The minimal effective volume (MEAV 95) for interscalene brachial plexus block for surgical anesthesia under sedation: A prospective observational dose finding study
Bibliographic record
Abstract
Background: Interscalene brachial plexus (ISB) block is routinely used to provide anesthesia and analgesia for shoulder surgery. Traditional local anesthetic volumes for ISB result in near universal ipsilateral phrenic nerve paresis potentially including oxygenation and ventilation.Aims: The purpose of this study was to determine the lowest minimal effective anesthetic volume in 95% of patients (MEAV 95) of ropivacaine 0.75% for ISB that provides surgical anesthesia for arthroscopic shoulder surgery.Methods: Prospective observational cohort study in patients undergoing arthroscopic shoulder surgery under ISB (C6 level) with sedation. The dose finding protocol used the Narayana rule for up/down sequential allocation to estimate the MEAV 95 of ropivacaine 0.75%. Successful ISB was defined as complete absence of pinprick sensation in the C5 and C6 dermatomes 30 min postblock. Secondary outcomes assessed included ability to complete surgery with propofol sedation, change in slow vital capacity, room air oxygen saturation postblock, block duration, ISB complications, and numeric rating scale for pain immediately after surgery.Results: The study was stopped early due to futility. Among 225 participants approached, 54 consented to participate. The MEAV 95 for ultrasound-guided ISB of ropivacaine 0.75% for shoulder surgery was unable to be accurately estimated. Local anesthetic volumes between 5 and 20 ml did not influence any of the predefined secondary outcomes.Conclusions: The MEAV 95 (at 30 min) of ropivacaine 0.75% for ultrasound-guided ISB exceeds the local anesthetic volumes that consistently produces hemidiaphragmatic impairment. ISB cannot be guaranteed to provide surgical anesthesia at 30 min without the potential for concomitant phrenic nerve block.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.010 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".