that biological systems such as gene regulatory networks and spatially distributed ecosystems often exhibit a high degree of multistability and nonlinearity, this raises important questions of how to analyse prospective mechanisms for self-organisation.

Concentration-Dependent Domain Evolution in Reaction-Diffusion Systems.

Pattern formation has been extensively studied in the context of evolving (time-dependent) domains in recent years, with domain growth implicated in ameliorating problems of pattern robustness and selection, in addition to more realistic modelling in developmental biology. Most work to date has considered prescribed domains evolving as given functions of time, but not the scenario of concentration-dependent dynamics, which is also highly relevant in a developmental setting. Here, we study such concentration-dependent domain evolution for reaction-diffusion systems to elucidate fundamental aspects of these more complex models. We pose a general form of one-dimensional domain evolution and extend this to N-dimensional manifolds under mild constitutive assumptions in lieu of developing a full tissue-mechanical model. In the 1D case, we are able to extend linear stability analysis around homogeneous equilibria, though this is of limited utility in understanding complex pattern dynamics in fast growth regimes. We numerically demonstrate a variety of dynamical behaviours in 1D and 2D planar geometries, giving rise to several new phenomena, especially near regimes of critical bifurcation boundaries such as peak-splitting instabilities. For sufficiently fast growth and contraction, concentration-dependence can have an enormous impact on the nonlinear dynamics of the system both qualitatively and quantitatively. We highlight crucial differences between 1D evolution and higher-dimensional models, explaining obstructions for linear analysis and underscoring the importance of careful constitutive choices in defining domain evolution in higher dimensions. We raise important questions in the modelling and analysis of biological systems, in addition to numerous mathematical questions that appear tractable in the one-dimensional setting, but are vastly more difficult for higher-dimensional models.

VisualPDE: Rapid Interactive Simulations of Partial Differential Equations.

Computing has revolutionised the study of complex nonlinear systems, both by allowing us to solve previously intractable models and through the ability to visualise solutions in different ways. Using ubiquitous computing infrastructure, we provide a means to go one step further in using computers to understand complex models through instantaneous and interactive exploration. This ubiquitous infrastructure has enormous potential in education, outreach and research. Here, we present VisualPDE, an online, interactive solver for a broad class of 1D and 2D partial differential equation (PDE) systems. Abstract dynamical systems concepts such as symmetry-breaking instabilities, subcritical bifurcations and the role of initial data in multistable nonlinear models become much more intuitive when you can play with these models yourself, and immediately answer questions about how the system responds to changes in parameters, initial conditions, boundary conditions or even spatiotemporal forcing. Importantly, VisualPDE is freely available, open source and highly customisable. We give several examples in teaching, research and knowledge exchange, providing high-level discussions of how it may be employed in different settings. This includes designing web-based course materials structured around interactive simulations, or easily crafting specific simulations that can be shared with students or collaborators via a simple URL. We envisage VisualPDE becoming an invaluable resource for teaching and research in mathematical biology and beyond. We also hope that it inspires other efforts to make mathematics more interactive and accessible.

Minimal Morphoelastic Models of Solid Tumour Spheroids: A Tutorial.

Tumour spheroids have been the focus of a variety of mathematical models, ranging from Greenspan's classical study of the 1970 s through to contemporary agent-based models. Of the many factors that regulate spheroid growth, mechanical effects are perhaps some of the least studied, both theoretically and experimentally, though experimental enquiry has established their significance to tumour growth dynamics. In this tutorial, we formulate a hierarchy of mathematical models of increasing complexity to explore the role of mechanics in spheroid growth, all the while seeking to retain desirable simplicity and analytical tractability. Beginning with the theory of morphoelasticity, which combines solid mechanics and growth, we successively refine our assumptions to develop a somewhat minimal model of mechanically regulated spheroid growth that is free from many unphysical and undesirable behaviours. In doing so, we will see how iterating upon simple models can provide rigorous guarantees of emergent behaviour, which are often precluded by existing, more complex modelling approaches. Perhaps surprisingly, we also demonstrate that the final model considered in this tutorial agrees favourably with classical experimental results, highlighting the potential for simple models to provide mechanistic insight whilst also serving as mathematical examples.

Preserved ß-adrenergic-mediated vasodilation in skeletal muscle of young adults with obesity despite shifts in cyclooxygenase and nitric oxide synthase.

Central adiposity is associated with greater sympathetic support of blood pressure. ß-adrenergic receptors (ß-AR) buffer sympathetically mediated vasoconstriction and ß-AR-mediated vasodilation is attenuated in preclinical models of obesity. With this information, we hypothesized ß-AR vasodilation would be lower in obese compared with normal weight adults. Because ß-AR vasodilation in normal weight adults is limited by cyclooxygenase (COX) restraint of nitric oxide synthase (NOS), we further explored the contributions of COX and NOS to ß-AR vasodilation in this cohort. Forearm blood flow (FBF, Doppler ultrasound) and mean arterial blood pressure (MAP, brachial arterial catheter) were measured and forearm vascular conductance (FVC) was calculated (FVC = FBF/MAP). The rise in FVC from baseline (ΔFVC) was quantified during graded brachial artery infusion of isoproterenol (Iso, 1-12 ng/100 g/min) in normal weight (n = 36) and adults with obesity (n = 22) (18-40 yr old). In a subset of participants, Iso-mediated vasodilation was examined before and during inhibition of NOS [NG-monomethyl-l-arginine (l-NMMA)], COX (ketorolac), and NOS + COX (l-NMMA + ketorolac). Iso-mediated increases in FVC did not differ between groups (P = 0.57). l-NMMA attenuated Iso-mediated ΔFVC in normal weight (P = 0.03) but not adults with obesity (P = 0.27). In normal weight adults, ketorolac increased Iso-mediated ΔFVC (P < 0.01) and this response was lost with concurrent l-NMMA (P = 0.67). In contrast, neither ketorolac (P = 0.81) nor ketorolac + l-NMMA (P = 0.40) altered Iso-mediated ΔFVC in adults with obesity. Despite shifts in COX and NOS, ß-AR vasodilation is preserved in young adults with obesity. These data highlight the presence of a compensatory shift in microvascular control mechanisms in younger humans with obesity.NEW & NOTEWORTHY We examined ß-adrenergic receptor-mediated vasodilation in skeletal muscle of humans with obesity and normal weight. Results show that despite shifts in the contribution of cyclooxygenase and nitric oxide synthase, ß-adrenergic-mediated vasodilation is relatively preserved in young, otherwise healthy adults with obesity. These data highlight the presence of subclinical changes in microvascular control mechanisms early in the obesity process and suggest duration of obesity and/or the addition of primary aging may be necessary for overt dysfunction.

Scheduled methadone reduces overall opioid requirements after pediatric posterior spinal fusion: A single center retrospective case series.

BACKGROUND: Posterior spinal fusion to correct adolescent idiopathic scoliosis is associated with significant postoperative pain. Different modalities have been reported as part of a multimodal analgesic plan. Intravenous methadone acts as a mu-opioid agonist and N-Methyl-D-aspartate (NMDA) antagonist and has been shown to have opioid-sparing effects. Our multimodal approach has included hydromorphone patient-controlled analgesia (PCA) with and without preincisional methadone, and recently postoperative methadone without a PCA. AIMS: We hypothesized that a protocol including scheduled postoperative methadone doses would reduce opioid usage compared to PCA-based strategy. METHODS: A retrospective chart review of patients undergoing posterior spinal fusion for adolescent idiopathic scoliosis between 2015 and 2020 was performed. There were three patient groups: Group PCA received a hydromorphone PCA without methadone; Group PCA + Methadone received preincisional methadone and a hydromorphone PCA; Group Methadone received preincisional methadone, scheduled postoperative methadone, and no PCA. The primary outcome was postoperative opioid use over 72 h. Secondary outcomes included pain scores, sedation scores, and length of stay. RESULTS: Group PCA (n = 26) consumed 0.33 mg/kg (95% CI [0.28, 0.38]) total hydromorphone equivalents, Group PCA + methadone (n = 39) 0.30 mg/kg (95% CI [0.25, 0.36]) total hydromorphone equivalents, and Group methadone (n = 22) 0.18 mg/kg (95% CI [0.15, 0.21]) total hydromorphone equivalents (p = .00096). There were no statistically significant differences between the groups for secondary outcomes. CONCLUSION: A protocol with intraoperative and scheduled postoperative methadone doses resulted in a 45% reduction in opioid usage compared to a PCA-based protocol with similar analgesia after pediatric posterior spinal fusion.

Nitric oxide synthase inhibition in healthy adults reduces regional and total cerebral macrovascular blood flow and microvascular perfusion.

The importance of nitric oxide (NO) in regulating cerebral blood flow (CBF) remains unresolved, due in part to methodological approaches, which lack a comprehensive assessment of both global and regional effects. Importantly, NO synthase (NOS) expression and activity appear greater in some anterior brain regions, suggesting region-specific NOS influence on CBF. We hypothesized that NO contributes to basal CBF in healthy adults, in a regionally distinct pattern that predominates in the anterior circulation. Fourteen healthy adults (7 females; 24 ± 5 years) underwent two magnetic resonance imaging (MRI) study visits with saline (placebo) or the NOS inhibitor, L-NMMA, administered in a randomized, single-blind approach. 4D flow MRI quantified total and regional macrovascular CBF, whereas arterial spin labelling (ASL) MRI quantified total and regional microvascular perfusion. L-NMMA (or volume-matched saline) was infused intravenously for 5 min prior to imaging. L-NMMA reduced CBF (L-NMMA: 722 ± 100 vs. placebo: 771 ± 121 ml/min, P = 0.01) with similar relative reductions (5-7%) in anterior and posterior cerebral circulations, due in part to the reduced cross-sectional area of 9 of 11 large cerebral arteries. Global microvascular perfusion (ASL) was reduced by L-NMMA (L-NMMA: 42 ± 7 vs. placebo: 47 ± 8 ml/100g/min, P = 0.02), with 7-11% reductions in both hemispheres of the frontal, parietal and temporal lobes, and in the left occipital lobe. We conclude that NO contributes to macrovascular and microvascular regulation including larger artery resting diameter. Contrary to our hypothesis, the influence of NO on cerebral perfusion appears regionally uniform in healthy young adults. KEY POINTS: Cerebral blood flow (CBF) is vital for brain health, but the signals that are key to regulating CBF remain unclear. Nitric oxide (NO) is produced in the brain, but its importance in regulating CBF remains controversial since prior studies have not studied all regions of the brain simultaneously. Using modern MRI approaches, a drug that inhibits the enzymes that make NO (L-NMMA) reduced CBF by up to 11% in different brain regions. NO helps maintain proper CBF in healthy adults. These data will help us understand whether the reductions in CBF that occur during ageing or cardiovascular disease are related to shifts in NO signalling.

High-speed multifocal plane fluorescence microscopy for three-dimensional visualisation of beating flagella.

Analysis of flagellum and cilium beating in three dimensions (3D) is important for understanding cell motility, and using fluorescence microscopy to do so would be extremely powerful. Here, high-speed multifocal plane fluorescence microscopy, where the light path is split to visualise multiple focal planes simultaneously, was used to reconstruct Trypanosoma brucei and Leishmania mexicana movement in 3D. These species are uniflagellate unicellular parasites for which motility is vital. It was possible to use either a fluorescent stain or a genetically-encoded fluorescent protein to visualise flagellum and cell movement at 200 Hz frame rates. This addressed two open questions regarding Trypanosoma and Leishmania flagellum beating, which contributes to their swimming behaviours: 1) how planar is the L. mexicana flagellum beat, and 2) what is the nature of flagellum beating during T. brucei 'tumbling'? We showed that L. mexicana has notable deviations from a planar flagellum beat, and that during tumbling the T. brucei flagellum bends the cell and beats only in the distal portion to achieve cell reorientation. This demonstrates high-speed multifocal plane fluorescence microscopy as a powerful tool for the analysis of beating flagella.

Variation Between and Within Hospitals in Single Injection Caudal Local Anesthetic Dose: A Report From the Pediatric Regional Anesthesia Network.

BACKGROUND: Given that variation exists in health care utilization, expenditure, and medical practice, there is a paucity of data on variation within the practice of anesthesia. The Pediatric Regional Anesthesia Network (PRAN) data lend itself to explore whether different medical practice patterns exist and if there are nerve blocks with more local anesthetic dosing variation than others. The primary aim of this study was to quantify variation in single injection caudal block dosing, and the secondary aim was to explore possible causes for variation (eg, number of blocks performed versus geographic location). METHODS: We queried the PRAN database for single injection caudal blocks in children <1 year of age. Data were analyzed for local anesthetic dose, variation within and across institutions, and possible causes. RESULTS: Mean dose of bupivacaine equivalents per kilogram (BE·kg) among sites ranged from 1.39 to 2.22 with an interdecile range (IDR) containing the mid 80% of all doses ranging from 0.21 to 1.48. Mean dose (BE·kg) was associated with site, age, weight, and local anesthetic used (all P < .0001). Cohen's F effect size estimate was 10 times higher for site (0.65) than for age (0.05) or weight (0.02). Variation (IDR) was not related to number of blocks done at each site (P = .23). Mean volume per kilogram was 0.9± ± 0.2 (mean ± ±standard deviation) and was more strongly associated with site (Cohen's F 0.3) than age (0.04) or weight (0.07). CONCLUSIONS: Wide variation in caudal local anesthetic dosing and administered volume exists. This variation is independent of the number of cases performed at each center but rather is determined by study site (ie, variation between centers) with considerable additional variation within study centers, suggesting additional variability dependent on individual practitioners. While there are legitimate reasons to vary dosing, the current approach is inconsistent and not supported by strong evidence over giving a standardized dose.

Boundary behaviours of Leishmania mexicana: A hydrodynamic simulation study.

It is well established that the parasites of the genus Leishmania exhibit complex surface interactions with the sandfly vector midgut epithelium, but no prior study has considered the details of their hydrodynamics. Here, the boundary behaviours of motile Leishmania mexicana promastigotes are explored in a computational study using the boundary element method, with a model flagellar beating pattern that has been identified from digital videomicroscopy. In particular a simple flagellar kinematics is observed and quantified using image processing and mode identification techniques, suggesting a simple mechanical driver for the Leishmania beat. Phase plane analysis and long-time simulation of a range of Leishmania swimming scenarios demonstrate an absence of stable boundary motility for an idealised model promastigote, with behaviours ranging from boundary capture to deflection into the bulk both with and without surface forces between the swimmer and the boundary. Indeed, the inclusion of a short-range repulsive surface force results in the deflection of all surface-bound promastigotes, suggesting that the documented surface detachment of infective metacyclic promastigotes may be the result of their particular morphology and simple hydrodynamics. Further, simulation elucidates a remarkable morphology-dependent hydrodynamic mechanism of boundary approach, hypothesised to be the cause of the well-established phenomenon of tip-first epithelial attachment of Leishmania promastigotes to the sandfly vector midgut.

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.

Exercise vasodilation is greater in women: contributions of nitric oxide synthase and cyclooxygenase.

PURPOSE: We hypothesized exercise vasodilation would be greater in women due to nitric oxide synthase (NOS) and cyclooxygenase (COX) signaling. METHODS: 45 healthy adults (23 women, W, 22 men, M, 26 ± 1 years) completed two 10-min trials of dynamic forearm exercise at 15 % intensity. Forearm blood flow (FBF; Doppler ultrasound), arterial pressure (brachial catheter), and forearm lean mass were measured to calculate relative forearm vascular conductance (FVCrel) = FBF 100 mmHg(-1) 100 g(-1) lean mass. Local intra-arterial infusion of L-NMMA or ketorolac acutely inhibited NOS and COX, respectively. In Trial 1, the first 5 min served as control exercise (CON), followed by 5 min of L-NMMA or ketorolac over the last 5 min of exercise. In Trial 2, the remaining drug was infused during 5-10 min, to achieve combined NOS-COX inhibition (double blockade, DB). RESULTS: Are mean ± SE. Women exhibited 29 % greater vasodilation in CON (ΔFVCrel, 19 ± 1 vs. 15 ± 1, p = 0.01). L-NMMA reduced ΔFVCrel (p < 0.001) (W: Δ -2.3 ± 1.3 vs. M: Δ -3.7 ± 0.8, p = 0.25); whereas, ketorolac modestly increased ΔFVCrel (p = 0.04) similarly between sexes (W: Δ 1.6 ± 1.1 vs. M: Δ 2.0 ± 1.6, p = 0.78). DB was also found to be similar between the sexes (p = 0.85). CONCLUSION: These data clearly indicate women produce a greater exercise vasodilator response. Furthermore, contrary to experiments in animal models, these data are the first to demonstrate vascular control by NOS and COX is similar between sexes.

Ultrasound-guided rectus sheath block or wound infiltration in children: a randomized blinded study of analgesia and bupivacaine absorption.

BACKGROUND: Rectus sheath block can provide analgesia following umbilical hernia repair. However, conflicting reports on its analgesic effectiveness exist. No study has investigated plasma local anesthetic concentration following ultrasound-guided rectus sheath block (USGRSB) in children. OBJECTIVES: Compare the effectiveness and bupivacaine absorption following USGRSB or wound infiltration (WI) for umbilical hernia repair in children. METHODS: A randomized blinded study comparing WI with USGRSB in 40 children undergoing umbilical hernia repair was performed. Group WI (n = 20) received wound infiltration 1 mg·kg(-1) 0.25% bupivacaine. Group RS (n = 20) received USGRSB 0.5 mg·kg(-1) 0.25% bupivacaine per side in the posterior rectus sheath compartment. Pain scores and rescue analgesia were recorded. Blood samples were drawn at 0, 10, 20, 30, 45, and 60 min. RESULTS: Patients in the WI group had a twofold increased risk of requiring morphine (hazard ratio 2.06, 95% CI 1.01, 4.20, P = 0.05). When required, median time to first morphine dose was longer in the USGRSB group (65.5 min vs. 47.5 min, P = 0.049). Peak plasma bupivacaine concentration was higher following USGRSB than WI (median: 631.9 ng·ml(-1) IQR: 553.9-784.1 vs. 389.7 ng·ml(-1) IQR: 250.5-502.7, P = 0.002). Tmax was longer in the USGRSB group (median 45 min IQR: 30-60 vs. 20 min IQR: 20-45, P = 0.006). CONCLUSIONS: USGRSB provides more effective analgesia than WI for umbilical hernia repair. USGRSB with 1 mg·kg(-1) 0.25% bupivacaine is associated with safe plasma bupivacaine concentration that peaks higher and later than WI. Caution against using larger volumes of higher concentration local anesthetic for USGRSB is advised.

Altered neurovascular control of the resting circulation in human metabolic syndrome.

Young healthy adults exhibit an inverse linear relationship between muscle sympathetic nerve activity (MSNA) and α-adrenergic responsiveness. This balance may be reversed in metabolic syndrome (MetSyn) as animal models exhibit increased sympathetic activity and α-mediated vasoconstriction. We hypothesized humans with MetSyn would demonstrate increased α-adrenergic vasoconstriction and the inverse relationship between MSNA and adrenergic responsiveness would be lost. We measured MSNA (microneurography of the peroneal nerve) and forearm blood flow (FBF, Doppler ultrasound) in 16 healthy control subjects (31 ± 3 years) and 14 adults with MetSyn (35 ± 3 years; P > 0.05) during local administration of α-adrenergic agonists (phenylephrine (PE), α(1); clonidine (CL), α(2)). MSNA was greater in MetSyn subjects than in healthy controls (P < 0.05). A group difference in vasoconstriction to PE was not detected (P = 0.08). The level of α(1)-mediated vasoconstriction was inversely related to MSNA in control subjects (r = 0.5, P = 0.04); this balance between MSNA and α(1) responsiveness was lost in adults with MetSyn. MetSyn subjects exhibited greater vasoconstriction to CL infusion as compared with healthy controls (P < 0.01). A relationship between MSNA and α(2)-mediated vasoconstriction was not detected in either group. In summary, altered neurovascular control in human MetSyn is receptor specific. The observed uncoupling between MSNA and α(1)-adrenergic responsiveness and increased α(2) vasoconstriction may lead to reduced FBF, altered flow distribution, and/or severe hypertension with the progression toward diabetes and cardiovascular disease.

Pediatric Regional Anesthesia Network (PRAN): a multi-institutional study of the use and incidence of complications of pediatric regional anesthesia.

BACKGROUND: Regional anesthesia is increasingly used in pediatric patients to provide postoperative analgesia and to supplement intraoperative anesthesia. The Pediatric Regional Anesthesia Network was formed to obtain highly audited data on practice patterns and complications and to facilitate collaborative research in regional anesthetic techniques in infants and children. METHODS: We constructed a centralized database to collect detailed prospective data on all regional anesthetics performed by anesthesiologists at the participating centers. Data were uploaded via a secure Internet connection to a central server. Data were rigorously audited for accuracy and errors were corrected. All anesthetic records were scrutinized to ensure that every block that was performed was captured in the database. Intraoperative and postoperative complications were tracked until their resolution. Blocks were categorized by type and as single-injection or catheter (continuous) blocks. RESULTS: A total of 14,917 regional blocks, performed on 13,725 patients, were accrued from April 1, 2007 through March 31, 2010. There were no deaths or complications with sequelae lasting >3 months (95% CI 0-2:10,000). Single-injection blocks had fewer adverse events than continuous blocks, although the most frequent events (33% of all events) in the latter group were catheter-related problems. Ninety-five percent of blocks were placed while patients were under general anesthesia. Single-injection caudal blocks were the most frequently performed (40%), but peripheral nerve blocks were also frequently used (35%), possibly driven by the widespread use of ultrasound (83% of upper extremity and 69% of lower extremity blocks). CONCLUSIONS: Regional anesthesia in children as commonly performed in the United States has a very low rate of complications, comparable to that seen in the large multicenter European studies. Ultrasound may be increasing the use of peripheral nerve blocks. Multicenter collaborative networks such as the Pediatric Regional Anesthesia Network can facilitate the collection of detailed prospective data for research and quality improvement.

Predicting lumbar plexus depth in children and adolescents.

BACKGROUND: Lumbar plexus block provides effective analgesia for hip, thigh, and knee surgery. A simple measurement that accurately predicts lumbar plexus depth would be invaluable for clinicians performing this block in children, in whom plexus depth varies with age. METHODS: Surface anatomy measurements were taken on children having lower extremity surgery and lumbar plexus block. All blocks were placed under general anesthesia using peripheral nerve stimulation. The distance from the posterior superior iliac spine (PSIS) to the intercristal line (ICL), i.e., PSIS-ICL distance, and from midline to the intersection of a perpendicular line drawn from the PSIS and the ICL were measured. Lumbar plexus depth was recorded at the point at which maximum quadriceps stimulation was elicited using the lowest current output. Linear regression was used to explore the least squares line of best fit for each measure. RESULTS: Measurements were made on 350 consecutive patients aged 1 month to 24 years. A very strong linear relationship between lumbar plexus depth and PSIS-ICL distance was noted. The median (interquartile range) absolute difference between observed lumbar plexus depth and that predicted by PSIS-ICL distance was 2 mm (1-5 mm), 95% CI for median = 1.36 to 2.64. Ninety-two percent of patients (95% CI, 88.7%-94.6%) had lumbar plexus depths within ±10 mm of the predicted depth. The strongest correlation to lumbar plexus depth was found with PSIS-ICL distance (R(2) = 0.89, P < 0.0001). Weaker correlations were found for weight, height, body mass index, midline-PSIS line distance, and age. CONCLUSION: PSIS-ICL distance provides an accurate, patient-specific predictor for lumbar plexus depth in children over a wide range of age and body habitus. The strong linear relationship obviates the need for complex calculations. This measurement can be used as a guide for ultrasound location, to choose an appropriate needle length, and may reduce complications associated with this block.

Modelling Motility: The Mathematics of Spermatozoa.

In one of the first examples of how mechanics can inform axonemal mechanism, Machin's study in the 1950s highlighted that observations of sperm motility cannot be explained by molecular motors in the cell membrane, but would instead require motors distributed along the flagellum. Ever since, mechanics and hydrodynamics have been recognised as important in explaining the dynamics, regulation, and guidance of sperm. More recently, the digitisation of sperm videomicroscopy, coupled with numerous modelling and methodological advances, has been bringing forth a new era of scientific discovery in this field. In this review, we survey these advances before highlighting the opportunities that have been generated for both recent research and the development of further open questions, in terms of the detailed characterisation of the sperm flagellum beat and its mechanics, together with the associated impact on cell behaviour. In particular, diverse examples are explored within this theme, ranging from how collective behaviours emerge from individual cell responses, including how these responses are impacted by the local microenvironment, to the integration of separate advances in the fields of flagellar analysis and flagellar mechanics.