This study aims to determine the optimal interval for periodic alveolar recruitment maneuvers (PARM) that can achieve effective lung re-expansion in 90% of patients undergoing intraoperative mechanical ventilation during abdominal laparoscopic surgery in the low Trendelenburg position. Identifying the most effective frequency of PARM is crucial for establishing lung-protective ventilation strategies, with the ultimate goal of reducing intraoperative atelectasis, decreasing postoperative pulmonary complications, and accelerating recovery. Patients are randomized using a biased-coin sequential design. PARM is initially applied every 0.5 hours, and the effectiveness of lung re-expansion is evaluated before the end of surgery. The primary outcome is the effectiveness of recruitment, assessed by a combination of lung ultrasound scores and shunt fraction. Secondary outcomes include mechanical power at the end of surgery, time-weighted average mechanical power during ventilation, postoperative P/F ratio, dead space fraction, air test results, intraoperative adverse events, incidence of respiratory failure in the PACU and postoperative period, and postoperative length of stay. This trial is expected to provide robust evidence for defining the optimal RM interval in protective ventilation protocols for patients undergoing laparoscopic abdominal surgery, thereby contributing to improved perioperative respiratory outcomes.
This study is designed to evaluate the optimal interval of periodic alveolar recruitment maneuvers (PARM) to achieve effective lung re-expansion (defined as LUS ≤1 and shunt fraction \<10%) in 90% of elderly patients undergoing laparoscopic anterior resection in low Trendelenburg position. This is a single-arm, biased-coin sequential design study. The initial PARM interval is 30 min, adjusted in 10 min increments based on response. The primary outcome is recruitment efficacy. Secondary outcomes include intraoperative mechanical power, P/F ratio, postoperative pulmonary complications, and length of hospital stay. This study aims to inform optimal RM intervals in protective ventilation protocols.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
PREVENTION
Masking
NONE
Enrollment
52
The initial time interval of PARM was 0.5 hours/time, and the different interval of PARM was assigned by random partial coin sequential method.If the previous patient did not respond to postoperative assessment of lung opening, the interval between expansion of the lungs was shortened by 10 minutes for the next patient; If lung opening is effective, there is an 11% chance that the next patient will have an 10-minute expansion interval and an 89% chance that the time interval will remain unchanged.
The effectiveness of recruitment
The effectiveness of recruitment assessed by a combination of lung ultrasound scores and shunt fraction。At the end of surgery (with the patient in the supine position, after at least 5 minutes of apnea under mechanical ventilation without spontaneous breathing, and at the specified interval since the last recruitment maneuver), a lung ultrasound examination was performed. Lung re-expansion was considered effective if the 12-zone lung ultrasound score (LUS) was ≤1 per zone and the shunt fraction was \<10%.
Time frame: Intraoperative
Mechanical power at the end of surgery
Mean or median mechanical power
Time frame: With the patient in the supine position, after at least 5 minutes of apnea under mechanical ventilation without spontaneous breathing, and at the specified interval since the last recruitment maneuver
Time-weighted average mechanical power during surgery
Mechanical power per ventilation time
Time frame: During intraoperative mechanical ventilation
The P/F ratio at the end of surgery,
P/F ratio = PaO₂ / FiO₂.Statistical measure: Incidence of P/F ratio ≤400. The P/F ratio is an objective research parameter, and a P/F ratio ≤400 indicates the presence of atelectasis.
Time frame: At the end of surgery (with the patient in the supine position, after at least 5 minutes of apnea under mechanical ventilation without spontaneous breathing, and at the specified interval since the last recruitment maneuver)
Dead space rate
Arterial carbon dioxide partial pressure (PaCO2); partial pressure of carbon dioxide in end expiratory gas (PetCO2); Dead space fraction = (PaCO2-PetCO2)/ PaCO2.
Time frame: At the end of surgery (with the patient in the supine position, after at least 5 minutes of apnea under mechanical ventilation without spontaneous breathing, and at the specified interval since the last recruitment maneuver)
Air-breathing test
After completion of ultrasound and arterial blood gas measurements, the inspired oxygen concentration was adjusted to 21%. SpO₂ was observed and recorded after 5 minutes.The incidence of a positive air-breathing test, defined as SpO₂ ≤96%, was recorded
Time frame: At the end of surgery (with the patient in the supine position, after at least 5 minutes of apnea under mechanical ventilation without spontaneous breathing, and at the specified interval since the last recruitment maneuver)
Intraoperative hypotension
Defined as mean arterial pressure (MAP) \<60 mmHg from any cause, lasting for more than 3 minutes。
Time frame: During mechanical ventilation in the intraoperative period.
Intraoperative vasopressor use.
Defined as any episode of MAP \<60 mmHg during mechanical ventilation requiring the administration of catecholamine vasopressors, including dopamine, epinephrine, or norepinephrine. Occurrence of such an event was recorded as positive.
Time frame: During intraoperative mechanical ventilation
Intraoperative mild hypoxemia
SpO₂ ≤96% lasting for more than 3 minutes
Time frame: During intraoperative mechanical ventilation
Intraoperative severe hypoxemia
SpO₂ ≤92% lasting for more than 3 minutes
Time frame: During intraoperative mechanical ventilation
Lung ultrasound score (LUS) in the post-anesthesia care unit (PACU)
The 12-zone lung ultrasound score (LUS) ranges from 0 to 3 per zone (total 0-36). Higher scores indicate more severe atelectasis.
Time frame: Awake with spontaneous breathing before discharge from the PACU
Rate of respiratory failure at post-anesthesia care unit (PACU)
PaO₂/FiO₂ \<300 mmHg, or PaO₂ \<60 mmHg or SpO₂ \<90% while awake and breathing room air.
Time frame: Stay in the PACU for at least 20 minutes and at most 3 hours; assessed at 5 to 10 minutes before leaving PACU
Rate of postoperative respiratory failure
PaO₂/FiO₂ \<300 mmHg, or PaO₂ \<60 mmHg or SpO₂ \<90% while awake and breathing room air.
Time frame: Day1 to 5 after surgery
Rate of sustained hypoxaemia
Sustained hypoxaemia, hypoxaemia at any two consecutive days; hypoxaemia: during a follow-up visit when the patient was awake and breathing room air, SpO2 ≤ 92% or the change of SpO2 (ΔSpO2, preoperative SpO2 minus postoperative SpO2) ≥ 5%.
Time frame: Day 1 to 5 after surgery
Postoperative pulmonary complications, Grades 1-4
Operational Definitions of Postoperative Pulmonary Complications (Doi: 10.1001/jama.296.15.1851), graded on a scale from 1 to 4.
Time frame: Day 0 to 5 after surgery
Postoperative pulmonary complications, Grades 2-4
Operational Definitions of Postoperative Pulmonary Complications (Doi: 10.1001/jama.296.15.1851), graded on a scale from 2 to 4
Time frame: Day 0 to 5 after surgery
Pneumothorax
Defined as the presence of air within the pleural cavity, with the visceral pleura not being surrounded by a vascular pattern.
Time frame: Day 0 to 7 after surgery
Postoperative hospitalization days
The duration between the operation date and the actual discharge date.
Time frame: Day 0 to 30 after surgery
Unexpected admission to ICU
It does not include the patients who enter ICU at the request of surgeons but have normal spontaneous breathing, stable circulation and no disturbance of consciousness.
Time frame: within 30 days after surgery
Death from any cause
Intraoperative or postoperative death from any cause
Time frame: Day 0 to 30 after surgery
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