Intraoperative protective mechanical ventilation in patients requiring emergency abdominal surgery: the multicentre prospective randomised IMPROVE-2 study protocol

Emergency abdominal surgery is associated with a high risk of postoperative complications. One of the most serious is postoperative respiratory failure (PRF), with reported rates up to 20%–30% and attributable 30-day mortality that can exceed 20%. Lung-protective ventilation, especially the use of low tidal volume, may help reducing the risk of lung injury. The role of positive end-expiratory pressure (PEEP) and recruitment manoeuvre (RM) remains however debated. We aim to evaluate whether a strategy aimed at increasing alveolar recruitment by using higher PEEP levels and RM could be more effective at reducing PRF and mortality after emergency abdominal surgery than a strategy aimed at minimising alveolar distension by using lower PEEP levels without RM. METHODS AND ANALYSIS: The IMPROVE-2 study is a multicentre randomised, parallel-group clinical trial of 680 patients requiring emergency abdominal surgery under general anaesthesia. Patients will be randomly allocated in a 1:1 ratio to receive either low PEEP levels (≤5 cm H(2)O) without RM or high PEEP levels individually adjusted according to driving pressure in addition to RM, stratified by centre and according to the presence of shock and hypoxaemia at randomisation. The primary endpoint is a composite of PRF and all-cause mortality by day 30 or hospital discharge. Data will be analysed on the intention-to-treat principle and a per-protocol basis. ETHICS AND DISSEMINATION: IMPROVE-2 trial has been approved by an independent ethics committee for all study centres. Participant recruitment began in February 2021. Results will be submitted for publication in international peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT03987789.