Much Ado About Ultrasound John Wolfe, MD CA-2 Resident June 6, 2007 John Wolfe, MD CA-2 Resident June 6, 2007

Overview Rationale for performing peripheral nerve blocks Nerve stimulator technique Ultrasound technique Comparisons of the techniques Conclusions

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

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

Disadvantages of Nerve Blocks Anesthesiologist’s concerns Failed blocks Complications Nerve damage Toxicity Infection Hematoma

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

Nerve Stimulator Technique Strengths: Functional confirmation of proximity of the needle to the nerve Small, inexpensive, simple equipment

Nerve Stimulator Technique Weaknesses: Blind technique Variable anatomy Variability of thresholds for motor responses Pain with movement of injured extremities

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

Addition of Ultrasound Ultrasound imaging allows localization of the nerves Other structures are also visualized Blood vessels Pleura Bone Muscle

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

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

Interscalene

Supraclavicular

Infraclavicular

Axillary

Visualize the Needle Interscalene block placement

Visualize the Local Anesthetic Interscalene block placement

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

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)

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

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

Are They Additive Techniques? Nerve stimulation gives functional confirmation Ultrasound gives visual confirmation Is the block best done with both?

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

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

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

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

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

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%

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

Study Limitations Studies are small and not uniform in design Results are not uniform Proving a safety benefit is difficult

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

Future Directions Ultrasound equipment will continue to get better, smaller, and cheaper Ultrasound block techniques will be refined Outcomes and performance data will accumulate

Any Questions?

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): , May 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): , 2004 Oct. Horlocker TT. Wedel DJ. Ultrasound-guided regional anesthesia: in search of the holy grail. Anesthesia & Analgesia. 104(5): , 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): , May 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): , 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