Procedural sedation and analgesia for respiratory-gated MR-HIFU in the liver: a feasibility study.

Johanna M M Van Breugel,Chrit T W Moonen,Hermanus H B Vaessen,Joost W Wijlemans,Martijn De Greef,Mario G Ries,Maurice A A J Van Den Bosch

doi:10.1186/s40349-016-0063-x

Abstract

BackgroundPrevious studies demonstrated both pre-clinically and clinically the feasibility of magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) ablations in the liver. To overcome the associated problem of respiratory motion of the ablation area, general anesthesia (GA) and mechanical ventilation was used in conjunction with either respiratory-gated energy delivery or energy delivery during induced apnea. However, clinical procedures requiring GA are generally associated with increased mortality, morbidity, and complication rate compared to procedural sedation and analgesia (PSA). Furthermore, PSA is associated with faster recovery and an increased eligibility for non- and mini-invasive interventions.MethodsIn this study, we investigate both in an animal model and on a small patient group the kinetics of the diaphragm during free-breathing, when a tailored remifentanil/propofol-based PSA protocol inducing partial respiratory depression is used. Subsequently, we demonstrate in an animal study the compatibility of the resulting respiratory pattern of the PSA protocol with a gated HIFU ablation in the liver by direct comparison with gated ablations conducted under GA. Wilcoxon signed-rank tests were performed for statistical analysis of non-perfused and necrosed tissue volumes. Duty cycles (ratio or percentage of the breathing cycle with the diaphragm in its resting position, such that acoustic energy delivery with MR-HIFU was allowed) were statistically compared for both GA and PSA using student’s t tests.ResultsIn both animal and human experiments, the breathing frequency was decreased below 9/min, while maintaining stable vital functions. Furthermore an end-exhalation resting phase was induced by this PSA protocol during which the diaphragm is virtually immobile. Median non-perfused volumes, non-viable volumes based on NADH staining, and duty cycles were larger under PSA than under GA or equal.ConclusionsWe conclude that MR-HIFU ablations of the liver under PSA are feasible and potentially increase the non-invasive nature of this type of intervention.

Highlights

Previous studies demonstrated both pre-clinically and clinically the feasibility of magnetic resonanceguided high-intensity focused ultrasound (MR-High-intensity focused ultrasound (HIFU)) ablations in the liver
We investigated if comparable results can be achieved by releasing the requirement for general anesthesia and instead delivering acoustic energy during a partially depressed but free-breathing motion pattern, which results from a tailored procedural sedation and analgesia protocol
We explored in the second part of this study in three patients treated with magnetic resonanceguided high-intensity focused ultrasound (MR-HIFU) if the main findings, in particular the possibility to reduce the breathing frequency to 5/ min, while obtaining a long exhalation period in which the diaphragm is stationary, are transferable from the porcine model to patients

Summary

Introduction

Previous studies demonstrated both pre-clinically and clinically the feasibility of magnetic resonanceguided high-intensity focused ultrasound (MR-HIFU) ablations in the liver. High-intensity focused ultrasound (HIFU) ablation of liver tumors was one of the first HIFU applications under investigation [1]; even after several decades of methodological refinement, HIFU ablation in the liver faces still several challenges, which hamper widespread clinical adoption and remains a topic of research [2,3,4,5,6]. The high perfusion of the liver requires high acoustic intensities in the focus during a sonication for an efficient energy deposition to overcome this so-called heat-sink effect [9, 10], which in-turn limits the achievable ablation volume per sonication. MR-HIFU is a well-established treatment option for uterine fibroids and is currently investigated for, e.g., bone tumors [13], breast cancer [14, 15], prostate cancer [16], and liver cancer [10, 17]

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