Modified Rapid Sequence Induction in Morbidly Obese Patients

100 adult patients with a body mass index > 40 undergoing elective laparoscopic surgery will be included. Patients with a history of previous bariatric surgery or with an anticipated difficult airway will be excluded.

The randomization will be 1:1:1:1 stratified for gastro-esophageal reflux disease.

All groups will receive standardized preoperative continuous positive airway pressure (CPAP) therapy.

In the operation theater, Group one will receive pre-oxygenation for 3 minutes via a tight fitting face mask without positive end-expiratory pressure (PEEP). Induction agents will be administered as quick boluses (Propofol 2,5mg/kg total body weight, max 350mg, Fentanyl 250mcg, Rocuronium 1,2mg/kg ideal body weight) and tracheal intubation will be performed after 1 minute. No bag mask ventilation will be performed in-between.

Group 2 will receive pre-oxygenation via a tight face mask with a PEEP of 10 mbar for 3 minutes. The same induction agents as in group one will be administered. PEEP via facemask will be continued for one minute and tracheal intubation will be performed.

Group 3 will receive pre-oxygenation via a tight fitting facemask with a PEEP of 10 mbar with additional pressure support of 8 mbar and a back up ventilation frequency will be set to 10/min. After the same induction agents are given as in group 1, patients will receive non-invasive ventilation via ventilator at the settings described earlier for group 3.

Group 4 will receive the same induction as group 3, in addition a cricoid pressure will be applied during the non invasive ventilation.

• Rapid sequence induction t-RSI (Procedure): Preoxygenation via face mask, no ventilation with no PEEP until intubation
• Rapid sequence induction m-RSI-PEEP (Procedure): Preoxygenation via facemask with PEEP of 10 mbar. PEEP will be continued until intubation.
• Rapid sequence induction m-RSI-vent (Procedure): Preoxygenation via facemask with 10 mbar PEEP and 8 mbar pressure support. Backup frequency set at 10/min. Ventilation via anesthetic machine until intubation.
• m-RSI-vent-cric (Procedure): Preoxygenation via facemask with 10 mbar PEEP and 8 mbar pressure support. Backup frequency set at 10/min. Ventilation via anesthetic machine until intubation.
• Cricoid Pressure (Procedure): Cricoid Pressure will be applied during RSI until laryngoscopy
• Anesthetics (Drug), also known as Induction Agents: Induction agents will be administered as quick boluses (Propofol 2,5mg/kg total body weight, max 350mg, Fentanyl 250mcg, Rocuronium 1,2mg/kg ideal body weight).
• Aspiration of gastric air via nasogastric tube (Diagnostic test): A nasogastric tube will be inserted at the beginning of laparoscopy and the air from the stomach will be aspirated with a syringe. The amount of air will be measured in ml.
• Impression of gastric inflation at laparoscopy. (Diagnostic test): The impression of gastric inflation at laparoscopy. At the beginning of laparoscopy, images of the stomach will be recorded.
• Arterial blood gas (Diagnostic test): Arterial blood gases will we drawn at different time points to investigate oxygenation during the procedure. Blood gases will be taken before pre-oxygenation, before anesthesia induction, before laryngoscopy, immediately after intubation when the cuff of the tracheal tube is inflated.

Primary outcomes

• Amount of air aspirated with a gastric tube [at the beginning of the laparoscopy]: The amount of air that can be aspirated via a nasogastric tube at the beginning of laparoscopy. A nasogastric tube will be inserted at the beginning of laparoscopy and the air from the stomach will be aspirated with a syringe. The amount of air will be measured in ml.

Secondary outcomes

• Gastric inflation [at the beginning of laparoscopy]: The impression of gastric inflation at laparoscopy. At the beginning of laparoscopy, images of the stomach will be recorded. These images will afterwards be reviewed in a blinded fashion by three different investigators. The investigators will rate their impression of gastric inflation (empty, mildly inflated, inflated, very inflated).
• partial pressure of oxygen in arterial blood (paO2) [before pre oxygenation, before anesthesia induction, before laryngoscopy, immediately after intubation when the cuff of the tracheal tube is inflated]: Arterial blood gases will we drawn at different time points to investigate oxygenation during the procedure. Blood gases will be taken before pre-oxygenation, before anesthesia induction, before laryngoscopy, after intubation.

Sex: All, ages: 19 Years to any

Inclusion Criteria:

* BMI > 40
* American Society of Anesthesiology Class 1-3
* Elective laparoscopic surgery

Exclusion Criteria:

* Pregnant or breastfeeding patients
* Previous bariatric surgery
* Anticipated difficult airway

• Walter Plöchl, Professor, Principal investigator, Medical University of Vienna