The How and Why of
Ultrasound-Guided Regional Anesthesia
Physics
In a nutshell...crystals housed in the transducer are excited by electricity causing them to vibrate and produce sound waves (piezoelectric effect). These sound waves (ultrasound) are then focused and transmitted from the transducer into the surrounding media. As these waves encounter tissue with different characteristics and densities, echoes are reflected back to the transducer. These waves then cause the crystals to vibrate. This mechanical energy is then converted into an electrical signal. A computer processes these signals into points of light based on the anatomic position (distance from transducer) and the strength of the returning wave (depending on how much of the wave is absorbed or deflected) to create an image.
Advantages
Potential advantages of ultrasound-guidance for regional anesthesia:
Direct visualization of the anatomy (such as nerves, blood vessels, muscles)
Direct and indirect visualization of local anesthetic spread
Reduced likelihood of side effects (intravascular/intraneuronal injection)
Reduction in local anesthetic dose
Improved block performance (higher success rate, fewer needle passes, faster onset, prolonged duration)
The days of "it takes too long," "they never work," or "I'll just put local in at the end" can be a thing of the past.
Safety
Most of the procedures we do in the pediatric setting are under heavy sedation, or more likely, general anesthesia. For many years, the idea of performing a block under anesthesia was considered possible malpractice, as sedation may mask nerve damage—though, this conclusion wasn’t without dissension. Thanks to the work of countless others, including the ADARPEF study and the Pediatric Regional Anesthesia Network (now up to 21 centers and over 100,00 blocks!), the most recent data supports the safety of regional anesthesia in children without any discernible long-term sequelae.
Risk vs Benefit
Adapted from and inspired by an infographic from Dr. Aditya Pal and Dr. Maria Paz Sebastian. Modified with permission.
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Krane, E.J., Dalens, B.J., Murat, I. and Murrell, D., 1998. The safety of epidurals placed during general anesthesia. Regional Anesthesia and Pain Medicine, 23(5), p.433.
Ecoffey C, Lacroix F, Giaufré E, Orliaguet G, Courrèges P; Association des Anesthésistes Réanimateurs Pédiatriques d'Expression Française (ADARPEF). Epidemiology and morbidity of regional anesthesia in children: a follow-up one-year prospective survey of the French-Language Society of Paediatric Anaesthesiologists (ADARPEF). Paediatr Anaesth. 2010 Dec;20(12):1061-9. doi: 10.1111/j.1460-9592.2010.03448.x. PMID: 21199114.
Polaner, D.M., Taenzer, A.H., Walker, B.J., Bosenberg, A., Krane, E.J., Suresh, S., Wolf, C. and Martin, L.D., 2012. Pediatric Regional Anesthesia Network (PRAN): a multi-institutional study of the use and incidence of complications of pediatric regional anesthesia. Anesthesia & Analgesia, 115(6), pp.1353-1364.
Bosenberg, A., 2012. Benefits of regional anesthesia in children. Pediatric Anesthesia, 22(1), pp.10-18.
McCann, M.E., Withington, D.E., Arnup, S.J., Davidson, A.J., Disma, N., Frawley, G., Morton, N.S., Bell, G., Hunt, R.W., Bellinger, D.C. and Polaner, D.M., 2017. Differences in blood pressure in infants after general anesthesia compared to awake regional anesthesia (GAS study-a prospective randomized trial). Anesthesia and analgesia, 125(3), p.837.
Davidson, A.J., Morton, N.S., Arnup, S.J., De Graaff, J.C., Disma, N., Withington, D.E., Frawley, G., Hunt, R.W., Hardy, P., Khotcholava, M. and von Ungern Sternberg, B.S., 2015. Apnea after awake regional and general anesthesia in infants: the general anesthesia compared to spinal anesthesia study—comparing apnea and neurodevelopmental outcomes, a randomized controlled trial. Anesthesiology, 123(1), pp.38-54.
Walker, B.J., Long, J.B., De Oliveira, G.S., Szmuk, P., Setiawan, C., Polaner, D.M. and Suresh, S., 2015. Peripheral nerve catheters in children: an analysis of safety and practice patterns from the pediatric regional anesthesia network (PRAN). British journal of anaesthesia, 115(3), pp.457-462
Walker, B.J., Long, J.B., Sathyamoorthy, M., Birstler, J., Wolf, C., Bosenberg, A.T., Flack, S.H., Krane, E.J., Sethna, N.F., Suresh, S. and Taenzer, A.H., 2018. Complications in pediatric regional anesthesia: an analysis of more than 100,000 blocks from the pediatric regional anesthesia network. Anesthesiology, 129(4), pp.721-732
Suresh, S., Long, J., Birmingham, P.K. and De Oliveira Jr, G.S., 2015. Are caudal blocks for pain control safe in children? An analysis of 18,650 caudal blocks from the Pediatric Regional Anesthesia Network (PRAN) database. Anesthesia & Analgesia, 120(1), pp.151-156.
Disclaimer:
Some of the described content is still in its infancy (pun intended). Some techniques are more invasive and riskier than others. Some of this risk is skill-dependent, while some of it is unavoidable due to the anatomical location of the block. You are advised to use your own discretion and judgment when applying these techniques. We do not assume any responsibility, express or implied, for anyone who may rely upon the information contained on this website.