Reducing implant infection in orthopaedics (RIIiO): results of a pilot study comparing the influence of forced air and resistive fabric warming technologies on post-operative infections following orthopaedic implant surgery

BACKGROUND Active warming during surgery prevents perioperative hypothermia but the effectiveness and post-operative infection rates may differ between warming technologies. We report results of a pilot study in patients over the age of 65 undergoing hemiarthroplasty following fractured neck of femur. AIM To establish the recruitment and data management strategies needed for a full trial comparing post-operative infection rates associated with forced air versus resistive fabric warming. METHODS Participants were randomised 1:1 in permuted blocks to forced air or resistive fabric warming. Hypothermia was defined as a temperature of <36ºC at the end of surgery. Primary outcomes were the number of participants recruited and the number with definitive deep surgical site infections. FINDINGS 515 participants were randomised at 6 sites over a period of 18 months. Follow-up was completed for 70.1%. Thirty-seven participants were hypothermic (7.5% in the FAW group; 9.7 % in the RFW group). The mean temperatures before anaesthesia and at the end of surgery were similar. For the primary clinical outcome, there were 4 deep surgical site infections in the forced air warming group and 3 in the resistive fabric warming group. All participants who developed a post-operative infection had antibiotic prophylaxis, a cemented prosthesis and were operated under laminar airflow; none were hypothermic. There were no serious adverse events related to warming. CONCLUSION Surgical site infections were identified in both groups. Progression from the pilot to the full trial is possible but will need to take account of the high attrition rate. TRIAL REGISTRATION ISRCTN 74612906 (http://www.isrctn.com/ISRCTN74612906).