The time to perform spinal or general anaesthesia in COVID-19 positive parturients requiring emergency caesarean delivery: a prospective crossover simulation study

Background: Spinal anaesthesia is the commonest performed technique for caesarean deliveries except in the emergency setting where general anaesthesia is preferred due to its rapid onset and predictability. There are several modifications to performing general anaesthesia for COVID-19 patients in Australia. We hypothesised that the performance time of these techniques amongst specialist anaesthetists would be similar for COVID-19 parturients undergoing emergency caesarean delivery. Methods: We designed a simulation cross-over study. The primary outcome was the time taken to perform general anaesthesia or spinal anaesthesia in this setting. We also examined the decision-making process time, the decision to incision time and the level of stress associated with both scenarios. Results: Nine specialist anaesthetists participated in the research. There was no difference in the time taken to perform spinal or general anaesthesia (mean difference (GA–SA scenario) –1.2 (–5.3–2.8) minutes, p = 0.5). Irrespective of group allocation the mean time to complete the spinal anaesthesia scenario was 27.4 (standard deviation = 7.8) minutes, while for the general anaesthesia scenario was 24.0 (7.2) minutes. There was no difference between these times (mean difference (GA–SA scenario) = –3.5 minutes, 95th percent confidence interval –9.7–2.8 minutes, p = 0.24). There was no evidence of a carryover effect for the two scenarios based on the group allocation (p = 0.69) and no significant difference between stress levels (p = 0.44). Conclusions: The time to perform spinal anaesthesia was similar to the time to perform general anaesthesia for a confirmed COVID-19 parturient in a simulation environment

Tube Research and Development

Contains reports on two research projects

Conjunctive input processing drives feature selectivity in hippocampal CA1 neurons

Feature-selective firing allows networks to produce representations of the external and internal environments. Despite its importance, the mechanisms generating neuronal feature selectivity are incompletely understood. In many cortical microcircuits the integration of two functionally distinct inputs occurs nonlinearly through generation of active dendritic signals that drive burst firing and robust plasticity. To examine the role of this processing in feature selectivity, we recorded CA1 pyramidal neuron membrane potential and local field potential in mice running on a linear treadmill. We found that dendritic plateau potentials were produced by an interaction between properly timed input from entorhinal cortex and hippocampal CA3. These conjunctive signals positively modulated the firing of previously established place fields and rapidly induced new place field formation to produce feature selectivity in CA1 that is a function of both entorhinal cortex and CA3 input. Such selectivity could allow mixed network level representations that support context-dependent spatial maps.Howard Hughes Medical InstituteRikagaku Kenkyūjo (Japan

NMDA Receptors Mediate Synaptic Competition in Culture

Background: Activity through NMDA type glutamate receptors sculpts connectivity in the developing nervous system. This topic is typically studied in the visual system in vivo, where activity of inputs can be differentially regulated, but in which individual synapses are difficult to visualize and mechanisms governing synaptic competition can be difficult to ascertain. Here, we develop a model of NMDA-receptor dependent synaptic competition in dissociated cultured hippocampal neurons. Methodology/Principal Findings: GluN1-/- (KO) mouse hippocampal neurons lacking the essential NMDA receptor subunit were cultured alone or cultured in defined ratios with wild type (WT) neurons. The absence of functional NMDA receptors did not alter neuron survival. Synapse development was assessed by immunofluorescence for postsynaptic PSD-95 family scaffold and apposed presynaptic vesicular glutamate transporter VGlut1. Synapse density was specifically enhanced onto minority wild type neurons co-cultured with a majority of GluN1-/- neighbour neurons, both relative to the GluN1-/neighbours and relative to sister pure wild type cultures. This form of synaptic competition was dependent on NMDA receptor activity and not conferred by the mere physical presence of GluN1. In contrast to these results in 10 % WT and 90

Axons Amplify Somatic Incomplete Spikes into Uniform Amplitudes in Mouse Cortical Pyramidal Neurons

BACKGROUND: Action potentials are the essential unit of neuronal encoding. Somatic sequential spikes in the central nervous system appear various in amplitudes. To be effective neuronal codes, these spikes should be propagated to axonal terminals where they activate the synapses and drive postsynaptic neurons. It remains unclear whether these effective neuronal codes are based on spike timing orders and/or amplitudes. METHODOLOGY/PRINCIPAL FINDINGS: We investigated this fundamental issue by simultaneously recording the axon versus soma of identical neurons and presynaptic vs. postsynaptic neurons in the cortical slices. The axons enable somatic spikes in low amplitude be enlarged, which activate synaptic transmission in consistent patterns. This facilitation in the propagation of sequential spikes through the axons is mechanistically founded by the short refractory periods, large currents and high opening probability of axonal voltage-gated sodium channels. CONCLUSION/SIGNIFICANCE: An amplification of somatic incomplete spikes into axonal complete ones makes sequential spikes to activate consistent synaptic transmission. Therefore, neuronal encoding is likely based on spike timing order, instead of graded analogues

Le macrotron : accélérateur de 100 kW en régime permanent

Le macrotron est un accélérateur d'électrons où le faisceau traverse plusieurs dizaines de fois une cavité alimentée en régime permanent en ondes métriques. Il délivre un faisceau de très bonne qualité et de très grande puissance