Intracatheter air in continuous thoracic paravertebral block: distraction or assistance?
- 624 Downloads
KeywordsRopivacaine Pigtail Catheter Postoperative Chest Paravertebral Block Unnecessary Exposure
To the Editor,
Non-neuraxial techniques, such as bilateral paravertebral blocks (PVB), are increasingly offered for abdominal surgeries1 where identification of the catheter tip improves safety and efficacy. A variety of techniques (e.g., fluid, air,2,3 or colour Doppler4 have been described to locate the needle or catheter tip, each with its own advantages and drawbacks. We describe a case of bilateral PVB wherein intracatheter air was visualized on initial injection under ultrasound, localizing the catheter tip.
Air used as a contrast to identify the catheter tip is well described for extremity nerve blocks,2 but such descriptions are uncommon for truncal blocks. Hydro location is useful when the surrounding tissue, i.e., nerves and fascia, are hyperechoic or isoechoic, giving a clear contrast for the fluid, but PVS appears hypoechoic. Hence, liquids may not provide the required discriminative characteristics to locate the catheter tip. Although air is hypoechoic, its deposition around the catheter tip can provide better surrounding contrast to make the tip visible. We deliberately avoided injecting additional air to prevent difficulties in making further block attempts, if needed. While radiological confirmation of catheter tip location is common practice, confirming the catheter tip location while performing the block can avoid unnecessary exposure to radiation.5 Further studies are needed to evaluate the utility of this technique. There is no foolproof method to identify the catheter tip in the PVS, especially with interference from pleural movements with colour Doppler. Clinicians often have to rely on pleural displacement resulting from injection of a drug. Use of the sonocurl pigtail catheter likely allowed the catheter to remain in the intercostal space once it was inserted, thus facilitating insonation of the catheter tip.
In summary, there are multiple recognized techniques to locate the position of the catheter tip for continuous PVB, and intracatheter air may serve as an additional tool for this purpose.
Conflicts of interest
Pajunk provided free curlsono kits for this study.
Video. Real-time ultrasound clip of intracatheter air dislodgment (in normal speed and slow motion) revealing catheter tip location. Supplementary material 1 (MP4 3338 kb)