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Commentary and Perspective   |    
The Continued Search for the Perfect AnalgesicCommentary on an article by Anshu Singh, MD, et al.: “Ultrasound-Guided Interscalene Block Anesthesia for Shoulder Arthroscopy. A Prospective Study of 1319 Patients”
Ashley Shilling, MD1
1 University of Virginia Medical Center, Charlottesville, Virginia
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The author has not received payments or services, either directly or indirectly (i.e., via her institution), from a third party in support of any aspect of this work. Neither the author, nor her institution, has had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. The author has not had any other relationships, or engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article.


Copyright © 2012 by The Journal of Bone and Joint Surgery, Inc.
J Bone Joint Surg Am, 2012 Nov 21;94(22):e170 1-2. doi: 10.2106/JBJS.L.01066
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When queried about perioperative concerns, patients have rated postoperative pain as being of greater concern than making a full surgical recovery1. A study of >10,000 ambulatory surgery patients demonstrated that orthopaedic patients had the highest incidence of severe postoperative pain2. Therefore, finding safe, effective, and efficient means of perioperative pain control is of paramount importance to both anesthesiologists and orthopaedic surgeons. In the current study, Singh et al. examined the use of ultrasound-guided interscalene brachial plexus block in patients undergoing arthroscopic shoulder surgery. Their approach was ambitious; they prospectively followed 1319 patients with the goal of evaluating ultrasound-guided interscalene block in terms of safety, efficacy, and patient satisfaction.
The most striking strengths of this study are the large patient cohort and the exclusive use of ultrasound guidance, thus making this the largest prospective study to date on the use of this modality for interscalene block. In the competitive era of “customer service,” patient satisfaction is a valuable addition to the study design. The authors concluded that 99% of patients were either very satisfied or satisfied with the interscalene block, but, probably more telling, 98% of patients who were queried stated that they would undergo an interscalene block again. As all of the blocks had likely worn off at the time of the follow-up telephone interview and the patients were facing the painful truth of surgery “post-block,” this is an impressively high percentage.
The authors’ finding of 99.6% efficacy of ultrasound-guided interscalene block remains somewhat unclear. Their definition of efficacy is block failure; that is, inadequate sensory blockade after thirty minutes of block placement. Unfortunately, these metrics are never defined further. Were all nerves of the brachial plexus tested for complete sensory loss? The authors assert that the addition of an interscalene block improves operative conditions due to relaxation but never tested motor blockade. While many institutions use an interscalene block as the primary anesthetic as it avoids the vasodilatory effects of general anesthetics and allows for an intraoperative examination of cerebral perfusion, the majority of study patients were managed with a general anesthetic and the block was never tested as a surgical anesthetic.
A critical omission is that the authors do not comment on pain scores or the use of narcotics in the immediate postoperative period. They report that only one patient was admitted for pain. However, the reader is left to wonder if the 1318 remaining patients received copious doses of narcotics in the recovery room. While the authors acknowledge this exclusion, the reader would be more convinced of their claimed 99.6% efficacy with the inclusion of these valuable data.
Surgeons may wonder if the addition of ultrasound guidance to the performance of peripheral nerve blocks is simply an academic toy for anesthesiologists or, more cynically, a means of increasing billing for nerve block procedures. Studies have validated the addition of ultrasound guidance to peripheral nerve blocks, with benefits including reduced local anesthetic dose, improved block quality, decreased needle passes, shortened performance time, and decreased block onset time3-5. Ultrasound guidance should theoretically decrease complications of local anesthetic systemic toxicity as it allows for reduced local anesthetic volumes and visualization of vulnerable surrounding structures like blood vessels. In addition, we suspect that the incidence of nerve injury is reduced with the visualization of needle-nerve contact and nerve swelling with an intraneural injection. Despite these proposed advantages, studies have not yet proven these safety outcome benefits by adding ultrasound guidance to peripheral nerve blocks.
In this study, the authors concluded that ultrasound-guided interscalene block is safe for patients undergoing arthroscopic shoulder surgery. Of note, this study was not powered to detect the two most concerning safety outcomes: local anesthetic systemic toxicity and neurological injury. The incidence of local anesthetic systemic toxicity has been estimated to be 0.2% in association with brachial plexus blocks6. Short-term neurological complications are highly variable, depending largely on study design and how aggressively complications are assessed. Most studies have demonstrated the prevalence of short-term neurological deficits associated with interscalene block to be between 3% and 14%, although one demonstrated a rate of as low as 0.6% (95% confidence interval [CI], 0.1% to 2%)6-8. Long-term neurological injuries resulting from peripheral nerve blocks are thought to occur much less frequently, with an incidence of between 1 of 2000 to 1 of 15,0006,7. While the present study was not powered to detect long-term complications, it could be instrumental in detecting short-term neurological deficits. The protocol for detecting these findings, however, is not robust. Patients were called at twenty-four hours postoperatively, at which time they likely were experiencing pain and were immobilized in a sling with a wound dressing. These circumstances could prevent realization of a subtle motor or sensory change from baseline. After twenty-four hours, the authors relied on self-reporting and postoperative visits. If a patient sought care at an outside institution, a complication would be missed. For these reasons, it is likely that the study underestimates short-term neurological findings. Despite this limitation, the authors detected eight cases of digital numbness, one case of ulnar neuropathy, and three reported cases of brachial plexitis. Excluding ear numbness, which was attributed to the beach-chair position in most cases, the incidence of short-term neurological deficits was 0.9% (95% CI, 0.5% to 1.6%), which was lower than most contemporary estimates. It is impossible to know if the low incidence is due to a low complication rate or if the authors’ methodology merely underestimates the incidence of short-term neuropathies. Of the three long-term neurological complications, one transient plexitis could have been attributed to the interscalene block, whereas the other two were presumed to be related to other patient comorbidities (transverse myelitis and multiple sclerosis). This finding emphasizes the importance of preexisting neurological comorbidities that may be undiagnosed or missed in patients.
Do we care about short-term neurological deficits that are transient and self-limited? Simply stated, yes. Even a short-term neurological insult adds stress to patients, anesthesiologists, and surgeons, who are unsure if the injury is surgery-related or is due to the peripheral nerve block. Knowing the incidence helps us to better inform patients of their risks and also reassures them and us. With the prospective design of this study, this potentially huge opportunity for discovery was lost.
Despite the shortcomings of the study design with respect to neurological findings, the authors were very rigorous in their collection of data on immediate perioperative complications. While most of the reported short and long-term complications were unrelated to the interscalene block, the reader does gain insight into complications and their frequency in “healthy” American Society of Anesthesiologists (ASA) class 1 and 2 patients undergoing arthroscopic shoulder surgery.
The labor-intensive study by Singh et al. certainly sheds light on patient satisfaction as it relates to interscalene blocks. Additionally, we are optimistic but not completely convinced that ultrasound guidance leads to extremely high efficacy of interscalene blocks. The paucity of complications directly related to the block is reassuring to both orthopaedic surgeons and anesthesiologists; however, the authors’ methodology may underestimate these complications. This large case series endorses the use of this technique for arthroscopic shoulder surgery. Better pain control, reduced narcotics with fewer side effects, improved functional outcomes, and high patient satisfaction are but a few literature-supported reasons to consider regional anesthesia as a primary anesthetic or an adjuvant to amenable surgeries. Other outcome benefits related to morbidity and mortality are still in question. While this study was not designed to answer these important questions, it supports the use of the interscalene block in this patient population.
Apfelbaum  JL;  Chen  C;  Mehta  SS;  Gan  TJ. Postoperative pain experience: results from a national survey suggest postoperative pain continues to be undermanaged. Anesth Analg.  2003 Aug;97(  2):534-40,  table of contents.[CrossRef]
 
Chung  F;  Ritchie  E;  Su  J. Postoperative pain in ambulatory surgery. Anesth Analg.  1997 Oct;85(  4):808-16.
 
Abrahams  MS;  Aziz  MF;  Fu  RF;  Horn  JL. Ultrasound guidance compared with electrical neurostimulation for peripheral nerve block: a systematic review and meta-analysis of randomized controlled trials. Br J Anaesth.  2009 Mar;102(  3):408-17.  Epub 2009 Jan 26.[CrossRef]
 
Casati  A;  Baciarello  M;  Di Cianni  S;  Danelli  G;  De Marco  G;  Leone  S;  Rossi  M;  Fanelli  G. Effects of ultrasound guidance on the minimum effective anaesthetic volume required to block the femoral nerve. Br J Anaesth.  2007 Jun;98(  6):823-7.  Epub 2007 May 3.[CrossRef]
 
Antonakakis  JG;  Ting  PH;  Sites  B. Ultrasound-guided regional anesthesia for peripheral nerve blocks: an evidence-based outcome review. Anesthesiol Clin.  2011 Jun;29(  2):179-91.  doi: 10.1016/j.anclin.2011.04.008. Epub 2011 May 5.[CrossRef]
 
Brull  R;  McCartney  CJ;  Chan  VW;  El-Beheiry  H. Neurological complications after regional anesthesia: contemporary estimates of risk. Anesth Analg.  2007 Apr;104(  4):965-74.[CrossRef]
 
Borgeat  A;  Ekatodramis  G;  Kalberer  F;  Benz  C. Acute and nonacute complications associated with interscalene block and shoulder surgery: a prospective study. Anesthesiology.  2001 Oct;95(  4):875-80.[CrossRef]
 
Liu  SS;  Gordon  MA;  Shaw  PM;  Wilfred  S;  Shetty  T;  Yadeau  JT. A prospective clinical registry of ultrasound-guided regional anesthesia for ambulatory shoulder surgery. Anesth Analg.  2010 Sep;111(  3):617-23.  Epub 2010 Aug 4.[CrossRef]
 

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References

Apfelbaum  JL;  Chen  C;  Mehta  SS;  Gan  TJ. Postoperative pain experience: results from a national survey suggest postoperative pain continues to be undermanaged. Anesth Analg.  2003 Aug;97(  2):534-40,  table of contents.[CrossRef]
 
Chung  F;  Ritchie  E;  Su  J. Postoperative pain in ambulatory surgery. Anesth Analg.  1997 Oct;85(  4):808-16.
 
Abrahams  MS;  Aziz  MF;  Fu  RF;  Horn  JL. Ultrasound guidance compared with electrical neurostimulation for peripheral nerve block: a systematic review and meta-analysis of randomized controlled trials. Br J Anaesth.  2009 Mar;102(  3):408-17.  Epub 2009 Jan 26.[CrossRef]
 
Casati  A;  Baciarello  M;  Di Cianni  S;  Danelli  G;  De Marco  G;  Leone  S;  Rossi  M;  Fanelli  G. Effects of ultrasound guidance on the minimum effective anaesthetic volume required to block the femoral nerve. Br J Anaesth.  2007 Jun;98(  6):823-7.  Epub 2007 May 3.[CrossRef]
 
Antonakakis  JG;  Ting  PH;  Sites  B. Ultrasound-guided regional anesthesia for peripheral nerve blocks: an evidence-based outcome review. Anesthesiol Clin.  2011 Jun;29(  2):179-91.  doi: 10.1016/j.anclin.2011.04.008. Epub 2011 May 5.[CrossRef]
 
Brull  R;  McCartney  CJ;  Chan  VW;  El-Beheiry  H. Neurological complications after regional anesthesia: contemporary estimates of risk. Anesth Analg.  2007 Apr;104(  4):965-74.[CrossRef]
 
Borgeat  A;  Ekatodramis  G;  Kalberer  F;  Benz  C. Acute and nonacute complications associated with interscalene block and shoulder surgery: a prospective study. Anesthesiology.  2001 Oct;95(  4):875-80.[CrossRef]
 
Liu  SS;  Gordon  MA;  Shaw  PM;  Wilfred  S;  Shetty  T;  Yadeau  JT. A prospective clinical registry of ultrasound-guided regional anesthesia for ambulatory shoulder surgery. Anesth Analg.  2010 Sep;111(  3):617-23.  Epub 2010 Aug 4.[CrossRef]
 
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