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Ultrasound application allows for noninvasive visualization of tissue structures. Real-time ultrasound images are integrated images resulting from reflection of organ surfaces and scattering within heterogeneous tissues. Ultrasound scanning is an interactive procedure involving the operator, patient, and ultrasound instruments. Although the physics behind ultrasound generation, propagation, detection, and transformation into practical information is rather complex, its clinical application is much simpler. Understanding the essential ultrasound physics presented in this chapter should be useful for comprehending the principles behind ultrasound-guided peripheral nerve blockade.
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In 1880, French physicists Pierre Curie, and his elder brother Jacques Curie, discovered the piezoelectric effect in certain crystals. Paul Langevin, a student of Pierre Curie, developed piezoelectric materials, which can generate and receive mechanical vibrations with high frequency (therefore ultrasound). During WWI, ultrasound was introduced in the navy as a means to detect enemy submarines. In the medical field, however, ultrasound was initially used for therapeutic rather than diagnostic purposes. In the late 1920s, Paul Langevin discovered that high power ultrasound could generate heat in bone and disrupt animal tissues. As a result, ultrasound was used to treat patients with Ménière disease, Parkinson disease, and rheumatic arthritis throughout the early 1950s. Diagnostic applications of ultrasound began through the collaboration of physicians and SONAR engineers. In 1942, Karl Dussik, a neuropsychiatrist and his brother, Friederich Dussik, a physicist, described ultrasound as a diagnostic tool to visualize neoplastic tissues in the brain and the cerebral ventricles. However, limitations of ultrasound instrumentation at the time prevented further development of clinical applications until the early 1970s.
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With regard to regional anesthesia, as early as 1978, P. La Grange and his colleagues were the first anesthesiologists to publish a case-series report of ultrasound application for peripheral nerve blockade. They simply used a Doppler transducer to locate the subclavian artery and performed supraclavicular brachial plexus block in 61 patients (Figure 26-1). Reportedly, Doppler guidance led to a high block success rate (98%) and absence of complications such as pneumothorax, phrenic nerve palsy, hematoma, convulsion, recurrent laryngeal nerve block, and spinal anesthesia.
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In 1989, P. Ting and V. Sivagnanaratnam reported the use of B-mode ultrasonography to demonstrate the anatomy of the axilla and to observe the spread of local anesthetics during axillary brachial plexus block. In 1994, Stephan Kapral and colleagues systematically explored brachial plexus with B-mode ultrasound. Since that time, multiple teams worldwide have worked tirelessly on defining and improving the application of ultrasound imaging in regional anesthesia. Ultrasound-guided nerve blockade is currently used routinely in the practice of regional anesthesia in many centers worldwide.
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Here is a summary of ultrasound quick facts:
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- 1880: Pierre and Jacques Curie discovered the piezoelectric effect in crystals.
- 1915: Ultrasound was used by the navy for detecting submarines.
- 1920s: ...