Postoperative respiratory complications, such as bacterial pneumonia, are common and serious problems after general anesthesia. They can lead to longer hospital stays, more complications, and increased mortality. One possible cause is that bacteria from the mouth and throat enter the lower airways during tracheal intubation.

The mouth and throat naturally contain many bacteria, including potentially harmful microorganisms. During general anesthesia, coughing and swallowing reflexes are reduced or absent. When a tracheal tube is inserted, secretions from the mouth and throat may be carried into the trachea. The tube may also support the movement of contaminated fluid into the lower airways.

ORAL-PROTECT I is a prospective, randomized, controlled study. It investigates whether simple oral hygiene before surgery can reduce the transfer of bacteria into the trachea during airway management under general anesthesia.

The study includes patients aged 60 years or older undergoing elective surgery under general anesthesia with tracheal intubation. Participants are randomly assigned to an intervention group or a control group. The intervention group performs oral hygiene immediately before anesthesia. This includes brushing the teeth and tongue for about 3 minutes, followed by rinsing and gargling for about 1 minute with a chlorhexidine antiseptic solution. The control group receives standard care without additional oral hygiene.

Oral, pharyngeal, and tracheal swabs will be collected at predefined time points. The primary outcome is based on the perioperative tracheal bacterial load, sampled every 30 minutes and assessed at two hours after induction of anesthesia. The co-primary outcome is based on the oral bacterial load immediately before endotracheal intubation.

Secondary outcomes include changes in oral and tracheal bacterial load over time and identification of the microorganisms detected. The study aims to clarify early bacterial transfer during airway management and to evaluate whether a simple preoperative oral hygiene measure can reduce this process.

ORAL-PROTECT I is a prospective, randomized, controlled, unblinded, parallel-group trial investigating whether preoperative oral hygiene can reduce early bacterial transmission from the mouth and throat into the trachea during airway management under general anesthesia.

Postoperative respiratory complications, including bacterial pneumonia, are common and clinically relevant adverse events after general anesthesia. They can contribute to increased morbidity, prolonged hospital stay, and mortality. One possible mechanism is the transmission of bacteria from the oral cavity and pharynx into the lower airways during tracheal intubation. The oral cavity and pharynx naturally contain a broad bacterial flora, including potentially pathogenic microorganisms. During general anesthesia, protective swallowing and coughing reflexes are reduced or absent. During tracheal intubation, bacteria-contaminated secretions from the mouth and throat may enter the trachea and lower airways.

The study includes patients aged 60 years or older undergoing elective surgery under general anesthesia with tracheal intubation. Potentially eligible patients are screened before surgery. Patients are screened for eligibility during pre-admission testing and are approached for study participation. On the day of surgery, patients are reassessed for eligibility before randomization to confirm that eligibility criteria are still met. Patients who performed oral hygiene less than four hours before induction are excluded before randomization.

Eligible participants are randomly assigned to either the intervention group or the control group using a REDCap-based randomization tool. Participants in the intervention group undergo supervised oral hygiene immediately before induction of anesthesia, consisting of 3 minutes of tongue and tooth brushing and 1 minute of chlorhexidine gargling. Participants in the control group receive standard clinical care without additional preoperative oral hygiene measures. All other perioperative procedures, including anesthetic management, airway management, surgical care, and postoperative treatment, are at the discretion of the treating anesthesiologist and independent of study participation.

Bacterial load is assessed using swab-based microbiological sampling at predefined time points. Samples are collected from the oral cavity, pharynx, and trachea to describe perioperative bacterial contamination and its development over time. The perioperative tracheal bacterial load is sampled at 30-minute intervals.

Sample handling and microbiological processing follow a standardized operating procedure. This includes uniform transport conditions, timely laboratory processing, neutralization of residual antiseptic activity, serial dilution, plating on appropriate culture media, aerobic incubation, and quantitative colony counting. Samples from both study groups are processed identically to minimize systematic bias and allow reliable comparison of bacterial load. Additional assessments include the intraoperative course of tracheal bacterial load, tracheal bacterial load before extubation, oral bacterial load approximately 24 hours after surgery, and qualitative microbiological characterization of detected bacteria. Adverse events are evaluated after the intervention and anesthesia.

The study aims to provide insight into early perioperative bacterial transmission during airway management and to evaluate whether a simple, low-risk preoperative oral hygiene intervention can influence bacterial contamination of the trachea under general anesthesia.

Inclusion Criteria:

• Age ≥ 60 years
• Elective surgery under general anesthesia with endotracheal intubation
• Expected duration of surgery ≥ 2 hours
• Ability to provide written informed consent

Exclusion Criteria:

• Systemic antibiotic therapy within 7 days before surgery
• Planned postoperative systemic antibiotic therapy
• Known hypersensitivity or allergy to chlorhexidine
• Pneumonia or clinically relevant respiratory infection within 7 days before surgery
• Inability to perform the study intervention as intended
• Preoperative oral hygiene on the day of surgery, less than four hours prior to induction of the general anesthesia