Mechanism of Thermal Injury After a Heat-Based Therapy for Central Line Associated Bloodstream Infection

Definitive source control for CLABSI often requires catheter removal and loss of critical vascular access. We previously developed a salvage strategy using oscillating heated perfusate to reduce biofilm from infected catheters in an animal model. However, subsequent histopathology demonstrated intravenous and subcutaneous tissue damage and remodeling. We sought to elucidate the extent of vascular endothelial injury in response to heat and shear and identify potential targets for ameliorating adverse effects. We hypothesize that vascular endothelium exposed to supraphysiological heat and oscillatory shear will have decreased barrier function and increased cytotoxicity. As oscillatory shear has been shown to increase oxidative stress, we also hypothesize that observed adverse effects may correlate with increased generation of reactive oxygen species (ROS).

We designed and built a custom heated perfusate cycling apparatus for in vitro testing of cultured human endothelial (HUVEC) monolayers to closely mimic our in vivo setup. Heated phosphate-buffered saline was cycled over the apical surface for 20 minutes at heater setpoints of 37°C (control), 45°C, 50°C, 55°C, and 60°C. Transendothelial electrical resistance (TEER), indicating barrier function, and adenylate kinase (AK), indicating cytotoxicity were measured before and after treatment. Malondialdehyde (MDA) was measured following treatment as a biomarker of lipid peroxidation. Experiments were conducted with 3–9 independent biological replicates per condition.

We observed a temperature dependent reduction in TEER after treatment (p=0.033). AK significantly increased in the 60°C group (26.41 to 53.00 RLU, p=0.017), but not in the 37°C group (36.63 to 24.14 RLU, p=0.72). While not statistically significant (p=0.057), an upward trend was observed in MDA formation as a function of increasing temperature.

Our findings suggest that tissue damage following heat and shear treatment may be due to decreased barrier function and cell viability, as well as an increase in lipid peroxidation and oxidative stress. These effects appear to be temperature-dependent, and additional studies are needed to determine the specific contribution of oscillatory shear. ROS generation may be a potential drug target for mitigating adverse effects of heat treatment and preventing further complications such as thrombosis.