Generation of structured light by multilevel orbital angular momentum holograms.

Structured light has been created by a myriad of near-and far-field techniques and has found both classical and quantum applications. In the case of orbital angular momentum (OAM), continuous spiral phase patterns in dynamic or geometric phase are often employed with the phase patterns existing across the entire transverse plane. Here, we exploit the uncertain relationship between OAM and angle in order to create structured OAM fields by using multilevel OAM holograms. We show theoretically and experimentally that only a multilevel angular phase contour in the near-field is needed to create structured OAM light in the far-field, exploiting the reciprocal nature of angular momentum and angle. We use this approach to demonstrate exotic 3D structured light control to show the Poynting vector's evolution in such fields and to highlight the physics underlying this phenomenon.

A comparison of a flexometallic tracheal tube with the intubating laryngeal mask tracheal tube for nasotracheal fibreoptic intubation using the two-scope technique.

We compared the incidence and site of impingement of a flexometallic tracheal tube with those of the re-usable intubating laryngeal mask (ILMA) tube in 60 anaesthetised patients undergoing nasotracheal fibreoptic intubation for oral surgery. A two-scope technique was used, observing the site of impingement with one scope whilst intubating with the other. The tubes were 6.0-mm in females and 6.5-mm in males. Impingement occurred with 10 (33%) flexometallic and 2 (7%) ILMA tubes (p < 0.032). In all but one case, the impingement was posterior to the right arytenoid cartilage. When impingement was observed, a single disempaction with a 90 degrees anticlockwise rotational manoeuvre overcame impingement in every case except one, allowing successful intubation. We conclude that the incidence of impingement of the tracheal tube, and therefore of potential laryngeal trauma from nasotracheal fibreoptic intubation, is significantly greater with the flexometallic tube than with the ILMA tube.

Remifentanil target-controlled infusion vs propofol target-controlled infusion for conscious sedation for awake fibreoptic intubation: a double-blinded randomized controlled trial.

BACKGROUND: Awake fibreoptic intubation (AFOI) is a technique used in patients with difficult airways. This study compares the suitability of remifentanil target-controlled infusion (TCI) to propofol TCI for conscious sedation during AFOI in patients with bona fide difficult airways. METHODS: We recruited 24, ASA I-III patients, who were undergoing sedation for elective AFOI. Patients were randomized to one of the two groups, Group P (n=10) received propofol TCI and Group R (n=14) received remifentanil TCI. Primary outcome measures were conditions achieved at endoscopy, intubation, and post-intubation, which were graded using scoring systems. Other parameters measured were the endoscopy time, intubation time, and number of attempts at intubation. A postoperative interview was conducted to determine recall of events and level of patient satisfaction. RESULTS: Endoscopy scores (0-5) and intubation scores (0-5) were significantly different [Group P 3 (1-4) vs Group R 1 (0-3) P<0.0001, Group P 3 (2-4) vs Group R 1 (0-3) P<0.0001, respectively]; with much better conditions in Group R, endoscopy times and intubation times were also significantly different, being shorter in Group R (P<0.007 and P<0.023, respectively). Patient tolerance of the procedure, judged by the discomfort scores (P<0.004) and the post-intubation scores (P<0.08), was significantly better in Group R. The level of recall for events was higher in Group R. However, there were no significant differences in the patient satisfaction scores. CONCLUSIONS: Remifentanil TCI appears to provide better conditions for AFOI when compared with propofol TCI. The disadvantage of remifentanil in this setting may be a higher incidence of recall.

Antenatal anaesthetic assessment of high-risk pregnancy: a survey of UK practice.

BACKGROUND: Anaesthetists are frequently involved in the management of high-risk pregnancy. Antenatal referral permits time to prepare an appropriate management plan for labour and delivery. This survey looked at current methods of referral in the UK and the role of a formal clinic. METHOD: A postal questionnaire was sent to lead consultant anaesthetists of 256 UK obstetric units enquiring into methods of referral for high-risk pregnancy. RESULTS: Replies were received from 196 units (response rate 77%). Only 30% of units that responded ran a formal anaesthetic pre-assessment clinic, the remaining 70% relying on ad hoc referrals of high-risk cases. Larger units were more likely to run formal clinics. Some units wishing to introduce a formal clinic had not been able to do so because of financial constraints. CONCLUSION: Most hospitals were satisfied with current arrangements for referral of high-risk pregnancy. A mechanism for anaesthetic referral of high-risk pregnancy is vital, but in many units is not via a formal clinic.

The Glidescope system: a clinical assessment of performance.

The Glidescope is a new videolaryngoscope. It has a digital camera incorporated in the blade which displays a view of the vocal cords on a monitor. This allows the placement of a tracheal tube to be visualised. We describe its performance in 50 patients who required orotracheal intubation for elective surgery. Two investigators performed 25 intubations each. Intubation with the Glidescope was successful in 47 of the 50 cases. The three failures occurred early in the series and were attributed to the initial learning curve. The success rate after the first eight patients in each series was 100%. The median (IQR [range]) time to intubation was 40 (30-55 [15-105]) s. The Glidescope provided a grade I view of the glottis in 44 cases and a grade II view in six cases. The view of the larynx was improved in almost half (23) of the cases. The Glidescope improved the view by one grade in 22 and by two grades in one patient. We conclude that the Glidescope is an effective device for tracheal intubation and provides an improved view of the larynx. Further clinical studies are necessary to evaluate its role in airways that are difficult to manage.

Angiotensin-converting enzyme inhibitor related angioedema and the anaesthetist.

Angioedema of the face and neck is an uncommon but potentially life-threatening complication of angiotensin-converting enzyme (ACE) inhibitor therapy. This condition is of particular concern to the anaesthetist as it can rapidly progress to upper airway obstruction. We describe the presentation and management of five cases of ACE inhibitor related angioedema, all of which were associated with significant upper airway obstruction.

Day of surgery cancellations after nurse-led pre-assessment in an elective surgical centre: the first 2 years.

We describe a nurse-led pre-assessment system at an elective surgical centre. A targeted referral system was used by trained nurses to direct referrals to a supervising consultant anaesthetist or to the surgical team. Of 2726 patients pre-assessed in the first 2 years, 105 patients (3.9%) were cancelled or postponed for medical optimisation after pre-assessment. There were 137 cancellations (5.0%) on the day of surgery, despite pre-assessment, but only 36 were for anaesthetic or medical reasons. Only eight of these 36 were considered a 'failure' of the pre-assessment system. These results are much better than the cancellation rate of about 11% in the Trust as a whole. There were 18 transfers of patients postoperatively from the elective centre to another hospital. A review suggested that four of these transfers could have been reasonably predictable from the patients' medical history. We conclude that a pre-assessment clinic has an important role to play in minimizing cancellations on the day of surgery and also in reducing the number of patients transferred to other hospitals. This last conclusion has an important implication for the planning of systems in hospitals that perform only elective surgery.