Aims
Open spine surgery exposes internal tissues to operating room air, predisposing it to drying and cooling. Such exposure of internal tissues may disrupt homeostasis and exacerbate tissue damage. The study determined if intraoperative delivery of warm humidified air (WHA, 37ºC) to the surgical site maintains normothermia of exposed internal tissues and the subsequent effects it has on tissue physiology and post-operative wound outcomes.
Methods
Wound temperatures were measured in a patient trial. Twenty-eight patients undergoing elective 1-2 level open spinal decompression were equally randomized to standard care (control, exposed to room air) or WHA and measurements were made using a thermal camera. Porcine models of simulated open spine surgery were used to examine tissue perfusion, oxygenation, damage, healing, and bacterial growth (n=5 per group). Histological assessment was performed on biopsies taken upon opening (T0), after 60-min (T60) and 180-min (T180) of exposure, and at Day 14. Bacterial growth was measured by enumeration three days after inoculating the wound surface with ~106 CFU/mL Staphylococcus aureus.
Results
Wound temperature was 29°C ± 0.4 after 45 minutes in control patients. WHA maintained normothermia (~37°C) throughout the procedure (p<0.05). In porcine studies, WHA delivery improved perfusion (p=0.003) and mean oxygen saturation (60% vs 72.8% StO2, p=0.063) compared to control. Muscle damage depth was 92% less with WHA compared to control at T180 (p<0.001). Granulation tissue appeared more mature at Day-14. Under infection challenge, there was 84% less bacteria growth with WHA compared to control (p<0.05).
Conclusions
Intraoperative WHA delivery reduced tissue damage by mitigating cooling and improving perfusion and oxygenation during wound exposure. These effects were associated with improved wound healing and enhanced defence against bacteria. The findings highlight the potential of WHA as a prophylatic to reduce the risk of post-operative wound complications in open spine surgery.