High vs low tidal volume intra-operative ventilation

In the third of his series of important randomised controlled trials in anaesthesia, Dr Jeremy Fabes summarises two papers about intra-operative tidal volumes with conflicting conclusions.

 

Intra-operative ventilation

IMPROVE Trial

Multicenter trial of 400 with intermediate to high risk of pulmonary complications after major abdominal surgery, Futier, E. et al. N Engl J Med 2013;369:428-37.

Methods

Non-protective mechanical ventilation or lung-protective ventilation

– 10-12ml/kg with no PEEP and no recruitment manoeuvres

– 6-8ml/kg with PEEP and recruitment manoeuvres

Primary outcome – composite of major pulmonary and extra-pulmonary complications within 7 days

 

Results

Reduction in complications (primary outcome) – 10.5% vs. 27.5%

Reduction in need for NIV or intubation for acute respiratory failure

Shorter length of hospital stay by 2.5 days

 

Criticism

Non-protective ventilation is strategy outdated

Existing evidence prior to study that non-protective strategy associated with markers of lung injury/inflammation

Lack of PEEP may have increased the risk of microaspiration

 

PROVHILO Trial

High versus low positive end-expiratory pressure during general anaesthesia for open abdominal surgery (PROVHILO trial): a multicentre randomised controlled trial, The PROVE Network Investigators, Lancet 2004 384:9942, 495–503.

 

Methods

900 patients at risk of post-operative pulmonary complications undergoing open abdominal surgery

Intervention arm: Fixed tidal volume of 8ml/kg with recruitment manoeuvres

Control arm: 12cmH2O + recruitment vs. < 2cmH2O without recruitment

Composite endpoint of pulmonary complications

 

Results

There was no difference in primary outcome between the two groups

More hypotension and need for vasoactive drugs in high PEEP group

 

Criticism

Risk of barotrauma in high PEEP group may have confounded outcomes

Abrupt withdrawal of high PEEP may have induced LV dysfunction

 

Impact

Progressive uptake of more lung-protective ventilation techniques – see in observation studies

Development of summative evidence-based guidelines

ALPINE study in association with NELA assessing post-op respiratory outcomes following emergency laparotomy and ventilatory practice is in progress

 

Summaries by Dr Jeremy Fabes

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