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An Ultrasound Anesthesia Needle Improves Peripheral Nerve Blocks
An Ultrasound Anesthesia Needle Improves Peripheral Nerve Blocks
A new generation of ultrasound anesthesia needle is designed to improve the success rate, speed, and safety of peripheral nerve blocks1.ultrasound anesthesia needle The technique allows real-time visualization of both the insertion site and the local anesthetic distribution along and around the targeted structures. In the hands of a skilled anesthesiologist, this can significantly enhance regional anesthesia procedures.
The needle is positioned at the puncture site and guided to the target by direct ultrasound imaging.ultrasound anesthesia needle This is made possible by the fact that the needle itself reflects ultrasound emitted from tissue within its vicinity, resulting in a double-echo return at the beveled surface of the needle shaft (Table 1). The needle can then be distinguished from surrounding tissue and the ultrasound probe. Once the needle is positioned, it is injected under continuous ultrasound imaging.
In a cadaver study, Moayeri et al found that ultrasound monitoring can detect the injection of as little as 0.5 mL local anesthetic, enabling immediate withdrawal if penetration of a nerve is detected. This can greatly reduce the likelihood of nerve injury, especially when using long needles for plexus block.
Ultrasound imaging can also aid in avoiding vascular complications with certain block techniques. Specifically, when attempting to perform an interscalene block in the presence of a first rib (and possibly pulmonary pleura), it is essential to avoid piercing through the pleura. This can be done by ensuring that the needle is placed at a perpendicular angle to the artery. The anesthesiologist can accomplish this by observing the infusion on the ultrasound screen and adjusting the needle position as needed.
In addition, a multiinjection approach is recommended for plexus blocks to avoid a complication such as pneumothorax. This can be accomplished by performing a skin puncture 1 cm cranial to the ultrasound probe and inserting a 22-gauge needle with a fasciette tip into the interscalene space, followed by a series of small injections of anesthetic solution to ensure complete plexus block.
Another potential complication is the occurrence of motor response during an ultrasound-guided nerve stimulation (UGRA) block. When this occurs, the anesthesiologist should immediately stop the current delivery and withdraw the needle. In the absence of ultrasound guidance, a motor response at this current delivery setting almost always indicates needle-nerve contact or intraneural needle placement2.
The use of an ultrasound anesthesia needle may decrease the risk of complications in a variety of blocks and increase the speed and ease with which they can be performed. However, a number of challenges remain to be overcome. These include the difficulty in identifying the location of the needle based on its physical properties, the need to be very careful to maintain a constant in-plane orientation to the ultrasound transducer, and the possibility that novice anesthesiologists will not use this tool appropriately. These limitations can be overcome by a combination of education, practice and training.
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