a trial of intraoperative low tidal-volume ventilation in abdominal
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TRANSCRIPT
N Engl J Med. 2013 Aug 1;369(5):428-37
Dr Peter Sherren
Background
• Ventilator-associated lung injury and biotrauma• Barotrauma/Volutrauma• Atelectasis• Hyperoxia
• Low vs high tidal volume ventilation in ALI/ARDS. N Engl J Med. 2000 May 4;342(18):1301-8.
• Lung protective ventilation in the critically ill without ARDS. JAMA 2012; 308: 1651-1659.
• Relevant to perioperative ventilation?
Current practice
• High tidal volume/zero PEEP perioperative ventilation N Engl J Med. 1963 Nov 7;269:991-6.
• Only historical practice? Anaesthesia. 2012 Sep;67(9):999-1008.
• Problem just in theatres? BMJ. 2012 Apr 5;344:e2124.
Study question relevant and original?
Hypothesis
Prophylactic lung-protective ventilation that combines low tidal volumes, PEEP, and recruitment manoeuvres will improve outcomes after abdominal surgery
Study design• Multi-centre RCT (Double blind, stratified, parallel
groups)
• Pts undergoing major elective abdominal surgery (>2Hrs), >40yrs old, Post-operative risk index for pulmonary complications >2.
• Exclusion criteria – IPPV/respiratory failure/sepsis within 2 weeks, BMI>35, emergency or thoracic surgery or neuromuscular disease.
• Randomised to• TV 6-8 mL/kg IBW; PEEP 6-8 cm H2O; recruitment manoeuvres every 30
minutes.• TV 10-12ml/kg; No PEEP or recruitment manoeuvres
Outcome measures
• Primary Outcome - Composite measure of major pulmonary and extra-pulmonary complications within 7 days.
• Multiple secondary outcomes – Gas exchange, adverse ventilation related events, unexpected ICU admission, ICU/hospital LOS, ARDS……
Statistics
• Assumed 20% postoperative complication rate. Arch Surg 2003;138:596-602.
• 400 pts need to detect a 50% change in complication rate. Power of 80% and α level 0.05.
• Modified intention-to-treat population.
• Appropriate descriptive and comparative statistics used
Results• 1803 underwent surgery over the 18 month period.
601 screened and 400 randomised.
• Well matched groups
• Major postoperative complications occurred in 27.5% vs 10.5% of those receiving high vs low tidal volume ventilation (P=0.001).
• 5% of patients in the protective ventilation group required postoperative ventilatory assistance for acute respiratory failure vs. 17% in the control group (P=0.001),
Authors’ conclusion
“As compared with a practice of non-protective mechanical ventilation, the use of a lung-protective ventilation strategy in intermediate-risk and high-risk patients undergoing major abdominal surgery was associated with improved clinical outcomes and reduced health care utilisation”
Limitations
• Authors – No standardised fluid administration and criteria for initiation of NIV.
• Other - Ventilatory parameters in the control group not representative of standard anaesthetic practice?
Will it change our practice?
Questions?