a trial of intraoperative low tidal-volume ventilation in abdominal

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?