Maintaining local tissue health intraoperatively to reduce the risk of surgical site infection (SSI)

Author(s):
Rebecca Hu; Simon Manners; John Cunningham; Joseph Baker

Background:

Tissues heal most effectively in optimal conditions of oxygenation, perfusion and body temperature. Thus a number of SSI prevention guidelines recommend maintaining these patient conditions during surgery. This is attempted systemically as opposed to at the surgical site. Tissues in the surgical site are most vulnerable to damage and particle deposition during surgical manipulation and exposure to the cold and dry environment in operating rooms.

Hypothesis:

We hypothesize that maintaining local tissue health intraoperatively during open surgery is a key missing mechanism to reduce SSI risk. By minimizing the avoidable desiccation, improving the local tissue temperature to encourage perfusion and oxygenation, surgical site tissues are in a favourable status to fight against SSI.

Methods:

A device was developed by Fisher & Paykel Healthcare to deliver warmed, humidified air (37°C, 100% relative humidity) over an open wound. Studies were performed in porcine models to determine the effect of intraoperative delivery of warmed, humidified air on healing and fighting infection. Assessment was done on tissue biopsies from the surgical site with spinal processes and lamina exposed for 3-hrs, at wound closure and after 3-days (infection study) and 7-days (wound healing study). The device was also used in a randomized controlled study with 28 patients undergoing elective 1-2 level posterior lumbar decompression. Wound edge temperature was measured at 15-mins intervals.

Results:

In the wound healing study, histopathology of the skeletal muscle showed lower damage scores (average 2.1 vs. 2.7) and lower fibrosis score (average 2.2 vs. 2.9) in the device group than in the controls.

A porcine infection model was developed by inoculating open wounds with S. aureus causing a tolerable infection post-surgery. At 3-days post-surgery, the average bacteria count in the wound site tissues were significantly less in the device group than in the controls (p=0.035).

In patients, the average wound edge temperature dropped to 30°C by 30mins after the initial incision and to 29°C by 60mins in wounds that were exposed to the OR environment. In contrast, the average wound edge temperature was 37°C throughout the surgery (p<0.01) in the device group. Tissues were noted as appearing more red, moist, and healthier by the operating surgeons.

Conclusions:

Overall the above studies demonstrated the potential for maintaining local tissue health intraoperatively on wound healing and fighting against infection.