ASRA Pain Medicine Update

Congratulations to the following abstract award recipients who were not able to accept their awards in person due to the cancellation of the 45th Annual Regional Anesthesiology and Acute Pain Medicine Meeting. 

Best of Meeting Abstract Awards

Dr. Hannah Lin

Dose-Response Relationship of Local Anesthetic Volume and Diaphragmatic Paresis Following Ultrasound-Guided Supraclavicular Block (Abstract #714)

Abstract authors: Hannah Lin, Kane Pryor, Virginia Tangel, Daniel Pak, Hannah Oden-Brunson, Jenna Yousif, Kaitlyn Sbrollini, Tiffany Tedore, New York Presbyterian Hospital - Weill Cornell Medicine, New York, NY

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I am thrilled and honored to receive one of the Best of Meeting Awards at ASRA 2020 for our abstract titled “Dose-Response Relationship of Local Anesthetic Volume and Diaphragmatic Paresis Following Ultrasound-Guided Supraclavicular Block.” It is beyond my wildest expectations to have won a second Best of Meeting Award following my first at ASRA 2017. It speaks to the amazingly dedicated researchers and educators who have supported me during my anesthesia residency and regional fellowship at New York Presbyterian Hospital- Weill Cornell Medicine.

We found that there is diaphragmatic paresis even at the lowest study volume of 5mL.

I have been an active member of ASRA throughout training. The annual meetings are invaluable for life-long learning, exchange of ideas, skills training, leadership development, and sense of community. I look forward to many more wonderful memories and friendships at ASRA.

There is no consensus regarding what volume of local anesthetic should be used to achieve a supraclavicular block for surgery while minimizing diaphragmatic paresis. Interestingly, we found that there is diaphragmatic paresis even at the lowest study volume of 5mL. This knowledge helps to better understand the risks of the “spinal of the arm” and enable regional anesthesiologists to provide safer care to patients. Considerations include evaluating the diaphragm before a supraclavicular block especially in patients with respiratory disease, as well as performing more distal brachial plexus blocks when suitable for surgery.

We have recently submitted our manuscript to ASRA’s Regional Anesthesia & Pain Medicine journal for consideration.

— Hannah Lin, MD

Early Ambulation After Hip Arthroplasty: A Double-Blind Randomized, Controlled Trial

Abstract authors: Andrew Mendelson, Jordan Smoker, Vincent Kasper, William Hozack, Matthew Austin, Scot Brown, Alyson Nemeth, Eric Czerwinski, Johnathan Li, Alexa Cohen, Jamie Baratta, Chris Wahal, Marc Torjman, Eric Schwenk, Thomas Jefferson University Hospital, Philadelphia, PA

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Spinal anesthesia with the drug mepivacaine allows for earlier ambulation after total hip arthroplasty than either form of bupivacaine, according to Mendelson et al. The sooner patients can walk after surgery, the faster they can be discharged, allowing for more comfortable recovery at home, lower overall cost of care, and increased availability of critical hospital resources. Although spinal anesthesia offers several advantages over general anesthesia, it also limits sensory and motor function when blocking nerves and may delay patients’ ability to ambulate.

One of the most commonly used drugs for spinal anesthesia is bupivacaine, a long-acting amide local anesthetic available in several forms, including hyperbaric and isobaric. Both of those forms can produce partial motor blockade for 2.5–3 hours. Mepivacaine, an intermediate-acting amide local anesthetic, produces reliable spinal anesthesia for 1.5–2 hours, and studies with total knee arthroplasty suggested that it allows for earlier postsurgical ambulation than bupivacaine.

Mendelson et al. performed a prospective, randomized, double-blind trial comparing mepivacaine to hyperbaric and isobaric bupivacaine in 154 patients receiving spinal anesthesia during total hip arthroplasty to determine which drug allows for earlier ambulation. They found that patients who received mepivacaine were more likely to ambulate at 3.5 hours than those who received either form of bupivacaine. The mepivacaine group also had significantly shorter length of stay and more same-day discharges than patients in the other two groups. However, patients receiving mepivacaine had higher pain ratings and opioid consumption—but only in postanesthesia care unit. No other differences existed among the groups, including incidence of transient neurologic symptoms.

“Patients who received mepivacaine spinal anesthesia were more likely to ambulate early and be discharged on the day of surgery, and mepivacaine spinal anesthesia should be considered in appropriate outpatient total hip arthroplasty candidates,” Mendelson et al. concluded.

Desmond Fun

Motor Block Produced By Quaternary Lidocaine Derivatives: A Preclinical Comparison of Qx-572 and Qx-222 Versus Qx-314 in Mice (Abstract # 1055)

Abstract authors: Desmund Fung, Helia Shariati, Michael Smith, Bernard MacLeod, Ernest Puil, Stephan Schwarz, The University of British Columbia, Vancouver, BC

In the search for a long-lasting, nonopioid, postoperative local anesthetic that would reduce the need for opioid-based pain control, various lidocaine derivatives have been suggested. In this study, researchers tested three experimental quaternary lidocaine derivatives—QX-314, QX-572, and QX-222—in mice to compare efficacy and toxicity rates. The investigators conducted a randomized, double-controlled, blinded in vivo study using the sciatic nerve blockade assay in mice. They injected QX-314, QX-572, and QX-222, with lidocaine as the positive control and saline as the negative control, into the mice’s popliteal fossa on the left hindlimb. They monitored the animals for recovery from motor blockade and behavioral signs of systemic toxicity.

Hydrophobic properties influence the potency and duration of motor blockade produced by quaternary compounds

All three derivatives produced motor blockade at certain concentrations. QX-314 (at ≥ 3 mM) offered reversible motor blockade that lasted longer than that of lidocaine. QX-572 produced longer-lasting motor blockade than lidocaine; however, the nerve block became irreversible at > 10 mM. QX-222 resulted in reversible motor blockade similar to lidocaine at an equimolar concentration. When given at an equimolar 70 mM concentration, the median motor block durations were 0.5 hours for lidocaine, 44 hours for QX-314, and 10 minutes for QX-222. In comparison, at just 30 mM, the median block duration was 24 hours for QX-572.

“The order of potency was QX-572 > QX-314 > QX-222, which is similar to the findings from our companion study on sensory blockade,” Fung et al. said. “QX-222 may confer more favorable toxicity and sensory-motor nerve separation profiles compared to QX-314, but it did not produce long-lasting motor blockade like QX-314.

“Overall, these results indicate that hydrophobic properties influence the potency and duration of motor blockade produced by quaternary compounds,” they concluded. “Future studies with other quaternary compounds may reveal specific structural modifications that produce greater sensory-motor fiber separation with respect to local anesthetic-blocking profiles.”

This abstract was also awarded a Resident/Fellow Travel Award.

Resident/Fellow Travel Awards

Dr. Lisa Sun

Erector Spinae Plane Block For Total Shoulder Arthroplasty Avoids Phrenic Nerve Complication: A Randomized Trial (Abstract # 790)

Lisa Sun, Shruthi Basireddy, Lynn Ngai Gerber, Jason Lamano, John Costouros, Emilie Cheung, Jan Boublik, Jean-Louis Horn, Ban Tsui, Stanford University, Stanford, CA

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The interscalene brachial plexus nerve block is currently a commonly-used block for postoperative analgesia after total shoulder arthroplasty, but it has undesired side effects, including hemidiaphragm weakness. During my fellowship in regional anesthesia and acute pain medicine at Stanford University, my mentor, Dr. Ban Tsui, and I conducted a randomized study showing the high-thoracic erector spinae plane block (HT-ESPB) provides satisfactory pain control with the advantages of no phrenic nerve complications, less adverse events, and no upper extremity weakness. I am honored to have received the Best of Meeting/Fellow Travel Award for this work at the 45th Annual Regional Anesthesia and Acute Pain Medicine Meeting.

Conducting a study for an emerging and relatively newly described block in a safe and ethical manner requires a supportive clinical atmosphere, a well-functioning healthcare system, and experienced research team members.

Although very effective for pain control after shoulder surgery, the interscalene nerve block can cause a high incidence of phrenic nerve palsy, which leads to shortness of breath in 9-12% of patients. In addition, this block frequently causes weakness of the upper extremity, which can be uncomfortable to patients, and it can cause Horner’s syndrome and hoarseness. The HT-ESPB is a more recently described block, which in case reports appears to provide effective analgesia after shoulder surgery while also being diaphragm-sparing. In this randomized, double-blind study we compared the continuous HT-ESPB (n=12) as a diaphragm-sparing analgesic alternative to the continuous interscalene block (n=14) in patients undergoing total shoulder arthroplasty.

The results of our study showed that all patients who received a HT-ESPB catheter preserved their respiratory function. The HT-ESPB group had no sonographic evidence of hemidiaphragm paresis. This was significantly less than the interscalene catheter group, which had a 100% incidence of partial or full paresis. The interscalene group also had a significantly greater decrease in incentive spirometry volume in the recovery room and on postoperative day 1, compared to the HT-ESPB group (44% vs. 9%, p<0.001; 38% vs. 7%, p<0.001).  One patient in the interscalene group had shortness of breath postoperatively, requiring a decrease in the perineural infusion rate.

The interscalene block had an initial benefit in analgesia over the HT-ESPB, with lower average median pain scores in the postoperative recovery room (1.3 ± 2.02 vs. 3.8 ± 3.11, p=0.023). Subsequently, there was no significant difference in pain scores for postoperative day 0 through 2. The groups had no significant difference in cumulative opioid consumption through postoperative day 2, although the HT-ESPB group did have higher opioid consumption for postoperative day 0. Patient satisfaction with the nerve block was 100% in both groups.

No patients in the HT-ESPB group experienced motor function loss, compared to 8 patients in the interscalene group. One patient in the interscalene group reported subjective difficulty with physical therapy due to nerve block, although there was no significant difference between the groups in basic mobility and activity scores by physical therapy on postoperative day 1.

Overall, the interscalene group had a significantly higher number of patients with any adverse events, with 7% experiencing dyspnea, 7% experiencing hoarseness, 7% experiencing Horner’s syndrome, 7% reporting subjective difficulty with physical therapy. There were no differences in time to discharge from the recovery room.

This study shows that the HT-ESPB can be a satisfactory analgesic alternative to the interscalene block for total shoulder arthroplasty, particularly when any risk of phrenic nerve palsy would be concerning.

Conducting a study for an emerging and relatively newly described block in a safe and ethical manner requires a supportive clinical atmosphere, a well-functioning healthcare system, and experienced research team members. I am grateful to have had the opportunity to conduct such a study under the guidance of mentors including Dr. Tsui and in the supportive atmosphere of my fellowship program. The enthusiasm for academic pursuit among the healthcare providers, researchers, and patients at Stanford Hospital enabled this collaborative work. I am also very appreciative of the forum that ASRA provides to trainees to present and discuss our research experiences – the feedback from regional and acute pain medicine experts around the world at the 45th Annual Regional Anesthesia and Acute Pain Medicine Meeting was invaluable.

— Lisa Sun, MD

Mentoring Dr. Lisa Sun

It has been a pleasure and a privilege to mentor Lisa throughout her training at Stanford.  Lisa has been a superb clinician and passionate researcher. I am incredibly proud of her being awarded the Best of Meeting/Fellow Travel Award for her excellent work in evaluating an emerging regional anesthesia technique for total shoulder arthroplasty - erector spinae plane block (ESP).  With further clinical studies, an effective and novel analgesic alternatives approach for at-risk patients with compromised respiratory function may become a reality.

I am very thankful for this meaningful award as it is a tremendous morale-booster that will encourage and motivate young and talented anesthesiologists in pursuing academics in the field of regional anesthesia. No doubt, this extra motivation and encouragement from the society has provided a catalyst for the next generation of regional anesthesiologists. As a regional anesthesia enthusiast, I am also very indebted to ASRA for the time and effort the society has put into this annual award process.

— Ban C.H. Tsui, MD MSc, Professor, Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University

Dr. Lynn Ngai Gerber

10-Milliliter Normal Saline Washout Aliquots Are Insufficient to Reliably Reverse Phrenic Blockade From Interscalene Nerve Block (Abstract # 770)

Lynn Ngai Gerber, Lisa Sun, Wen Ma, Nan Guo, John Costouros, Emilie Cheung, Jan Boublik, Jean-Louis Horn, Ban Tsui, Stanford University, Stanford, CA

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Although an effective regional anesthesia technique for upper-extremity surgeries, the interscalene nerve block is associated with a high rate of phrenic nerve palsy, which can result in respiratory compromise. My mentor, Dr. Ban Tsui, and I have previously published case reports using normal saline to “washout” or dilute the local anesthetic from an interscalene nerve block to restore diaphragmatic function, while preserving the analgesic effect. We ventured to perform a randomized clinical trial to evaluate this concept. Ultrasonographic diaphragmatic thickening ratio was our primary outcome to objectively measure diaphragmatic paralysis and thus phrenic nerve blockade, using the previously described ABCDE ultrasound technique. The other primary outcome was pain scores. Our secondary outcome measures were brachial plexus motor and sensory exams.

Normal saline washout in 10 milliliter increments did not reverse phrenic nerve blockade clinically; however, it did reduce the degree of phrenic nerve palsy upon ultrasound examination.

Sixteen patients who received interscalene nerve block catheters for their shoulder surgeries were randomized to receive either three doses of 10 mL normal saline washouts (n = 8) or sham washouts (n = 8). Although no clinically significant difference was demonstrated in reversal of diaphragmatic paralysis, there was a significant difference in the number of patients who ultimately displayed partial versus full paralysis of the diaphragm in a sub-group analysis. Furthermore, there was no significant difference in pain scores or opioid requirement in post anesthesia care unit. There was no difference in motor or sensory blockade between the two groups at baseline, post-intervention, or when comparing individual change in exam scores.

Our randomized clinical trial demonstrated that normal saline washout in 10 milliliter increments did not reverse phrenic nerve blockade clinically; however, it did reduce the degree of phrenic nerve palsy upon ultrasound examination. No reduction in analgesic effect was observed in our study. In contrast to previous experience, when larger volumes (30 mL) of normal saline successfully reversed phrenic block, perhaps our intent of minimizing potential rebound pain from using lower volumes was insufficient to unveil a clinically beneficial effect. More patients in the washout group showed an improvement from full to partial paralysis, suggesting that a larger volume of normal saline may be needed to completely reverse diaphragmatic paralysis. Further investigations of dose-finding may benefit from this information when determining the minimum volume of normal saline washout required to produce a reversal of phrenic nerve blockade while preserving analgesia.

I am honored to have received the Best of Meeting/ Fellow Travel Award for this abstract at the 45th Annual Regional Anesthesia and Acute Pain Medicine Meeting, and I am also grateful to have had the opportunity to undertake this original research during my residency and fellowship at Stanford. Executing a randomized clinical trial from a nascent idea during my anesthesiology training at first seemed like an unattainable task; however, working with Dr. Ban Tsui and receiving departmental support in terms of resource for research at Stanford contributed hugely to my success. The outstanding clinical and academic training and support from world-renowned mentors such as Dr. Tsui, have been essential to enrich my research experience, making it fulfilling and worthwhile.

— Lynn Ngai Gerber, MD

Mentor’s Perspective

As a practicing anesthesiologist, I am honored to have the privilege to mentor young professional such as Lynn early in their career and guide them to discover their own potentials. The Best of Meeting/Fellow Travel Award promotes the development for the next generation of regional anesthesiologists, and I am incredibly proud for my mentee to receive such a meaningful award under my guidance. Indeed, I have to thank ASRA for their continual support for the trainees. It is incredibly satisfying having mentored Lynn from when she was a junior trainee till now, as she soon becomes an attending physician and regional anesthesiologist, who will be a great future mentor herself.

Lynn has been a dedicated and enthusiastic regional fellow. She performed excellently throughout her training at Stanford and learned quickly to overcome hurdles in her research on the phrenic nerve blockade reversal concept by using normal saline washout. Through further dose-finding studies, interscalene block may one day be a regional technique to maintain analgesia with minimal phrenic nerve blockade for the upper extremity surgery.

— Ban C.H. Tsui, MD MSc, Professor, Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University