Electrocardiographic and haemodynamic alterations caused by three different test solutions of local anaesthetics to detect accidental intravascular injection in children

Background The aim of this study was to investigate ECG and haemodynamic alterations provoked by a test dose of bupivacaine, epinephrine, and their combination. Methods Paediatric patients undergoing general anaesthesia were randomized into three groups. After anaesthesia induction and tracheal intubation, 0.2 ml kg−1 (max. 3 ml) of the corresponding test solution was i.v. injected: bupivacaine 0.125% (Group B), bupivacaine 0.125% plus epinephrine 1:200 000 (Group BE), or epinephrine 1:200 000 (Group E). ECG was printed and analysed post hoc. Non-invasive arterial pressure (AP) was measured at 1 and 2 min after test dose injection. Increases in T-wave of ≥25%, in heart rate (HR) of ≥10 beats min−1, and in systolic AP of ≥15 mm Hg above baseline value were considered a positive result. Results A total of 105 children aged 0.2-16 (median 6.8) yr were enrolled. Test dose injection provoked T-wave elevation in 0%, 85%, and 89% of patients in Groups B, BE, and E, respectively. A positive increase in HR was found in 0%, 68%, and 76%. A positive increase in AP at 1 min was found in 0%, 88%, and 94% and at 2 min in 0%, 42%, and 59%. A decrease in HR of ≥10 beats min−1 was observed in 6%, 76%, and 69%. Alterations in T-wave and HR were significantly influenced by age. Conclusions ECG and haemodynamic alterations after i.v. injection of a local anaesthetic test dose were significantly influenced by epinephrine. T-wave elevation, increase in AP, and changes in HR are highly reliable variables, particularly when age is taken into accoun

Quantum Noise and Superluminal Propagation

Causal "superluminal" effects have recently been observed and discussed in various contexts. The question arises whether such effects could be observed with extremely weak pulses, and what would prevent the observation of an "optical tachyon." Aharonov, Reznik, and Stern (ARS) [Phys. Rev. Lett., vol. 81, 2190 (1998)] have argued that quantum noise will preclude the observation of a superluminal group velocity when the pulse consists of one or a few photons. In this paper we reconsider this question both in a general framework and in the specific example, suggested by Chiao, Kozhekin, and Kurizki [Phys. Rev. Lett., vol. 77, 1254 (1996)], of off-resonant, short-pulse propagation in an optical amplifier. We derive in the case of the amplifier a signal-to-noise ratio that is consistent with the general ARS conclusions when we impose their criteria for distinguishing between superluminal propagation and propagation at the speed c. However, results consistent with the semiclassical arguments of CKK are obtained if weaker criteria are imposed, in which case the signal can exceed the noise without being "exponentially large." We show that the quantum fluctuations of the field considered by ARS are closely related to superfluorescence noise. More generally we consider the implications of unitarity for superluminal propagation and quantum noise and study, in addition to the complete and truncated wavepackets considered by ARS, the residual wavepacket formed by their difference. This leads to the conclusion that the noise is mostly luminal and delayed with respect to the superluminal signal. In the limit of a very weak incident signal pulse, the superluminal signal will be dominated by the noise part, and the signal-to-noise ratio will therefore be very small.Comment: 30 pages, 1 figure, eps

Negative phase time for Scattering at Quantum Wells: A Microwave Analogy Experiment

If a quantum mechanical particle is scattered by a potential well, the wave function of the particle can propagate with negative phase time. Due to the analogy of the Schr\"odinger and the Helmholtz equation this phenomenon is expected to be observable for electromagnetic wave propagation. Experimental data of electromagnetic wells realized by wave guides filled with different dielectrics confirm this conjecture now.Comment: 10 pages, 6 figure

The Faraday Quantum Clock and Non-local Photon Pair Correlations

We study the use of the Faraday effect as a quantum clock for measuring traversal times of evanescent photons through magneto-refractive structures. The Faraday effect acts both as a phase-shifter and as a filter for circular polarizations. Only measurements based on the Faraday phase-shift properties are relevant to the traversal time measurements. The Faraday polarization filtering may cause the loss of non-local (Einstein-Podolsky-Rosen) two-photon correlations, but this loss can be avoided without sacrificing the clock accuracy. We show that a mechanism of destructive interference between consecutive paths is responsible for superluminal traversal times measured by the clock.Comment: 6 figure

Can a falling tree make a noise in two forests at the same time?

It is a commonplace to claim that quantum mechanics supports the old idea that a tree falling in a forest makes no sound unless there is a listener present. In fact, this conclusion is far from obvious. Furthermore, if a tunnelling particle is observed in the barrier region, it collapses to a state in which it is no longer tunnelling. Does this imply that while tunnelling, the particle can not have any physical effects? I argue that this is not the case, and moreover, speculate that it may be possible for a particle to have effects on two spacelike separate apparatuses simultaneously. I discuss the measurable consequences of such a feat, and speculate about possible statistical tests which could distinguish this view of quantum mechanics from a ``corpuscular'' one. Brief remarks are made about an experiment underway at Toronto to investigate these issues.Comment: 9 pp, Latex, 3 figs, to appear in Proc. Obsc. Unr. Conf.; Fig 2 postscript repaired on 26.10.9

Electrocardiographic and haemodynamic alterations caused by three different test solutions of local anaesthetics to detect accidental intravascular injection in children

BACKGROUND: The aim of this study was to investigate ECG and haemodynamic alterations provoked by a test dose of bupivacaine, epinephrine, and their combination. METHODS: Paediatric patients undergoing general anaesthesia were randomized into three groups. After anaesthesia induction and tracheal intubation, 0.2 ml kg(-1) (max. 3 ml) of the corresponding test solution was i.v. injected: bupivacaine 0.125% (Group B), bupivacaine 0.125% plus epinephrine 1:200 000 (Group BE), or epinephrine 1:200 000 (Group E). ECG was printed and analysed post hoc. Non-invasive arterial pressure (AP) was measured at 1 and 2 min after test dose injection. Increases in T-wave of ≥ 25%, in heart rate (HR) of ≥ 10 beats min(-1), and in systolic AP of ≥ 15 mm Hg above baseline value were considered a positive result. RESULTS: A total of 105 children aged 0.2-16 (median 6.8) yr were enrolled. Test dose injection provoked T-wave elevation in 0%, 85%, and 89% of patients in Groups B, BE, and E, respectively. A positive increase in HR was found in 0%, 68%, and 76%. A positive increase in AP at 1 min was found in 0%, 88%, and 94% and at 2 min in 0%, 42%, and 59%. A decrease in HR of ≥ 10 beats min(-1) was observed in 6%, 76%, and 69%. Alterations in T-wave and HR were significantly influenced by age. CONCLUSIONS: ECG and haemodynamic alterations after i.v. injection of a local anaesthetic test dose were significantly influenced by epinephrine. T-wave elevation, increase in AP, and changes in HR are highly reliable variables, particularly when age is taken into account

Multibarrier tunneling

We study the tunneling through an arbitrary number of finite rectangular opaque barriers and generalize earlier results by showing that the total tunneling phase time depends neither on the barrier thickness nor on the inter-barrier separation. We also predict two novel peculiar features of the system considered, namely the independence of the transit time (for non resonant tunneling) and the resonant frequency on the number of barriers crossed, which can be directly tested in photonic experiments. A thorough analysis of the role played by inter-barrier multiple reflections and a physical interpretation of the results obtained is reported, showing that multibarrier tunneling is a highly non-local phenomenon.Comment: RevTex, 7 pages, 1 eps figur

Conditional probabilities in quantum theory, and the tunneling time controversy

It is argued that there is a sensible way to define conditional probabilities in quantum mechanics, assuming only Bayes's theorem and standard quantum theory. These probabilities are equivalent to the ``weak measurement'' predictions due to Aharonov {\it et al.}, and hence describe the outcomes of real measurements made on subensembles. In particular, this approach is used to address the question of the history of a particle which has tunnelled across a barrier. A {\it gedankenexperiment} is presented to demonstrate the physically testable implications of the results of these calculations, along with graphs of the time-evolution of the conditional probability distribution for a tunneling particle and for one undergoing allowed transmission. Numerical results are also presented for the effects of loss in a bandgap medium on transmission and on reflection, as a function of the position of the lossy region; such loss should provide a feasible, though indirect, test of the present conclusions. It is argued that the effects of loss on the pulse {\it delay time} are related to the imaginary value of the momentum of a tunneling particle, and it is suggested that this might help explain a small discrepancy in an earlier experiment.Comment: 11 pages, latex, 4 postscript figures separate (one w/ 3 parts

Time of arrival in the presence of interactions

We introduce a formalism for the calculation of the time of arrival t at a space point for particles traveling through interacting media. We develop a general formulation that employs quantum canonical transformations from the free to the interacting cases to construct t in the context of the Positive Operator Valued Measures. We then compute the probability distribution in the times of arrival at a point for particles that have undergone reflection, transmission or tunneling off finite potential barriers. For narrow Gaussian initial wave packets we obtain multimodal time distributions of the reflected packets and a combination of the Hartman effect with unexpected retardation in tunneling. We also employ explicitly our formalism to deal with arrivals in the interaction region for the step and linear potentials.Comment: 20 pages including 5 eps figure