A Mean Field to Capture Asynchronous Irregular Dynamics of Conductance-Based Networks of Adaptive Quadratic Integrate-and-Fire Neuron Models.

Mean-field models are a class of models used in computational neuroscience to study the behavior of large populations of neurons. These models are based on the idea of representing the activity of a large number of neurons as the average behavior of mean-field variables. This abstraction allows the study of large-scale neural dynamics in a computationally efficient and mathematically tractable manner. One of these methods, based on a semianalytical approach, has previously been applied to different types of single-neuron models, but never to models based on a quadratic form. In this work, we adapted this method to quadratic integrate-and-fire neuron models with adaptation and conductance-based synaptic interactions. We validated the mean-field model by comparing it to the spiking network model. This mean-field model should be useful to model large-scale activity based on quadratic neurons interacting with conductance-based synapses.

Differences in the association between epidural analgesia and length of stay by surgery type: an observational study.

INTRODUCTION: Despite a decline in the use of thoracic epidural analgesia related in part to concerns for delayed discharge, it is unknown whether changes in length of stay (LOS) associated with epidural analgesia vary by surgery type. Therefore, we determined the degree to which the association between epidural analgesia (vs no epidural) and LOS differed by surgery type. METHODS: We conducted an observational study using data from 1747 patients who had either non-emergent open abdominal, thoracic, or vascular surgery at a single tertiary academic hospital. The primary outcome was hospital LOS and the incidence of a prolonged hospital LOS defined as 21 days or longer. Secondary endpoints included escalation of care, 30-day all-cause readmission, and reason for epidural not being placed. The association between epidural status and dichotomous endpoints was examined using logistic regression. RESULTS: Among the 1747 patients, 85.7% (1499) received epidural analgesia. 78% (1364) underwent abdominal, 11.5% (200) thoracic, and 10.5% (183) vascular surgeries. After adjustment for differences, receiving epidural analgesia (vs no epidural) was associated with a 45% reduction in the likelihood of a prolonged LOS (p<0.05). This relationship varied by surgery type: abdominal (OR 0.42, 95% CI 0.23 to 0.79, p<0.001), vascular (OR 1.66, 95% CI 0.17 to 16.1, p=0.14), and thoracic (OR 1.07, 95% CI 0.20 to 5.70, p=0.93). Among abdominal surgical patients, epidural analgesia was associated with a median decrease in LOS by 1.4 days and a 37% reduction in the likelihood of 30-day readmission (adjusted OR 0.63, 0.41 to 0.97, p<0.05). Among thoracic surgical patients, epidural analgesia was associated with a median increase in LOS by 3.2 days. CONCLUSIONS: The relationship between epidural analgesia and LOS appears to be different among different surgical populations.