Intrathecal opioid versus ultrasound guided fascia iliaca plane block for analgesia after primary hip arthroplasty: study protocol for a randomised, blinded, noninferiority controlled trial.

BACKGROUND: Hip replacement surgery is increasingly common due to an ageing population, and rising levels of obesity. The provision of excellent pain relief with minimal side effects is important in order to facilitate patient mobilisation and rehabilitation.Spinal opioids provide excellent analgesia but are associated with adverse effects. The fascia-iliaca block is an alternative technique which provides analgesia to the nerves innervating the hip. The success of fascia iliaca blocks has been demonstrated to be superior when using ultrasound compared to landmark techniques. However, the clinical benefit of this improvement has yet to be investigated.The aim of this study is to compare the efficacy and safety of ultrasound guided fascia iliaca block with spinal morphine for hip replacement surgery.

METHODS/DESIGN: This study is a randomised, blinded, placebo-controlled, noninferiority trial. Patients scheduled to undergo unilateral primary hip arthroplasty will receive a study information sheet and consent will be obtained in keeping with the Declaration of Helsinki. Patients will be randomised to receive either; (i) Ultrasound guided fascia iliaca block using levobupivacaine, plus spinal anaesthesia with hyperbaric bupivacaine containing no morphine, or (ii) sham ultrasound guided fascia iliaca block performed with sterile saline, and spinal anaesthesia containing hyperbaric bupivacaine and 0.1 mg of spinal morphine.A total of 108 patients will be recruited. Primary outcome is post-operative morphine consumption in a 24 hour period. Secondary outcomes include; pain scores at 3, 6, 12, 24, 36 and 48 hours, episodes of respiratory depression, hypotension, nausea and vomiting, pruritus, sedation, time to first mobilisation and patient satisfaction.

CONCLUSIONS: There are no studies to date comparing ultrasound guided fascia iliaca block with spinal morphine for pain control after hip arthroplasty. If the ultrasound guided fascia iliaca block provides pain relief which is not inferior to spinal morphine, then morphine could be removed from the spinal injection. This could reduce side effects and improve patient safety.

TRIAL REGISTRATION: This study has been approved by the West of Scotland Research Ethics Committee 4 (reference no. 10/S0704/43) and is registered with ClinicalTrials.gov (reference no. NCT01217294).