The Effect of an Opioid on the Lower Esophageal Sphincter During Anesthesia Induction

During anesthesia induction and tracheal intubation one major concern is to avoid passive regurgitation of gastric content and aspiration.

The lower esophageal sphincter is a muscle located at the distal end of the esophagus. It plays an important role in creating a barrier between the stomach and the esophagus. The term "barrierpressure" is defined as the pressure difference between the lower esophageal sphincter pressure and the pressure in the stomach (intragastric pressure).

There are studies showing that opioids given iv/im, in the vein or in the muscle, may decrease the pressure in the lower esophageal sphincter and hereby increase the risk of aspiration.

Nevertheless,other studies shows that opioids are still frequently given to patients during anesthesia induction. This is done in order to prevent the cardiovascular response to (the painful) intubation which can often be seen as an equally high risk for the patient as the risk of aspiration.

In light of the above description, the investigators are planning a study in volunteers with the primary aim of investigating the effects of an opioid (alfentanil) on the pressures in the lower esophageal sphincter.

Another safety measure taken during anesthesia induction is the so called "cricoid pressure". This is based on the theory that passive regurgitation of gastric content may be prevented by occluding the esophagus by pressing on the cricoid cartilage. However, there are studies indicating that the application of cricoid pressure also may decrease the tonus of the lower esophageal sphincter.

The secondary aim of the study is to investigate the effect of cricoid pressure application on the pressure in the lower esophageal sphincter.

Measurements are being done using high-resolution solid-state manometry.