Performance of adjustable pressure-limiting (APL) valves in two different modern anaesthesia machines
The ability to gently ventilate a patient's lungs using a self-inflating bag requires a properly working adjustable pressure-limiting (APL) valve. We compared the performance of the APL valves of the GE Aisys CS2 and the Draeger Fabius anaesthetic machines during closure and opening from 1-20 and from 20-1 cmH2O, using standardised experimental baby and adolescent patient lung models. Airway pressures and inspiratory tidal volumes were measured using an ASL-5000 test lung and a GE Aisys CS2 near-patient spirometry sensors. In both lung models, the GE Aisys CS2 APL valves demonstrated non-linear behaviours for airway pressures and for inspiratory tidal volumes, with a sharp increase at set APL pressure levels of 8–10 cmH2O. With further closure of the GE Aisys CS2 APL valves up to 20 cmH2O, inspiratory tidal volumes decreased to ~50% of the highest values measured. Airway pressures in the Draeger Fabius APL valves demonstrated a near linear increase and decrease. Airway pressure values measured in the Draeger Fabius were never higher than those set by the APL valves, whereas in the GE Aisys CS2, they considerably exceeded set pressures (by up to 27 cmH2O). We conclude that the performance of the GE Aisys CS2 APL valve does not allow safe bag-assisted ventilation of a patient's lungs.
A large number of randomised trials authored by Yoshitaka Fujii have been retracted, in part as a consequence of a previous analysis finding a very low probability of random sampling. Dr Yuhji Saitoh co-authored 34 of those trials and he was corresponding author for eight of them. We found a number of additional randomised, controlled trials that included baseline data, with Saitoh as corresponding author, that Fujii did not co-author. We used Monte Carlo simulations to analyse the baseline data from 32 relevant trials in total as well as an outcome (muscle twitch recovery ratios) reported in several. We also compared a series of muscle twitch recovery graphs appearing in a number of Saitoh's publications. The baseline data in 14/32 randomised, controlled trials had p < 0.01, of which seven p values were < 0.001. Eight trials reported four ratios of the time for the return of muscle activity after neuromuscular blockade, the distributions of which were homogeneous: the p values for the observed Q statistics were 0.0055, 0.031, 0.016 and 0.0071. Comparison of graphs revealed multiple coincident or near-coincident curves across a large number of publications, a finding also inconsistent with random sampling. Combining the continuous and categorical probabilities of the 32 included trials, we found a very low likelihood of random sampling: p = 1.27 × 10−8 (1 in 100,000,000). The high probability of non-random sampling and the repetition of lines in multiple graphs suggest that further scrutiny of Saitoh's work is warranted.
The effects of tracheal tube cuffs filled with air, saline or alkalinised lidocaine on haemodynamic changes and laryngotracheal morbidity in children: a randomised, controlled trial
We studied the effects of tracheal tube cuffs filled with air, saline or alkalinised lidocaine on haemodynamic changes during tracheal extubation and postoperative laryngotracheal morbidity in children. We randomly allocated 164 children aged 3–13 years undergoing general anaesthesia to one of four groups; tracheal tube cuffs filled with air (n = 41); saline (n = 41); alkalinised lidocaine 0.5% (n = 41); or alkalinised lidocaine 1% (n = 41). Intracuff pressure was monitored and maintained below 20 cmH2O. The mean (SD) increases in systolic blood pressure after tracheal extubation compared with before extubation were 10.9 (10.8) mmHg, 7.3 (17.7) mmHg, 4.1 (10.5) mmHg and 1.9 (9.5) mmHg in the air, saline, 0.5% and 1% alkalinised lidocaine groups, respectively (p = 0.021). The mean (SD) increases in diastolic blood pressure after tracheal extubation compared with before extubation were 3.9 (9.7) mmHg, 7.9 (14.6) mmHg, 0.7 (10.4) mmHg and 3.6 (6.9) mmHg in the air, saline, 0.5% and 1% alkalinised lidocaine groups, respectively (p = 0.019). The mean (SD) increases in heart rate after tracheal extubation compared with before extubation were 14.2 (7.6) beats.min−1, 15.5 (13.1) beats.min−1, 5.2 (9.6) beats.min−1 and 4.1 (6.6) beats.min−1 in the air, saline, 0.5% and 1% alkalinised lidocaine groups, respectively (p < 0.001). The incidence of sore throat 8 h after tracheal extubation was 22.0% in the air-filled group, 9.8% in the saline group, 4.9% in the 0.5% alkalinised lidocaine group and 2.4% in the 1% alkalinised lidocaine group, p = 0.015. We conclude that filling the tracheal tube cuff with alkalinised lidocaine-filled reduces the haemodynamic response to tracheal extubation and postoperative laryngotracheal morbidity in children.
Neuronal damage biomarkers in the identification of patients at risk of long-term postoperative cognitive dysfunction after cardiac surgery
Biomarkers of neurological injury can potentially predict postoperative cognitive dysfunction. We aimed to identify whether classical neuronal damage-specific biomarkers, including brain fatty acid-binding protein, neuron-specific enolase and S100 calcium-binding protein β, as well as plasma-free haemoglobin concentration as a measure of haemolysis, could be used to predict the risk of long-term cognitive decline after coronary artery bypass grafting with or without cardiopulmonary bypass. We assessed cognitive function using the CogState brief computerised cognitive test battery at 3 months and at 15 months after surgery. Blood samples were obtained pre-operatively, after sternal closure, and at 6 h and 24 h postoperatively. We found signs of cognitive decline at 3 months in 15 of 57 patients (26%), and in 13 of 48 patients (27%) at 15 months. Brain fatty acid-binding protein was already significantly higher before surgery in patients with postoperative cognitive dysfunction at 15 months, with pre-operative plasma levels of 22.8 (8.3–33.0 [0–44.6]) pg.ml−1 compared with 9.7 (3.9–17.3 [0–49.0]) pg.ml−1 in patients without cognitive dysfunction. This biomarker remained significantly higher in patients with cognitive decline throughout the entire postoperative period. At 3 months after surgery, high levels of plasma-free haemoglobin at sternal closure were associated with a negative influence on cognitive performance, as were high baseline scores on neuropsychological tests, whereas a higher level of education proved to beneficially influence cognitive outcome. We found that postoperative cognitive dysfunction at 3 months was associated with cognitive decline at 15 months after surgery, and served as a valuable prognostic factor for declines in individual cognitive performance one year later. Classical neuronal injury-related biomarkers were of no clear prognostic value.
A multicentre snapshot study of the incidence of serious procedural complications secondary to central venous catheterisation
Despite the high number of central venous access devices inserted annually, there are limited data on the incidence of the associated procedural complications, many of which carry substantial clinical risk. This point was highlighted in the recently published Association of Anaesthetists of Great Britain and Ireland ‘Safe vascular access 2016’ guidelines. This trainee-led snapshot study aimed to identify the number of central venous catheter insertions and the incidence of serious complications across multiple hospital sites within a fixed two-week period. Secondary aims were to identify the availability of resources and infrastructure to facilitate safe central venous catheter insertion and management of potential complications. Fifteen hospital sites participated, completing an initial resource survey and daily identification of all adult central venous catheter insertions, with subsequent review of any complications detected. A total of 487 central venous catheter insertions were identified, of which 15 (3.1%) were associated with a significant procedural complication. The most common complication was failure of insertion, which occurred in seven (1.4%) cases. Facilities to enable safer central venous catheter insertion and manage complications varied widely between hospitals, with little evidence of standardisation of guidelines or protocols.
The Universal Anaesthesia Machine (UAM): assessment of a new anaesthesia workstation built with global health in mind
The Universal Anaesthesia Machine has been developed as a complete anaesthesia workstation for use in low- and middle-income countries, where the provision of safe general anaesthesia is often compromised by unreliable supply of electricity and anaesthetic gases. We performed a functional and clinical assessment of this anaesthetic machine, with particular reference to novel features and functioning in the intended environment. The Universal Anaesthesia Machine was found to be reliable, safe and consistent across a range of tests during targeted functional testing.
A feasibility study of awake videolaryngoscope-assisted intubation in patients with periglottic tumour using the channelled King Vision® videolaryngoscope
Airway management in patients with periglottic tumour is a high-risk procedure with potentially serious consequences. There is no consensus on how best to secure the airway in this group of patients. We conducted a feasibility study of awake tracheal intubation using a King Vision® videolaryngoscope with a channelled blade in a cohort of 25 patients, with a periglottic tumour requiring diagnostic or radical surgery. We used 10% and 4% lidocaine to topicalise the airway and midazolam and remifentanil for sedation. We recorded the success rate, number of attempts, time to obtain glottic view, time to intubation and complications. Twenty-three of the 25 patients (92%, 95%CI 75–98%) were intubated with the awake videolaryngoscope-assisted technique, with 17/23 (74%, 95%CI 54–87%) intubations achieved at the first attempt. Five patients required two and one patient, three attempts at intubation. Two patients (8%, 95%CI 2–25%) could not tolerate the procedure due to inadequate topical anaesthesia. Median (IQR [range]) times to obtain glottic view and to intubate were 19 (17–22 [10–30]) s and 49 (42–71 [33–107]) s, respectively. Traces of blood in the airway were observed in 4/25 (16%, 95%CI 6–35%) patients. Although airway management in this group of patients was expected to be difficult, successful awake intubation with the King Vision videolaryngoscope was achieved in the majority of patients within less than a minute. This study highlights a number of potential advantages of awake videolaryngoscope-assisted intubation over other awake methods of securing the airway in patients with upper airway obstruction due to periglottic mass.