Association of Anaesthetists of Great Britain and Ireland: Safe vascular access 2016.

Safe vascular access is integral to anaesthetic and critical care practice, but procedures are a frequent source of patient adverse events. Ensuring safe and effective approaches to vascular catheter insertion should be a priority for all practitioners. New technology such as ultrasound and other imaging has increased the number of tools available. This guidance was created using review of current practice and literature, as well as expert opinion. The result is a consensus document which provides practical advice on the safe insertion and removal of vascular access devices.

Predictive validity of a selection centre testing non-technical skills for recruitment to training in anaesthesia.

BACKGROUND: Assessment centres are an accepted method of recruitment in industry and are gaining popularity within medicine. We describe the development and validation of a selection centre for recruitment to speciality training in anaesthesia based on an assessment centre model incorporating the rating of candidate's non-technical skills. METHODS: Expert consensus identified non-technical skills suitable for assessment at the point of selection. Four stations-structured interview, portfolio review, presentation, and simulation-were developed, the latter two being realistic scenarios of work-related tasks. Evaluation of the selection centre focused on applicant and assessor feedback ratings, inter-rater agreement, and internal consistency reliability coefficients. Predictive validity was sought via correlations of selection centre scores with subsequent workplace-based ratings of appointed trainees. RESULTS: Two hundred and twenty-four candidates were assessed over two consecutive annual recruitment rounds; 68 were appointed and followed up during training. Candidates and assessors demonstrated strong approval of the selection centre with more than 70% of ratings 'good' or 'excellent'. Mean inter-rater agreement coefficients ranged from 0.62 to 0.77 and internal consistency reliability of the selection centre score was high (Cronbach's α=0.88-0.91). The overall selection centre score was a good predictor of workplace performance during the first year of appointment. CONCLUSIONS: An assessment centre model based on the rating of non-technical skills can produce a reliable and valid selection tool for recruitment to speciality training in anaesthesia. Early results on predictive validity are encouraging and justify further development and evaluation.

Multicentre evaluation of the adenosine agonist GR79236X in patients with dental pain after third molar extraction.

BACKGROUND: Adenosine is analgesic in humans, and the selective adenosine A1 receptor agonist GR79236X has significant anti-nociceptive activity in an animal pain model of inflammatory pain. METHODS: Seventy-nine patients with moderate pain after third molar extraction under general anaesthesia were randomized to receive a 15 min double-blind infusion containing either GR79236X 4 microg kg-1, GR79236X 10 microg kg-1, diclofenac 50 mg, or saline placebo. Rescue analgesia was promptly available to all patients. RESULTS: Meaningful pain relief (mild or no pain) was attained by 9 (47%) patients in the placebo group, 12 (63%) patients in the GR79236 4 microg kg-1 group, 10 (48%) patients in the 10 microg kg-1 group, and 16 (80%) patients in the diclofenac 50 mg group. Neither dose of GR79236 produced a significant improvement over placebo, but diclofenac was superior to both placebo (P=0.036) and GR79236 10 microg kg-1 (P=0.034). Median times to rescue or additional analgesia were 62, 100, 60, and 363 min for patients receiving placebo, GR79236 4 microg kg-1, 10 microg kg-1, and diclofenac 50 mg, respectively (diclofenac significantly longer than placebo, P=0.002 log-rank test). Pain control was poor in the placebo group and in both GR79236 groups, with between 79 and 86% of patients having good pain control (i.e. mild or no pain) for <20% of the time compared with only 30% of patients who received diclofenac. CONCLUSION: We found no evidence of efficacy of GR79236 compared with placebo, but the active control diclofenac was effective. It is possible that a higher dose of GR79236 might have been effective or that i.v. administration of this drug does not achieve appropriate concentrations in the brain or peripheral nerves.

Correlating obstetric epidural anaesthesia performance and psychomotor aptitude.

We investigated the correlation between the scores attained on computerised psychometric tests, measuring psychomotor and information processing aptitudes, and learning obstetric epidural anaesthesia. Ten anaesthetic trainees performed an adaptive tracking task (ADTRACK 3) and one information management task (MAZE) from the MICROPAT testing system. They then embarked on a standardised obstetric anaesthesia training programme prior to performing obstetric on-call duties. The success or failure of their first 50 obstetric epidurals was recorded. There was a significant correlation between mean obstetric epidural failure rate for the second 25 consecutive epidurals and ADTRACK 3 (r = -0.579, p = 0.04) scores. The correlation between the means of the first 25 and 50 consecutive epidurals and ADTRACK 3 scores was not significant. There was no significant correlation between epidural failure rate and MAZE scores. The ratios of the mean epidural failure rate for the last 25 epidurals to the mean for the first 25 epidurals were not significantly correlated with ADTRACK 3 or MAZE scores. Psychomotor abilities appear to be poor determinants of trainees' initial proficiency at obstetric epidural anaesthesia or of trainees' rates of progress during early obstetric epidural training, but may be determinants of an individual's performance after the initial training phase.

An investigation into the effects of midazolam and propofol on human respiratory cilia beat frequency in vitro.

OBJECTIVE: Patients in intensive care are known to be prone to both upper and lower respiratory tract infection. Respiratory mucus forms a barrier to infection. Mucus transport rate (MTR) depends upon both the physical properties of mucus and the action of respiratory cilia. Patients undergoing anaesthesia are known to have a reduced MTR that may be related to a depressant effect on cilia beat frequency (CBF) by anaesthetic drugs. The aim of this study was to investigate the effects of two commonly used intensive care sedative agents, midazolam and propofol, on CBF using human nasal turbinate explants in vitro. DESIGN: We exposed ciliated tissue from human nasal turbinate explants to midazolam and propofol in supraclinical concentrations (20 microM midazolam and 70 microM propofol) in a controlled and blinded manner for 90 min and measured CBF by the transmitted light technique. RESULTS: After 90 min, mean (SEM) CBF in the group exposed to midazolam and its control group were 13.0 (0.2) Hz and 12.9 (0.3) Hz, respectively. Mean (SEM) CBF in the group exposed to propofol was 13.6 (0.4) Hz and in the control group the value was 12.0 (0.6) Hz. There was no significant change in CBF (midazolam: p = 0.21, propofol: p = 0.31, MANOVA for repeated measures). CONCLUSIONS: We have found no effect of midazolam or propofol in supra-clinical concentrations upon CBF in human turbinate explants after a 90-min exposure. This contrasts with previous work that has shown a depressant effect of inhalational anaesthetic agents on CBF.

Recovery characteristics using single-breath 8% sevoflurane or propofol for induction of anaesthesia in day-case arthroscopy patients.

We studied the induction and recovery characteristics following inhalational induction with 8% sevoflurane in nitrous oxide and oxygen compared with intravenous propofol in 40 patients presenting for arthroscopy of the knee. Patients were randomly allocated to receive either induction agent, and anaesthesia was then maintained with sevoflurane in oxygen and nitrous oxide. A computerised test of hand--eye co-ordination and a p-deletion test were used to measure psychomotor recovery. The sevoflurane group had a faster onset of anaesthesia time. No significant differences between the groups were found in time to eye opening or psychomotor tests. Nausea and vomiting scores were significantly higher at 30 min in the sevoflurane group (p = 0.04); this difference was no longer significant by 90 min. We conclude that inhalational induction with sevoflurane in these patients has no important clinical advantages and causes more nausea and vomiting than propofol.

The site of airway irritation during induction of anaesthesia.

The aim of this investigation was to study the role of the nasal airway in mediating upper airway reflexes during induction of anaesthesia when the commonly used irritant inhalational anaesthetic agent enflurane is used. In a prospective randomised study, 40 ASA 1 & 2 day-case patients undergoing body surface surgery were recruited. Following intravenous induction using propofol, 20 patients received enflurane administered via a laryngeal mask airway (LMA), the anaesthetic vapour therefore bypassing the nasal airway. In the other group, 20 patients received enflurane anaesthesia administered using a face mask, the nasal airway therefore being exposed to inhalation anaesthetic. We were unable to demonstrate any significant (p < 0.05) differences between the two groups in relation to upper airway complications (cough, breath holding, laryngeal spasm, bronchospasm and excitement). Previous work has identified the nose as a possible important reflexogenic site for upper airway reflexes in humans during anaesthesia. We have been unable to demonstrate any difference in upper airway complications when the nasal airway was included or excluded from exposure to irritant anaesthetic vapours, when administered in a clinical setting.

Effect of an upper respiratory tract infection on upper airway reactivity.

Patients presenting for elective anaesthesia and surgery may be suffering with, or recovering from, a recent upper respiratory tract infection (URTI). It is a frequent clinical problem as to whether to postpone surgery in such patients as they may be more likely to suffer adverse respiratory events related to administration of general anaesthesia. Using dilute ammonia vapour as a chemical stimulus, we measured upper airway reactivity in 11 healthy volunteers (six males), mean age 39.8 (range 30-58) yr, who had symptoms of an URTI. Volunteers were recruited 24-72 h after symptoms first began, and followed-up at regular intervals for the next 8 weeks. Measurements of upper airway reactivity were made on the following days (+/- 24h) after commencement of URTI symptoms: 3, 6, 9, 15, 20 and 27. Additional measurements were obtained 56 days after symptoms first began, and these were regarded as baseline measurements. Upper airway reactivity was increased on days 3, 6 and 9 compared with baseline measurements (P < 0.01, Wilcoxon). There was no significant change in airway reactivity from day 15 onwards, by which time 10 of the 11 subjects were completely devoid of symptoms. All subjects were asymptomatic by day 20 and remained so until the study ended on day 56. We conclude that upper airway reactivity was increased during the acute phase of an URTI, and that this appeared to be related to the presence of symptoms.

Effect of nebulised lignocaine on the quality of induction of anaesthesia in cigarette smokers.

We have assessed the effect of nebulised lignocaine, given pre-operatively, upon the quality of induction of anaesthesia in cigarette smokers. Seventy-five patients were studied in a double-blind randomised fashion, receiving a nebuliser of either 4 ml 0.9% NaCl or 4 ml 4% lignocaine. All patients received a standardised anaesthetic consisting of thiopentone followed by progressive increments of enflurane. Thirty-three out of 38 patients (87%) who received nebulised lignocaine had induction without adverse events, compared with 25 out of 37 patients (68%) in the nebulised saline group (Chi-squared test p < 0.05). We conclude that the use of nebulised lignocaine, administered pre-operatively, improves the quality of induction of anaesthesia in cigarette smokers.

Recovery of respiratory ciliary function after depression by inhalation anaesthetic agents: an in vitro study using nasal turbinate explants.

We have developed a human tissue preparation suitable for measurement of cilia beat frequency derived from nasal turbinates. Cilia beat frequency of turbinate explants from 11 patients did not change significantly over a 10-day observation period while maintained in an incubator, with mean cilia beat frequency of 13.1 (SEM 0.3) Hz to 14.4 (0.2) Hz (ANOVA for repeated measures, P = 0.168). We have used this preparation to investigate recovery of ciliary function after depression by inhalation anaesthetic agents. Eight or nine turbinate explants were exposed to three times the minimum alveolar concentration (MAC) of halothane, enflurane or isoflurane for a period of 1 h and thereafter to a period of air washout. After exposure to the inhalation agent there was a significant reduction in cilia beat frequency with all three agents: halothane 14.3 (0.4) Hz to 9.5 (0.3) Hz; enflurane 13.7 (0.6) Hz to 10.5 (0.5) Hz;isoflurane 15.9 (0.6) Hz to 10.6 (0.3) Hz. Cilia beat frequency returned to values after air washout that were not significantly different from baseline after 90 min of washout of halothane and 60 min of washout of enflurane and isoflurane (repeated measures ANOVA, unpaired t test; P = 0.01 at 60 min and P = 0.31 at 90 min washout for halothane; P = 0.83 at 60 min washout for enflurane; P = 0.26 at 60 min washout for isoflurane).

Effects of topical benzocaine and lignocaine on upper airway reflex sensitivity.

We studied the degree and duration of effect on upper airway reflex sensitivity of oral benzocaine lozenges, nebulised lignocaine and lignocaine sprayed onto the vocal cords under direct vision, using low concentrations of ammonia as a stimulus to upper airway receptors. Ten minutes after the administration of oral benzocaine 20 mg the threshold response of the upper airway to ammonia (NH3TR) had risen significantly from baseline mean (SEM) of 680 (95) to 975 (109) ppm of ammonia with a return to baseline values after 25 min (n = 8, p < 0.05, repeated measures of ANOVA; p < 0.001, t-test). A direct spray of lignocaine 100 mg onto the vocal cords resulted in a significant elevation in NH3TR from a baseline mean (SEM) of 665 (81) to a maximum of 1600 (88) ppm of ammonia with a significant elevation in the threshold persisting for 100 min (n = 7, p < 0.001, repeated measures of ANOVA; p < 0.05, t-test). The application of 4% nebulised lignocaine 4 ml significantly increased NH3TR from a baseline mean (SEM) of 770 (56) to a maximum of 1190 (63) ppm of ammonia with a significant elevation in the threshold persisting for 30 min (n = 8, p < 0.001, repeated measures of ANOVA; p < 0.05, t-test). The maximum elevations in NH3TR with the two methods of lignocaine delivery were significantly different (p < 0.01, 2-way ANOVA).

Effects of morphine on human nasal cilia beat frequency in vitro.

Using human nasal cytological brushings, we have investigated the effects of morphine on ciliary function by measurement of cilia beat frequency in vitro, and we have also determined opioid receptor binding in these specimens. We obtained ciliated samples from seven volunteers, and measured cilia beat frequency using the transmitted light technique during exposure to morphine 10 mumol litre-1 for 4 h. Mean cilia beat frequency of the samples exposed to morphine was 11.1 (95% confidence interval 10.9-11.5) Hz and that of the controls 11.3 (11.1-11.7) Hz. There was no significant effect of morphine on human cilia beat frequency in vitro (MANOVA for repeated measures and nested, F = 0.61, P = 0.66). In a separate study, we obtained nasal brushings from 20 patients and measured the binding of the opioid antagonist tritiated diprenorphine ([3H]DPN). Mean disintegrations per minute (dpm) for total and non-specific binding were 9036 (8105-9967) dpm and 9130 (8054-10206) dpm, respectively. These values did not differ significantly (paired t test, t = 0.22, P = 0.83). We conclude that morphine had no effect on cilia beat frequency in vitro and we were unable to demonstrate any significant numbers of opioid receptors on nasal ciliated epithelium.

A perfusion system for in vitro measurement of human cilia beat frequency.

We have designed and built a perfusion system and perfusion chamber to allow investigation of the effects of anaesthetic agents on human cilia in vitro. Using this system, samples of human respiratory cilia can be maintained in a stable and controlled environment for several hours. We measured cilia beat frequency of nasal respiratory epithelium from 10 healthy volunteers; cilia beat frequency was constant over a 4-h period, and measurements were found to be in good agreement with previously published work [1]. In a separate study we investigated the effect of a sleep dose of propofol on cilia beat frequency in samples from six patients undergoing minor surgery; samples were obtained before and immediately after induction of anaesthesia with propofol 2-3 mg kg-1. There was no statistically significant difference in cilia beat frequency between data obtained before and after induction with propofol.

Effects of 3 MAC of halothane, enflurane and isoflurane on cilia beat frequency of human nasal epithelium in vitro.

We have measured the effects of three times the minimum alveolar concentration (MAC) of halothane, enflurane and isoflurane on cilia beat frequency of human nasal epithelial brushings from 18 healthy adult patients. Using the transmitted light technique and paired perfusion chambers, the cilia were exposed to 2.25% halothane, 5% enflurane or 3.6% isoflurane in air, or air alone, in a controlled and blinded manner. Over a 4-h observation period, cilia beat frequency of the samples exposed to inhalation anaesthetic agents demonstrated a significant reduction in frequency compared with controls exposed to air alone. Mean cilia beat frequency for the samples exposed to halothane was 9.3 (SEM 1.3) compared with its controls of 11.4 (1.0); for the samples exposed to enflurane, 10.9 (1.3) compared with its controls of 11.6 (1.2); and for the samples exposed to isoflurane, 10.8 (1.1) compared with its controls of 11.6 (1.2). There was a statistically significant difference between the samples exposed to all three volatile agents and their associated controls (halothane, P = 0.01; enflurane, P = 0.03; isoflurane, P = 0.01; nested repeated measures analysis of variance utilizing polynomial contrasts).

Postoperative laryngeal competence. The laryngeal mask airway and tracheal tube compared.

We investigated the incidence of postoperative laryngeal incompetence in 40 patients undergoing lower limb arthroplasty. Patients were randomly allocated to one of two groups using a standardised general anaesthetic/muscle relaxant technique; in group A the patients' lungs were ventilated via a laryngeal mask airway and in group B via a tracheal tube. Following recovery from general anaesthesia, at a time when patients were considered safe for discharge back to the general ward, they were asked to swallow 20 ml of barium, and an immediate portable chest X ray was taken. The X rays were examined for evidence of tracheopulmonary aspiration. Contrary to previous studies the incidence of aspiration was low, occurring in only one patient. This aspiration was, however, clinically silent. The exact mechanism of this apparent laryngeal incompetence, which occurred in a patient from the tracheal tube group, is unclear. Due to the relatively small numbers of patients studied no conclusions can be drawn about the relative benefits of the use of the laryngeal mask airway with regard to postoperative laryngeal competence.

The output of an 'empty' Tec 3 vaporizer.

The output of 30 Tec 3 vaporizers (halothane, enflurane and isoflurane) was studied, starting at the point where no liquid was visible in the content window. At 6 l.min-1 and 1% v/v initial output, consistent delivery was on average maintained for in excess of 90 (range 55-120) min. Thereafter, output declined rapidly. At the flows and concentrations studied there is a significant reserve in the vaporizing chamber, but it is likely that when higher flows and concentrations are used this reserve may be substantially reduced.