Search

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., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany.)

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.