Search

This paper presents a novel interconnecting approach for the permanent-magnet synchronous generator-based offshore wind farm, where cascaded pulsewidth modulated (PWM) current-source converters (CSCs) are employed on both generator- and grid-side. The total numbers of cascaded PWM CSCs for the onshore grid connection are equal to the number of wind generators installed in the wind farm. The proposed interconnecting method enables simple configuration without the need for a bulky and costly offshore converter substation. Furthermore, a new decoupled control scheme for the independent active and reactive power control with variable dc-link current regulation is developed for the grid-side converters. The key feature of the control scheme is that the minimized dc-link current control is achieved without the use of a long-distance communication link. Both simulation and experimental results are provided to verify the effectiveness of the proposed control scheme. [ABSTRACT FROM PUBLISHER]

Summary Tracheal extubation is a high-risk phase of anaesthesia. The majority of problems that occur during extubation and emergence are of a minor nature, but a small and significant number may result in injury or death. The need for a strategy incorporating extubation is mentioned in several international airway management guidelines, but the subject is not discussed in detail, and the emphasis has been on extubation of the patient with a difficult airway. The Difficult Airway Society has developed guidelines for the safe management of tracheal extubation in adult peri-operative practice. The guidelines discuss the problems arising during extubation and recovery and promote a strategic, stepwise approach to extubation. They emphasise the importance of planning and preparation, and include practical techniques for use in clinical practice and recommendations for post-extubation care. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Oxygen Therapy and Anaesthesia: Too Much of a Good Thing?" in the 2015 issue.

A letter to the editor is presented regarding the use of a flexible intubating fiberscope in placement of gastric tube.

A response by J. J. Pandit and colleagues to a letter to the editor about their article "The Difficult Airway Society 'ADEPT' Guidance on selecting airway devices: the basis of a strategy for equipment evaluation," in the 2011 issue is presented.

A letter to the editor is presented in response to the article "Difficult Airway Society Guidelines for the management of tracheal extubation," by L. Ogilve in 2012 issue.

The Obstetric Anaesthetists' Association and Difficult Airway Society have developed the first national obstetric guidelines for the safe management of difficult and failed tracheal intubation during general anaesthesia. They comprise four algorithms and two tables. A master algorithm provides an overview. Algorithm 1 gives a framework on how to optimise a safe general anaesthetic technique in the obstetric patient, and emphasises: planning and multidisciplinary communication; how to prevent the rapid oxygen desaturation seen in pregnant women by advocating nasal oxygenation and mask ventilation immediately after induction; limiting intubation attempts to two; and consideration of early release of cricoid pressure if difficulties are encountered. Algorithm 2 summarises the management after declaring failed tracheal intubation with clear decision points, and encourages early insertion of a (preferably second-generation) supraglottic airway device if appropriate. Algorithm 3 covers the management of the 'can't intubate, can't oxygenate' situation and emergency front-of-neck airway access, including the necessity for timely perimortem caesarean section if maternal oxygenation cannot be achieved. Table 1 gives a structure for assessing the individual factors relevant in the decision to awaken or proceed should intubation fail, which include: urgency related to maternal or fetal factors; seniority of the anaesthetist; obesity of the patient; surgical complexity; aspiration risk; potential difficulty with provision of alternative anaesthesia; and post-induction airway device and airway patency. This decision should be considered by the team in advance of performing a general anaesthetic to make a provisional plan should failed intubation occur. The table is also intended to be used as a teaching tool to facilitate discussion and learning regarding the complex nature of decision-making when faced with a failed intubation. Table 2 gives practical considerations of how to awaken or proceed with surgery. The background paper covers recommendations on drugs, new equipment, teaching and training. [ABSTRACT FROM AUTHOR]

The effect of Al substitution on Mössbauer signature and hyperfine interaction parameters of copper ferrite (CuFeO) is studied at 300 K. The X-ray powder diffraction pattern analysis shows that all the four compositions of the ferrite system, CuAlFeO ( x = 0.0, 0.2, 0.4, and 0.6), have single-phase fcc spinel structure. On the other hand, Mössbauer spectral analysis reveals that x = 0.0 and 0.2 compositions possess paramagnetic singlet of delafossite (CuFeO) phase along with two magnetic sextets of spinel ferrite phase. On Al substitution for Fe in the system ( x ≥ 0.4), formation of this secondary unwanted phase of CuFeO is found to be prevented. The hyperfine interaction parameters are determined and found to be influenced by Al substitution. The noncollinear spin arrangement in the system is verified and the actual cationic distributions are suggested. [ABSTRACT FROM AUTHOR]

Concise guidelines are presented that relate abnormalities of coagulation, whether the result of the administration of drugs or that of pathological processes, to the consequent haemorrhagic risks associated with neuraxial and peripheral nerve blocks. The advice presented is based on published guidelines and on the known properties of anticoagulant drugs. Four separate Tables address risks associated with anticoagulant drugs, neuraxial and peripheral nerve blocks, obstetric anaesthesia and special circumstances such as trauma, sepsis and massive transfusion. [ABSTRACT FROM AUTHOR]

We reviewed the literature on obstetric failed tracheal intubation from 1970 onwards. The incidence remained unchanged over the period at 2.6 (95% CI 2.0 to 3.2) per 1000 anaesthetics (1 in 390) for obstetric general anaesthesia and 2.3 (95% CI 1.7 to 2.9) per 1000 general anaesthetics (1 in 443) for caesarean section. Maternal mortality from failed intubation was 2.3 (95% CI 0.3 to 8.2) per 100000 general anaesthetics for caesarean section (one death per 90 failed intubations). Maternal deaths occurred from aspiration or hypoxaemia secondary to airway obstruction or oesophageal intubation. There were 3.4 (95% CI 0.7 to 9.9) front-of-neck airway access procedures (surgical airway) per 100000 general anaesthetics for caesarean section (one procedure per 60 failed intubations), usually carried out as a late rescue attempt with poor maternal outcomes. Before the late 1990s, most cases were awakened after failed intubation; since the late 1990s, general anaesthesia has been continued in the majority of cases. When general anaesthesia was continued, a laryngeal mask was usually used but with a trend towards use of a second-generation supraglottic airway device. A prospective study of obstetric general anaesthesia found that transient maternal hypoxaemia occurred in over two-thirds of cases of failed intubation, usually without sequelae. Pulmonary aspiration occurred in 8% but the rate of maternal intensive care unit admission after failed intubation was the same as that after uneventful general anaesthesia. Poor neonatal outcomes were often associated with preoperative fetal compromise, although failed intubation and lowest maternal oxygen saturation were independent predictors of neonatal intensive care unit admission., (Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Guidelines are presented for the organisational and clinical peri-operative management of anaesthesia and surgery for patients who are obese, along with a summary of the problems that obesity may cause peri-operatively. The advice presented is based on previously published advice, clinical studies and expert opinion., (© 2015 The Authors. Anaesthesia published by John Wiley & Sons Ltd on behalf of Association of Anaesthetists of Great Britain and Ireland.)

Intra-operative local anaesthetic infiltration provides good early pain relief after Unicompartmental Knee Replacement (UKR). However, appreciable pain may occur on the day after surgery. The purpose of this double-blinded, prospective randomised controlled trial was to evaluate the effectiveness of a bolus of local intra-articular anaesthetic given early on the day after surgery. Forty-four patients were randomised to receive an intra-articular injection, via an epidural catheter inserted at operation, of either 20 ml 0.5% plain bupivacaine or 20 ml normal saline. All patients received a femoral nerve block with 20 ml prilocaine 1% and local anaesthetic infiltration by the surgeon. Patients injected with bupivacaine had significantly less (p<0.001) pain than control patients immediately (mean pain score 1.82 v 6.1) and 6 hours (2.5 v 5.7) after injection. Patient satisfaction was also significantly greater (p<0.001) in the local anaesthetic group. We conclude that a bolus dose of intra-articular bupivacaine early on the day after surgery dramatically improves pain control after UKR and improves patient satisfaction., (Copyright © 2011 Elsevier B.V. All rights reserved.)

A survey of anaesthetists in the Oxford region was conducted to determine their skills and practice in performing awake fibreoptic intubation. Forty-two consultant obstetric anaesthetists (group O), 21 consultant anaesthetists with an interest in difficult airway management (group D) and 20 anaesthetic specialist registrars in their final training year (group S) were sent a questionnaire on management of a patient with a known difficult airway for elective caesarean section. All but one responded. If regional anaesthesia was unsuccessful or contraindicated, 75/82 respondents (91.5%) would choose to secure the airway by awake intubation. Of the remaining seven, six would use general anaesthesia and spontaneous respiration, five (6.1%) with the laryngeal mask airway and one (1.2%) with mask and airway and one (1.2%) local infiltration by the surgeon. Although awake fibreoptic intubation was the technique chosen by 98.7%, only six (8.1%) had experience of its performance in an obstetric patient. Of the 68 anaesthetists without such experience, only 12/31 (38.7%) group O compared to 13/18 (72.2%) group D and 12/19 (63.2%) group S would be confident to perform awake fibreoptic intubation in an obstetric patient. Only one anaesthetist in the survey practised awake fibreoptic intubation in non-obstetric patients regularly (>3/month). However, 69/82 respondents replied that all consultant obstetric anaesthetists should be experienced in performing awake fibreoptic intubation. We conclude that despite the value of awake fibreoptic intubation, consultant obstetric anaesthetists are less confident in performing it than those with an interest in difficult airway management and final year specialist registrars.

A novel positioning technique was tested to see whether the unpredictability of block height and haemodynamic instability during spinal anaesthesia for caesarean section could be reduced. In this 'Oxford' position, the woman is placed left lateral with an inflated bag under the shoulder and pillows supporting the head. Following spinal injection the woman is turned to an identical right lateral position. This is maintained until just before incision to minimise aorto-caval compression, when she is placed in the wedged supine position. Sixty women undergoing elective caesarean section were randomised to receive spinal anaesthesia using hyperbaric bupivacaine in either the Oxford (group O), or the sitting position followed immediately by the wedged supine position (group S). Ephedrine 6 mg was given every minute that systolic blood pressure was less than 80% of baseline. In group S, 9/30 women lost pinprick sensation up to T4 at 5 minutes compared with 2/30 in group O (chi2 test, P = 0.04). Block height was more variable in group S than in group O (f test, P = 0.001). Blood pressure decreased by a greater amount initially: group S women required more ephedrine (15.5 +/- 12.9 versus 9.2 +/- 7.7 mg, t test, P = 0.03). Block height with spinal anaesthesia for caesarean section is more predictable and haemodynamically stable if the Oxford position is used whilst anaesthesia develops.

The effectiveness of postoperative pain relief and the frequency of side effects with three different doses of epidural diamorphine (2.0, 3.5 and 5 mg) was investigated. The study was carried out double-blind in 30 women undergoing awake elective caesarean section. Postoperative pain intensity was measured on a linear analogue scale. The time to onset of analgesia (TOA), time taken to reach a pain score of zero or become comfortable, and time to next analgesia (TNA) were not significantly different between groups. Three patients in the 2 mg group failed to achieve scores of zero but were comfortable. No nausea or vomiting was seen but the incidence of itching was 0, 30% and 80% in the 2.0, 3.5 and 5 mg groups respectively. We conclude that epidural diamorphine 2 mg is adequate for relief of post-caesarean pain and higher doses may increase the incidence of unwanted side-effects.