Influence of thoracic epidural analgesia on cardiovascular autonomic control after thoracic surgery

Background. Thoracic epidural analgesia (TEA) is effective in alleviating pain after major thoracoabdominal surgery and may also reduce postoperative mortality and morbidity. This study investigated cardiovascular autonomic control in patients undergoing elective thoracic surgery and its modulation by continuous TEA. Methods. Thirty‐eight patients were randomly assigned to receive patient‐controlled analgesia (PCA group) or thoracic epidural analgesia (TEA group) with doses of bupivacaine (0.25% during operation, 0.125% after operation) and fentanyl (2 µgml-1). Heart rate variability (HRV), baroreflex function and pressure response to nitroglycerine and phenylephrine were assessed before operation, 4 h after the end of surgery (POD 0) and on the first and second postoperative days (POD1 and POD2). Results. Early after surgery, all HRV variables and baroreflex sensitivities were markedly decreased in both groups. In the TEA group, total HRV and its high‐frequency components (HF) increased towards preoperative values at POD1 and POD2, whereas the ratio of low to high frequencies (LF/HF) was significantly reduced (mean (sd), -44 (15)% at POD 0, -38 (17)% at POD1, -37 (18%) at POD2) and associated with blunting of the postoperative increase in heart rate and blood pressure. In the PCA group, the ratio of LF/HF remained unchanged and the decrements in HRV variables persisted until POD2. In the two groups, baroreflex sensitivities and pressure responses recovered preoperative values at POD2. Conclusions. In contrast with PCA management, TEA using low concentrations of bupivacaine and fentanyl blunted cardiac sympathetic neural drive, resulting in vagal predominance, while HRV variables were better restored after surgery. Br J Anaesth 2003; 91: 525-3

Early improvement of respiratory function after surgical plication for unilateral diaphragmatic paralysis

We reported an unusual case of symptomatic diaphragmatic paralysis in an elderly patient with progressive respiratory-dependent limitation of her daily activities. Surgical plication of the affected hemidiaphragm resulted in early clinical and physiological improvement

Non-parametric Estimation of Geometric Anisotropy from Environmental Sensor Network Measurements

This paper addresses the estimation of geometric anisotropy parameters from scattered data in two dimensional spaces. The parameters involve the orientation angle of the principal anisotropy axes and the anisotropy ratio (i.e., the ratio of the principal correlation lengths). The mathematical background is based on the covariance Hessian identity (CHI) method developed in [3, 1]. CHI links the expectation of the first-order sample derivatives tensor with the Hessian matrix of the covariance function [6]. The paper focuses on the application of CHI to samples that require segmentation into clusters, either due to sampling density variations or due to systematic changes in the process values. A non-parametric isotropy test is also presented. Finally, a composite (real and synthetic) data set is used to investigate the impact of CHI anisotropy estimation on spatial interpolation with ordinary kriging

Protective subpleural blanketing of intrathoracic esogastric anastomosis after esophagectomy

Esophagectomy followed by intrathoracic anastomosis is threatened by leakage which may prove all the more serious that mediastinal contamination is extensive. In the technique presented, the esogastric anastomosis is slipped under the upper mediastinal pleura which is kept intact, after the azygos vein has been ligated and divided. This pleural ‘blanket' may act as an efficient barrier against potential digestive spillage into the mediastinu

Mean field limits of particle-based stochastic reaction-drift-diffusion models

We consider particle-based stochastic reaction-drift-diffusion models where particles move via diffusion and drift induced by one- and two-body potential interactions. The dynamics of the particles are formulated as measure-valued stochastic processes (MVSPs), which describe the evolution of the singular, stochastic concentration fields of each chemical species. The mean field large population limit of such models is derived and proven, giving coarse-grained deterministic partial integro-differential equations (PIDEs) for the limiting deterministic concentration fields' dynamics. We generalize previous studies on the mean field limit of models involving only diffusive motion, with care to formulating the MVSP representation to ensure detailed balance of reversible reactions in the presence of potentials. Our work illustrates the more general set of PIDEs that arise in the mean field limit, demonstrating that the limiting macroscopic reactive interaction terms for reversible reactions obtain additional nonlinear concentration-dependent coefficients compared to the purely diffusive case. Numerical studies are presented which illustrate that two-body repulsive potential interactions can have a significant impact on the reaction dynamics, and also demonstrate the empirical numerical convergence of solutions to the PBSRDD model to the derived mean field PIDEs as the population size increases.Comment: added numerical result