Focusing on Fascial Planes: Study focusses on New Era of Drug Observation with Ultrasound Contrast Agents

A novel perfluoropropane ultrasound contrast agent (UCA) was investigated for its feasibility in monitoring drug diffusion within the fascial plane during fascial plane blocks (FPBs), specifically the transverse abdominis plane block (TAPB), utilizing two-dimensional (2D) ultrasound. The motivation for this recent study emerged from the limitations of current ultrasound techniques in accurately assessing local anesthetic (LA) diffusion. The research highlighted the potential of UCAs, particularly perfluoropropane, to provide improved visualization of drug spread compared to traditional methods. Initial experiments confirmed that perfluoropropane UCA met commercial specifications for particle size and did not alter the pH of 0.375% ropivacaine (ROP). Various dilution ratios and concentrations of UCA mixed with ROP were tested to optimize imaging results, with undiluted UCA demonstrating superior contrast and stability in imaging over time. A TAPB was performed on rabbits to evaluate the diffusion of LA, where the selected solutions (undiluted UCA and 10-fold diluted UCA) provided distinct imaging of drug spread without stratification.

Results

The study further compared drug diffusion areas observed via UCA against microbubble (MB) diffusion after dissection, revealing no significant statistical discrepancies. A strong correlation was found between both measurement methods, which suggests that UCA offers a reliable means to visualize LA distribution. Safety assessments performed in vivo and in vitro indicated that the addition of perfluoropropane UCA did not exacerbate the known toxicities associated with ROP, maintaining neuronal and muscular integrity.

Toxicity Evaluation

Toxicity evaluation on rabbit nerve and muscle tissues showed acceptable results, with varying degrees of damage across treatment groups but without enhanced toxicity due to the UCA. Cell viability assays and apoptosis detection demonstrated no significant cytotoxic responses attributable to the UCA across multiple cell lines, thus indicating its biocompatibility.

Discussion and Future Directions

Key limitations of the study include the small sample size and that results may not fully extrapolate to human subjects, particularly regarding systemic absorption and toxicity, as large volumes of LA are often utilized in clinical settings. Future research is emphasized to include broader sampling and clinical applicability, with anticipation for dedicated ultrasound imaging techniques to aid in drug diffusion monitoring during FPBs. This preliminary investigation thus presents a promising avenue for enhancing FPB techniques using novel ultrasound contrast agents.

Key Points

- A novel perfluoropropane ultrasound contrast agent (UCA) was evaluated for monitoring drug diffusion in the transverse abdominis plane block (TAPB) utilizing two-dimensional (2D) ultrasound, addressing limitations of current techniques in assessing local anesthetic (LA) distribution.

- Initial experiments demonstrated that the perfluoropropane UCA adhered to commercial specifications for particle size and did not alter the pH of ropivacaine (ROP). Different concentrations and dilution ratios were tested, finding that undiluted UCA provided superior imaging contrast and stability.

- The TAPB performed on rabbits using selected UCA solutions showed distinct imaging of LA diffusion without drug stratification, with comparisons against microbubble (MB) diffusion revealing no statistically significant discrepancies, indicating the reliability of UCA for visualizing LA distribution.

- Safety assessments indicated that perfluoropropane UCA did not exacerbate the toxicity associated with ROP, maintaining neuronal and muscular integrity in both in vivo and in vitro scenarios.

- Toxicity evaluations on rabbit nerve and muscle tissues showed no enhanced damage due to the UCA, with cell viability assays demonstrating no significant cytotoxic responses across multiple cell lines, highlighting the biocompatibility of the UCA.

- The study identified limitations, including a small sample size and the need for further research to extrapolate findings to human subjects, particularly regarding system toxicity and absorption, recommending broader sampling and advanced ultrasound imaging techniques for enhanced monitoring of drug diffusion during fascial plane blocks.

Reference –

Zhicheng Zhang et al. (2025). Preliminary Study On The Use Of Perfluoropropane Contrast Agent In Monitoring Drug Diffusion During Fascial Plane Blocks. *BMC Anesthesiology*, 25. https://doi.org/10.1186/s12871-025-03028-8.