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

Effect of Nitrous Oxide in Treating Neuropathic Pain: A Pilot 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.

Inclusion Criteria:

• 18 to 80 years old at time of the first procedure
• Male or female
• History of chronic low back pain for longer than 6 months due to radiculopathy, symptomatic spinal canal stenosis, disc prolapse, postlaminectomy syndrome
• magnetic resonance imaging or electromyographic evidence of nerve root damage
• Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) score of >12
• No or minimal evidence of facet joint pathology

Exclusion Criteria:

• Known contraindications for epidural injection
• Patients with ongoing workers' compensation claims
• unstable or heavy opioid use (400 mg of morphine equivalents daily),
• psychiatric disorders
• medical illness, including conditions that could interfere with the interpretation of the outcome assessments
• pregnant or lactating women
• Current or recent drug abuse (within past 6 months).
• Patient refuses regional analgesia.
• Alcohol or drug abuse