Impact of an Open Lung Extubation Strategy on Postoperative Pulmonary Complications

Impact of an Open Lung Extubation Strategy on Postoperative Pulmonary Complications Compared to a Conventional Extubation Strategy: a Pilot Study

Perioperative respiratory complications are a major source of morbidity and mortality. Postoperative atelectasis plays a central role in their development. Protective "open lung" mechanical ventilation aims to minimize the occurrence of atelectasis during the perioperative period. Randomized controlled studies have been performed comparing various "open lung" ventilation protocols, but these studies report varying and conflicting effects. The interpretation of these studies is complicated by the absence of imagery supporting the pulmonary impact associated with the use of different ventilation strategies. Imaging studies suggest that the gain in pulmonary gas content in "open lung" ventilation regimens disappears within minutes after the extubation. Thus, the potential benefits of open-lung ventilation appear to be lost if, at the time of extubation, no measures are used to keep the lungs well aerated. Recent expert recommendations on good mechanical ventilation practices in the operating room conclude that there is actually no quality study on extubation. Extubation is a very common practice for anesthesiologists as part of their daily clinical practice. It is therefore imperative to generate evidence on good clinical practice during anesthetic emergence in order to potentially identify an effective extubation strategy to reduce postoperative pulmonary complications.

The aim of this study is to establish the feasibility of a multicenter randomized controlled clinical trial comparing two clinical strategies called "open lung" and "conventional" during extubation. The investigators also aim to estimate the rates of postoperative pulmonary complications in the two intervention groups and verify the hypothesis that the "open lung" extubation strategy improves postoperative lung aeration as measured by the quantitative Lung Ultrasound Score compared to a conventional extubation strategy. Methods A pilot, prospective, randomized and controlled triple-blind study. Sixty-nine patients scheduled to undergo elective surgery at the CHUM and at moderate or high risk of postoperative pulmonary complications according to the ARISCAT score will be recruited. Following the administration of standardized mechanical ventilation and after obtaining consent, participants will be randomly assigned to two groups: Intervention group, "open lung" extubation strategy and Control group, "conventional" extubation strategy.

Before starting emergence from anesthesia, the patient will be transferred to their hospital bed or stretcher and seated at 30 degrees. Secretions from the patients' oropharynx will be suctioned. To prevent the patient from coughing, the anesthetic gas or intravenous agent will be stopped after the transfer and suction procedure are completed. The FiO2 will be maintained at the same level or increased to 50% (minimum FiO2) with a fresh gas flow rate greater than or equal to 10 L.min-1. The ventilation mode will be changed to pressure support. The level of pressure support will be modified by the anesthesiologist to generate the same volumes as with controlled ventilation. The PEEP will be maintained at the same level. The minimum respiratory rate will be reduced by 4 min-1. The inspiratory flow for triggering will be 2 L.min-1.

Before starting emergence from anesthesia, the patient will be transferred to his hospital bed or stretcher and kept in the supine position. Secretions from the patients' oropharynx will be suctioned. To prevent the patient from coughing, the anesthetic gas or intravenous agent will be stopped after the transfer and suction procedure are completed. The FiO2 will be increased to 100% with a fresh gas flow rate greater than or equal to 10 L.min-1. The ventilator will be stopped with the APL valve open to atmosphere. The patient will be manually ventilated with the reservoir bag until spontaneous ventilation resumes. Then, the patient may be manually assisted if the treating anesthesiologist deems it necessary.

During emergence from general anesthesia, a research assistant will observe the adherence to the protocol. The adherence rate will be defined as the number of extubations performed according to the protocol and the patient assigned group divided by the total number of awakenings. In the event of a breach of the protocol, the specific elements that led to the deviation will be noted as well as the reasons given by the treating anesthesiologist to justify it.

Postoperative pulmonary complications will be defined using the definition recommended by the StEP group. These will be compiled from the patient's arrival in the recovery room until the 7th postoperative day or, if earlier, until discharge from hospital. Adjudication of complications will be performed by 2 investigators blinded to the treatment group. Any disagreement will be resolved by discussion between the two reviewers.

A lung ultrasound will be performed on each patient during pre-emergence preparations and 15 minutes after the patient arrives in the recovery room. The quantitative Lung Ultrasound Score will be calculated for each ultrasound examination. The physician performing the ultrasound examinations will be kept blind from the intervention group.

Inclusion Criteria: Patients over 18 years of age requiring elective surgery under general anesthesia and hospitalization. Patients with a moderate or high risk of postoperative pulmonary complication according to the ARISCAT score (score of 26 or more) Exclusion Criteria: Expected or known difficult intubation according to the treating anesthesiologist Postoperative mechanical ventilation (planned or unplanned) Neuromuscular disease Intrathoracic surgery Respiratory failure, sepsis or mechanical ventilation in the month preceding anesthesia Pregnancy Patient refusal Ultrasound sub-study: Body mass index greater than 40 kg.m-2 Extensive postoperative chest dressings Clinician's refusal to participate