Background and Aims This audit had the aim to clear how the Uni-knee replacement procedures are anesthetised in the NOC with a special focus on the adductor canal block technique regarding the used volume, agent and concentration.

Methods 41 patients where reviewed in a retrospective way. Uni-knee replacement was picked up to try to standardise the surgical technique to eliminate the surgical technique as a source of pain.

The methods of adductor canal administration were reviewed and the post operative pain, reflected by the amount of postoperative opioid consumption, was collected.

Results The Adductor canal block was performed in 10 different ways with varying drugs, concentration and volumes. Only 11% of the cases received the standard technique which would be the volume of 20 ml and the Ropivacaine 0.7% (Bupivacaine 0.5%) as the local anaesthetic agent.

Because of the technique was highly variable, accurate data was not obtained, as more cases needed to demonstrate a significant statistical difference between techniques. In general, a volume of 10–15 ml of bupivacaine 0.5% had a non significant statistical difference in opioid consumption postoperatively compared with 20 ml of the same agent, which indicates a volume of 10–15 ml of bupivacaine 0.5%, or Ropivacaine 0.7% have the same effect of higher volumes but with a wider margin of safety.

Conclusions Standard technique would suggest a volume of 10–15 ml of 0.3% Ropivacaine with discarding 10 ml of the local anaesthesia solution prepared by the surgeons to achieve safety. Re-audit regarding the post-operative opioid consumptions is required.