Use of Nitrous Oxide for Analgesia During Colonoscopy - A Randomised Trial

Background

Colonoscopy is the gold standard for diagnosis and endoscopic treatment of diseases in the colon and rectum (1). However, many patients experience discomfort during the procedure. Therefore, IV sedation and/or analgesia is routinely given during colonoscopy at the majority of centers around the world.

Midazolam, the most frequent sedative, is a benzodiazepine with hypnotic and sedative effects (2). The half-life of the substance is about 1-2.5 hours, and thus substantially longer than the duration of a colonoscopy (approximately 30 minutes). Additionally, Midazolam gives pronounced amnesia that lasts even longer than the hypnotic effect. Opioids are also frequently used during colonoscopy, with Pethidine as the most common one (half-life: 3 hours).

Use of the above mentioned drugs make it necessary to closely monitor the patients after colonoscopy for several hours, often in specially designed resource-demanding recovery units. Furthermore, due to the amnesia, it is often not possible to give information about findings and further work-up or surveillance to patients after colonoscopy. Finally, patients are not allowed to drive a car for the rest of the day after IV sedation during colonoscopy (2).

Nitrous oxide (N2O) is used as an inhalative gas during anesthesia, labour and at some dentist practices, most frequent in a fixed 50:50 combination with O2. N2O has a strong analgetic effect, and none or only slight sedative effects in concentrations < 80%. N2O has a very rapid onset of effect (a few seconds), and its half-life in the human body after the stop of inhalation is shorter than 1 minute (3). Patients receiving N2O in a 50:50 combination with O2 are awake, don't need post-procedure recovery and may drive their own car home (4). However, as N2O diffuses quickly through biological membranes, caution is warranted when used for patients with the following conditions: sinusitis, otitis, ileus, bowl obstruction, and megacolon. Pregnant women should not be exposed to N2O.