The use of ketamine in cancer palliation

Cancer pain is caused by continuous tissue injury, which may be due to surgery, infiltration of the surrounding organs including nerves, as well as from mucositis after chemo- or radiotherapy. Nerve involvement, chronic opioid therapy and continuous nociceptive input cause hyperalgesia. Chronic stimulation of the dorsal root neurons leads to hyperalgesia and resistance (tolerance) to μ opioid analgesics (hyperalgesia-tolerance). The NMDA receptor antagonist ketamine reverses tolerance to morphine. Ketamine aggravates the sedative effect of opioids and other drugs used for neuropathic pain, such as sodium valproate and amitriptyline. The pain experienced by cancer patients needs a multimodal approach, including ketamine. Although ketamine appears to be a useful analgesic, the literature dealing with ketamine as an analgesic lacks randomised controlled trials

Haemodynamic response to laryngoscopy with and without tracheal intubation

IntroductionTracheal intubation is accompanied by an increased blood pressure and heart rate. The aim of this study was to find the most important source of this haemodynamic response, namely laryngoscopy or intubation.MethodA standard induction technique was used for all patients. Eighty patients were randomly allocated to one of two groups, one group to undergo laryngoscopy followed by intubation (Group I), and the other laryngoscopy only of duration similar to intubation (Group L). Blood pressure and heart rate were recorded in the ward, before induction of anaesthesia and one, two, three, and four minutes after instrumentation.ResultsThe instrumentation times did not differ significantly (p = 0.20). Over time mean arterial pressures were significantly higher in Group I than in Group L (p = 0.038). Over time the ratios of mean blood pressure and heart rate relative to the preoperative heart rate were significantly greater in Group I than in Group L (p < 0.01).ConclusionBlood pressures and heart rates were significantly greater after laryngoscopy followed by intubation than after laryngoscopy of the same duration not followed by intubation. The induction technique, consisting of lignocaine, alfentanil, and propofol, may have attenuated expected increases in blood pressure but not increases in heart rate after intubation

Rapid metabolic pathway assembly and modification using serine integrase site-specific recombination

Synthetic biology requires effective methods to assemble DNA parts into devices and to modify these devices once made. Here we demonstrate a convenient rapid procedure for DNA fragment assembly using site-specific recombination by ϕC31 integrase. Using six orthogonal attP/attB recombination site pairs with different overlap sequences, we can assemble up to five DNA fragments in a defined order and insert them into a plasmid vector in a single recombination reaction. ϕC31 integrase-mediated assembly is highly efficient, allowing production of large libraries suitable for combinatorial gene assembly strategies. The resultant assemblies contain arrays of DNA cassettes separated by recombination sites, which can be used to manipulate the assembly by further recombination. We illustrate the utility of these procedures to (i) assemble functional metabolic pathways containing three, four or five genes; (ii) optimize productivity of two model metabolic pathways by combinatorial assembly with randomization of gene order or ribosome binding site strength; and (iii) modify an assembled metabolic pathway by gene replacement or addition

Analgesia after total hip replacement: epidural versus psoas compartment block

Background The objective of this paper is to evaluate the effectiveness of a psoas compartment block, as compared with an epidural, for postoperative analgesia following total hip replacement surgery. The research design was a double-blinded randomised control trail, in the setting of a university hospital. Methods Patients scheduled for hip arthroplasty received either a psoas compartment or epidural infusion of bupivacaine. The outcome measures that were examined were  postoperative pain, local anaesthetic and morphine consumption, and side effects. Results  There was no significant difference between the two groups regarding postoperative pain. Local anaesthetic and opiate consumption was significantly higher in the psoas compartment block group. Postoperative morphine as covariate had a significant influence on the mean postoperative pain. There was no significant difference between side effects in each group. Conclusion  Epidural analgesia was more effective than the psoas compartment block after hip replacement surgery. Although pain did not differ significantly, local anaesthetic and opiate consumption was significantly higher in the psoas compartment group

Entropy of the electroencephalogram as applied in the M-Entropy S/5TM Module (GE Healthcare) during increases in nitrous oxide and constant sevofl urane concentrations

Background: It has been suggested that spectral entropy of the electroencephalogram as applied in the M-Entropy S/5TM Module (GE Healthcare) does not detect the effects of nitrous oxide (N2O). The aim of this study was to investigate the effect on entropy by graded increases in N2O concentrations in the presence of a constant concentration of sevoflurane, in the absence of surgical stimulation.Method: This single-blind, randomised study was conducted at an altitude of approximately 1 400 m. Patients received sevoflurane 2% (1.7% at sea level) and N2O, at end-tidal concentrations of 0%, 10%, 20%, 30%, 40%, 50%, 60% or 70% (equivalent to 8.5%, 17%, 25.5%, 34%, 42.6%, 51.1% and 59.6% at sea level). Entropy was measured before, during and after N2O administration. The absolute changes and ratios o f entropy relative to the baseline were calculated. Between- and within-group comparisons were made using analysis of variance and covariance.Results: None of the entropy variables differed significantly within and between groups before and after N2O administration. Within-group analysis revealed that entropy during N2O administration was significantly lower than before or after N2O administration (P 20%) was noted at N2O > 60% (> 51% at sea level).Conclusions: The M-Entropy Module S/5TM responds to increasing concentrations of N2O in the presence of 2% (1.7% at sea level) sevoflurane, in the absence of surgical stimulation. There is a linear relationship between increasing N2O concentrations and decreasing entropy with a steep and clinically important decrease at N2O > 60% (> 51% at sea level). The influence of ambient pressure on the partial pressures, which determine the effects of anaesthetic agents, must be taken into account. Keywords: monitoring; depth of anaesthesia; monitoring; electroencephalography; monitoring; entropy; anaesthetics volatile; sevoflurane; anaesthetic gases; nitrous oxid

Electron energy loss and induced photon emission in photonic crystals

The interaction of a fast electron with a photonic crystal is investigated by solving the Maxwell equations exactly for the external field provided by the electron in the presence of the crystal. The energy loss is obtained from the retarding force exerted on the electron by the induced electric field. The features of the energy loss spectra are shown to be related to the photonic band structure of the crystal. Two different regimes are discussed: for small lattice constants $a$ relative to the wavelength of the associated electron excitations $\lambda$, an effective medium theory can be used to describe the material; however, for $a\sim\lambda$ the photonic band structure plays an important role. Special attention is paid to the frequency gap regions in the latter case.Comment: 12 pages, 7 figure

Are Causality Violations Undesirable?

Causality violations are typically seen as unrealistic and undesirable features of a physical model. The following points out three reasons why causality violations, which Bonnor and Steadman identified even in solutions to the Einstein equation referring to ordinary laboratory situations, are not necessarily undesirable. First, a space-time in which every causal curve can be extended into a closed causal curve is singularity free--a necessary property of a globally applicable physical theory. Second, a causality-violating space-time exhibits a nontrivial topology--no closed timelike curve (CTC) can be homotopic among CTCs to a point, or that point would not be causally well behaved--and nontrivial topology has been explored as a model of particles. Finally, if every causal curve in a given space-time passes through an event horizon, a property which can be called "causal censorship", then that space-time with event horizons excised would still be causally well behaved.Comment: Accepted in October 2008 by Foundations of Physics. Latex2e, 6 pages, no figures. Presented at a seminar at the Universidad Nacional Autonoma de Mexico. Version 2 was co-winner of the QMUL CTC Essay Priz

Composites of resonant dielectric rods: A test of their behavior as metamaterial refractive elements

We report numerical experiments of optical wave propagation in composites of high refractive index dielectric rods at frequencies where their first electric and magnetic Mie resonances are excited. The arrays of these particles have been extensively studied and proposed as non-absorbing and isotropic metamaterials. We show that negative refraction, observed in ordered particle arrays, is due to diffraction and that an effective medium theory yields constitutive parameters that do not reproduce the observations in these composites, whose transmission also depends on the sample shape. This is further confirmed by disordering the arrays, a case in which large transmission losses appear due to extinction by resonant scattering from the particles. Therefore, these composites although little absorbing have large extinction due to scattering

Resolving the ‘Nitrogen Paradox’ of arbuscular mycorrhizas : fertilization with organic matter brings considerable benefits for plant nutrition and growth

Arbuscular mycorrhizal fungi (AMF) can transfer nitrogen (N) to host plants but the ecological relevance is debated, as total plant N and biomass do not generally increase. The extent to which the symbiosis is mutually beneficial is thought to rely on the stoichiometry of N, phosphorus (P) and carbon (C) availability. While inorganic N fertilisation has been shown to elicit strong mutualism, characterised by improved plant and fungal growth and mineral nutrition, similar responses following organic N addition are lacking. Using a compartmented microcosm experiment, we determined the significance to a mycorrhizal plant of placing a 15N‐labelled, nitrogen‐rich patch of organic matter in a compartment to which only AMF hyphae had access. Control microcosms denied AMF hyphal access to the patch compartment. When permitted access to the patch compartment, the fungus proliferated extensively in the patch and transferred substantial quantities of N to the plant. Moreover, our data demonstrate that allowing hyphal access to an organic matter patch enhanced total plant N and P contents, with a simultaneous and substantial increase in plant biomass. Moreover, we demonstrate that organic matter fertilization of arbuscular mycorrhizal plants can foster a mutually beneficial symbiosis based on nitrogen transfer, a phenomenon previously thought irrelevant