Effect of Positive End-expiratory Pressure on the Gastric Volume

Not Applicable

Not yet recruiting

• Conditions: Gastric Volume; Breast Cancer Female; Anesthesia Complication

• Registration Number: NCT06861569
• Lead Sponsor: Seoul National University Bundang Hospital

Brief Summary

The main purpose of this study is to quantitatively evaluate the effect of applying PEEP during the use of SGA on gastric volume, aiming to provide objective evidence regarding the potential side effects, such as gastric volume increase. It is expected that this will contribute to improving the quality of patient management through the safe clinical use of SGA and PEEP.

Detailed Description

General anesthesia has positive effects in relieving pain and unpleasant memories during surgery by blocking the patient's voluntary movements and reflexes to stimuli. However, it can lead to side effects such as severe impairment or absence of spontaneous breathing, necessitating artificial respiration. Among the conventional airway management methods for artificial respiration, the supraglottic airway device (SGA) has the advantage of reducing hemodynamic changes, intracranial pressure, and intraocular pressure caused by airway stimulation, as it does not pass through the airway, and it reduces airway-related complications. However, a disadvantage is its inability to adequately seal the airway, making it difficult to use in cases where there is a high risk of aspiration or when high airway pressures are required.

Positive End Expiratory Pressure (PEEP) has the advantage of preventing atelectasis, improving oxygen exchange capacity, and preventing pulmonary complications by maintaining lung expansion. However, applying PEEP increases airway pressure, and if the SGA does not adequately seal the airway, there is a possibility of air entering the stomach. If air enters the stomach and increases gastric volume, the risk of postoperative vomiting and aspiration pneumonia increases due to increased gastric pressure. Also, increased intra-abdominal pressure and diaphragmatic elevation can lead to respiratory distress due to decreased lung volume during postoperative recovery.

While there are studies suggesting that PEEP can be safely used with SGA, there is a need for verification as there are no studies objectively measuring changes in gastric volume using methods such as ultrasound when using PEEP with SGA. The main purpose of this study is to quantitatively evaluate the effect of applying PEEP during the use of SGA on gastric volume, aiming to provide objective evidence regarding the potential side effects, such as gastric volume increase. It is expected that this will contribute to improving the quality of patient management through the safe clinical use of SGA and PEEP.

Before entering the operating room, patients will be placed in a sitting and right lateral decubitus (RLD) position to measure the cross sectional area(CSA) of the stomach antrum using ultrasound. One investigator will scan the sagittal plane in the upper abdominal region using a low-frequency ultrasound probe (2-5 MHz) and measure the major diameter (D1) and transverse diameter (D2) of the observed antrum. CSA can be calculated from the measured values as in formula (a) below. The investigator will scan three times for each posture, and calculate the average.

CSA = D1 x D2 x 1/4 ------- (a) Using CSA, gastric volume (GV) is estimated using formula (b) below. GV (ml) = 27.0 + 14.6 × CSA - 1.28×age ------- (b) Midazolam premedication is not administered before surgery. When patients enter the operating room, standard monitoring devices (electrocardiogram, pulse oximetry, non-invasive blood pressure monitor, BIS or SedLine) are attached for vital sign monitoring, and target-controlled infusion of propofol is initiated at a target concentration of 4.0 µg/ml, and remifentanil at a target concentration of 3.0 ng/ml.

After confirming loss of consciousness and loss of spontaneous respiration, SGA is inserted, and the position of the SGA is evaluated and recorded using the fiberoptic scoring system.

During surgery, maintenance of anesthesia is managed with target-controlled infusion of propofol to keep BIS (Bispectral Index) between 40-60 or PSI (Patient State Index) between 25-49. For adequate analgesia during surgery, remifentanil is continuously infused using target-controlled infusion.

At 5 minutes (T0), 30 minutes (T1), and 60 minutes (T2) after SGA insertion, the following values related to mechanical ventilation are measured: FiO2 (Fraction of Inspired Oxygen), PIP (Peak Inspiratory Pressure), RR (Respiratory Rate), lung compliance, SpO2 (Oxygen Saturation), EtCO2 (End-tidal Carbon Dioxide), TV (Tidal Volume), OLP (Oropharyngeal Leak Pressure), leak volume, and leak fraction.

Immediately after surgery, CSAright-lat and GV are measured as described in above. After confirming that respiration and consciousness levels have returned to clinically normal conditions post-surgery, the patient is discharged to the recovery room, and assessments are made for nausea or vomiting, respiratory depression, sore throat, and blood staining.

Study Timeline

• Status Verified: 2024-04
• Study First Submitted: 2025-02-15
• Study First Submitted QC: 2025-03-02
• Last Update Submitted: 2025-03-02
• Study First Posted: 2025-03-06
• Last Update Posted: 2025-03-06
• Study Start: 2025-03-15
• Primary Completion: 2026-02-01
• Study Completion: 2026-02-02

Recruitment & Eligibility

• Status: NOT_YET_RECRUITING
• Sex: All
• Target Recruitment: 128

Inclusion Criteria

• Adult patients aged 19 and above.
• Patients scheduled for general anesthesia for elective surgery.
• American society of anesthesiologists physical status classification 1 or 2

Exclusion Criteria

• Individuals who have not provided prior consent for participation in the study
• Patients showing cognitive impairment to the extent that voluntary consent is difficult
• Obesity with a BMI of 30 kg/m² or higher
• Patients with anatomical abnormalities in the airway structure making supraglottic airway device application difficult
• Patients with respiratory diseases making PEEP application difficult (e.g., chronic obstructive pulmonary disease, asthma)
• Patients suspected of delayed gastric emptying (e.g., not adhering to fasting guidelines, medication use affecting gastric motility [anticholinergics, narcotic analgesics], neurological disorders [Parkinson's disease, multiple sclerosis], diabetes, hypothyroidism)
• Patients with a history of gastrointestinal surgery
• Pregnant women
• Patients undergoing concurrent surgeries or collaborative procedures
• Patients transferred from the intensive care unit

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Primary Outcome Measures

Name	Time	Method
Gastric volume difference before and after surgery	Baseline and end of surgery 0 minute	Before and after the surgery, the patient is positioned in a sitting position and then in the right lateral decubitus (RLD) position. Ultrasound is used to measure the cross-sectional area (CSA) of the gastric antrum and then it is substituted into the following equation to estimate gastric volume.; GV (ml) = 27.0 + 14.6 × CSAright-lat - 1.28×age The scanning is performed three times for each position to obtain the average value.

Secondary Outcome Measures

Name	Time	Method
Fraction of Inspired Oxygen	5 minutes, 30 minutes, 60 minutes after SGA insertion	The measured values during mechanical ventilation are averaged.
Peak Inspiratory pressure	5 minutes, 30 minutes, 60 minutes after SGA insertion	The measured values during mechanical ventilation are averaged.
Respiratory rate	5 minutes, 30 minutes, 60 minutes after SGA insertion	The measured values during mechanical ventilation are averaged.
Lung compliance	5 minutes, 30 minutes, 60 minutes after SGA insertion	The measured values during mechanical ventilation are averaged.
Oxygen Saturation	5 minutes, 30 minutes, 60 minutes after SGA insertion	The measured values during mechanical ventilation are averaged.
End-tidal carbon dioxide	5 minutes, 30 minutes, 60 minutes after SGA insertion	The measured values during mechanical ventilation are averaged.
Tidal volume	intraoperative period	The measured values during mechanical ventilation are averaged.
Oropharyngeal leak pressure	5 minutes, 30 minutes, 60 minutes after SGA insertion	The measured values during mechanical ventilation are averaged.
Leak volume and leak fraction	5 minutes, 30 minutes, 60 minutes after SGA insertion	The measured values during mechanical ventilation are averaged. Leak volume is defined as the difference between inspired and expired tidal volume. Leak fraction is defined as the ratio of leak volume/inspired tidal volume.
Presence of blood staining on SGA	Immediately after the end of anesthesia	When the SGA is removed after the surgery, check whether there is blood staining on the SGA.
The duration of stay in the recovery room after surgery	upto 1 hour after entering the recovery room	The time from admission to the recovery room to discharge
Presence of postoperative nausea and vomiting	upto 1 hour after entering the recovery room	Postoperative nausea and vomiting which occur during the time from the end of surgery until discharge from the recovery room.
Presence of respiratory depression	upto 1 hour after entering the recovery room	Respiratory depression which occurs during the time from the end of surgery until discharge from the recovery room.
Presence of sore throat	upto 1 hour after entering the recovery room	Sore throat which occurs during the time from the end of surgery until discharge from the recovery room.