The Impact of Local Anesthetic Dilution on Possible Blinding for Nerve Blocks
NCT ID: NCT06668116
Last Updated: 2025-11-28
Study Results
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Basic Information
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COMPLETED
NA
17 participants
INTERVENTIONAL
2024-12-11
2025-10-31
Brief Summary
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The goal is to find a placebo solution that can:
* Mimic the sensations of a real nerve block
* Not provide actual pain relief
* Allow for effective blinding in future studies
By developing an appropriate placebo, researchers hope to:
* Enable more rigorous investigations into the efficacy of nerve blocks for pain management
* Conduct comprehensive placebo-controlled studies, which are currently lacking in the field
* Overcome the obstacle of ensuring successful blinding in nerve block research This study is focused to establish a methodology for creating a convincing placebo that can be used in future research to more accurately assess the true effects of nerve blocks in pain medicine.
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Detailed Description
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Prognostic nerve blocks serve a different function; they are used to test whether a future treatment might be successful. If a temporary nerve block alleviates pain, it indicates that a more permanent treatment targeting that nerve could be effective. Therapeutic nerve blocks aim to provide long-lasting pain relief, helping patients engage in physical therapy or acting as a treatment on their own.
Despite their widespread use, there is insufficient solid scientific evidence to fully support the effectiveness of nerve blocks. Most studies conducted so far rely on observational data rather than controlled experiments. This lack of robust evidence raises concerns because diagnostic and prognostic blocks may lead to incorrect diagnoses or ineffective treatments. Additionally, therapeutic blocks can be invasive and costly, yet their effectiveness is not always guaranteed.
One significant challenge in researching nerve blocks is the difficulty of conducting placebo-controlled studies. For these studies to be valid, researchers need to ensure that neither the patients nor the assessors know who received the actual treatment and who received a placebo. However, this is complicated by the fact that nerve blocks often cause noticeable numbness or weakness, making it easy to identify who received the real treatment.
Researchers are exploring the possibility of using very low doses of anesthetic that might provide pain relief without causing noticeable numbness or weakness. If successful, this approach could allow for proper "blinded" studies where neither patients nor researchers can tell who received the actual treatment.
In summary, while nerve blocks play an important role in pain medicine, more research is needed to confirm their effectiveness. Finding ways to conduct proper placebo-controlled studies is crucial for ensuring that these treatments truly benefit patients.
Conditions
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Study Design
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RANDOMIZED
CROSSOVER
OTHER
DOUBLE
Study Groups
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Ropivacaine-Placebo Arm
Participants will first receive a nerve block with ropivacaine, starting at 0.1% concentration and adjusted according to Dixon's up-and-down method as described in the intervention section. Pain sensitivity and presence of sensory or motor block will be assessed 60 minutes post-injection using a Numerical Rating Scale (NRS). After a washout period, participants will cross over to receive a placebo (saline) injection, followed by the same assessments.
Ropivacaine 0,1%
The study uses ropivacaine for nerve blocks, starting at 0.1% concentration and capped at 0.5% for safety. Concentration adjustments are made based on each participant's response 60 minutes post-injection:
* Increase by 0.025% if pain reduction is \<50%
* Increase by 0.025% if reduction is 50-75% without sensory/motor block
* Decrease by 0.025% if reduction is 50-75% with sensory/motor block
* Decrease by 0.025% if reduction is \>75%. Pain is assessed using a Numerical Rating Scale. The study employs Dixon's up-and-down method for five cycles to determine the optimal concentration for effective pain relief without significant numbness or weakness.
NaCl (placebo)
0.9 % NaCl solution (saline) injection
Placebo-Ropivacaine Arm
Participants will first receive a placebo (saline) nerve block injection. Pain sensitivity and any reported sensory or motor changes will be assessed 60 minutes post-injection using a Numerical Rating Scale (NRS). After a washout period, participants will cross over to receive the ropivacaine injection, with concentration determined by Dixon's up-and-down method as described in the intervention section, followed by the same assessments.
Ropivacaine 0,1%
The study uses ropivacaine for nerve blocks, starting at 0.1% concentration and capped at 0.5% for safety. Concentration adjustments are made based on each participant's response 60 minutes post-injection:
* Increase by 0.025% if pain reduction is \<50%
* Increase by 0.025% if reduction is 50-75% without sensory/motor block
* Decrease by 0.025% if reduction is 50-75% with sensory/motor block
* Decrease by 0.025% if reduction is \>75%. Pain is assessed using a Numerical Rating Scale. The study employs Dixon's up-and-down method for five cycles to determine the optimal concentration for effective pain relief without significant numbness or weakness.
NaCl (placebo)
0.9 % NaCl solution (saline) injection
Interventions
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Ropivacaine 0,1%
The study uses ropivacaine for nerve blocks, starting at 0.1% concentration and capped at 0.5% for safety. Concentration adjustments are made based on each participant's response 60 minutes post-injection:
* Increase by 0.025% if pain reduction is \<50%
* Increase by 0.025% if reduction is 50-75% without sensory/motor block
* Decrease by 0.025% if reduction is 50-75% with sensory/motor block
* Decrease by 0.025% if reduction is \>75%. Pain is assessed using a Numerical Rating Scale. The study employs Dixon's up-and-down method for five cycles to determine the optimal concentration for effective pain relief without significant numbness or weakness.
NaCl (placebo)
0.9 % NaCl solution (saline) injection
Eligibility Criteria
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Inclusion Criteria
* ≥ 18 years old
* \< 65 years old
* Written informed consent as documented by signature
Exclusion Criteria
* Any history of chronic or acute pain at the moment of enrollment into the study
* Treatment with any substance having a relation to pain or pain modulation (antidepressants, opioids, benzodiazepines, anticonvulsants)
* Intake of any analgesic 48 hours prior to the conduction of any of the study stages
* Severe coagulopathy
* History of cardiovascular disease
* History of alcohol abuse or the intake of psychotropic drugs
* Pregnancy, ruled out by history
* Infection at the injection site or a systemic infection
* Fever of unknown origin
* Motor or sensory abnormalities in the arm
* Previous enrollment into the current study
18 Years
65 Years
ALL
Yes
Sponsors
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Balgrist University Hospital
OTHER
Responsible Party
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Principal Investigators
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Hagen Bomberg, Medical Doctor
Role: PRINCIPAL_INVESTIGATOR
Deputy Head of Anesthesiology
Locations
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Balgrist University Hospital
Zurich, Canton of Zurich, Switzerland
Countries
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References
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Dahan TH, Fortin L, Pelletier M, Petit M, Vadeboncoeur R, Suissa S. Double blind randomized clinical trial examining the efficacy of bupivacaine suprascapular nerve blocks in frozen shoulder. J Rheumatol. 2000 Jun;27(6):1464-9.
Adey-Wakeling Z, Crotty M, Shanahan EM. Suprascapular nerve block for shoulder pain in the first year after stroke: a randomized controlled trial. Stroke. 2013 Nov;44(11):3136-41. doi: 10.1161/STROKEAHA.113.002471. Epub 2013 Aug 22.
Lord SM, Barnsley L, Bogduk N. The utility of comparative local anesthetic blocks versus placebo-controlled blocks for the diagnosis of cervical zygapophysial joint pain. Clin J Pain. 1995 Sep;11(3):208-13. doi: 10.1097/00002508-199509000-00008.
Engel A, MacVicar J, Bogduk N. A philosophical foundation for diagnostic blocks, with criteria for their validation. Pain Med. 2014 Jun;15(6):998-1006. doi: 10.1111/pme.12436. Epub 2014 Apr 9.
Curatolo M, Petersen-Felix S, Arendt-Nielsen L. Sensory assessment of regional analgesia in humans: a review of methods and applications. Anesthesiology. 2000 Dec;93(6):1517-30. doi: 10.1097/00000542-200012000-00025. No abstract available.
Sveticic G, Gentilini A, Eichenberger U, Zanderigo E, Sartori V, Luginbuhl M, Curatolo M. Combinations of bupivacaine, fentanyl, and clonidine for lumbar epidural postoperative analgesia: a novel optimization procedure. Anesthesiology. 2004 Dec;101(6):1381-93. doi: 10.1097/00000542-200412000-00019.
Curatolo M, Kaufmann R, Petersen-Felix S, Arendt-Nielsen L, Scaramozzino P, Zbinden AM. Block of pinprick and cold sensation poorly correlate with relief of postoperative pain during epidural analgesia. Clin J Pain. 1999 Mar;15(1):6-12. doi: 10.1097/00002508-199903000-00003.
Vadhanan P, Tripaty DK, Adinarayanan S. Physiological and pharmacologic aspects of peripheral nerve blocks. J Anaesthesiol Clin Pharmacol. 2015 Jul-Sep;31(3):384-93. doi: 10.4103/0970-9185.161679.
Curatolo M, Schnider TW, Petersen-Felix S, Weiss S, Signer C, Scaramozzino P, Zbinden AM. A direct search procedure to optimize combinations of epidural bupivacaine, fentanyl, and clonidine for postoperative analgesia. Anesthesiology. 2000 Feb;92(2):325-37. doi: 10.1097/00000542-200002000-00012.
Inan LE, Inan N, Karadas O, Gul HL, Erdemoglu AK, Turkel Y, Akyol A. Greater occipital nerve blockade for the treatment of chronic migraine: a randomized, multicenter, double-blind, and placebo-controlled study. Acta Neurol Scand. 2015 Oct;132(4):270-7. doi: 10.1111/ane.12393. Epub 2015 Mar 13.
Other Identifiers
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2024-01431
Identifier Type: -
Identifier Source: org_study_id
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