The Forces Associated with Bolus Injection and Continuous Infusion Techniques during Ultrasound-Targeted Nerve Contact:An Ex Vivo Study

Ultrasound-guided regional anaesthesia with real-time visualization of anatomical structures and needle trajectory has become the standard method for accurately achieving nerve block procedures. Nevertheless, ultrasound is particularly limited in accurately detecting the needle tip in tissues with complex echogenicity. Fat-filled circumneural fascial tissue provides a barrier to local anaesthetic diffusion. Injection during gentle needle nerve contact is more likely to spread under the circumneurium (halo sign). On the other hand, excessive force may cause hematoma or activate the piezo ion channels and intraneural calcium release. Therefore, it is vital to understand the mechanics of needle–tissue interaction for optimizing the procedural outcomes and patients’ safety. We hypothesised that continuous fluid infusion would reduce the needle force applied on the nerve compared to that of bolus injection. Thus, the primary objective of this study was to compare the forces associated with the bolus injection and continuous infusion techniques on the sciatic nerves of fresh lamb legs ex vivo. A needle combining pressure and force was inserted into six legs of lambs ex vivo using a motor stage at a constant velocity and imaged with a linear transducer. Saline injections were block randomised to bolus injection or infusion in the muscle upon gently touching and indenting of the epineurium at nine sites on six sciatic nerves at three angles (30°, 45° and 60°) in each location. The bolus was delivered over 6 s and infused for over 60 s. The result showed less force was generated during the infusion technique when gently touching the epineurium than that of the bolus technique, with p = 0.004, with significant differences observed at a 60° angle (0.49 N, p = 0.001). The injection pressure was also lower when light epineurium touches were applied (9.6 kPa, p = 0.02) and at 60° (8.9 kPa). The time to peak pressure varied across the insertion angles (p < 0.001), with the shortest time at 60° (6.53 s). This study explores future applications by emphasizing the significance of understanding needle–tissue interaction mechanics. This understanding is crucial for optimizing the procedural outcomes and enhancing patients’ safety in ultrasound-guided regional anaesthesia administration. Specifically, continuous infusion demonstrated a notable reduction in needle force compared to that of the bolus injection, especially during gentle epineurium contact

Electrical impedance of an ultrasonic needle device as an indicator of interstitial needle tip position

Ultrasound-guided percutaneous needle procedures, commonly employed in regional anaesthesia and tissue biopsy, face challenges in accurately localizing the needle tip. This study explores the potential of using real-time electrical impedance measurements from an ultrasonic needle device as an indicator of the needle tip location, with reference to insertion force. The device utilizes a Langevin piezoelectric ultrasound transducer to actuate a general anaesthesia needle, while an adaptive control system provides impedance measurements in real time. Gelatin phantoms with varying concentrations, a skin-mimicking layer made of silicone, and a medical plastic gloves layer were used to create single- and multi-layer testing objects. The results suggest that the impedance magnitude is comparable to the force in identifying key events during needle insertions, such as puncturing and layer transitions. Furthermore, impedance proves particularly reliable when the needle is stationary, indicating a strong potential as a valuable feedback signal for enhancing percutaneous needle procedures.</p

Electrical impedance of an ultrasonic needle device as an indicator of interstitial needle tip position

Ultrasound-guided percutaneous needle procedures, commonly employed in regional anaesthesia and tissue biopsy, face challenges in accurately localizing the needle tip. This study explores the potential of using real-time electrical impedance measurements from an ultrasonic needle device as an indicator of the needle tip location, with reference to insertion force. The device utilizes a Langevin piezoelectric ultrasound transducer to actuate a general anaesthesia needle, while an adaptive control system provides impedance measurements in real time. Gelatin phantoms with varying concentrations, a skin-mimicking layer made of silicone, and a medical plastic gloves layer were used to create single- and multi-layer testing objects. The results suggest that the impedance magnitude is comparable to the force in identifying key events during needle insertions, such as puncturing and layer transitions. Furthermore, impedance proves particularly reliable when the needle is stationary, indicating a strong potential as a valuable feedback signal for enhancing percutaneous needle procedures.</p

Degradation of bisphenol AF in water by periodate activation with FeS (mackinawite) and the role of sulfur species in the generation of sulfate radicals

© 2020 Elsevier B.V. The heterogeneous catalyst Mackinawite (FeS) was applied to activate periodate (IO4−) to degrade endocrine disruptors bisphenol AF (BPAF). This study investigated the influence of FeS dosage, periodate dosage, BPAF concentration, initial pH value and inorganic ions on BPAF degradation by FeS/IO4− system. The results showed that the BPAF was effectively degraded by FeS/IO4− system. The acidic pH exhibited higher efficiency in BPAF degradation compared with alkaline and neutral conditions. Furthermore, the BPAF degradation was dramatically promoted in the presence of Cl− and SO42−, whereas CO32− inhibited BPAF degradation. The radical scavenging tests and EPR indicated that singlet oxygen (1O2), superoxide radicals (O2[rad]−) and SO4[rad]− were committed to the degradation of BPAF, among which O2[rad]−, 1O2 were predominant radicals. The separate experiments showed that Fe(Ⅱ) participated in the activation of periodate. Furthermore, the effects of sulfur species (including the S2−, SO32−) on BPAF degradation by FeS/IO4− system were studied. The radical quenching tests suggested that S2− and SO32− were responsible for producing SO4[rad]−. The findings of this study elucidated an approach for the removal of micro-pollutants in the water environment through heterogeneous activation of periodate by FeS