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“Evidence for compromised data integrity in studies of liberal peri‐operative inspired oxygen.” Myles P. S. et al. Anaesthesia 2019

Background

  • The World Health Organization (2016) made a strong recommendation that adult patients undergoing general anaesthesia for surgical procedures should receive an 80% fraction of inspired oxygen to reduce the risk of surgical site infection based upon a meta-analysis of 15 randomised controlled trails
  • Five of these trials have been retracted, two of which were by the Mario Schiertoma’s group
  • The merits of liberal peri-operative inspired oxygen have been disputed

Aim

  • To identify compromised data by Mario Schietroma’s group
  • To undertake a meta-analysis of other randomised trials of liberal peri-operative inspired oxygen

Methods

  • Literature search for papers with Dr Mario Schietroma as author, included RCTs and observation series published in English
  • Use of ‘Carlisle method’ to calculate probability of distribution of baseline characteristics for participants use RCTs.
  • Checked calculations of p values represented in any paper.
  • Compared figures for duplication
  • Meta-analysis of liberal trials using Cochrane Collaboration software

Results

  • Identification of 40 papers that’s fulfilled criteria: 24 RCTS with 5064 participants and 16 observational studies with 1847 patients
  • Evidence that data intergrity was compromised in 38 of the 40 analysed papers
  • Meta-analysis of 20 other randomised trials of liberal peri‐operative inspired oxygen in 8357 participants. Pooled results without trials by Schietroma et al. and not, did not show an effect of liberal peri‐operative inspired oxygen on wound infection (OR (95%CI) 0.89 (0.73–1.08); p = 0.23).
  • Liberal inspired oxygen reduced the rate of postoperative wound infection if trials by Schietroma et al. were included (OR (95%CI) 0.77 (0.61–0.96); p = 0.02 ).

Discussion
Strengths

  • Extreme p values for baseline distributions identified
  • Identification of replication of graphs and data amongst papers
  • Only systematic and randomised trials were used in the meta-analysis. All of the reported data in each of the relevant studies were checked. This resulted in the identification of numerous discrepancies

Weakness

  • Inherent problems of
    o Carlisle method:
    – Inherent with statistics
    – error may not be secondary to fraud
    o Meta-analysis
  • The WHO has already revised its guidelines on liberal peri-operative inspired oxygen following a series of retractions by the Schietroma group.
  • Ethics behind using Carlisle method to discredit data in a public domain

Summary by Dr Rose Beesley

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“Dexamethasone as an adjuvant for peripheral nerve blockade: a randomised, triple-blinded crossover study in volunteers” Marhofer, P et al. British Journal of Anaesthesia, 122 (4): 525e531 (2019)

Background

  • No ideal agent exists for use in peripheral nerve blockade (one which would allow motor and sensory blockade intraoperatively and then prolonged sensory blockade postoperatively).
  • Therefore adjuncts have been added to prolong postoperative sensory blockade.
  • Dexamethasone is one such adjunct.

Rationale

  • Efficacy of dexamethasone administered perineurally or systemically has been evaluated in 7 recent systematic reviews and meta-analyses.
  • Authors suggest low quality of trials and heterogeneity mean no reliable conclusions can be drawn regarding efficacy of perineural dexamethasone in combination with local anaesthetics.
  • Therefore decided to conduct their own study.

Method

  • Volunteer study
  • Randomised, triple-blinded crossover study
  • Assessing effects of dexamethasone as an additive to ropivicaine in a standardised peripheral nerve block.
  • Ethics approval obtained.
  • Male volunteers aged 18 – 55 with BMIs 18-35 recruited.
  • Underwent Ulnar Nerve blockade on non-dominant hand by single investigator. 
  • Three study groups: control, perineural group, i.v. group.

Assessment of sensory block

VAS (0-100mm) in response to pinprick testing over the hypothenar area. 

Results

  • 24 volunteers, 72 blocks. 19 volunteers had blocks on left arm, 5 on right arm. 
  • Median age 30, mean BMI 23. 
  • No difference in duration.
  • No difference in outcome.
  • Full recovery of sensation in all patients for each block and no other sequelae.

Discussion

  • No new local anaesthetics in last 20 years, therefore adjuvants been investigated.
  • Dexamethasone has been heavily investigated but with heterogenous study designs and no uniformity in practice.
  • Clinical studies leave gaps in assessment of duration.
  • This study is highly standardised and employed crossover design. The dose of dexamethasone  and concentration of local anaesthetic allows full blockade of a peripheral nerve.
  • Well powered: 99% for a difference in duration of block of 4  hours and 98% for a difference of 2 hours.
  • Dexamethasone may have an effect on neural blood flow and therefore may be efficacious in chronic pain due to the inflammatory component, therefore future studies should focus on this.

Group discussion/overall thoughts

  • Not applicable to our practice as no surgical stimulus and fit and well people assessed.
  • Only used ropivacaine not other local anaesthetics, conceivably differing effects of dexamethasone with other local anaesthetics.
  • The paper didn’t investigate higher doses of dexamethasone than 4mg and the potential effects.
  • There was no assessment of motor blockade and effect of dexamethasone on this.
  • They chose 4 hours as clinically significant, however it would be interesting to see if there was a block duration difference of 1 hour and how well the paper was powered for this.

Summary by Dr Anish Amlani

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EOLIA TRIAL

‘Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome’ Combes et al. N Engl J Med 2018; 378:1965-1975

Background:

  • ARDS (acute respiratory distress syndrome) is associated with high mortality
  • Oxygenation and carbon dioxide removal can be performed by VV-ECMO (veno-venous extracorporeal membrane oxygenation), however it is associated with significant complications. A previous RCT (CESAR trial – Conventional VentilatorySupport versus Extracorporeal MembraneOxygenation for Severe Adult Respiratory Failure), yielded promising results, however came under criticism for methodological issues and limited conclusions could be drawn. 
  • The question of whether ECMO improves outcomes in ARDS compared to standard lung-protective ventilation remains unanswered. 

Aim:The ECMO to rescue lung injury in severe ARDS (EOLIA) trial was designed to determine the effect of early initiation of ECMO in patients with the most severe form of ARDS. 

Methods:

  • Prospective, randomised controlled trial, 64 centres, mainly France
  • Patient selection
    • Ventilated for < 7 days
    • American-European ARDS definition, 1994
  • Randomization was stratified according to center and the duration of ventilation before randomization (<72 hours vs ≥72 hours)
  • Target sample size was 331 patients
    • Based an expected 60 day mortality rate of 60%, and an estimated 40% mortality in the ECMO group (absolute risk reduction 20%)
    • For 80% power at an alpha level of 5% and with a group­ sequential analysis occurring after the randomization of every 60 participants
  • Stopping rules, using the two sided triangular design methodology, were defined prior to the commencement of the trial. The trial could be stopped due to:
    • Safety (due to excess mortality in the ECMO arm)
    • Efficacy
    • Futility 

INTERVENTION:

  • Venovenous ECMO
    • Percutaneous cannulas, with the access cannula inserted into the femoral vein and return cannula inserted into the SVC via the jugular vein

CONTROL:

Volume-assist-controlled ventilation

  • FIO2 (0.21–1) was adjusted to obtain sats between 88-95% and a PaO2 55-80 mmHg
  • VT set at 6 ml per kg PBW
  • PEEP set so as not to exceed a Pplat of 28–30 cmH2
  • NMBAs and prone positioning encouraged for control patients

Results:

  • Trial was stopped early at 249/331 (75% of recruitment) due to predefined futility rules.
  • Primary outcome: No statistical difference in mortality at day 60
    • ECMO group 44/124 (35%) vs Control group 57/125 (46%)
    • Relative risk, 0.76; 95% confidence interval [CI], 0.55 to 1.04; P=0.09
  • Secondary outcomes:
    • Compared to control group, the ECMO group had:
      • Lower relative risk of treatment failure 0.62 (95% CI, 0.47 to 0.82; P<0.001)
        • Treatment failure was defined as death by day 60 in patients in the ECMO group, and as crossover to ECMO or death in patients in the control group
      • Lower risk of Renal replacement therapy (RRT) at day 60 (50 vs. 32 days; median difference, 18 days; 95% CI, 0 to 51)
    • Cross over to ECMO occurred in 35/125 (28%) of control patients

Discussion:

Strengths:

  • Largest multicenter ECMO RCT to date
  • Standardised criteria for entry into the trial/ initiation of rescue ECMO
  • Almost all patients who were randomized to ECMO received it (unlike the previous RCT, CESAR)
  • Protocolized delivery of ECMO and MV àhence standardised treatments in intervention and control arms (patients were included from both ECMO and non-ECMO centres on the proviso ECMO could be initiated with 2 hours of randomisation).

Weaknesses:

  • Underpowered to detect mortality -> trial stopped early! (75% recruitment)
  • Implausible power calculation (mortality in the control group was 46%, not 60%)
  • High cross over rate of controls
  • Lack of blinding 
  • Slow recruitment of 249 patients over 6 years à trial fatigue and/or change of practice

Conclusion:

ECMO for severe ARDS showed no significant mortality benefit at day 60 as compared with a strategy of conventional mechanical ventilation.

Summary by Dr Clare Morkane

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Background

  • Both transversus abdominis plane block and intrathecal morphine may produce prolonged postoperative analgesia, but the respective clinical outcomes of these anaesthetic techniques in resource-limited settings are not well described.
  • This study was performed to compare these two methods of postoperative pain control and find out which was better for the patients in resource-limited setting, and to allow them to develop robust protocols for analgesia in our institution that could be more widely applied.

Methods

  • Prospective randomised study 
  • Inclusion criteria: between 15 and 49 years old, ASA 1 or 2, spinal anaesthetic without sedation, uncomplicated LSCS, able to give informed consent 
  • Consecutive sampling to recruit following decision to LSCS
  • Patients blinded to study allocation. Blocks done by clinical investigator
  • Spinal anaesthetic with or without preservative free morphine
  • Post-op, in recovery room, dermatomal level of spinal block assessed using blunt pin
  • Pain scores assessed – before block, before discharge from recovery and in ward using numerical rating scale
  • Intrathecal morphine group received sham block and the TAP block group received B/L TAP block( 15 ml each side of 0.25% bupivacaine with 1:200,000 adrenaline
  • All patients – Paracetamol 1g and Diclofenac 50 mg at the time of block and at 8,16 and 24 hrs post-op
  • Reviewed by research assistant – qualified midwife who is blinded to group assignment collected data at 8, 26 and 24 hours
  • Pain levels – rest, on coughing and on movement (numerical rating score) 
  • Side effects – nausea, vomiting, respiratory depression, sedation and  pruritus noted
  • For breakthrough pain – rescue analgesia – rectal Diclofenac 100 mg

Results

  • For statistical power of 80% and type 1 error of 5%- 63 PST each group needed – to allow dropout 65 PST each group recruited
  • Between group and within group differences in numerical rating scores analysed using repeated measures ANOVA
  • P value < 0.05- statically significant 
  • Statistically significant low pain score in TAP block group of patients only in 24 hrs during movement. No statistically significant different in pain scores between groups in the 8 and 16 hours period, between side effects, ambulation and patient satisfaction scores

Discussion

  • Primary Outcome: Clinically similar for both groups, although pain scores statistically lower in rest and movement at 24 hr with TAP block
  • Incidence of iatrogenic side effects – low both groups
  • Satisfaction scores – good in both groups

Rescue Diclofenac PR- requested more frequently both groups at 16 and 24 hrs

Overall paper analysis/review

  • It was discussed that this study cannot be compared or applied to our current practise in the developed countries with available resources. 
  • We routinely use diamorphine intrathecally and do not have preservative free morphine
  • But the practice of TAP block in post – caesarean patients who had GA can be encouraged with these results. 

‘The analgesic effects of intrathecal morphine in comparison with ultrasound- guided transverse abdominis  plane block after caesarean section: a randomised controlled trial at a Ugandan regional referral hospital’ Kwikiriza A, et al. Anaesthesia 2019, 74: 167-173 

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Predictors of Difficult Videolaryngoscopy with GlideScope or C-Mac with D-blade: secondary analysis from a large comparative videolaryngoscopy trial Aziz et al. British Journal of Anaesthesia 117 (1): 118-23 (2016)

“Life is simple, but we insist on making it complicated.” – Confucius.

Background

  • Acute-angle videolaryngoscopes are designed to overcome some predictors of difficult direct laryngoscopy, and are intended to improve the view of the relatively anterior airway or when cervical motion is limited.
  • However, it’s a different technique to direct laryngoscopy with different challenges, and it is unclear what specific factors make acute angle videolaryngoscopy difficult.  This paper aimed to identify potential predictors of difficult videolaryngoscopy.

Methods

  • Secondary analysis of comprehensive data set from original study which compared 2 acute angle videolaryngoscopy blades in patients with predicted difficult direct laryngoscopy[i]
    • Original study – Single blinded, two-parallel arm, non-inferiority RCT
    • 1100 patients with predicted difficult airway recruited across three academic institutions in the US; GlideScope n = 552, C-MAC n=548
    • Primary outcome – successful first intubation attempt
    • All patients going under GA, with neuromuscular blockade and single lumen tube with predicted difficult airway defined as 1 or more of the following:
      • MP III/IV
      • Reduced MO < 3cm (but not <2cm)
      • Large neck circumference (>40cm M/>38cm F)
    • Exclusion criteria – known easy intubation previously, history of failed intubation or difficult BMV, unstable c-spine injury, age < 18yrs, emergency surgery, planned awake technique, nasal intubations, MO < 2cm
    • Laryngoscopists – > 6/12 clinical anaesthesia & undefined level of experience with videolaryngoscopy
  • Secondary measures recorded including patient variables, surgical approach, head positioning and provider characteristics. These were subsequently analysed for this paper
    • Primary outcome to determine difficult acute angle videolaryngoscopy – 1st attempt failure or time >60s to secure airway
    • Univariate analysis of potential predictors of difficult vs. non-difficult laryngoscopy carried out
    • Multivariate logistic regression model and stepwise model selection techniques conducted to identify independent predictors of difficult videolaryngoscopy

Results

  • 301/1100 difficult videolaryngoscopy
    • 244 > 60s
    • 27 > 1x intubation attempt
    • 30 > 60s + >1x intubation attempted
  • Four predictors identified as being associated with difficult videolaryngoscopy – limited mouth opening, type of surgical procedure, laryngoscopist training level, and patient positioning
  • When compared to the ‘supine neutral’ position, the ‘supine sniffing’ position was associated with an increased risk of difficult videolaryngoscopy (p=0.023, OR 1.625, CI 1.142 – 2.315)
  • Difficult videolaryngoscopy was associated more with particular surgeries (p=0.0021) when compared with general surgery: ENT/oral surgery (OR 1.891, CI 1.190 – 3.006) and cardiac surgery (OR 6.133, CI 1.847 – 20.367)
  • Resident anaesthetists have a higher likelihood of success when using videolaryngoscopy compared with attending anaesthetists (p<0.0001, OR 0.546, CI 0.342 – 0.873)
  • Difficult videolaryngoscopy is more likely to occur in patients with reduced mouth opening (p=0.0225, OR 0.848, CI 1.190-3.006)

Discussion

  • Difficulty with supine sniffing position was attributed to a more challenging blade insertion
  • ENT/oral surgery also known to be associated with difficult direct laryngoscopy.  The reasons for an association of difficult videolaryngoscopy with cardiac surgery are poorly explained.  The numbers in the original data set for cardiac surgery are not specified but fall into the category of ‘other’ which totals just 40.  The small data set and wide CI question the authenticity of this association
  • A higher likelihood of attendings encountering difficulty is potentially due to them performing fewer intubations day to day as they are frequently in a supervisory role
  • Small MO may hinder initial scope placement and subsequent tube insertion

Overall paper analysis/review

  • Large database from which to draw information from, with appropriate exclusion criteria and a credible aim in trying to identify predictors of difficult videolaryngoscopy

However

  • Study design not powered towards secondary analysis of the data set
  • Multiple variables not randomised so the results are associations at best
  • Criteria for predicting a difficult airway too broad (could include neck circumference alone)
  • Unable to assess the predictors of difficult airway in direct laryngoscopy independently
  • Primary outcome of defining difficult videolaryngoscopy as >60s to secure airway arguably too severe in view of identified potential difficulty, broad range of skill across those intubating, and lack of required structured training with both videolaryngoscopes
  • Provider background in academic institutions and in a well controlled theatre environment not necessarily transferable to other institutions or clinical areas e.g. ICU/A&E
  •  Not transferable to other types of videolaryngoscope (eg. Channeled/non acute angle)
  • Other potential factors associated with difficult videolaryngoscopy, not in the data set, were not examined

[i] ‘First-attempt intubation success of video laryngoscopy with anticipated difficult direct laryngoscopy: a multicentre randomised controlled trial comparing the C-Mac D-Blade vs the GlideScope in a Mixed Provider and Diverse Patient Population’ M F Aziz, R O Abrons, D Cattano, E O Bayman, D E Swanson, CA Hagber, M M Todd, A M Brambrink Anesth Analog 2016: 122: 740 – 50

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Advanced care planning and end-of-life discussions in the perioperative period: a review of healthcare professionals’ knowledge, attitudes and training. Blackwood et al

Background

  • There are 20–25, 000 post-operative deaths in the UK each year
  • High risk surgical patients (12.5% of surgical patients) account for more than 80% of perioperative deaths
  • There is a move towards greater patient involvement in the own care (e.g. Advanced Care Planning – ‘ACP’)

Aims

  • This is a systematic review with the intention to identify the knowledge and attitudes of health care professionals towards ACPs prior to surgery, and also to identify examples of current practice and barriers to delivery

Methods

  • A review of peer reviewed journal articles in variety of databases and the grey literature  
  • PICOS framework informed the search strategy
  • They also screened articles for references
  • There were four main search questions: themes – attitudes if health care professionals (‘HCP’s) to ACPs; level of knowledge of HCPs around ACPs; barriers to ACP discussions and presence of interventions aimed to improve ACP discussions

Results

  • Of 1566 papers, only 7 met the criteria for inclusion and therefore there is very limited data on which to make conclusions regarding the search questions

Discussion

  • There is a lack of evidence in this area
  • Health care professionals are positive about Advanced Care Planning
  • There is currently a lack of training and resources to improve the delivery of ACP discussions

Summary by Dr Nisha Sriram

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Hypersensitivity incidence after sugammadex administration in healthy subjects: a randomised controlled trial. Min et al British Journal of Anaesthesia, 121 (4): 749-757 (2018)

Method:

  • A multicentre, double-blind study
  • Subjects randomised 2:2:1 to Sugammadex 4mg/kg, 16mg/kg or placebo (normal saline)
  • Doses were administered 5 weeks apart, to unanaesthetised healthy subjects
  • Hypersensitivity signs and symptoms were assessed at 0.5, 4 and 24hrs
  • Tryptase levels were assessed pre dose and at 3hrs
  • IgG and IgE levels checked as an exploratory endpoint
  • Hypersensitivity signs/symptoms were then adjudicated by a blinded committee
  • The Sampson Criteria were used for assessing anaphylaxis
  • The primary endpoint of the study was confirmed hypersensitivity

Results:

  • 375 subjects recruited
  • 94 subjects with 137 adverse events were sent for review by the independent adjudication committee
  • Of the 94, 25 subjects were deemed to have “adjudicated” hypersensitivity, with a total of 43 events. This is a hypersensitivity rate of 6.7%.
  • In the 4mg/kg cohort: 10/151 (6.6%)
  • In the 16mg/kg cohort: 14/148 (9.5%)
  • In the Placebo cohort: 1/76 (1.3%)
  • 3 subjects from 16mg/kg required antihistamines/corticosteroids, and did not receive further doses
  • 1 subject had anaphylaxis

Discussion:

  • Hypersensitivity can occur on first exposure
  • Signs and symptoms usually presented within minutes (one after 22hrs)
  • There was no increase in severity with exposures ie no sensitisation. There was no significant tryptase rise. It is therefore unlikely to be mast cell mediated.
  • They quoted the incidence of anaphylaxis as 1 in 199 or 3.3%
  • It is unclear from this study if reactions are dose related
  • They found no IgE antibodies to sugammadex
  • Limited numbers to subgroup analysis of race or ethnicity

Analysis of the paper and take home thoughts:

  • It is unclear who the Independent Adjudication Committee was, or how they reduced the number of hypersensitivity reactions from 94 to 25.
  • The authors quoted 1 in 199 or 3.3% anaphylaxis, however they had one case in 299 subjects receiving sugammadex. I believe that this figure should therefore be 1 in 299 or 0.33%.
  • This rate of anaphylaxis is far higher than the approximate 1:10,000 cases seen in NAP6, and is very worrying if sugammadex is to become more frequently used. We should definitely consider the risks and benefits prior to administration of sugammadex in our patients.
  • No Asian subjects were included in the study
  • Some subjects were unaccounted for in the results
  • The study was funded by Merck and Co. who make Sugammadex.

Summary by Dr Leonora Bowen

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Effect of Cricoid Pressure Compared With a Sham Procedure in the Rapid Sequence Induction of Anaesthesia: The IRIS Randomized Clinical TrialAurélie Birenbaum et al., JAMA Surg 2018 Oct 17. doi: 10.1001/jamasurg.2018.3577

“We can’t act under pressure from anybody when we think that pressure will force an injustice” – José Sulaimán

Background

  • Cricoid pressure was first suggested in 1961 by Sellick to combat regurgitation during head down positioning for intubation.
    • Sellick described “tonsillectomy position” head extension to straighten oesophagus, with pressure on cricoid cartilage to occlude oesophagus against C6 vertebral body
    • “Moderate” pressure whilst patient awake, increased to “firm” once asleep
  • There is no level 1 evidence for efficacy, wide international variation in adoption
  • Cricoid pressure remains standard of care during RSI according to UK guidelines e.g. DAS
  • There are some concerns that cricoid pressure may worsen laryngoscopic view.

Aims

  • The IRIS trial aimed to demonstrate that a sham procedure mimicking cricoid pressure was not inferior to the real thing in preventing pulmonary aspiration

Methods

  • Sham vs real cricoid pressure in patients presenting to theatre for emergency surgery under GA, with risk factors for aspiration
  • Ten academic hospitals in France, 1:1 randomisation in blocks of 6 to cricoid or sham
  • A total of 3472 patients were recruited; 1729 patients in Sellick group, 1730 in sham group
  • Intubators & patients blinded to allocation
  • Exclusions: pregnancy, pneumonia, “consciousness disorder”

Statistical design: Non-inferiority RCT

  • Authors decided that at worst, sham pressure could have 1.5x higher risk of aspiration and still be deemed not inferior
  • This meant that upper limit of 95% confidence interval needed to be ≤1.5
  • 1:1 randomisation in blocks of 6
  • Powered for 2.8% incidence of aspiration (based on Martin et al, Anaesthesiology 2011)

Results

  • Primary outcome: pulmonary aspiration, per-protocol analysis
    • 10/1729 cricoid pressure patients aspirated (0.6%)
    • 9/1730 sham pressure patients aspirated (0.5%)
    • RR 0.90 (95% CI 0.39-2.00)
  • Secondary outcomes:
    • Intubation time (seconds, IQR): 27(19-40) cricoid vs 23(15-37) sham
    • Incidence of CL view 3 or 4: cricoid 8%, sham 4%

Discussion

  • Based on pre-specified threshold, authors conclude sham pressure is not “non-inferior” to cricoid pressure
  • They failed to show sham pressure is no worse than cricoid pressure, according to their own definition
  • The overall incidence of aspiration significantly lower than expected
  • Although a secondary outcome, the IRIS trial reports that cricoid worsens laryngoscopic view
  • Strengths:
    • Standardised anaesthetic technique and application of cricoid by trained operators
    • Randomisation & blinding techniques
    • No significant between group differences at baseline
  • Flaws:
    • There was a large overestimation of the risk of aspiration risk which meant that the study was underpowered
    • Theatients at highest risk of desaturation, difficult airway, aspiration were excluded
      • Pregnancy, ICU/ED, cardiac arrest, low GCS, pneumonia
    • Suxamethonium was used rather than rocuronium which means the results are possibly less applicable in some centres

Should this trial change our practice?

  • This trial does not inform most of the highest risk situations in which cricoid is employed
  • IRIS trial does not seriously undermine either of the two camps: cricoid is dangerous (worse view, ineffective) or necessary (not dangerous, might prevent aspiration in higher risk patients, can always be removed)
  • Cricoid pressure remains recommended by DAS and used routinely in UK obstetric practice (Desai IJOA 2018)

Summary by Dr Charles McFadyen

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Assessment of functional capacity before major non-cardiac surgery: an international, prospective cohort study. Duminda N Wijeysundera et al. Lancet 2018

Unless you’re good at guessing, it’s not much use being a detective – Agatha Christie

Introduction

  • This study sought to compare the accuracy of pre-operative subjective assessment (METS) with cardiopulmonary exercise testing (CPET, the Duke Activity Index Score (DASI) questionnaire and pre-operative NT pro-BNP levels.
  • The prognostic accuracy of these values for predicting post-operative morbidity and mortality was also assessed.

Methods

  • An International, multi-centre, prospective cohort study conducted in 25 hospitals (Canada, UK, Australia and New Zealand).
  • Primary outcome = Death or myocardial infarction within 30 days after surgery
  • Secondary outcome = Death within one year after surgery
  • Other outcomes:
    • Death or myocardial injury within 30 days
    • Moderate or severe post-operative complications defined by the Clavien-Dindo classification
  • Inclusion criteria were patients >40 years of age undergoing elective non-cardiac surgery (with an anticipated overnight stay or longer) with at least one risk factor for cardiac complications.
  • Exclusion criteria included; planned endovascular approach, pregnancy, cardiac conditions or absolute contraindications to CPET.
  • All patients recruited underwent pre-operative subjective functional assessment (by an anaesthetist), DASI questionnaire, CPET and NT Pro-BNP measured. Anaesthetist s blinded to these results (except whereby adverse events during CPET warranted unmasking eg. arrhythmia).
  • Patients were assessed with daily ECG and Troponin until day 3 post-operatively. Further follow up was conducted at 30 days and 1 year.

Results

  • 6548 met inclusion criteria with 1741 consenting to participate.
  • 1401 underwent both surgery and CPET and were included in analysis.
  • Subjective assessment of functional capacity had a sensitivity of 19.2% for identifying peak oxygen consumption of less than 14 mL/kg per min and a specificity was 94·7%.
  • Peak oxygen consumption was positively correlated with DASI scores (p<00001), and negatively correlated with NT pro­BNP concentrations (p<0·0001).
  • Subjectively assessed preoperative functional capacity had no significant adjusted association with the four main study outcomes.
  • DASI scores were associated with the primary outcome (OR 0.91 CI 0.83-0.99) and 30-day death or myocardial injury (OR 0.96 CI 0.92-0.99)
  • NT Pro-BNP was associated with 30-day death or myocardial injury (OR 1.78 CI 1.21-2.62) and 1-year death (OR 2.91 CI 1.54-5.49).
  • Peak oxygen consumption was associated with in-hospital moderate or severe complications (OR 0.86 CI 0.78-0.97).

Discussion 

  • Only 27% of patients approached consented to the study. Those that did consent may be a skewed cohort of patients ie. those willing to undergo pre-operative CPET for the purpose of the study.
  • Study did not adequately explain what happened to patients who were deemed unfit for surgery based on subjective assessment.
  • The sample size was based on a 5% primary outcome event rate. The actual event rate only 2% meaning the study was underpowered for this.
  • No adjustments were made for multiple testing.
  • Subjective assessment may influence complication rates in terms of minimising post-operative risks through augmentation of anaesthetic conduct. An effect that cannot be measured.
  • The author’s state that functional assessment should not be used for peri-operative risk evaluation. However, CPET failed also failed to predict MI, myocardial injury or death.
  • CPET did predict moderate to severe post-operative complications based on the Clavien-Dindo classification.
  • DASI scores proved a useful predictor of cardiac complications and are easily implemented.

Change to clinical practice?

  • Greater use of the DASI for pre-operative risk prediction should be considered.
  • Additionally pre-operative NT Pro-BNP should be considered for prediction of post-operative cardiac complications.

Summary by Dr Sam Curtis

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Fields A, Huang J, Schroeder D, Sprung J, Weingarten T. Agitation in adults in the post-anaesthesia care unit after general anaesthesia. Br J Anaesth. 2018;7(July):1–7.

“Fullness is always quiet; agitation will answer for empty vessels only.” – Amos Alcott.

Background

Agitation after general anaesthesia is rare but can be associated with self harm and violence against staff. Postoperative agitation is also associated with hyperactive delirium.

Emergence agitation in adult surgical patients has not been as well studied as in children.

Aim

The aims of this study were to:

  • evaluate the prevalence of emergence agitation in adults after general anaesthesia
  • assess for potential associations between patient and perioperative factors and agitation
  • describe the postoperative course of adult patients who have had agitation episodes

Methods

The authors examined electronic case records for 207,569 adult patients undergoing surgery between July 2010 and September 2016 at the Mayo Clinic Hospital, MN, USA.  They identified 510 cases of agitation in this group that were matched to case controls by age and procedure.

Agitation was defined as a Richmond Agitation Sedation Scale (RASS) score of +3 / +4 or the administration of haloperidol.

Results

The overall incidence of agitation was 510 patients (0.25%).

Variables associated with agitation were substance misuse, cognitive impairment, obesity, psychiatric problems, fall risk and the postoperative presence of an endotracheal tube, urinary catheter, nasogastric tube or chest drain.

Postoperative agitation was associated with postoperative delirium and pulmonary complications.

Discussion

The authors suggest identification of risk factors for agitation will allow development of processes to ensure safe care.

Analysis

Fields and colleagues have produced a retrospective case control study looking at perioperative factors associated with postoperative agitation.   We discussed the paper using the Critical Appraisal Skills Programme framework.

This paper is hypothesis generating but the methodology does not permit causative associations to be made.  We felt that several of the associations identified were plausible in line with our clinical experience.   The association of agitation with postoperative delirium and pulmonary complications is of clinical interest as postoperative morbidity is itself associated with reduced longterm survival.

The authors acknowledge in their discussion the likelihood of spurious associations being made when large numbers of variables are included.  Although we felt several of the associations were clinically plausible it is not possible to establish causation and there are likely to be unmeasured confounders.

Unfortunately the study design does not allow the association between agitation and age or procedure type to be established.

The primary outcome measure is agitation as defined in part by RASS score.  One of the criteria for RASS +3 is pulling at tubes.  We were not surprised therefore to see presence of tubes as a significant predictor of agitation.

Conclusion

This paper highlights the problem of postoperative agitation in a patient population similar to our own.  The methodology does not provide sufficiently robust evidence to recommend change in practice or policy at this time.

Summary by Dr Tom Salih

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