This topic was selected because an evidence synthesis beats a textbook on it: the trials disagree, or the guidance has moved recently.
THE EVIDENCE
What each source contributes, and how strong it is
Study design first — a cohort and a randomised trial do not carry the same weight.
Design
Year
Journal
What it found
Meta-analysis
2025
BMC anesthesiology
This meta-analysis found that co-administering bupivacaine and liposomal bupivacaine
Randomised trial
2025
development and therapy
This randomized trial found that for ASA I or II patients undergoing humeral surgery
Review
2024
Lithuania)
This review found that interscalene catheter position can be altered by neck or
Meta-analysis
2025
Brazilian journal of anesthesiolog
This meta-analysis of six randomized controlled trials found no statistically
Randomised trial
2025
The Clinical journal of pain
This randomized controlled trial found that adding 5 mg of perineural dexamethasone
Review
2023
Cureus
This review article highlights evidence that adding the alpha-2 adrenergic agonist
6 resolved citations behind this deck; every point above traces to one of them.
THE ANATOMY
The phrenic nerve sits millimetres from the target
An anterior view of the right scalene triangle with the clavicle and sternocleidomastoid cut, showing the upper, middle and lower trunks of the brachial plexus emerging between the anterior and middle scalene muscles, the phrenic nerve descending on the face of the anterior scalene, and the subclavian vessels crossing beneath — the white outline marks the surgical exposure window the illustration was drawn for, not a block target.
Nicholas Zaorsky, M.D. — An illustration of the relevant neurovascular anatomy in anterior supraclavicular neurosurgical approach to the brachial plexus and subclavian vessels for thoracic outlet syndrome.
Nicholas Zaorsky, M.D. · CC-BY-SA-3.0 · https://commons.wikimedia.org/wiki/File:Wikipedia_medical_illustration_thoracic_outlet_syndrome_brachial_plexus_anatomy_with_labels.jpg
The trunks lie in the groove between anterior and middle scalene, with the phrenic nerve on the front of the anterior scalene — the same anatomy that makes the interscalene block work is what takes the hemidiaphragm with it.
WHERE THE GUIDANCE SITS
What the guidelines and pooled evidence say
2 findings, each on the slide that follows.
BMC anesthesiology 2025
This meta-analysis found that co-administering bupivacaine and liposomal bupivacaine
This meta-analysis found that co-administering bupivacaine and liposomal bupivacaine for interscalene blocks in shoulder surgery reduces opioid…
Brazilian journal of anesthesiology (Elsevier) 2025
This meta-analysis of six randomized controlled trials found no statistically
This meta-analysis of six randomized controlled trials found no statistically significant difference between anterior and posterior approaches in…
WHERE THE GUIDANCE SITS
This meta-analysis found that co-administering bupivacaine and liposomal bupivacaine
Meta-analysis · BMC anesthesiology
This meta-analysis found that co-administering bupivacaine and liposomal bupivacaine for interscalene blocks in shoulder surgery reduces opioid consumption on POD 3 and improves pain scores on POD 2, but increases the risk of hoarseness on POD 1 compared to bupivacaine alone or with other adjuvants.
Efficacy and safety of co-administered bupivacaine and liposomal bupivacaine in interscalene brachial plexus block for shoulder surgery: a systematic review and meta-analysis, BMC anesthesiology 2025 · PMID 41310439
WHERE THE GUIDANCE SITS
This meta-analysis of six randomized controlled trials found no statistically
Meta-analysis · Brazilian journal of anesthesiolog
This meta-analysis of six randomized controlled trials found no statistically significant difference between anterior and posterior approaches in complete sensory block rates or time to block completion, so the choice should be based on provider comfort and proficiency rather than expected superiority of either technique.
Comparative effectiveness of anterior and posterior approaches for interscalene brachial plexus block: a systematic review and meta-analysis, Brazilian journal of anesthesiology (Elsevier) 2025 · PMID 39551468
WHAT THE TRIALS FOUND
Where randomised evidence moved the question
2 findings, each on the slide that follows.
development and therapy 2025
This randomized trial found that for ASA I or II patients undergoing humeral surgery
This randomized trial found that for ASA I or II patients undergoing humeral surgery with an interscalene block, low-dose esketamine (0.2 mg/kg…
The Clinical journal of pain 2025
This randomized controlled trial found that adding 5 mg of perineural dexamethasone
This randomized controlled trial found that adding 5 mg of perineural dexamethasone to ropivacaine for interscalene brachial plexus block in shoulder…
WHAT THE TRIALS FOUND
This randomized trial found that for ASA I or II patients undergoing humeral surgery
Randomised trial · development and therapy
This randomized trial found that for ASA I or II patients undergoing humeral surgery with an interscalene block, low-dose esketamine (0.2 mg/kg bolus, 0.15 mg/kg/h infusion) improved postoperative day 1 recovery quality and caused less sedation and heart rate reduction than dexmedetomidine.
Comparison Between Low-Dose Esketamine and Dexmedetomidine on Postoperative Recovery Quality Among Patients Undergoing Humeral Trauma Surgery in Interscalene Brachial Plexus Block: A Randomized, Double-Blind, Controlled Trial, Drug design, development and therapy 2025 · PMID 40351348
WHAT THE TRIALS FOUND
This randomized controlled trial found that adding 5 mg of perineural dexamethasone
Randomised trial · The Clinical journal of pain
This randomized controlled trial found that adding 5 mg of perineural dexamethasone to ropivacaine for interscalene brachial plexus block in shoulder arthroscopy patients did not significantly prolong the duration of analgesia compared to ropivacaine alone.
Postoperative Analgesia Effect Evaluation of Perineural Dexamethasone Plus Various Doses of Ropivacaine in Interscalene Brachial Plexus Block: A Randomized Controlled Trial, The Clinical journal of pain 2025 · PMID 40401460
IN PRACTICE
What the cohorts and reviews add
2 findings, each on the slide that follows.
Lithuania) 2024
This review found that interscalene catheter position can be altered by neck or
This review found that interscalene catheter position can be altered by neck or shoulder movement, such as during physiotherapy, leading to secondary…
Cureus 2023
This review article highlights evidence that adding the alpha-2 adrenergic agonist
This review article highlights evidence that adding the alpha-2 adrenergic agonist dexmedetomidine as an adjunct to interscalene brachial plexus…
IN PRACTICE
This review found that interscalene catheter position can be altered by neck or
Review · Lithuania)
This review found that interscalene catheter position can be altered by neck or shoulder movement, such as during physiotherapy, leading to secondary dislocation that causes side effects or loss of effectiveness hours or days after initially correct placement.
Continuous Interscalene Brachial Plexus Blocks: An Anatomical Challenge between Scylla and Charybdis?, Medicina (Kaunas, Lithuania) 2024 · PMID 38399521
IN PRACTICE
This review article highlights evidence that adding the alpha-2 adrenergic agonist
Review · Cureus
This review article highlights evidence that adding the alpha-2 adrenergic agonist dexmedetomidine as an adjunct to interscalene brachial plexus blocks for shoulder surgery improves pain control and patient outcomes compared to traditional techniques.
Advances in Anesthesia for Shoulder Surgery: A Comprehensive Review of Dexmedetomidine-Enhanced Interscalene Brachial Plexus Block, Cureus 2023 · PMID 38106768
INDICATIONS
When this is the right block
Suprascapular versus interscalene block meta-analysis, Anesthesiology 2017
Shoulder surgery, where it remains the reference block
In a meta-analysis of 16 trials and 1152 patients, interscalene block reduced pain during recovery room stay by 1.5 cm compared with suprascapular block, and the 24-hour area-under-curve difference of 1.1 cm/h favoured it, although that difference was not clinically important.
Rebound pain after interscalene block RCT, Can J Anaesth 2024
Arthroscopic shoulder surgery, to carry the first half-day
In a two-centre randomised trial, mean time to first rescue analgesia after a single-injection interscalene block was 11.3 hours and mean time to worst pain was 14.6 hours. Plan the oral regimen around that window rather than around discharge time.
Low-dose ultrasound-guided interscalene block RCT, Reg Anesth Pain Med 2009
Low-volume ultrasound technique when respiratory reserve is tight
With 10 mL of ropivacaine 0.75% delivered under ultrasound at the C7 root, hemidiaphragmatic paresis occurred in 13% of patients versus 93% with nerve stimulation at the same dose, and forced expiratory volume, forced vital capacity and peak expiratory flow were all better preserved.
CONTRAINDICATIONS
When it is not
Hemidiaphragmatic paralysis after supraclavicular versus interscalene block, Braz J Anesthesiol 2019
Severe respiratory disease or a contralateral diaphragm you cannot lose
In a prospective cohort of shoulder surgery patients, hemidiaphragmatic paralysis followed interscalene block in 95.3% of cases, and paradoxical diaphragm movement was twice as common as after supraclavicular block. Phrenic palsy is close to universal, so this is the wrong block for a patient whose other hemidiaphragm is already compromised.
Suprascapular versus interscalene block meta-analysis, Anesthesiology 2017
A patient for whom a suprascapular block would do
Suprascapular block matched interscalene on 24-hour morphine consumption and on pain at every time point except the recovery room, while reducing the odds of block-related and respiratory complications. When the analgesic gap is that small, the side-effect difference decides.
Postoperative neurological symptoms after interscalene block, Reg Anesth Pain Med 2023
Pre-existing brachial plexopathy or an unrecorded neurologic baseline
After single-injection ultrasound-guided interscalene block for arthroscopic shoulder surgery, postoperative neurological symptoms occurred in 83 of 477 patients (17.4%) at 14 days, and 12% of those still had symptoms at six months. No patient, surgical or anaesthetic factor reliably predicted who. Consent and baseline documentation carry the weight here.
ASRA antithrombotic guidelines, 5th edition, Reg Anesth Pain Med 2025
Antithrombotic therapy still inside the ASRA interval
ASRA's fifth edition proposes conservative interruption times before neural blockade and now describes anticoagulant doses as low or high rather than prophylactic or therapeutic, because the same dose serves different indications. Check the interval against the agent before the patient is positioned.
PEARLS
What experience adds
Rebound pain after interscalene block RCT, Can J Anaesth 2024
Rebound pain is not fixed by an oral opioid on a timer
Oral hydromorphone 2 mg given six hours after the block did not reduce the worst 24-hour pain score compared with placebo (6.5 versus 5.9), nor change the pain trajectory or opioid use.
Prophylactic dexamethasone for rebound pain meta-analysis, Br J Anaesth 2024
Dexamethasone is what has moved rebound pain
Across seven randomised trials in 574 patients, prophylactic dexamethasone reduced the incidence of rebound pain with an odds ratio of 0.16, and trial sequential analysis confirmed an adequate information size. Both intravenous and perineural routes worked.
Trace the trunk in from the supraclavicular fossa
Start the probe low, find the plexus where it is unmistakable, and slide up counting what you follow rather than dropping straight onto the interscalene groove and naming what you hope you see. The structure you traced is the structure you can defend.
IN THE ROOM
What this changes about the next case
Colour is the strength of the evidence behind each step, not the urgency.
1
1
This meta-analysis found that co-administering bupivacaine and liposomal bupivacaine for interscalene blocks in shoulder surgery reduces opioid consumption on POD 3 and improves pain scores on POD 2, but increases the risk of hoarseness on POD 1 compared to bupivacaine alone or with other adjuvants.
2
2
This meta-analysis of six randomized controlled trials found no statistically significant difference between anterior and posterior approaches in complete sensory block rates or time to block completion, so the choice should be based on provider comfort and proficiency rather than expected superiority of either technique.
3
3
This randomized trial found that for ASA I or II patients undergoing humeral surgery with an interscalene block, low-dose esketamine (0.2 mg/kg bolus, 0.15 mg/kg/h infusion) improved postoperative day 1 recovery quality and caused less sedation and heart rate reduction than dexmedetomidine.
4
4
This randomized controlled trial found that adding 5 mg of perineural dexamethasone to ropivacaine for interscalene brachial plexus block in shoulder arthroscopy patients did not significantly prolong the duration of analgesia compared to ropivacaine alone.
5
5
This review found that interscalene catheter position can be altered by neck or shoulder movement, such as during physiotherapy, leading to secondary dislocation that causes side effects or loss of effectiveness hours or days after initially correct placement.
KEY TAKEAWAYS
What to carry into the next case
This meta-analysis found that co-administering bupivacaine and liposomal bupivacaine
BMC anesthesiology 2025
This randomized trial found that for ASA I or II patients undergoing humeral surgery
development and therapy 2025
This review found that interscalene catheter position can be altered by neck or
Lithuania) 2024
This meta-analysis of six randomized controlled trials found no statistically
Brazilian journal of anesthesiology (Elsevier) 2025
This meta-analysis found that co-administering bupivacaine and liposomal bupivacaine
Questions I'll ask you in the room
How does your plan change if the patient is not optimised?
What is the physiology behind what we just did?
Talk me through the trade-off you made there.
What would make you abandon this plan and do something else?
Board questions
1. In the ultrasonographic study that established how often the hemidiaphragm is affected by interscalene brachial plexus block, thirteen patients received a block sufficient for shoulder surgery. How many developed hemidiaphragmatic paresis, and how quickly?
All 13, with paradoxical hemidiaphragmatic motion within 5 minutes of injection
About three-quarters, with onset over 30 to 60 minutes
About half, within 30 minutes
About a quarter, and only after the first hour
Show answer
A. All 13, with paradoxical hemidiaphragmatic motion within 5 minutes of injection
Thirteen of thirteen, eleven of them within two minutes, and diaphragmatic motion did not return to normal until three to five hours after injection. The authors' conclusion is that diaphragmatic paresis appears to be an inevitable consequence of an interscalene block giving anaesthesia sufficient for shoulder surgery — a strong statement resting on 13 patients given 34-52 ml by a paresthesia technique, volumes far above what is injected today. Read at that width it is a reason to treat the block as a respiratory decision as much as an analgesic one, rather than a rule about which patients may never receive one.
Urmey WF et al., One hundred percent incidence of hemidiaphragmatic paresis associated with interscalene brachial plexus anesthesia as diagnosed by ultrasonography, Anesth Analg 1991 · PMID 2006740
2. In a randomised double-blind trial, patients having arthroscopic shoulder surgery received an ultrasound-guided interscalene block at the level of the cricoid cartilage with either 20 ml or 10 ml of ropivacaine 0.5%. What happened to hemidiaphragmatic paresis 15 minutes after the block?
It was unchanged — 14 of 15 patients in each group
It fell from 14 of 15 to 7 of 15 with the lower volume
It fell from 14 of 15 to 2 of 15 with the lower volume
It was unchanged, but the spirometric reduction was avoided in the 10 ml group
Show answer
A. It was unchanged — 14 of 15 patients in each group
Halving the volume at the cricoid level bought nothing: the same paresis rate, the same reduction in forced vital capacity, forced expiratory volume in 1 second and peak flow, and 13 of 15 in each group still paretic at recovery-room discharge. What the trial shows is that reducing volume alone, at the cricoid level, does not spare the phrenic nerve. It did not compare injection levels or planes, so it cannot tell you that a lower or more lateral injection would do better — only that the millilitres were not the lever here.
Sinha SK et al., Decreasing the local anesthetic volume from 20 to 10 mL for ultrasound-guided interscalene block at the cricoid level does not reduce the incidence of hemidiaphragmatic paresis, Reg Anesth Pain Med 2011 · PMID 21751435
3. Seventy patients having major shoulder surgery were randomised to a continuous interscalene catheter placed with its tip either inside the brachial plexus sheath or immediately outside it, midway between C5 and C6, all receiving the same ropivacaine bolus and infusion. Give the rates of hemidiaphragmatic paresis on the first postoperative day and say what it cost analgesically.
Show answer
Paresis on postoperative day 1 was 41% with the intrafascial tip and 15% with the extrafascial tip. No analgesic cost could be measured: the investigators were unable to detect a difference between the groups in forced vital capacity, forced expiratory volume in 1 second, or rest pain scores, which were a median of 3 on a 1-10 scale in both (p = 0.93). With 70 patients that is a failure to detect a difference rather than a demonstration that none exists. The authors' conclusion is that routine placement of the catheter tip inside the sheath is not supported.
Moving the tip outside the sheath more than halved the rate of paresis while the trial could detect no difference in rest pain — the trade the study was designed to look for. The familiar explanation, that the local anaesthetic still reaches the plexus and simply has further to travel towards the phrenic nerve, is an account offered for that result and not something the trial measured. Note also that the intrafascial rate here was 41%, not 100%: a low-volume continuous infusion is a different exposure from a large single-shot bolus.
Albrecht E et al., Reduced hemidiaphragmatic paresis with extrafascial compared with conventional intrafascial tip placement for continuous interscalene brachial plexus block: a randomized, controlled, double-blind trial, Br J Anaesth 2017 · PMID 28403412
The bottom lineThis meta-analysis found that co-administering bupivacaine and liposomal bupivacaine
Sources
[1] Efficacy and safety of co-administered bupivacaine and liposomal bupivacaine in interscalene brachial plexus block for shoulder surgery: a systematic review and meta-analysis, BMC anesthesiology 2025 · PMID 41310439 open
[2] Comparison Between Low-Dose Esketamine and Dexmedetomidine on Postoperative Recovery Quality Among Patients Undergoing Humeral Trauma Surgery in Interscalene Brachial Plexus Block: A Randomized, Double-Blind, Controlled Trial, Drug design, development and therapy 2025 · PMID 40351348 open
[3] Continuous Interscalene Brachial Plexus Blocks: An Anatomical Challenge between Scylla and Charybdis?, Medicina (Kaunas, Lithuania) 2024 · PMID 38399521 open
[4] Comparative effectiveness of anterior and posterior approaches for interscalene brachial plexus block: a systematic review and meta-analysis, Brazilian journal of anesthesiology (Elsevier) 2025 · PMID 39551468 open
[5] Postoperative Analgesia Effect Evaluation of Perineural Dexamethasone Plus Various Doses of Ropivacaine in Interscalene Brachial Plexus Block: A Randomized Controlled Trial, The Clinical journal of pain 2025 · PMID 40401460 open
[6] Advances in Anesthesia for Shoulder Surgery: A Comprehensive Review of Dexmedetomidine-Enhanced Interscalene Brachial Plexus Block, Cureus 2023 · PMID 38106768 open
[7] Suprascapular versus interscalene block meta-analysis, Anesthesiology 2017 · PMID 28968280 open
[8] Rebound pain after interscalene block RCT, Can J Anaesth 2024 · PMID 37833472 open
[9] Low-dose ultrasound-guided interscalene block RCT, Reg Anesth Pain Med 2009 · PMID 19920426 open
[10] Hemidiaphragmatic paralysis after supraclavicular versus interscalene block, Braz J Anesthesiol 2019 · PMID 31796298 open
[11] Postoperative neurological symptoms after interscalene block, Reg Anesth Pain Med 2023 · PMID 37295793 open
[12] ASRA antithrombotic guidelines, 5th edition, Reg Anesth Pain Med 2025 · PMID 39880411 open
[13] Prophylactic dexamethasone for rebound pain meta-analysis, Br J Anaesth 2024 · PMID 38501226 open