Entonox® inhalation to reduce pain in common diagnostic and therapeutic outpatient urological procedures: a review of the evidence

Abstract

Entonox(®) (50% nitrous oxide and 50% oxygen; BOC Healthcare, Manchester, UK) is an analgesic and anxiolytic agent that is used to successfully reduce pain and anxiety during dental, paediatric and emergency department procedures. In this article we review the application and efficacy of Entonox(®) in painful local anaesthesia urological procedures by performing a systematic review of the literature. A MEDLINE(®) search was performed using the terms 'nitrous oxide', 'Entonox', 'prostate biopsy', 'flexible cystoscopy' and 'extracorporeal shock wave lithotripsy'. English language publications of randomised studies were identified and reviewed. The search yielded five randomised studies that investigated the clinical efficacy of Entonox(®) as an analgesic for day case urological procedures. Three randomised controlled trials (RCTs) investigated Entonox(®) in transrectal ultrasonography guided prostate biopsy. All three reported significant reductions in pain score in the Entonox(®) versus control groups. One RCT reported significant reduction in pain during male flexible cystoscopy in the Entonox(®) group compared with the control group. One RCT, which examined the use of Entonox(®) during extracorporeal shock wave lithotripsy, found its use significantly decreased the pain score compared with the control group and this was comparable to intravenous pethidine. Evidence from varied adult and paediatric procedures has shown Entonox(®) to be an effective, safe and patient acceptable form of analgesia. All published studies of its use in urological day case procedures have found it to significantly reduce procedural pain. There is huge potential to use this cheap, safe, effective analgesic in our current practice.