Magill Department of Anaesthesia, Intensive Care and Pain Management, Chelsea & Westminster Hospital, London, UK

We found the new Association of Anaesthetists of Great Britain and Ireland guidelines for intra-operative cell salvage informative and useful [1]. However, we would like to draw attention to an important omission regarding the use of cell salvage in obstetric haemorrhage. The predominant concern in this setting has been the risk of re-infusing amniotic fluid into the maternal circulation thus precipitating amniotic fluid embolus syndrome. This syndrome is poorly understood but current theories include the idea that fetal material within the amniotic fluid initates a severe anaphylactoid reaction. Although these concerns were discussed in the Anaesthetists of Great Britain and Ireland guideline document, no mention was made of the techniques commonly used to diminish the risk of re-infusing fetal and amniotic fluid contaminants. These were detailed in a recent review article on cell salvage in obstetrics [2]. We advocate using a separate suction system at the time of amniotic membrane rupture until there is complete delivery of the fetus and placenta at caesarean section, in order to minimise amniotic fluid contamination of the collected blood. We also advocate the use of a leucodepletion filter when re-infusing salvaged red cells. Use of a Pall RS leucodepletion filter (Pall Medical, Portsmouth UK) significantly reduces levels of fetal squames, phospholipids and bacterial contamination in centrifuged, washed blood [3]. The current National Institute for Health and Clinical Excellence guidelines, Intraoperative Blood Cell Salvage in Obstetrics [4], state that ‘a leucocyte depletion filter is nearly always used in this process to reduce the amount of amniotic fluid contaminants in transfused blood to levels approaching those found in maternal blood.’ There is growing experience in the use of intra-operative cell salvage in obstetric haemorrhage, with reassuringly few reports of adverse incidents and no convincing cases of amniotic fluid embolus syndrome. In occasional cases of very massive obstetric haemorrhage it may be reasonable to forgo the use of a leucocyte depletion filter to maximise the speed of transfusion. However, in the majority of cases, we feel that it is unwise to overlook such a simple and commonly-used technique aimed at preventing a rare, but devastating, complication.

Background: We assessed the effect of warming intravenous fluids during elective caesarean section under combined spinal-epidural anaesthesia in a blinded, randomised controlled trial.Method: Seventy-five women having elective caesarean section were randomly assigned to receive all intravenous fluids at room temperature, or heated in a cabinet set at 45 degrees C or via a Hotline (R) fluid warmer (Smiths Medical International Ltd, Watford, Herts, UK). After 10 mL/kg crystalloid preload, combined spinal-epidural anaesthesia was performed. Core and ambient temperatures, thermal comfort and shivering were measured every 15 min thereafter. The primary outcome was the temperature at 60 min.Results: Temperature decreased in all groups. Although the temperature decrease at 60 min was similar in the heated cabinet and Hotline (R) groups, the room temperature group exhibited a greater decrease [difference 0.4 degrees C (95% CI 0.2-0.6 degrees C); P = 0.015]. More women felt cold in the room temperature group (8: 32%) than in the heated cabinet set (3: 12%) and Hotline (R) (1: 4%) groups (P = 0.02), but the incidence of shivering was similar: 11 (44%), 9 (36%) and 7 (28%) respectively. Apgar scores and neonatal cord gases were similar.Conclusion: Warming intravenous fluids mitigates the decrease in maternal temperature during elective caesarean section under combined spinal-epidural anaesthesia and improves thermal comfort, but does not affect shivering. Intravenous fluids should be warmed routinely in elective caesarean section, especially for cases of expected long duration, but the use of pre-warmed fluids is as efficient and cheaper than using a Hotline (R) fluid warmer. (C) 2009 Elsevier Ltd. All rights reserved.

We contacted the duty obstetric anaesthetist in 219 of the 220 consultant-led maternity units in the UK (99.5%) and asked about departmental and individual practice regarding temperature management during Caesarean section. Warming during elective Caesarean section was routine in 35 units (16%). Intravenous fluid warmers were available in 213 units (97%), forced air warmers were available in 211 (96%) and warming mattresses were available in 42 (19%). Only 18 (8%) departments had specific guidelines for temperature management during Caesarean section. Personal intra-operative practice was variable, although all of those contacted would initiate some form of active temperature management after a mean (SD) volume of blood loss of 1282 (404) ml, length of surgery of 78 (24) min, or core body temperature (if measured) of median (IQR [range]), 36 (35.5-36 [34-37.2]) degrees C.

We report Larmor precession in bulk InSb observed up to 300K in the time domain by means of the circularly polarized pump-probe technique. We show that provided we include only the dilational change of the energy gap with temperature, we obtain reasonable agreement between experiment and k.p theory for the high temperature g-factor in InSb.

Background: Lidocaine-bicarbonate-adrenal in e mixtures are commonly used for epidural bolus doses for emergency caesarean section. Previous research has shown that adrenaline degrades completely 24 h after mixing. Anecdotal enquiries suggest that anaesthetists who use such mixtures commonly prepare the solution ahead of use, despite a lack of data about its stability between 0 and 24 h. The aim of this study was to monitor the degradation of adrenaline in the above mixture over 20 h.Methods: 2 mL of sodium bicarbonate 8.4% was added to 20 mL of 2% lidocaine; 2 mL of this mixture was discarded and 0.1 mL of adrenaline 1:1000 added. The mixtures were stored in plastic syringes at 24 degrees C unprotected from light (n = 3) or in the dark (n = 3). Non-alkalinised controls were also prepared. Adrenaline and lidocaine were assayed by high performance liquid chromatography at 0, 2, 4, 6 and 20 It.Results: In the bicarbonated mixture exposed to light, chemical degradation of adrenaline was fast at room temperature, only 73.0 +/- 3.6% of adrenaline remaining after 6 It. In the dark, the stability of adrenaline improved and 95.8 +/- 3.6% remained after 6 h. Negligible degradation occurred in the absence of bicarbonate in either condition. Lidocaine concentrations remained unchanged regardless of the storage conditions.Conclusions: This study suggests that preparation of pH-adjusted lidocaine-adrenaline mixtures in advance and prolonged storage in the light is inadvisable. (c) 2008 Elsevier Ltd. All rights reserved.

We have used time resolved spectroscopy to measure the relaxation of spin polarisation in InSb/AlInSb quantum wells as a function of temperature and mobility. The results are consistent with the degenerate D'Yakonov-Perel (DP) mechanism over the temperature range from 77K to 300K. The spin-diffusion length in this regime is shown to rise with well width and band gap, but is independent of density, mobility and spin lifetime, the effects of which cancel out.

The safety of cell salvage in obstetrics has been questioned because of the presumed risk of precipitating amniotic fluid embolism and, to a lesser extent, maternal alloimmunisation. For these reasons, experience in this field is limited and has lagged far behind that in other surgical specialties. There has, however, been renewed interest in its use over recent years, mainly as a result of problems associated with allogeneic blood transfusion. Our aim was to review the medical literature to ascertain the principles of cell salvage, the ability of the process to remove contaminants, and its safety profile in the obstetric setting. The search engines PubMed and Google Scholar were used and relevant articles and websites hand searched for further references. Existing cell salvage systems differ in their ability to clear contaminants and all require the addition of a leucocyte depletion filter. Although large prospective trials of cell salvage with autotransfusion in obstetrics are lacking, to date, no single serious complication leading to poor maternal outcome has been directly attributed to its use. Cell salvage in obstetrics has been endorsed by several bodies based on current evidence. Current evidence supports the use of cell salvage in obstetrics, which is likely to become increasingly commonplace, but more data are required concerning its clinical use.

Obstetric Anesthesia Digest: December 2008 - Volume 28 - Issue 4 - p 239-241 doi: 10.1097/01.aoa.0000337939.48900.9f

Epidural mixtures containing lidocaine with or without additives are commonly used to convert epidural analgesia in labour to anaesthesia for emergency Caesarean section, but direct comparisons with alternative, single agents in this situation are few. In a prospective double-blinded trial, we compared a freshly prepared lidocaine-bicarbonate-adrenaline mixture (final concentrations 1.8%, 0.76% and 1:200,000, respectively) with our standard agent, levobupivacaine 0.5%, for extending epidural blockade for emergency Caesarean section. Using a sequential analysis technique, with data analysed in blocks of 40, women receiving epidural analgesia in labour who required top-up for Caesarean section were randomly assigned to receive 20 ml of epidural solution over 3 min. The first analysis (n = 40) indicated that the study should be stopped, as significant differences were found in our primary outcome data. Median (IQR [range]) times to reach a block to touch to T5 and cold to T4 were, respectively, 7 (6-9 [5-17]) min and 7 (5-8 [4-17]) min for lidocaine-bicarbonate-adrenaline, and 14 (10 -17 [9-31]) min and 11 (9-14 [6-30]) min for levobupivacaine (p = 0.00004 and 0.001, respectively). Pre- and intra-operative supplementation/pain, maternal side-effects and neonatal outcomes (excluding five women who underwent instrumental delivery) were similar between the groups. Intra-operative maternal sedation (scored by the mother on a 10-point scale) was greater with lidocaine-bicarbonate-adrenaline (4.5 (3-8 [1-9])) than with levobupivacaine (3 (1-4 [1-7])), but not significantly so (p = 0.07). We conclude that epidural lidocaine-bicarbonate-adrenaline halves the onset time when extending epidural analgesia for Caesarean section although there is a possibility of increased maternal sedation.

We report on investigation of the spin dynamics in InAs and InSb films grown on GaAs at a temperature range from 77 K to 290 K. For both materials, the large lattice mismatch with the GaAs substrate results in the formation of an interface accumulation layer with a large defect concentration, which strongly affects the spin relaxation in these areas. Moreover, the native surface defect in the InAs films resulted in an additional charge accumulation layer with high conductivity, but very short spin lifetime. In contrast, in InSb layers, the surface states introduce a depletion region. We have correlated the spin relaxation with a multi-layer analysis of the transport properties, and find that in a 1 μm thick InAs film, approximately 70% of the total current flows through the interface and surface accumulation layers, which have sub-picosecond lifetimes, whereas in InSb films of the same thickness, the semiconducting layer carries more than 90% of the total current, and the spin lifetime in the accumulation layer is only slightly less than that of the central semiconducting layer. We suggest that InSb could be a more attractive candidate for spintronic applications than InAs.

The spin relaxation in undoped InSb films grown on GaAs has been investigated in the temperature range from 77to290K. Two distinct lifetime values have been extracted, 1 and 2.5ps, dependent on film thickness. Comparison of this data with a multilayer transport analysis of the films suggests that the longer time (∼2.5ps at 290K) is associated with the central intrinsic region of the film, while the shorter time (∼1ps) is related to the highly dislocated accumulation region at the film-substrate interface. Whereas previous work on InAs films grown on GaAs showed that the native surface defect resulted in an additional charge accumulation layer with high conductivity but very short spin lifetime, in InSb layers the surface states introduce a depletion region. We infer that InSb could be a more attractive candidate for spintronic applications than InAs.

Optical waveguides containing high percentages of colloidal nanocrystals have been fabricated by layer-by-layer deposition on planar and patterned glass substrates. The two- and one-dimensional waveguidings in these structures are demonstrated by propagation loss experiments. The experimental results obtained for various film thicknesses and widths of the waveguide stripes together with simulations of the light propagation indicate that the losses are dominated by surface roughness. The variable stripe length method is used to determine the optical gain of 230cm−1 from the amplified spontaneous emission. This high value makes the authors’ waveguide structures very promising for applications in amplifiers and lasers with reduced threshold powers.

We report investigation of the spin relaxation in InAs films grown on GaAs at a temperature range from 77 K to 290 K. InAs is known to have a surface accumulation layer and the depth profile of the concentration and mobility is strongly nonuniform. We have correlated the spin relaxation with a multilayer analysis of the transport properties and find that the surface and the interface with the GaAs substrate both have subpicosecond lifetimes (due to the high carrier concentration), whereas the central semiconducting layer has a lifetime of an order of 10 ps. Even for the thickest film studied (1 mu m), the semiconducting layer only carried 30% of the total current (with 10% through the interface layer and 60% through the surface accumulation layer). Designs for spintronic devices that utilize InAs, which is attractive due to its narrow gap and strong Rashba effect, will need to include strategies for minimizing the effects of the surface.

We have used time resolved spectroscopy to measure the relaxation of spin polarization in InSb/AlInSb quantum wells (QWs) as a function of temperature and mobility. The results are consistent with the D'yakonov - Perel (DP) mechanism for high mobility samples over the temperature range from 50 to 300 K. For low mobility samples at high temperature the Elliott - Yafet and DP mechanisms become comparable. We show that the mobility can in certain circumstances determine which mechanism is dominant, and that above 1 m(2) V-1 s(-1) in 20 nm wide InSb QWs it is the DP mechanism. We also give a criterion for the maximum spin lifetime in terms of mobility and temperature, and show that for our 20 nm wide QWs this corresponds to 0.5 ps at 300 K and mobility 1 m(2) V-1 s(-1).

We investigate the evolution of short-duration pulses injected into laser diodes biased above threshold with the use of spectrally and temporally resolved experimental and numerical methods. We show that stable transients may be formed as a result of spatially re-distributing the cavity energy. By controlling the phase of injected pulses with respect to the diode cavity radiation we show through simulation that it is possible to directly generate and control stable streams of pulses.