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Wiley Online Library : Anaesthesia
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The association of abdominal muscle with outcomes after scheduled abdominal aortic aneurysm repair

25. July 2017 - 10:15
Summary

Sarcopenia is the degenerative loss of core muscle mass. It is an aspect of frailty, which is associated with increased rates of peri-operative harm. We assessed the association of the cross-sectional areas of abdominal muscles, including psoas, with survival during a median (IQR [range]) follow-up of 3.8 (3.2–4.4 [0.0–5.1]) years after scheduled endovascular (132) or open (5) abdominal aortic aneurysm repair in 137 patients. In multivariate analysis, mortality hazard (95%CI) was independently associated with: age, 1.06 (1.01–1.13) per year, p = 0.03; and the adjusted area of the left psoas muscle, 0.94 (0.81–1.01) per mm2.kg−0.83, p = 0.08. Shortened hospital stay was independently associated with haemoglobin concentration and adjusted left psoas muscle area, hazard ratio (95%) 1.01 (1.00–1.02) per g.l−1 and 1.05 (1.02–1.07) per mm2.kg−0.83, p = 0.04 and 0.001, respectively.

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A network meta-analysis of the clinical properties of various types of supraglottic airway device in children

24. July 2017 - 12:12
Summary

We conducted both conventional pairwise and Bayesian network meta-analyses to compare the clinical properties of supraglottic airway devices in children. We searched six databases for randomised clinical trials. Our primary end-points were oropharyngeal leak pressure, risk of insertion failure at first attempt, and blood staining risk. The risk of device failure, defined as the abandonment of the supraglottic airway device and replacement with a tracheal tube or another device, was also analysed. Sixty-five randomised clinical trials with 5823 participants were identified, involving 16 types of supraglottic airway device. Network meta-analysis showed that the i-gel™, Cobra perilaryngeal airway™ and Proseal laryngeal mask airway (LMA®-Proseal) showed statistically significant differences in oropharyngeal leak pressure compared with the LMA®-Classic, with mean differences (95% credible interval, CrI) of 3.6 (1.9–5.8), 4.6 (1.7–7.6) and 3.4 (2.0–4.8) cmH2O, respectively. The i-gel was the only device that significantly reduced the risk of blood staining of the device compared with the LMA-Classic, with an odds ratio (95%CrI) of 0.46 (0.22–0.90). The risk (95%CI) of device failure with the LMA-Classic, LMA®-Unique and LMA-Proseal was 0.36% (0.14–0.92%), 0.49% (0.13–1.8%) and 0.50% (0.23–1.1%), respectively, whereas the risk (95%CI) of the i-gel and PRO-Breathe was higher, at 3.4% (2.5–4.7%) and 6.0% (2.8–12.5%), respectively. The risk, expressed as odds ratio (95%CrI), of insertion failure at first attempt, was higher in patients weighing < 10 kg at 5.1 (1.6–20.1). We conclude that the LMA-Proseal may be the best supraglottic airway device for children as it has a high oropharyngeal leak pressure and a low risk of insertion. Although the i-gel has a high oropharyngeal leak pressure and low risk of blood staining of the device, the risk of device failure should be evaluated before its routine use can be recommended.

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The association between peri-operative acute risk change (ARC) and long-term survival after cardiac surgery

13. July 2017 - 6:10
Summary

Acute risk change has been described as the difference in calculated mortality risk between the pre-operative and postoperative periods of cardiac surgery. We aimed to assess whether this was associated with long-term survival after cardiac surgery. We retrospectively analysed 22,570 cardiac surgical patients, with minimum and maximum follow-up of 1.0 and 6.7 years. Acute risk change was calculated as the arithmetic difference between pre- and postoperative mortality risk. ‘Rising risk’ represented an increase in risk from pre- to postoperative phase. The primary outcome was one-year mortality. Secondary outcomes included mortality at 3 and 5 years and time to death. Univariable and multivariable analyses were undertaken to examine the relationship between acute risk change and outcomes. Rising risk was associated with higher mortality (5.6% vs. 3.5%, p < 0.001). After adjusting for baseline risk, rising risk was independently associated with increased 1-year mortality (OR 2.6, 95%CI 2.2–3.0, p < 0.001). The association of rising risk with long-term survival was greatest in patients with highest baseline risk. Cox regression confirmed rising risk was associated with shorter time to death (HR 1.86, 1.68–2.05, p < 0.001). Acute risk change may represent peri-operative clinical events in combination with unmeasured patient risk and noise. Measuring risk change could potentially identify patterns of events that may be amenable to investigation and intervention. Further work with case review, and risk scoring with shared variables, may identify mechanisms, including the interaction between miscalibration of risk and true differences in peri-operative care.

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Arterial to end-tidal carbon dioxide difference in children undergoing mechanical ventilation of the lungs during general anaesthesia

11. July 2017 - 12:21
Summary

Capnography (ETCO2) is routinely used as a non-invasive estimate of arterial carbon dioxide (PaCO2) levels in order to modify ventilatory settings, whereby it is assumed that there is a positive gap between PaCO2 and ETCO2 of approximately 0.5 kPa. However, negative values (ETCO2 > PaCO2) can be observed. We retrospectively analysed arterial to end-tidal carbon dioxide differences in 799 children undergoing general anaesthesia with mechanical ventilation of the lungs in order to elucidate predictors for a negative gap. A total of 2452 blood gas analysis readings with complete vital sign monitoring, anaesthesia gas analysis and spirometry data were analysed. Mean arterial to end-tidal carbon dioxide difference was −0.18 kPa (limits of 95% agreement −1.10 to 0.74) and 71.2% of samples demonstrated negative values. The intercept model revealed PaCO2 to be the strongest predictor for a negative PaCO2-ETCO2 difference. A decrease in PaCO2 by 1 kPa resulted in a decrease in the PaCO2-ETCO2 difference by 0.23 kPa. This study demonstrates that ETCO2 monitoring in children whose lungs are mechanically ventilated may paradoxically lead to overestimation of ETCO2 (ETCO2 > PaCO2) with a subsequent risk of unrecognised hypocarbia.

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Ultrasonographic gastric volume before unplanned surgery

11. July 2017 - 12:21
Summary

We aimed to measure gastric antral cross-sectional area with ultrasound and estimate the gastric volume of 300 patients before unplanned surgery, fasted for at least six hours. Measurements were successfully recorded in 263 semi-recumbent patients. The median (IQR [range]) area was 333 (241–472 [28–1803]) mm2 and the mean (SD) estimated volume was 45.8 (34.0) ml. The area exceeded 410 mm2 in 92/263 (35%) measurements. Body mass index and morphine administration were associated with larger gastric areas on multivariable linear regression analysis, with beta coefficient (95%CI) 0.02 (0.01–0.04), p = 0.01, 0.23 (0.01–0.46), p = 0.04, respectively. Fasting time was not associated with gastric area and therefore could not substitute for ultrasound measurements in this cohort.

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Strength of commonly used spinal needles: the ability to deform and resist deformation

11. July 2017 - 12:21
Summary

We investigated the strength of commonly used spinal needles in relation to the amount of deformation, and registered forces during standardised testing. We investigated differences between manufacturers for the same length and gauge of Luer and non-Luer needles, and examined the effect of the internal stylet in terms of needle strength. A specialised rig was designed to perform the testing in both the horizontal and axial plane, reflecting common industrial tests and clinical use. Needles from four commonly used manufacturers were used (Vygon, Becton Dickinson, B Braun, and Pajunk). Needles of 25 G and 27 G were tested in 90-mm and 120-mm lengths. We found significant differences in terms of the size of final deformation and ‘toughness’/resistance to deformation between needles of different brands. There were also significant differences between horizontal tests conducted as an industry standard and our own axial test. This may have bearing on clinical use in terms of the incidence of bending and breakage. The presence of the internal stylet resulted in significantly greater toughness in many needles, but had little effect on the degree of deformation. Comparison of Luer and non-Luer needles of the same brand and size showed few significant differences in strength. This result is reassuring, given the imminent change from Luer to non-Luer needles that is to occur in the UK.

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Optimising Glidescope performance

11. July 2017 - 8:47
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Patient-controlled analgesia with remifentanil vs. alternative parenteral methods for pain management in labour: a Cochrane systematic review

11. July 2017 - 8:47
Summary

We aimed to assess the effectiveness of remifentanil used as intravenous patient-controlled analgesia for the pain of labour. We performed a systematic literature search in December 2015 (updated in December 2016). We included randomised, controlled and cluster-randomised trials of women in labour with planned vaginal delivery receiving patient-controlled remifentanil compared principally with other parenteral and patient-controlled opioids, epidural analgesia and continuous remifentanil infusion or placebo. The primary outcomes were patient satisfaction with pain relief and the occurrence of adverse events for mothers and newborns. We assessed risk of bias for each included study and applied the GRADE approach for the quality of evidence. We included total zero event trials, using a constant continuity correction of 0.01 and a random-effect meta-analysis. Twenty studies were included in the qualitative analysis; within these, 3713 participants were randomised and 3569 analysed. Most of our pre-specified outcomes were not studied in the included trials. However, we found evidence that women using patient-controlled remifentanil were more satisfied with pain relief than women receiving parenteral opioids (four trials, 216 patients, very low quality evidence) with a standardised mean difference ([SMD] 95%CI) of 2.11 (0.72–3.49), but were less satisfied than women receiving epidural analgesia (seven trials, 2135 patients, very low quality evidence), −0.22 (−0.40 to −0.04). Data on adverse events were sparse. However, the relative risk (95%CI) for maternal respiratory depression for patient-controlled remifentanil compared with epidural analgesia (three trials, 687 patients, low-quality evidence) was 0.91 (0.51–1.62). Compared with continuous intravenous infusion of remifentanil (two trials, 135 patients, low-quality evidence) no conclusion could be reached as all study arms showed zero events. The relative risk (95%CI) of Apgar scores less than 7 at 5 min after birth compared with epidural analgesia (five trials, 1322 participants, low-quality evidence) was 1.26 (0.62–2.57).

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THRIVE and airway fires

11. July 2017 - 8:47
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Intra-operative protective mechanical ventilation in lung transplantation: a randomised, controlled trial

11. July 2017 - 8:47
Summary

Primary graft dysfunction occurs in up to 25% of patients after lung transplantation. Contributing factors include ventilator-induced lung injury, cardiopulmonary bypass, ischaemia-reperfusion injury and excessive fluid administration. We evaluated the feasibility, safety and efficacy of an open-lung protective ventilation strategy aimed at reducing ventilator-induced lung injury. We enrolled adult patients scheduled to undergo bilateral sequential lung transplantation, and randomly assigned them to either a control group (volume-controlled ventilation with 5 cmH2O, positive end-expiratory pressure, low tidal volumes (two-lung ventilation 6 ml.kg−1, one-lung ventilation 4 ml.kg−1)) or an alveolar recruitment group (regular step-wise positive end-expiratory pressure-based alveolar recruitment manoeuvres, pressure-controlled ventilation set at 16 cmH2O with 10 cmH2O positive end-expiratory pressure). Ventilation strategies were commenced from reperfusion of the first lung allograft and continued for the duration of surgery. Regular PaO2/FIO2 ratios were calculated and venous blood samples collected for inflammatory marker evaluation during the procedure and for the first 24 h of intensive care stay. The primary end-point was the PaO2/FIO2 ratio at 24 h after first lung reperfusion. Thirty adult patients were studied. The primary outcome was not different between groups (mean (SD) PaO2/FIO2 ratio control group 340 (111) vs. alveolar recruitment group 404 (153); adjusted p = 0.26). Patients in the control group had poorer mean (SD) PaO2/FIO2 ratios at the end of the surgical procedure and a longer median (IQR [range]) time to tracheal extubation compared with the alveolar recruitment group (308 (144) vs. 402 (154) (p = 0.03) and 18 (10–27 [5–468]) h vs. 15 (11–36 [5–115]) h (p = 0.01), respectively). An open-lung protective ventilation strategy during surgery for lung transplantation is feasible, safe and achieves favourable ventilation parameters.

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