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Table of Contents for Anaesthesia. List of articles from both the latest and EarlyView issues.
Updated: 8 min 11 sec ago

Cardiac output monitoring with thermodilution pulse‐contour analysis vs. non‐invasive pulse‐contour analysis

19. March 2019 - 11:08
Summary

Intravenous fluid boluses guided by changes in stroke volume improve some outcomes after major surgery, but invasive measurments may limit use. From October 2016 to May 2018, we compared the agreement and trending ability of a photoplethysmographic device (Clearsight) with a PiCCO, calibrated by thermodilution, for haemodynamic variables in 20 adults undergoing major elective surgery. We analysed 4519 measurement pairs, including before and after 68 boluses of 250 ml crystalloid. The bias and precision of stroke volume measurement by Clearsight were −0.89 ± 4.78 ml compared with the invasive pulse‐contour cardiac output device. The coefficient of agreement for stroke volume variation after fluid boluses between the two devices was 0.79 (‘strong’). Fluid boluses that increased stroke volume by ≥ 10% increased mean absolute volume (SD) and mean percentage (SD) stroke volume measurements similarly for the invasive pulse‐contour cardiac output and Clearsight devices: 9 (4) ml vs. 8 (4) ml and 16% (8%) vs. 15% (10%), respectively, p > 0.05. The non‐invasive Clearsight pulse‐contour analysis was similar to an invasive pulse‐contour device in measuring absolute and changing stroke volumes during major surgery.

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‘Humanware’: the human in the system

18. March 2019 - 18:27
Anaesthesia, EarlyView.
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Mathematical model of the risk of drug error during anaesthesia: the influence of drug choices, injection routes, operation duration and fatigue

18. March 2019 - 18:11
Summary

The incidence of an anaesthetic drug error can be directly observed in large trials. In an alternative approach, we developed a probabilistic mathematical model in which the anaesthetist is modelled as a ‘fallible entity’ who makes repeated drug administration choices during an operation. This fallibility was factored in the model as an initial ‘intrinsic error rate’. The choices faced included: dose; timing of administration; and the routes available for injection (e.g. venous, arterial, epidural, etc.). Additionally, we modelled the effect of fatigue as a factor that magnifies the cumulative error rate. For an initial intrinsic error rate of 1 in 1000 (which from first principles we consider a reasonable estimate), our model predicted a cumulative probability of error over a ~12 h operation of ~10%; that is, 1 in 10 operations this long results in some drug error. This is similar to the rate reported by large observational trials. Serious errors constitute a small fraction of all errors; our model predicts a Poisson distribution for the uncommon serious errors, also consistent with independent observations. Even modest assumptions for the development of fatigue had a dramatic and adverse impact on the cumulative error rate. The practice implications of our modelling include: exercising caution or avoiding starting work if under par; added vigilance in unfamiliar environments; keeping anaesthetic recipes simple; and recognising that operation durations > 5–6 h constitute a time of exaggerated risk. These implications are testable predictions in observational trials. If validated, our model could serve as a potential research tool to investigate the impact of safety interventions on the rate of intrinsic error using simulation.

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A right to be unconscious

14. March 2019 - 11:49
Anaesthesia, EarlyView.
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Regional anaesthesia for rib fractures: too many choices, too little evidence

11. March 2019 - 17:27
Anaesthesia, EarlyView.
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Analgesic strategies for day‐case knee surgery

7. March 2019 - 17:22
Anaesthesia, Volume 74, Issue 4, Page 529-533, April 2019.
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A physiological study to determine the mechanism of carbon dioxide clearance during apnoea when using transnasal humidified rapid insufflation ventilatory exchange (THRIVE)

7. March 2019 - 17:22
Summary

Clinical observations suggest that compared with standard apnoeic oxygenation, transnasal humidified rapid‐insufflation ventilatory exchange using high‐flow nasal oxygenation reduces the rate of carbon dioxide accumulation in patients who are anaesthetised and apnoeic. This suggests that active gas exchange takes place, but the mechanisms by which it may occur have not been described. We used three laboratory airway models to investigate mechanisms of carbon dioxide clearance in apnoeic patients. We determined flow patterns using particle image velocimetry in a two‐dimensional model using particle‐seeded fluorescent solution; visualised gas clearance in a three‐dimensional printed trachea model in air; and measured intra‐tracheal turbulence levels and carbon dioxide clearance rates using a three‐dimensional printed model in air mounted on a lung simulator. Cardiogenic oscillations were simulated in all experiments. The visualisation experiments indicated that gaseous mixing was occurring in the trachea. With no cardiogenic oscillations applied, mean (SD) carbon dioxide clearance increased from 0.29 (0.04) ml.min−1 to 1.34 (0.14) ml.min−1 as the transnasal humidified rapid‐insufflation ventilatory exchange flow rate was increased from 20 l.min−1 to 70 l.min−1 (p = 0.0001). With a cardiogenic oscillation of 20 ml.beat−1 applied, carbon dioxide clearance increased from 11.9 (0.50) ml.min−1 to 17.4 (1.2) ml.min−1 as the transnasal humidified rapid‐insufflation ventilatory exchange flow rate was increased from 20 l.min−1 to 70 l.min−1 (p = 0.0014). These findings suggest that enhanced carbon dioxide clearance observed under apnoeic conditions with transnasal humidified rapid‐insufflation ventilatory exchange, as compared with classical apnoeic oxygenation, may be explained by an interaction between entrained and highly turbulent supraglottic flow vortices created by high‐flow nasal oxygen and cardiogenic oscillations.

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High‐flow nasal oxygen vs. standard flow‐rate facemask pre‐oxygenation in pregnant patients: a randomised physiological study

7. March 2019 - 17:22
Summary

High‐flow nasal oxygen has been shown to provide effective pre‐oxygenation and prolong apnoeic time during intubation attempts in non‐pregnant patients. We aimed to compare pre‐oxygenation using high‐flow nasal oxygen (30–70 l.min−1 oxygen flow) via nasal prongs with standard 15 l.min−1 oxygen breathing via a tight‐fitting facemask. Forty healthy parturients were randomly allocated to these two groups, and furthermore each patient underwent the selected pre‐oxygenation method with both 3‐min tidal volume breathing and 30s tidal breathing followed by eight vital capacity breaths. With 3‐min tidal volume breathing, the respective estimated marginal means for high‐flow nasal oxygen and standard flow rate facemask pre‐oxygenation were 87.4% (95%CI 85.5–89.2%) and 91.0% (95%CI 89.3–92.7%), p = 0.02; with eight vital capacity breaths the estimated marginal means were 85.9% (95%CI 84.1–87.7%) and 91.8% (95%CI 90.1–93.4%, p < 0.0001). Furthermore, high‐flow nasal oxygen did not reliably achieve a mean end‐tidal oxygen concentration ≥ 90% compared with the standard flow rate facemask. In this physiological study, high‐flow nasal oxygen pre‐oxygenation performed worse than standard flow rate facemask pre‐oxygenation in healthy term parturients.

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The effect of sleep deprivation and disruption on DNA damage and health of doctors

7. March 2019 - 17:22
Summary

Observational studies have highlighted the detrimental health effects of shift work. The mechanisms through which acute sleep deprivation may lead to chronic disease have not been elucidated, but it is thought that increased DNA damage or decreased repair can lead to disease. The objective of this study was to examine the effects of acute sleep deprivation on DNA damage. This was a cross‐sectional observational study on 49 healthy, full‐time doctors. Baseline blood was sampled from each participant after three consecutive days of adequate sleep. Participants (n = 24) who were required to work overnight on‐site had additional blood sampled on a morning after acute sleep deprivation. DNA damage and expression of DNA repair genes were quantified. Information on health, working patterns and sleep diaries were collected. Independent t‐tests were used to compare differences between groups and standardised mean differences expressed as Cohen's d. Overnight on‐site call participants had lower baseline DNA repair gene expression and more DNA breaks than participants who did not work overnight (= 1.47, p = 0.0001; and 1.48, p = 0.0001, respectively). In overnight on‐site call participants, after acute sleep deprivation, DNA repair gene expression was decreased (= 0.90, p = 0.0001) and DNA breaks were increased (= 0.87, p = 0.0018). Sleep deprivation in shift workers is associated with adverse health consequences. Increased DNA damage has been linked to the development of chronic disease. This study demonstrates that disrupted sleep is associated with DNA damage. Furthermore, larger prospective studies looking at relationships between DNA damage and chronic disease development are warranted, and methods to relieve, or repair, DNA damage linked to sleep deprivation should be investigated.

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Team planning discussion and clinical performance: a prospective, randomised, controlled simulation trial

7. March 2019 - 17:22
Summary

Planning held before emergency management of a critical situation might be an invaluable asset for optimising team preparation. The purpose of this study was to investigate whether a brief planning discussion improved team performance in a simulated critical care situation. Forty‐four pairs of trainees in anaesthesia and intensive care were randomly allocated to either an intervention or control group before participating in a standardised simulated scenario. Twelve different scenarios were utilised. Groups were stratified by postgraduate year and simulated scenario, and a facilitator was embedded in the scenario. In the intervention group, the pairs had an oral briefing followed by a 4‐min planning discussion before starting the simulation. The primary end‐point was clinical performance, as rated by two independent blinded assessors on a score of 0–100 using video records and pre‐established scenario‐specific checklists. Crisis resource management and stress response (cognitive appraisal ratio) were also assessed. Two pairs were excluded for technical reasons. Clinical performance scores were higher in the intervention group; mean (SD) 51 (9) points vs. 46 (9) in the control group, p = 0.039. The planning discussion was also associated with higher crisis resource management scores and lower cognitive appraisal ratios, reflecting a positive response. A 4‐min planning discussion before a simulated critical care situation improved clinical team performance and cognitive appraisal ratios. Team planning should be integrated into medical education and clinical practice.

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Impact of a physician‐led pre‐hospital critical care team on outcomes after major trauma

7. March 2019 - 17:22
Summary

The deployment of physician‐led pre‐hospital enhanced care teams capable of critical care interventions at the scene of injury may confer a survival benefit to victims of major trauma. However, the evidence base for this widely adopted model is disputed. Failure to identify a clear survival benefit has been attributed to several factors, including an inherently more severely injured patient group who are attended by these teams. We undertook a novel retrospective analysis of the impact of a regional enhanced care team on observed vs. predicted patient survival based on outcomes recorded by the UK Trauma Audit and Research Network (TARN). The null hypothesis of this study was that attendance of an enhanced care team would make no difference to the number of ‘unexpected survivors’. Patients attended by an enhanced care team were more seriously injured. Analysis of Trauma Audit and Research Network patient outcomes did not demonstrate an improved adjusted survival rate for trauma patients who were treated by a physician‐led enhanced care team, but confirmed differences in patient characteristics and severity of injury for those who were attended by the team. We conclude that a further prospective multicentre analysis is warranted. An essential prerequisite for this would be to address the current blind spot in the Trauma Audit and Research Network database – patients who die from trauma before ever reaching hospital. We speculate that early on‐scene critical care may convert this cohort of invisible trauma deaths into patients who might survive to reach hospital. Routine collection of data from these patients is warranted to include them in future studies.

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The weekend effect in status epilepticus: a national cohort study

7. March 2019 - 17:22
Summary

Higher mortality following admission to hospital at the weekend has been reported for several conditions. It is unclear whether this variation is due to differences in patients or their care. Status epilepticus mandates hospital admission and usually critical care: its study might provide new insights into the nature of any weekend effect. We studied 20,922 adults admitted to UK critical care with status epilepticus from 2010 to 2015. We used multiple logistic regression to evaluate the association between weekend admission and in‐hospital mortality, comparing university hospitals with other hospitals. There were 2462 in‐hospital deaths (12%). There was no difference in mortality after weekend admission to university hospitals, adjusted odds ratio (95%CI) 0.99 (0.84–1.16), p = 0.89. Mortality was less after weekend admission than after admissions Monday to Friday in hospitals not associated with a university, adjusted odds ratio (95%CI) 0.74 (0.64–0.87), p = 0.0001. There is no evidence that adults admitted to UK critical care at the weekend in status epilepticus are more likely to die than similar patients admitted during the week.

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The association of early postoperative desaturation in the operating theatre with hospital discharge to a skilled nursing or long‐term care facility

7. March 2019 - 17:22
Summary

It is unclear which criteria should be used to define readiness for tracheal extubation in the operating theatre. We studied the effects of desaturation in the operating theatre immediately after tracheal extubation on long‐term outcomes. Performing a pre‐specified, retrospective analysis of 71,025 cases involving previously independent adults undergoing non‐cardiac surgery, we evaluated the association between desaturation events (oxygen saturation < 90%) within 10 min of tracheal extubation and adverse discharge (to a skilled nursing facility or long‐term care facility). A total of 404 (12.3%) cases with, and 5035 (7.4%) cases without, early postoperative desaturation had an adverse discharge. Early postoperative desaturation was associated with higher odds of being discharged to a nursing facility (adjusted odds ratio 1.36 (95%CI 1.20–1.54); p < 0.001). Increased duration of desaturation augmented the effect (p for trend < 0.001). Desaturation was associated with a higher risk of respiratory, renal and cardiovascular complications as well as increased duration of hospital stay, postoperative intensive care unit admission frequency and cost. Several modifiable factors were associated with desaturation including: high intra‐operative long‐acting opioid administration; high neostigmine dose; high intra‐operative inspired oxygen concentration; and low oxygen delivery immediately before tracheal extubation. There was substantial provider variability between anaesthetists in the incidence of postoperative desaturation unexplained by patient‐ and procedure‐related factors. Early postoperative desaturation is a potentially preventable complication associated with a higher risk of adverse discharge disposition. Anaesthetists may consider developing guidelines to define tracheal extubation readiness that contain postoperative desaturation as an adverse outcome after tracheal extubation.

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A trial comparing emergency front of neck airway performance in a novel obese‐synthetic neck, meat‐modified obese neck and conventional slim manikin

7. March 2019 - 17:22
Summary

Conventional emergency front of neck airway training manikins mimic slim patients and are associated with unrealistic procedural ease. We have described previously a pork belly‐modified manikin that more realistically simulated an obese patient's neck. In this study, we compared a novel obese‐synthetic manikin (obese‐synthetic manikin) with a pork belly‐modified manikin (obese‐meat manikin) and a conventional slim manikin (slim manikin). Thirty‐three experienced anaesthetists undertook simulated emergency front of neck airway procedures on each manikin (total 99 procedures). Time to ventilation was longer on both obese manikins compared with the slim manikin (median (IQR [range]) time to intubation 159 (126–243 [73–647]) s in the obese‐synthetic, 105 (72–138 [43–279]) s in the obese‐meat and 58 (47–74 [30–370]) s in the slim manikin; p < 0.001 between each manikin). Cricothyroidotomy success rate was similar in the both obese manikins but lower when compared with the slim manikin (15/33 obese‐synthetic vs. 14/33 obese‐meat vs. 27/33 slim manikin). Participant feedback indicated performance difficulty was similar between both obese manikins, which were both more difficult than the slim manikin. The tissues of the obese‐meat manikin were judged more realistic than those of either other manikin. Overall, the obese‐synthetic manikin performed broadly similarly to the obese‐meat manikin and was technically more difficult than the conventional slim manikin. The novel obese‐synthetic manikin maybe useful for training and research in front of neck airway procedures.

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Anaesthetic machine leak not detected by the universal leak test

7. March 2019 - 17:22
Anaesthesia, Volume 74, Issue 4, Page 545-546, April 2019.
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Discounting risk prediction models

7. March 2019 - 17:22
Anaesthesia, Volume 74, Issue 4, Page 535-536, April 2019.
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Pre‐operative gum chewing: forbidden, allowed or recommended

7. March 2019 - 17:22
Anaesthesia, Volume 74, Issue 4, Page 539-539, April 2019.
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Doubt about pre‐operative carbohydrate supplementation

7. March 2019 - 17:22
Anaesthesia, Volume 74, Issue 4, Page 540-541, April 2019.
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Paratracheal force, cricoid pressure and obstetric anaesthesia

7. March 2019 - 17:22
Anaesthesia, Volume 74, Issue 4, Page 547-547, April 2019.
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