Ultrasound visibility of regional anesthesia catheters: an in vitro study

Color Doppler ultrasonography of an agitated solution is predictive of accurate catheter placement for a continuous popliteal sciatic nerve block

Background

Continuous peripheral nerve catheters (PNCs) have been shown to provide superior postoperative analgesia, decrease opioid consumption, and improve patient satisfaction compared with single injection techniques. In order to achieve success and reliability, accurate catheter positioning is an essential element of PNC placement. An agitated solution of normal saline, D5W, or a local anesthetic solution can be produced by the introduction of air to the injectate, creating air bubbles that can enhance ultrasonographic visualization and possibly improve block success.

Methods

Eighty-three patients were enrolled. Ultrasound-guided continuous popliteal sciatic nerve blocks were performed by positioning the tip of a Tuohy needle between the tibial and common peroneal branches of the sciatic nerve and threading a catheter. An agitated local anesthetic solution was injected through the catheter, viewed with color Doppler ultrasound and video recorded. A peripheral block score (lower score = greater blockade, range 0-14) was calculated based upon the motor and sensory testing at 10, 20, and 30 min after block completion. The color Doppler agitation coverage pattern for the branches of the sciatic nerve was graded as follows: complete (> 50%), partial (> 0%, ≤ 50%), or none (0%).

Results

The degree of nerve blockade at 30 min as judged by median (10th, 90th percentile) peripheral block score was significant for partial or complete color Doppler coverage of the sciatic nerve injectate compared to no coverage [3 (0, 7) vs 8 (4, 14); p < 0.01] and block onset was faster (p = 0.03). The block success was higher in groups with partial or complete coverage of the branches of the sciatic nerve vs no coverage (96% vs 70%; p = 0.02).

Conclusions

Injection of an agitated solution through a popliteal sciatic perineural catheter is predictive of accurate catheter placement when partial or complete coverage of the sciatic nerve branches is visualized with color Doppler ultrasound.

Trial registration

NCT01591603

Establishing a Technique for Pectoral II-Block Catheter Insertion with Ultrasound Guidance: A Randomized Controlled Trial

Purpose

To assess the efficacy and safety of a modified technique for ultrasound-guided pectoral II block for postoperative pain control after mastectomy.

Methods

In this randomized controlled trial, patients were randomly allocated into two groups (40 patients each). Group I patients were subjected to ultrasound-guided pectoral II block with injection of 10 mL lidocaine 1% as a dissecting solution before attempting catheter insertion, while group II patients underwent the standard procedure without a dissecting solution. Measured outcomes included catheter visibility, pain, patient satisfaction, performance time, and complications.

Results

Compared with group II, group I had significantly lower median catheter-visibility scores, shorter block performance time, and fewer insertion attempts. Group I had a nonsignificantly higher rate of complications than group II.

Conclusion

The modified technique facilitated the procedure, shortened the catheter-insertion time, and showed higher patient satisfaction. However, it was associated with lower catheter visibility on ultrasonography. Further studies are required to confirm the present findings and assess the safety of the modified technique.

Ultrasound Identifies Broken Drainage Tube Postthyroidectomy

Drains are routinely used after thyroidectomy and lateral neck dissection. In rare cases, the drainage tube is broken and retained in the neck. It is difficult to identify the sonographic features of the remnant tube due to variable reasons. However, through comparative and phantom observations, we noticed the double-tract sign of the tube wall and drainage holes as the key points to solving this problem. We report such a case of the ultrasound-guided localization of a broken drainage tube that was retained in the patient.

A pilot in vitro evaluation of the "air test" for perineural catheter tip localization by a novice regional anesthesiologist

The "air test" is used clinically to infer perineural catheter location and has been recently evaluated for use by experts. However, its utility for practitioners with less experience is unknown. We tested the hypothesis that the air test, when performed by a novice regional anesthesiologist, will improve assessment of perineural catheter tip position in a validated porcine-bovine model and determined the test's positive and negative predictive values, sensitivity, and specificity for a novice. In contrast to the results of the expert study, the air test did not improve the novice's assessment of perineural catheter tip location over chance.

[Seeing more : Technical innovations in regional anesthesia]

Visualization and verification are key factors since the implementation of ultrasound-guided regional anesthesia. This article reviews and discusses newer technical innovations in regional anesthesia with regard to optimization of needle guidance, improvements in needle visibility, technical improvements in ultrasound techniques and innovative technologies in regional anesthesia. Clinically available applications are presented as well as experimental tools and techniques with a potential for clinical implementation in the future. Mechanical needle guides are used to improve alignment of needle axis and ultrasound beam axis. Compound imaging technology improves needle visibility in steep needle insertion angles and is already implemented in daily clinical practice. Sonoelastography improves tissue discrimination and detection of small amounts of fluids. Benefits of 3D and 4D ultrasound in regional anesthesia are discussed as well as experimental tools for tissue discrimination, such as optical reflection spectrophotometry.

Application of echogenic technology for catheters used in ultrasound-guided continuous peripheral nerve blocks

Limited data exist regarding the echogenicity of perineural catheters, but visualization is crucial to ensure accurate placement and efficacy of the subsequent local anesthetic infusion. The objective of this study was to determine the comparative echogenicity of various regional anesthesia catheters. In an in vitro porcine-bovine model, we compared the echogenic qualities of 3 commercially available regional anesthesia catheters and 1 catheter under development to optimize echogenicity. Outcomes included visual echogenicity ranking, image quality, and scanning time, as assessed by 2 blinded investigators. The experimental catheter was found to be more echogenic than 2 of the 3 comparators.