J McGhie1, K Grady2. 1. Anaesthesia and Pain Medicine, Queen Elizabeth University Hospital, Glasgow G51 4TF, UK Faculty of Pain Medicine of the Royal College of Anaesthetists and Pain Medicine and Anaesthesia, University Hospital of South Manchester, Manchester M23 9LT, UK j.mcghie@nhs.net. 2. Anaesthesia and Pain Medicine, Queen Elizabeth University Hospital, Glasgow G51 4TF, UK Faculty of Pain Medicine of the Royal College of Anaesthetists and Pain Medicine and Anaesthesia, University Hospital of South Manchester, Manchester M23 9LT, UK.