Haemodynamic response to pre-hospital emergency anaesthesia in trauma patients within an urban helicopter emergency medical service.

PURPOSE: Pre-hospital emergency anaesthesia is routinely used in the care of severely injured patients by pre-hospital critical care services. Anaesthesia, intubation, and positive pressure ventilation may lead to haemodynamic instability. The aim of this study was to identify the frequency of new-onset haemodynamic instability after induction in trauma patients with a standardised drug regime. METHODS: A retrospective database analysis was undertaken of all adult patients treated by a physician-led urban pre-hospital care service over a 6-year period. The primary outcome measure was the frequency of new haemodynamic instability following pre-hospital emergency anaesthesia. The association of patient characteristics and drug regimes with new haemodynamic instability was also analysed. RESULTS: A total of 1624 patients were included. New haemodynamic instability occurred in 231 patients (17.4%). Patients where a full-dose regime was administered were less likely to experience new haemodynamic instability than those who received a modified dose regime (9.7% vs 24.8%, p < 0.001). The use of modified drug regimes became more common over the study period (p < 0.001) but there was no change in the rates of pre-existing (p = 0.22), peri-/post-anaesthetic (p = 0.36), or new haemodynamic instability (p = 0.32). CONCLUSION: New haemodynamic instability within the first 30 min following pre-hospital emergency anaesthesia in trauma patients is common despite reduction of sedative drug doses to minimise their haemodynamic impact. It is important to identify non-drug factors that may improve cardiovascular stability in this group to optimise the care received by these patients.

A New Era of Image Guidance with Magnetic Resonance-guided Radiation Therapy for Abdominal and Thoracic Malignancies.

Magnetic resonance-guided radiation therapy (MRgRT) offers advantages for image guidance for radiotherapy treatments as compared to conventional computed tomography (CT)-based modalities. The superior soft tissue contrast of magnetic resonance (MR) enables an improved visualization of the gross tumor and adjacent normal tissues in the treatment of abdominal and thoracic malignancies. Online adaptive capabilities, coupled with advanced motion management of real-time tracking of the tumor, directly allow for high-precision inter-/intrafraction localization. The primary aim of this case series is to describe MR-based interventions for localizing targets not well-visualized with conventional image-guided technologies. The abdominal and thoracic sites of the lung, kidney, liver, and gastric targets are described to illustrate the technological advancement of MR-guidance in radiotherapy.

Numerical simulations of current generation and dynamo excitation in a mechanically forced turbulent flow.

The role of turbulence in current generation and self-excitation of magnetic fields has been studied in the geometry of a mechanically driven, spherical dynamo experiment, using a three-dimensional numerical computation. A simple impeller model drives a flow that can generate a growing magnetic field, depending on the magnetic Reynolds number Rm=micro0sigmaVa and the fluid Reynolds number Re=Vanu of the flow. For Re<420, the flow is laminar and the dynamo transition is governed by a threshold of Rmcrit=100, above which a growing magnetic eigenmode is observed that is primarily a dipole field transverse to the axis of symmetry of the flow. In saturation, the Lorentz force slows the flow such that the magnetic eigenmode becomes marginally stable. For Re>420 and Rm approximately 100 the flow becomes turbulent and the dynamo eigenmode is suppressed. The mechanism of suppression is a combination of a time varying large-scale field and the presence of fluctuation driven currents (such as those predicted by the mean-field theory), which effectively enhance the magnetic diffusivity. For higher Rm, a dynamo reappears; however, the structure of the magnetic field is often different from the laminar dynamo. It is dominated by a dipolar magnetic field aligned with the axis of symmetry of the mean-flow, which is apparently generated by fluctuation-driven currents. The magnitude and structure of the fluctuation-driven currents have been studied by applying a weak, axisymmetric seed magnetic field to laminar and turbulent flows. An Ohm's law analysis of the axisymmetric currents allows the fluctuation-driven currents to be identified. The magnetic fields generated by the fluctuations are significant: a dipole moment aligned with the symmetry axis of the mean-flow is generated similar to those observed in the experiment, and both toroidal and poloidal flux expulsion are observed.