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Much Ado About Ultrasound
Much Ado About Ultrasound
John Wolfe, MDCA-2 ResidentJune 6, 2007
John Wolfe, MDCA-2 ResidentJune 6, 2007
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Overview
Rationale for performing peripheral nerve blocks
Nerve stimulator technique Ultrasound technique Comparisons of the techniques Conclusions
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Advantages of Nerve Blocks
Improved immediate analgesia post-op Reduced side effects of general anesthesia Reduced side effects of analgesics Provision for continued post-op analgesia
with catheter placement Improved patient satisfaction More rapid and effective rehabilitation More rapid recovery of postoperative
cognitive function
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Disadvantages of Nerve Blocks
Surgeon’s concerns: Time for block placement Time for block setup
Patient’s concerns: Anxiety Needle punctures and manipulation Movement of fractured extremities
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Disadvantages of Nerve Blocks
Anesthesiologist’s concerns Failed blocks Complications
Nerve damage Toxicity Infection Hematoma
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Nerve Stimulator Technique
Insulated needle advanced based on surface landmarks
Variable current applied through the needle
Motor responses sought in nerve territories that correspond to the surgical site
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Nerve Stimulator Technique
Strengths:Functional confirmation of proximity of the needle to the nerve
Small, inexpensive, simple equipment
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Nerve Stimulator Technique
Weaknesses: Blind technique Variable anatomy Variability of thresholds for motor
responses Pain with movement of injured
extremities
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Nerve Stimulator Technique
Weaknesses: Multiple injections needed for optimal
success rates Studies demonstrate this at the axillary,
interscalene, and infraclavicular locations Likely due to inaccurate placement or
spread of the anesthetic Inability to see other nearby structures
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Addition of Ultrasound
Ultrasound imaging allows localization of the nerves
Other structures are also visualized Blood vessels Pleura Bone Muscle
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What Does Ultrasound Do?
Piezoelectric crystals on the transducer vibrate in response to an electrical field
The vibrations (ultrasound waves) reflect, refract, and scatter when they encounter structures of different acoustic impedance
Reflected vibrations are converted back to electrical energy by the transducer
Software reconstructs an image
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What Does Ultrasound Do?
Systems vary in transducer size and shape
Higher frequency = better resolution but poorer penetration
Lower frequency = better penetration but poorer resolution
Doppler analysis allows identification of vascular structures
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Interscalene
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Supraclavicular
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Infraclavicular
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Axillary
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Visualize the Needle
Interscalene block placement
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Visualize the Local Anesthetic
Interscalene block placement
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Ultrasound Guidance
Advantages: Visual localization of nerves Visualization of hazards Visualization of local anesthetic spread Avoidance of painful muscle contractions
Disadvantages: Equipment cost, size, and complexity Learning curve
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Is Ultrasound Guidance Better?
Some studies have shown improvements in time to perform the block and onset time
Marhofer et al 1998 Ultrasound guidance for three in one block ~50% faster block onset time
Williams et al 2003 RCT comparing US vs. NS supraclavicular blocks US blocks were faster (5 vs. 10 min)
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Is Ultrasound Guidance Better?
Soeding et al 2005 Comparison of US guidance vs. surface
landmarks for interscalene and axillary blocks
Faster onset times Schwemmer et al 2005
US vs. NS axillary blocks Surgery could proceed 15 minutes
faster in the US group
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Is Ultrasound Guidance Better?
Results have not been uniform The best results have been seen if:
Needle redirection is used to spread the local anesthetic around the neural structure
The control NS group was single-injection
Outcome studies have been small in scale
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Are They Additive Techniques?
Nerve stimulation gives functional confirmation
Ultrasound gives visual confirmation Is the block best done with both?
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Studies of US + NS Blocks
Van Geffen and Gielen 2006: Sciatic nerve block catheter placement
in children Minimal current for muscle contraction
varied widely among patients Visualization of local anesthetic spread
predicted successful blocks
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Studies of US + NS Blocks
Beach et al 2006: Supraclavicular blocks with both US
and NS For ultrasound guided blocks, positive
nerve stimulation did not increase the success rate
Nerve stimulation had a high false negative rate
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Studies of US + NS Blocks
Dingemans et al 5/2007: 72 patients received infraclavicular
blocks Patients either had blocks with
ultrasound guidance alone or ultrasound plus nerve stimulation
Comparison of speed of execution and quality of block
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Injection Techniques: Ultrasound only
Goal was a U-shaped distribution posterior and to either side of the axillary artery
1, 2, or 3 injections (most were 1 injection) Ultrasound plus nervestim
Distal motor response at 0.3 to 0.6 mA Single injection
Studies of US + NS Blocks
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Results: Faster block placement in the US
only group Ultrasound only 3.1 ± 1.6 min Ultrasound + nerve stimulator 5.2 ± 4.7
min
Studies of US + NS Blocks
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Studies of US + NS Blocks
Better block quality in US only group Percent of patients with sensory block
in 4 major nerve territories Ultrasound only 86% Ultrasound + nerve stimulator 57%
Need for block supplementation Ultrasound only 8% Ultrasound + nerve stimulator 26%
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Conclusions
Multi-injection, ultrasound-guided nerve blockade is faster and better than single-injection nerve stimulator-guided nerve blockade
Multi-injection, ultrasound-guided nerve blockade may be faster and better than multi-injection nerve stimulator-guided nerve blockade
Adding nerve stimulation to ultrasound guided blocks may be more hindrance than help
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Study Limitations
Studies are small and not uniform in design
Results are not uniform Proving a safety benefit is difficult
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Practical Limitations
Learning curve for ultrasound Equipment cost Poor images (e.g. body habitus)
hinder US block placement Need for training with the nerve
stimulator in residency
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Future Directions
Ultrasound equipment will continue to get better, smaller, and cheaper
Ultrasound block techniques will be refined
Outcomes and performance data will accumulate
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Any Questions?
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References Dingemans, Emmanuel MD *; Williams, Stephan R. MD, PhD *; Arcand, Genevieve MD, FRCPC *; Chouinard,
Philippe MD, FRCPC *; Harris, Patrick MD, FRCSC +; Ruel, Monique RN *; Girard, Francois MD, FRCPC Neurostimulation in Ultrasound-Guided Infraclavicular Block: A Prospective Randomized Trial. Anesthesia & Analgesia. 104(5):1275-1280, May 2007.
Rodriguez J. Barcena M. Taboada-Muniz M. Lagunilla J. Alvarez J. A comparison of single versus multiple injections on the extent of anesthesia with coracoid infraclavicular brachial plexus block. Anesthesia & Analgesia. 99(4):1225-30, 2004 Oct.
Horlocker TT. Wedel DJ. Ultrasound-guided regional anesthesia: in search of the holy grail. Anesthesia & Analgesia. 104(5):1009-11, 2007 May
Beach ML. Sites BD. Gallagher JD. Use of a nerve stimulator does not improve the efficacy of ultrasound-guided supraclavicular nerve blocks. Journal of Clinical Anesthesia. 18(8):580-4, 2006 Dec.
Sites BD. Brull R. Ultrasound guidance in peripheral regional anesthesia: philosophy, evidence-based medicine, and techniques. Current Opinion in Anaesthesiology. 19(6):630-9, 2006 Dec.
Marhofer P. Sitzwohl C. Greher M. Kapral S. Ultrasound guidance for infraclavicular brachial plexus anaesthesia in children. Anaesthesia. 59(7):642-6, 2004 Jul.
Marhofer, Peter MD *; Chan, Vincent W. S. MD, Ultrasound-Guided Regional Anesthesia: Current Concepts and Future Trends. Anesthesia & Analgesia. 104(5):1265-1269, May 2007.
Williams SR. Chouinard P. Arcand G. Harris P. Ruel M. Boudreault D. Girard F. Ultrasound guidance speeds execution and improves the quality of supraclavicular block. Anesthesia & Analgesia. 97(5):1518-23, 2003 Nov.
Schwemmer U. Markus CK. Greim CA. Brederlau J. Roewer N. Ultrasound-guided anaesthesia of the axillary brachial plexus: efficacy of multiple injection approach. Ultraschall in der Medizin. 26(2):114-
9, 2005 Apr. Marhofer P. Schrogendorfer K. Wallner T. Koinig H. Mayer N. Kapral S. Ultrasonographic guidance
reduces the amount of local anesthetic for 3-in-1 blocks Regional Anesthesia & Pain Medicine. 23(6):584-8, 1998 Nov-Dec.
Soeding PE. Sha S. Royse CE. Marks P. Hoy G. Royse AG. A randomized trial of ultrasound-guided brachial plexus anaesthesia in upper limb surgery Anaesthesia & Intensive Care. 33(6):719-25, 2005 Dec.
New York School of Regional Anesthesia website www.nysora.com