Fernandez MM, González-Castro A, Magret M et al.
Intensive Care Medicine 2017: 43 (11): 1660-1667
Background
Post extubation failure in ICU are relatively high (5 – 30%), and it is known that re-intubation is associated with increased mortality. Mechanical ventilation is associated with generalised muscle weakness & reduced diaphragm thickness , and the authors propose the idea that prolonged ventilation leads to increased fatigability
Spontaneous Breathing Trials (SBT) are done in the ICU prior to Extubation, and there are set criteria that must be met, including :
- Stable / resolving lung disease
- Low FiO2 + PEEP requirement
- Haemodynamic stability
- Good neuromuscular function
- Low Rapid Shallow Breathing Index (RR/Tvol)
If these critera are met, an SBT can be done, involving
- Attaching patient to a T piece / ventilator (minimum vent settings)
- Duration 30-120minutes
- Vitals (tidal volume, RR, SPO2, HR) and levels of agitation / end ABG are recorded.
Clinical Question
Does reconnection to mechanical ventilation for 1 hour after successful SBT reduce reintubation rate in critically ill patients?
Methods
Prospective randomised controlled trial, 17 Spanish ICU (medical / surgical)
Oct 2013 -> Jan 2015
Registered with clinicaltrials.gov
Study Population
Inclusion: MV > 12 hours AND successfully completed SBT (screened daily)
Exclusion:
- < 18, tracheostomy,
- resp secretions ++,
- DNAR / DNRI
- Inability to follow commands
- Participation in other trials,
- Formal indication for NIV post extubation
Randomisation & Masking
Randomisation: Centralised, computer generated
Before SBT
- Stratified by centre & risk of extubation failure
- ->Allocation concealed – opaque envelopes
Investigators: excluded from clinical decisions
Impossible to mask staff / patients
Statistics
- Sample size calculation: 1372 pts – 5% absolute risk reduction
- ITT analysis
- Categorical variables: Cochran-Mantel-Haenszel χ2 / Fischers exact test
- Normally distributed variables: Student’s t-test
- Non-normally distributed variables: Mann-Whitney U test
- Multi-variate model assessed with area under receiver operating characteristic curve (AUROC) and the goodness-of-fit by Hosmer-Lemeshow test.
Methods
- Patients were screened daily: when ready for SBT, but before trial started, informed consent was gained.
- Classified into high/low predicted risk extubation failure
- SBT technique (TT, PS, CPAP) and duration (30,60, 120min) remained at discretion of physician / local protocol.
- Successful SBT: defined by international guidelines.
Group allocation
- Intervention: Rested on MV post SBT for 1 hour, then extubated
- Control: Extubated directly
Treatment common to both sides:
- Local weaning/physio protocols (Preoxygenation / suctioning / bronchodilators).
- Post extubation failure: local protocols / physician discretion used (reintubation / NIV)
Outcomes
- Primary outcome: Extubation failure
- Secondary outcome
- Reintubation
- Length of stay (LOS) (ICU & Hospital)
- Mortality (ICU & Hospital)
Results
Primary Outcomes Re-intubation within 48 hours – significantly more common in control group 14% vs. 5%, OR 0.33, 95% C.I. 0.16-0.65, p<0.001
Secondary Outcomes
- Post-extubation respiratory failure within 48 hours (need for re-intubation or ventilatory support with NIV due to predefined criteria) – significantly more common in control group 24% vs. 10%, OR 0.35 (0.21-0.61), p<0.001
- In both groups a similar proportion underwent rescue NIV and direct re-intubation
- Causes of respiratory failure, comparing control (n=58) vs. intervention (n=24) groups
- SpO2 <90%: 43% vs. 50%, p=0.57
- Tachypnoea: 62% vs. 50%, p=0.31
- Fatigue: 58% vs. 41%, p=0.16
- Respiratory acidosis: 17% vs. 12%, p=0.75
- Low GCS: 10% vs. 21%, p=0.2
Subgroup analysis
- Sub-group analysis, comparing control vs. intervention groups re-intubation within 48 hours
- High risk patients: 16% (control) vs. 6% (rest), p=0.001
- Low-risk patients: 7% (control) vs. 3% (rest), p=0.36
Authors Discussion
SBT is demanding : Combined with the fact that mechanical ventilation is known to cause diaphragmatic atropy (shown previously on USS and autopsy, and is evident after just 3 days of MV), it is unsurprising that a rest prior to extubation results in lower failed extubation rates.
NIV as a rescue method is dangerous, as it can mask fatigue: 60% of failed extubation went on to have NIV: 34% of these were reintubated
Intervention group could do better purely because of the effect on atelectasis / derecruitment: could extubation onto high flow nasal oxygen have the same effect?
Authors conclusions
“ Our main finding is that reconnection to the ventilator to rest for 1 h after a successful SBT reduces reintubation at 48 h in critically ill patients.”
“Postextubation respiratory failure within 48 h was more common in the control group than in the rest group, but no differences were observed in the duration of ICU stay or hospital stay.”
Critique of paper
The Good Bits
- RCT
- Multi-centre
- Intention to treat
- Registered with clinicaltrials.gov
- Allocation concealment
- Exclusion of clinicians who collected endpoints from clinical decisions
The Bad Bits
- Sample size – only after concluding study did the “realise” they had miscalculated sample size. 470 (1372) recruited
- No blinding
- Clinician preference / variability
- Longer SBT time hidden in text for control group
- Baseline characteristics: Secretions (C), Comorbidities (I)
Discussion from Kingston Journal Club: Should this paper change our practice?
- More research needed in this area (due to sample size miscalculations, longer SBT times in Control)
- But – evidence does point towards significantly reduced re-intubation rates in those who are rested on MV post SBT
- BUT no change in LOS or mortality in this small group – does intervention really make a difference?
Summary by Dr S Kipling. Journal Club Meeting 29 March 2018.
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