The Impact of Local Anesthetic Dilution on Possible Blinding for Nerve Blocks

NCT06668116 | Completed

• 1 other identifier: 2024-01431
• Study Type: interventional
• Target: 17
• Locations: 1 country
• Sites: 1

Brief Summary

This study aims to determine the appropriate dosage of a placebo anesthetic to enable future placebo-controlled studies that can more accurately examine the effects of nerve blocks. The main challenge in conducting such studies is the difficulty in blinding participants and researchers due to the noticeable effects of nerve blocks, such as numbness and motor impairments. 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.

Conditions

Healthy

Keywords

Peripheral nerve blocks; Placebo-controlled studies; Blinding in clinical trials

Outcome Measures

Primary Outcomes (3)

• Heat pain sensitivity

  Participants will rate their pain in response to heat stimulation using the Numerical Rating Scale (NRS). On this scale, 0 represents no pain at all, while 100 represents the worst pain imaginable.

  Heat pain sensitivity will be determined before (baseline), and every 5 minutes up to 60 minutes after injection.

• Self-report of sensory block

  Participants will be asked to self-report any sensory changes by responding to the question: "Do you feel any numbness in the forearm or hand on the side where the injection was given?" They will be required to answer either "yes" or "no" to this question.

  Self-report of sensory block will be assessed 30 and 60 minutes after injections.

• Self-report of motor block

  Participants will be asked to self-report any motor changes by responding to the question: "Do you feel any reduction of strength of your hand on the injection side?" They will be required to answer either "yes" or "no" to this question.

  Self-report of motor block will be assessed 30 and 60 minutes after injections.

Secondary Outcomes (5)

• Evaluation of the C-fiber block

  Measurement will be done at baseline, 30 and 60 minutes after injection.

• Evaluation of the A-delta fiber block

  Measurement will be done at baseline, 30 and 60 minutes after the injection.

• Evaluation of the A-beta fiber block

  Measurement will be done at baseline, 30 and 60 minutes after the injection.

• Evaluation of the A-alpha fiber block (motor block)

  Measurement will be done at baseline, 30 and 60 minutes after the injection.

• Offset analgesia

  Measurement will be done at 60 minutes after the injection.

Other Outcomes (2)

• Evaluating blinding of the participants_part1

  Measurement will be done 60 minutes after the injection.

• Evaluating blinding of the participants_part2

  Measurement will be done 60 minutes after the injection.

Study Arms (2)

Ropivacaine-Placebo Arm

OTHER

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.

Drug: Ropivacaine 0,1%; Other: NaCl (placebo)

Placebo-Ropivacaine Arm

OTHER

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.

Drug: Ropivacaine 0,1%; Other: NaCl (placebo)

Interventions

Ropivacaine 0,1% DRUG

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.

Placebo-Ropivacaine Arm; Ropivacaine-Placebo Arm

NaCl (placebo) OTHER

0.9 % NaCl solution (saline) injection

Placebo-Ropivacaine Arm; Ropivacaine-Placebo Arm

Eligibility Criteria

• Age: 18 Years - 65 Years
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• ASA I - II, both sexes
• ≥ 18 years old
• \< 65 years old
• Written informed consent as documented by signature

You may not qualify if:

• Known allergy or hypersensitivity to a ropivacaine, amide local anesthetics or ultrasound gel
• 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

Sponsors & Collaborators

• Balgrist University Hospital: lead

Study Sites (1)

Balgrist University Hospital

Zurich, Canton of Zurich, 8008, Switzerland

Location

Related Publications (10)

• 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.

  PMID: 11149448 BACKGROUND

• 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.

  PMID: 15564946 BACKGROUND

• 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.

  PMID: 10206562 BACKGROUND

• 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.

  PMID: 26330722 BACKGROUND

• 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.

  PMID: 10691217 BACKGROUND

• 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.

  PMID: 25765043 BACKGROUND

• 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.

  PMID: 10852272 BACKGROUND

• 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.

  PMID: 23970790 BACKGROUND

• 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.

  PMID: 8535040 BACKGROUND

• 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.

  PMID: 24716821 BACKGROUND

Study Officials

• Hagen Bomberg, Medical Doctor

  Deputy Head of Anesthesiology

  PRINCIPAL INVESTIGATOR

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, INVESTIGATOR
• Purpose: OTHER
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: October 30, 2024
• First Posted: October 31, 2024
• Study Start: December 11, 2024
• Primary Completion: October 31, 2025
• Study Completion: October 31, 2025
• Last Updated: November 28, 2025

Record last verified: 2025-11

Locations

CH (1)