Surgical Humidification (Humigard™) Reduces Bacterial Load in an Open Spine Animal Infection Model

Introduction Surgical site infections (SSIs) are a leading cause of revision operations, impacting patient outcomes and healthcare costs. Exposure of surgical wounds to the dry and cold theatre environment has been overlooked as a modifiable factor in reducing SSIs. The F&P HumiGardTM system is designed to deliver warm and humidified air intra-operatively to the wound bed. This study investigates the potential for HumiGard™ to reduce bacterial load in a porcine model of spinal surgery. Methods Pigs were randomised to the Control and HumiGard groups (n=6 per group). An open spine surgery was simulated, and the wound surface was inoculated with ~106 CFU/ml of Staphylococcus aureus. Infected wounds were exposed to the ambient theatre conditions (Control) or warm humidified air (HumiGard) for 180 min. Wounds were re-opened three days post-surgery and bacterial enumeration and histological analyses were performed on biopsies. Results At Day 3 post-surgery, the growth of Staphylococcus aureus was 84% less in the HumiGard group tissue than the Control (p<0.05). Large bacterial colonies infiltrated the deeper tissues in Control, while the HumiGard group tissues had smaller bacterial colonies confined to the superficial zone. Distribution of white blood cells varied significantly between the Control and HumiGard groups at Day 3 post-surgery. Neutrophil proportion in the HumiGard group (34% ± 5.1%) was significantly lower than the Control group (65% ± 6.1%). In contrast, the proportion of mononuclear cells was significantly higher in HumiGard tissues (66% ± 5.1%) than Control (35% ± 6.1%), implying a transition from the pro-inflammatory to the reparative stage of wound healing. Conclusion In this animal study, HumiGard offered a protective benefit against bacterial growth, indicated by the lower bacterial load and an advancement in the wound healing process. By maintaining physiological temperature and humidity of the wounds, HumiGard may reduce the risk of SSIs following orthopaedic surgery.