Surgical Humidification (HumiGard TM ) Reduces Bacterial Load in an Open Spine Animal Infection Model
John Cunningham, Simon Manners, Minah Kim, Callum Spence, Joseph F. BakerStudy Design
Randomised controlled study.
Objectives
Evaporative cooling of surgical wounds during open surgery was overlooked as a modifiable factor in reducing surgical site infections (SSIs). HumiGard TM is a system which delivers warm and humidified air to the wound bed intraoperatively. This study investigated the potential for HumiGard TM to reduce bacterial load in a porcine model of spine surgery.
Methods
Open spine surgery was simulated in a porcine model. The wound surface was inoculated with ∼10 6 CFU/mL of Staphylococcus aureus and remained exposed for 180 minutes to the ambient theatre conditions (control) or warm humidified air (HumiGard) (n=6 per group). Wounds were closed and re-opened three days post-surgery to collect muscle biopsies for bacterial enumeration and histological analyses.
Results
The growth of Staphylococcus aureus was 84% less in the HumiGard muscles than control at Day-3 post-surgery (p=0.041). Large bacterial colonies infiltrated the deeper muscle tissues in control, while the HumiGard muscles had smaller bacterial colonies confined to the superficial zone. Neutrophil proportion in the HumiGard group (34% ± 5.1%) was lower than control (65% ± 6.1%) (p=0.005). In contrast, HumiGard tissues had a higher proportion of mononuclear cells (66% ± 5.1%) than control (35% ± 6.1%) (p=0.005), implying a transition from the pro-inflammatory to the reparative stage of wound healing.
Conclusions
In this animal study, maintaining physiological temperature and humidity while the wounds were open reduced bacterial growth and advanced the wound healing process. HumiGard may offer a protective benefit by reducing the risk of SSIs following open spine surgery.