Comparison of Modified Lung Ultrasound Score (LUSS) in patients undergoing robot assisted abdominal and pelvic surgeries in Trendelenburg position under general anesthesia with driving pressure targeted individualized PEEP versus empiric fixed PEEP - A Randomized Controlled Trial

Background

Robotic surgery, while offering ergonomic benefits, can lead to increased intra-abdominal pressure (due to CO2 insufflation) and the Trendelenburg position, both of which heighten the risk of PPCs, including atelectasis. To mitigate these risks, lung protective ventilation strategies are recommended, but the optimal level of positive end-expiratory pressure (PEEP) remains unclear.

   

Study Hypothesis

Ventilation strategies targeting driving pressure—defined as the difference between plateau pressure and PEEP—will lead to lower lung ultrasound scores (LUSS) and reduced PPCs compared to conventional ventilation strategies using fixed PEEP. The driving pressure-based strategy will individualize PEEP levels to minimize atelectasis and other pulmonary complications.

Previous Research

In a prior study, the authors found that driving pressure-directed PEEP resulted in higher lung compliance, lower plateau pressures, and fewer lung injury biomarkers compared to fixed PEEP, although PPCs did not differ significantly.

Objectives:

Primary Objective: To compare LUSS (a proxy for atelectasis) in patients at high risk for PPCs undergoing robotic surgeries with driving pressure-directed PEEP vs conventional fixed PEEP.

Secondary Objectives:

1. Compare peak inspiratory pressure (PIP), plateau pressure, PEEP, and PaO2/FiO2.

2. Compare the incidence of PPCs between the two groups.

3. Correlate LUSS with PPC development.

4. Measure the levels of serum biomarkers (e.g., HS-CRP, IL-1β) to assess inflammation and lung injury.

Study Design:

• Participants:Adults (18-75 years) with ASA II or III, BMI 18-35 kg/m², and ARISCAT score >26, undergoing robotic abdominal/pelvic surgery.

• Interventions:

• Group DP (Targeted PEEP): PEEP adjusted to maintain a driving pressure of ≤13 cm H2O.

• Group C (Conventional PEEP): Fixed PEEP of 6 cm H2O.

  

• Randomization: Block randomization, with allocation concealment and double blinding.

• Data Collection: Measurements at multiple time points during surgery (e.g., PIP, plateau pressure, PEEP, LUSS, biomarkers). Lung ultrasound performed pre- and post-surgery to assess aeration and atelectasis.

Study Outcomes

1. LUSS: Used to assess lung aeration, with scores ranging from 0 (normal) to 3 (severe consolidation).

2. PPCs: Defined using a detailed classification (Grade 0–5), with Grade 2 or higher including clinically significant complications like atelectasis, hypoxemia, or pneumonia.

3. Biomarkers: Serum levels of HS-CRP and IL-1β will be measured pre- and post-surgery to evaluate the inflammatory response.

Inclusion/Exclusion Criteria:

• Inclusion: Patients with ARISCAT score >26, undergoing surgeries like prostate, rectal, and hysterectomy.

• Exclusion: Conditions like COPD, cardiac comorbidities, or pregnancy, among others.

Study Procedure

1. Preoperative Phase:

• Patient Enrollment: Patients aged 18-75 with an ARISCAT score >26 and scheduled for robotic abdominal/pelvic surgeries in the Trendelenburg position are enrolled.

• Consent: Written informed consent is obtained from all patients.

• Randomization: After preoperative assessment, patients are randomly assigned to one of two groups:

• Group DP: Targeted driving pressure-based PEEP.

• Group C: Conventional PEEP (fixed).

• Preoperative Data Collection:

• Baseline lung ultrasound is performed.

-Baseline serum sample is collected

• Preanesthetic assessment (including medical history, BMI, ASA status, etc.) is recorded.

 2. Intraoperative Phase:

• Anesthesia and Ventilation Setup:

• General anesthesia is induced with fentanyl, propofol, and vecuronium.

• Routine monitoring is established (e.g., ECG, blood pressure, SpO2).

• Volume-controlled ventilation is initiated with a tidal volume of 7 ml/kg and respiratory rate aimed at maintaining ETCO2 between 35-40 mmHg.

• PEEP is set to 6 cm H2O in both groups at the start.

  -Pneumoperitoneum and Trendelenburg Position:

• After creating pneumoperitoneum and positioning the patient in Trendelenburg, ventilation adjustments are made:

• Group DP: PEEP is increased stepwise to maintain a driving pressure ≤ 13 cm H2O.

• Group C: PEEP remains fixed at 6 cm H2O.

  - Ventilation Monitoring and Adjustments:

• Plateau pressures, PEEP, and compliance are monitored throughout surgery.

• Lung ultrasound is performed intraoperatively (post-pneumoperitoneum and Trendelenburg) to assess lung aeration.

• If necessary, adjustments to PEEP, FiO2, or recruitment maneuvers may be performed based on intraoperative desaturation (SpO2 ≤ 95%) or hypotension.

 3. Postoperative Phase:

• Post-surgery Extubation:

• After surgery, patients are extubated if they meet the criteria (e.g., TOF ratio >0.9, spontaneous breathing, adequate response to commands).

  - Postoperative Monitoring:

• Lung ultrasound is repeated immediately post-extubation and 15-30 minutes later to assess for changes in lung aeration.

• Blood samples are collected for analysis of serum biomarkers (IL-1β, HS-CRP).

• Postoperative complications (PPCs) are monitored for up to 3 days post-surgery.

• Chest X-ray is performed on postoperative day 1 to assess for signs of atelectasis or other pulmonary complications.

 4. Outcome Measurement:

• Primary Outcome:

• Lung ultrasound score (LUSS) is used to assess the extent of lung aeration and atelectasis

• Secondary Outcomes:

• PPCs are graded from 0 (no symptoms) to 5 (death) based on clinical findings.

• Serum levels of inflammatory markers (HS-CRP, IL-1β) are compared between the groups to assess the degree of inflammation and lung injury.

 5. Follow-up:

• Patients are followed up for 3 days postoperatively to monitor for any respiratory symptoms.

• Those discharged before the follow-up period will be contacted telephonically to assess any delayed symptoms.

Ethical Considerations

• The study will be conducted under standard anesthesia protocols with ethics approval and informed consent.

• Data monitoring will ensure safety, with an interim analysis planned after 50% of the participants are enrolled.

Conclusion

The study seeks to establish whether personalized ventilation strategies based on driving pressure can reduce postoperative pulmonary complications and improve lung function in patients at higher risk of PPCs undergoing robotic surgeries. If successful, this approach could lead to more tailored, effective ventilation strategies in high-risk surgical populations, reducing atelectasis and improving overall outcomes.