Effect of Nitrous Oxide in Treating Neuropathic Pain: A Study in Chronic Low Back Pain Patients

Epidural injection will be completed under fluoroscopy and all patients will receive 1-4 mg
of Midazolam for relaxation before procedure and, if needed, 50-100 mcg of Fentanyl
intravenous (IV). Radiopaque contrast (Omnipaque 300), for confirming the epidural position
of the needle, steroids and local anesthetic agents will be used according to the physician
performing the block and will not be controlled by the study. Patients will be randomly
assigned to receive either inhaled Entonox along with the interventional block they are
scheduled for or oxygen. They will be blinded about the treatment they are receiving. Those
randomized to Entonox will inhale the gas through a mouthpiece throughout the procedure and
also continue to receive it for a total of 4 hours in the recovery. Those randomized to the
oxygen group will receive oxygen through a similar mouthpiece for the entire duration of the
procedure and recovery for 4 hours. Following completion of procedure the patient will be
transferred to recovery and monitored for 3-5 hours then discharged home with instructions.
Possible side effects will be monitored and recorded, pain score of patient will be recorded
before discharge. All the patients will receive standard instructions regarding physical
back exercises. This will be repeated for every procedure up to maximum of three blocks.

The patients will be followed during each block and over a period of 1, 3, 6 and 12 months
and on each follow-up visit will complete computerized set of questionnaires as they did
before the procedure. The patients charts will be then reviewed for one year after the
initial procedure to determine if further epidural steroid injections or surgery for the
presenting problem were required. It is anticipated that the appropriate number of patients
will be enrolled within six months of study initiation.