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Ultrasound has rapidly become an important tool in anesthesiology, so much so that the American Society of Anesthesiologists recommends that current medical students intending to specialize in anesthesiology become familiar with the mechanism, uses, and techniques of ultrasound as they complete their clinical rotations in their third and fourth years of medical school.1 While ultrasound technology is most commonly associated with medical procedures today, it originates from Lazzaro Spallanzani’s study of bats’ echolocation abilities and initially found its main application in submarine navigation.2 This article will briefly overview the history of ultrasound in medicine and discuss the uses of this technology in anesthesiology in particular.
Ultrasound imaging was applied in medicine for the first time in the late 1900’s by physician Karl Dussik, who attempted to image an organ in vivo (one of the earliest such attempts) by placing transducers on either side of a patient’s partially submerged head and using a through-transmission technique to transmit sound waves of a known rate from one transducer to the other through the patient’s head. Dussik recorded changes in these sound waves photographically on heat-sensitive paper. He called the resulting images “ventriculograms,” which he believed to be a two-dimensional representation of the patient’s ventricles. Although it was later discovered that many of these echo variations were artifacts produced by normal reflections and attenuations of the skull, and although the limitations of the through-transmission technique caused it to be largely abandoned by the 1950s, this initial exploration of ultrasound in medicine led to the use of the now more common pulse-echo method of ultrasound imaging (in which the transducer both produces and receives the transmitted sound wave and its reflected echo), used in A-, B-, and M-method ultrasound imaging.2
Of these methods, B-mode (brightness), M-mode (motion), and the later developed color-Doppler methods of ultrasound imaging are the most frequently used in anesthesiology today. Their most common application is ultrasound-guided peripheral nerve blockade, considered to be the gold standard for regional anesthesia due to the advantages this technique confers: direct observation of the structure of the target area and direct observation of local anesthetic spread. This increases block success, resulting in faster onset and longer block duration.3 Around the time of its growing popularity (2009), Sites and Antonakakis profiled multiple successful clinical cases in which ultrasound guidance in anesthesiology allowed for successful operations with high-risk patients;4 these and many other studies have resulted in this technique becoming widely used in anesthesiology today.
Another critical application of ultrasound technology relevant to anesthesiology is perioperative point-of-care ultrasound (POCUS) assessments, which provide anesthesiologists with real-time information to help them dynamically alter perioperative patient management to ensure the patient’s safety and comfort and to address any intraoperative complications as soon as they arise. Cardiac conditions identifiable through POCUS include valvular abnormalities, biventricular function, pericardial tamponade, volume status, and cardiac ischemia. The last of these is particularly notable in that POCUS can reliably demonstrate ventricular wall hypo/akinesis, indicators of acute cardiac ischemia, where an intraoperative EKG would demonstrate no abnormal changes.5 Gastric POCUS is also gaining use as a way to verify that patients’ stomachs are empty and that it is safe to proceed with anesthesia and surgery. In modern practice, POCUS, and the use of ultrasound technology in general, is a critical point of competency for anesthesiologists to obtain.
References
(1) Ultrasound in Anesthesia. https://www.asahq.org/education-and-career/asa-medical-student-component/articles/ultrasound-in-anesthesia (accessed 2024-04-01).
(2) Kaproth-Joslin, K. A.; Nicola, R.; Dogra, V. S. The History of US: From Bats and Boats to the Bedside and Beyond: RSNA Centennial Article. RadioGraphics 2015, 35 (3), 960–970. https://doi.org/10.1148/rg.2015140300.
(3) Terkawi, A. S.; Karakitsos, D.; Elbarbary, M.; Blaivas, M.; Durieux, M. E. Ultrasound for the Anesthesiologists: Present and Future. The Scientific World Journal 2013, 2013, 1–15. https://doi.org/10.1155/2013/683685.
(4) Sites, B. Ultrasound Guidance in Regional Anesthesia: State of the Art Review through Challenging Clinical Scenarios. LRA 2009, 1. https://doi.org/10.2147/LRA.S3444.
(5) Naji, A.; Chappidi, M.; Ahmed, A.; Monga, A.; Sanders, J. Perioperative Point-of-Care Ultrasound Use by Anesthesiologists. Cureus 2021. https://doi.org/10.7759/cureus.15217.
