Pulmonary impairment after interscalene block for orthopedic shoulder surgery: a systematic review

Abstract

Background

Interscalene block (ISB) is the gold standard for regional anesthesia in shoulder surgery due to its proven efficacy in reducing post-operative pain and opioid use. However, ISB commonly causes temporary phrenic nerve palsy, resulting in ipsilateral hemidiaphragmatic paralysis and measurable declines in pulmonary function. While often well-tolerated in healthy individuals, these effects may pose significant risk in patients with limited pulmonary reserve or underlying cardiopulmonary disease. This systematic review aimed to quantify the impact of ISB on pulmonary function and identify patient-specific risk factors that may inform anesthetic decision-making for shoulder surgeons.

Methods

This systematic review was conducted in accordance with the 2020 Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. A comprehensive literature search of electronic databases (PubMed, Embase, Scopus, Web of Science) was conducted on March 23, 2025. Eligible studies were level I randomized controlled trials published in English. Data were extracted on study characteristics, patient demographics, block technique, and pulmonary outcomes.

Results

A total of 33 studies met inclusion criteria and included data on 1,481 patients. Diaphragmatic paralysis was reported in 25 studies, with an average of 53% (95% confidence interval [CI; 42%-64%]). Fifteen studies evaluated diaphragmatic excursion, with an average reduction from baseline of 48.6% (95% CI [37.1%-60.2%]). Changes in pulmonary function tests were reported in 18 studies for forced expiratory volume and 17 studies for forced vital capacity, with average reductions of 27.1% (95% CI, 23.0%–31.1%) and 24.8% (95% CI, 21.2%–28.4%), respectively. An unpaired t-test comparing patients above and below age 50 showed a significantly higher incidence of diaphragmatic paralysis in older patients (P = .029).

Conclusion

Interscalene block remains a highly effective technique for perioperative pain control in shoulder surgery, with well-established benefits in minimizing opioid use and improving early recovery. However, it is consistently associated with reductions in objective pulmonary function. Advanced patient age was associated with increased risk of diaphragmatic impairment, while anesthetic parameters did not demonstrate consistent associations with pulmonary outcomes. These findings highlight the importance of patient selection and suggest that further investigation into comorbidity-specific risk stratification may help guide anesthetic decision-making, particularly as surgical indications expand to include more medically complex populations.

Interscalene blocks (ISBs) have become a widely accepted and effective method of regional anesthesia for orthopedic shoulder procedures, including rotator cuff repair and shoulder arthroplasty. Over the past 2 decades, ISBs have emerged as an excellent option for post-operative pain control compared to supraclavicular, costoclavicular, and suprascapular nerve blocks.^1,21,48 As such, ISBs have become increasingly common, especially in ambulatory orthopedic surgery.¹⁵ However, ISBs are not without risks, particularly concerning pulmonary function. Due to the proximity of the phrenic nerve (originating from C3–C5), ISBs commonly result in transient hemidiaphragmatic paralysis.^2,4,44 This paresis can reduce forced vital capacity and forced expiratory volume (FEV1) by up to 25% to 30%, which may be clinically significant in patients with limited or reduced pulmonary reserve at baseline.⁴⁴ The extent to which ISBs independently contribute to post-operative pulmonary complications, such as pneumonia, atelectasis, and acute respiratory distress syndrome, remains unclear. While the hemidiaphragmatic paresis (HDP) associated with ISBs is typically transient, these physiological effects may become consequential in patients with underlying pulmonary disease or when combined with general anesthesia.

Phrenic nerve palsy is a known and well-studied complication of ISB,¹⁰ underscoring the need for further investigation into the pulmonary safety of ISBs. Furthermore, it is important for surgeons to understand the patient- and anesthetic-associated risk factors, along with the extent and duration of pulmonary complications, as these issues can compromise surgical outcomes, delay recovery, and increase medicolegal risk. Potential preventative measures include careful patient selection for ISB and thoughtful anesthetic design—lock approach, local anesthetic concentration, and dosage—to maximize analgesia while minimizing phrenic nerve involvement.

The pulmonary consequences of interscalene block, particularly phrenic nerve–mediated hemidiaphragmatic paralysis, are well recognized and have been evaluated in prior systematic reviews. However, much of the available literature has focused on describing the physiological effects of ISB rather than identifying which patients may be at greatest risk for clinically meaningful respiratory compromise. As the indications for shoulder surgery expand to include older and more medically complex populations, an updated synthesis of the randomized literature with attention to patient-related risk factors is needed.

This systematic review and meta-analysis aims to identify patient- and anesthetic-related factors that influence the risk of pulmonary complications. The primary objective is to synthesize current evidence on the pulmonary impact of ISBs in shoulder surgery, with a focus on hemidiaphragmatic paralysis, pulmonary function tests, and post-operative respiratory outcomes.

Materials and methods

Search strategy and eligibility criteria

A systematic review was performed in accordance with the 2020 Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines. A comprehensive literature search of electronic databases (PubMed, Embase, Scopus, Web of Science) was conducted from database inception through March 23, 2025. The search included a combination of the following terms combined with Boolean operators: “pulmonary function test”; “PFT,” “hemidiaphragmatic paralysis,” “hemidiaphragmatic excursion,” “shoulder surgery,” “orthopaedics,” “arthroplasty,” “interscalene,” “interscalene block,” and “ISB.” Inclusion criteria consisted of Level I randomized controlled clinical trials that were written in English, or with English translation, reporting pulmonary function testing parameters, hemidiaphragmatic paralysis or paresis, and post-operative pulmonary complications following interscalene block performed for orthopedic shoulder surgeries. Non-clinical studies, animal studies, cadaveric studies, review articles, case reports, letters to editors, conference abstracts, studies with overlapping cohorts, and expert opinions were excluded. Two independent authors conducted the initial title and abstract screening, followed by full-text screening. Any discrepancies were resolved by a third reviewer. References from all included studies were reconciled to ensure all relevant studies meeting inclusion criteria were identified.

Data extraction

Data were extracted from included studies by 2 authors and entered into Microsoft Excel (version 16.63; Microsoft Corp., Redmond, WA, USA) for additional analysis. The extracted data included the first author's name, publication year, patient demographics (age and sex), incidence of hemidiaphragmatic paralysis, pulmonary function testing data, anesthetic utilized, approach utilized for interscalene block, dose, and concentration of anesthetic. Age was dichotomized at 50 years based on known age-related decline in pulmonary function.

Statistical analysis

Data were stratified by patient demographics, anesthetic utilized, concentration, dosage of anesthetic utilized, and approach utilized for interscalene block. Weighted means were calculated based on sample size of patients from the included studies. Ninety-five percent confidence intervals (CIs) were calculated utilizing the standard deviation and weighted means of the included studies assuming a normally distributed population.¹⁴ One-way analysis of variance and unpaired t-tests were performed to analyze differences between anesthetic used, dosage, and concentration. Variables such as injection technique, block approach, and catheter use were not analyzed due to variability and inconsistent reporting across included studies. Outcomes were summarized using weighted descriptive statistics across studies; a formal meta-analysis with pooled effect estimates was not performed due to clinical and methodological heterogeneity.

Risk of bias assessment

Risk of bias (RoB) for included randomized controlled trials was assessed independently by 2 reviewers using the Cochrane RoB 1 tool. This tool evaluates potential sources of bias across 7 domains: sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessment, incomplete outcome data, selective outcome reporting, and other sources of bias.¹⁸ Each domain was rated as low RoB, high RoB, or unclear RoB. Any disagreements between reviewers were resolved via consultation from a third reviewer.

Results

The initial search yielded 861 studies for title and abstract review. Of these, 33 studies2, 3, 4^,8,9,11, 12, 13^{,16,17,19,20,}22, 23, 24, 25, 26, 27, 28, 29^,31,33, 34, 35, 36^{,38,39,41,43,45,46,49,51} met inclusion criteria (Fig. 1), all of which were Level 1 randomized controlled trials (Table I). Sample sizes ranged from 11 to 99 participants, resulting in a total of 1,481 patients included in final analysis (608 females, 848 males, 25 unreported). The average age was 49.5, and average body mass index (BMI) was 26.8. Table II summarizes included patient demographics. Comorbidity data, clinical outcomes, and patient-reported outcome measures were inconsistently reported across studies and therefore could not be reliably synthesized.

Figure 1.

PRISMA flow diagram demonstrating process of identification, screening, and inclusion of articles. PRISMA, Preferred Reporting Items for Systematic Review and Meta-Analysis.

Table I.

Comprehensive list of included studies.

Title	Authors	LOE	Year	Patients (n)	Average age
Respiratory effects and analgesic efficacy of different local anesthetic volumes in ultrasound-guided interscalene brachial plexus block for shoulder arthroscopy: prospective randomized study	Ahmed et al2	1	2024	71	42
Respiratory effects of low-dose bupivacaine interscalene block	Al-Kaisy et al3	1	1999	11	32.5
Reduced hemidiaphragmatic paresis with extrafascial compared with conventional intrafascial tip placement for continuous interscalene brachial plexus block: a randomized, controlled, double-blind trial	Albrecht et al4	1	2017	62	63
Comparison of anterior suprascapular, supraclavicular, and interscalene nerve block approaches for major outpatient arthroscopic shoulder surgery	Auyong et al8	1	2018	63	54
Hemidiaphragmatic paresis following extrafascial versus conventional intrafascial approach for interscalene brachial plexus block: A double-blind randomized, controlled trial	Ayyanagouda et al9	1	2019	59	38.5
Evaluation of diaphragmatic function after interscalene block with liposomal bupivacaine: a randomized controlled trial.	Berg et al11	1	2022	22	67
Phrenic nerve block caused by interscalene brachial plexus block: breathing effects of different sites of injection.	Bergmann et al12	1	2016	84	50.5
The effect of continuous interscalene brachial plexus block with 0.125% bupivacaine vs. 0.2% ropivacaine on pain relief, diaphragmatic motility, and ventilatory function	Choromanski et al13	1	2015	30	51
Incidence of hemidiaphragmatic paresis after peripheral nerve stimulator versus ultrasound guided interscalene brachial plexus block	Ghodki et al16	1	2016	60	49.5
Ultrasound-guided anterior suprascapular nerve block versus interscalene brachial plexus block for arthroscopic shoulder surgery: a randomized controlled study.	Gupta et al17	1	2023	30	34
The effect of initial local anesthetic dose with continuous interscalene analgesia on post-operative pain and diaphragmatic function in patients undergoing arthroscopic shoulder surgery: a double-blind, randomized controlled trial	Hartrick et al19	1	2012	36	52
Interscalene brachial plexus block. Effects on pulmonary function	Hortense et al20	1	2010	26	36
Superior trunk block provides non-inferior analgesia compared with interscalene brachial plexus block in arthroscopic shoulder surgery	Kang et al22	1	2019	40	59
A comparison of ultrasound-guided interscalene and supraclavicular blocks for post-operative analgesia after shoulder surgery	Kim et al23	1	2017	25	58
Superior trunk block: a phrenic-sparing alternative to the interscalene block: a randomized control trial	Kim et al24	1	2019	63	50
Analgesic efficacy of 2 interscalene blocks and 1 cervical epidural block in arthroscopic rotator cuff repair.	Kim et al25	1	2016	50	56.2
Hemidiaphragmatic paresis following interscalene brachial plexus block with 2-point injection technique	Kim et al26	1	2021	52	63.5
A randomized controlled trial comparing continuous supraclavicular and interscalene brachial plexus blockade for open rotator cuff surgery	Koh et al27	1	2016	38	64.7
Costoclavicular block as a diaphragm-sparing nerve block for shoulder surgery: a randomized controlled trial.	Lee et al28	1	2025	35	63
Randomized, controlled trial comparing respiratory and analgesic effects of interscalene, anterior suprascapular, and posterior suprascapular nerve blocks for arthroscopic shoulder surgery	Lim et al29	1	2020	20	42.8
Effects of different 0.2% ropivacaine infusion regimens for continuous interscalene brachial plexus block on post-operative analgesia and respiratory function after shoulder arthroscopic surgery: a randomized clinical trial	Meng et al31	1	2022	60	56.5
A randomized controlled trial in patients undergoing arthroscopic shoulder surgery comparing interscalene block with either 10 ml or 20 ml levobupivacaine 0.25%	Oliver-Fornies et al33	1	2022	48	50.5
Extrafascial injection for interscalene brachial plexus block reduces respiratory complications compared with a conventional intrafascial injection: a randomized, controlled, double-blind trial	Palhais et al34	1	2016	40	36
A randomized controlled trial of shoulder block vs. interscalene brachial plexus block for ventilatory function after shoulder arthroscopy	Rhyner et al35	1	2020	15	36.4
Effect of local anesthetic volume (20 vs. 5 ml) on the efficacy and respiratory consequences of ultrasound-guided interscalene brachial plexus block	Riazi et al36	1	2008	36	54.8
Superior trunk versus interscalene brachial plexus block in humerus surgery: a randomized controlled trial	Sinha et al38	1	2024	29	47.8
Comparison of tissue distribution, phrenic nerve involvement, and epidural spread in standard- low-volume ultrasound-guided interscalene plexus block using contrast	Stundner et al39	1	2016	30	26.5
Continuous interscalene versus phrenic nerve-sparing high-thoracic erector spinae plane block for total shoulder arthroplasty: a randomized controlled trial	Sun et al41	1	2022	14	70.4
Diaphragm function after interscalene brachial plexus block: a double-blind, randomized comparison of 0.25% and 0.125% bupivacaine	Thackery et al43	1	2013	28	54.6
Phrenic palsy and analgesic quality of continuous supraclavicular vs. interscalene plexus blocks after shoulder surgery	Wiesmann et al45	1	2016	56	53
Effect of local anesthetic concentration (0.2% vs. 0.1% ropivacaine) on pulmonary function, and analgesia after ultrasound-guided interscalene brachial plexus block: a randomized controlled study	Wong et al46	1	2016	50	44.4
Effects of a fixed low-dose ropivacaine with different volume and concentrations on interscalene brachial plexus block: A randomized controlled trial	Zhai et al49	1	2016	99	46
Supplemental interscalene blockade to general anesthesia for shoulder arthroscopy: effects on fast track capability, analgesic quality, and lung function	Zoremba et al51	1	2015	99	56

LOE, level of evidence.

Table II.

Risk of bias assessment in included studies.

Study ID	Sequence generation	Allocation concealment	Blinding of participants and personnel for all outcomes	Blinding of outcome assessors for all outcomes	Incomplete outcome data for all outcomes	Selective outcome reporting	Other sources of bias
Ahmed 20242	Low	Low	Low	Low	Low	Low	Low
Al-Kaisy 19993	Low	Unclear	Low	Low	Low	Low	Low
Albrecht 20174	Low	Low	Low	Low	Low	Low	Low
Auyong 20188	Low	Low	Low	Unclear	Low	Low	Low
Ayyanagouda 20199	Low	Low	Low	Low	Low	Low	Low
Berg 202211	Low	Low	Low	Unclear	Low	Low	Low
Bergmann 201612	Unclear	Unclear	Unclear	High	Low	Low	Low
Choromanski 201513	Unclear	Unclear	Unclear	Unclear	Unclear	Unclear	Unclear
Ghodki 201616	Low	Low	Unclear	Low	Low	Low	Low
Gupta 202317	Low	Low	Low	Low	Low	Low	Low
Hartrick 201219	Low	Low	Low	Low	Low	Low	Low
Hortense 201020	Low	Unclear	Low	Unclear	High	Low	Low
Kang 201922	Low	Low	Low	Low	Low	Low	Low
Kim 201625	Low	Low	Low	Unclear	Low	Low	Low
Kim 201723	Low	Low	High	Low	Low	Low	Low
Kim 201924	Low	Low	Low	Low	Low	Low	Low
Kim 202126	Low	Low	Low	Unclear	Low	Low	Low
Koh 201627	Low	Low	Low	Low	Low	Low	Low
Lee 202528	Low	Low	Low	Low	Low	Low	Low
Lim 202029	Low	Low	Low	Low	Low	Low	Low
Meng 202231	Low	Low	Low	Unclear	Low	Low	Low
Oliver-Fornies 202233	Low	Low	High	Unclear	Low	Low	Low
Palhais 201634	Low	Low	Low	Unclear	Low	Low	Low
Rhyner 202035	Low	Low	Low	Unclear	Low	Low	Low
Riazi 200836	Low	Low	Low	Low	Low	Low	Low
Sinha 202438	Low	Low	Low	Low	Low	Low	Low
Stundner 201639	Low	Low	Low	Low	Low	Low	Low
Sun 202241	Low	Low	Low	Low	High	Low	Low
Thackeray 201343	Low	Low	Low	Unclear	Low	Low	Low
Wiesmann 201645	High	Low	Low	Unclear	Low	Low	Low
Wong 201646	Low	Low	Low	Low	High	Low	Low
Zhai 201649	Low	Low	Low	Low	Low	Low	Low
Zoremba 201551	High	High	Low	Low	Low	Low	Low

Hemidiaphragmatic paralysis was reported in 25 studies, occurring in 53% of cases on average (95% CI [42%, 64%]). Fifteen studies quantified changes in diaphragmatic excursion, demonstrating an average reduction of 48.6% from baseline (95% CI [37.1%, 60.2%]). Eighteen studies reported FEV¹ outcomes, with an average reduction of 27.1% from baseline (95% CI [23.0%, 31.1%]). Seventeen studies reported forced vital capacity outcomes, showing an average reduction of 24.8% from baseline (95% CI [21.2%, 28.4%]).

An unpaired t-test demonstrated that patients older than 50 years had a significantly higher incidence of hemidiaphragmatic paralysis compared with those 50 years or younger (P = .029). Anesthetic drug type (P = .061), dosage (P = .768), and concentration (P = .234) were not associated with incidence of paralysis. Similarly, age, dosage, and concentration did not significantly affect changes in diaphragmatic excursion, FEV₁, or forced vital capacity (FVC). However, patients receiving levobupivacaine (n = 119) experienced significantly greater reductions in FEV₁ (P = .020) and FVC (P = .031) than those receiving other anesthetic agents (n = 1,362). Mean changes in pulmonary function parameters are presented in Figure 2.

Figure 2.

Bar graph demonstrating average percent decreases following Interscalene block.

RoB assessment data via the Cochrane RoB tool are demonstrated in Table II. Eleven of the included studies did not clearly delineate blinding of outcome assessors. The overall RoB for the included studies was noted as low, with the primary concern being the lack of methodology describing the blinding of outcome assessors as noted above.

Discussion

This systematic review highlights the pulmonary consequences of ISB, an increasingly common component of multimodal analgesia for shoulder surgery. Across 33 studies, ISB was consistently associated with significant—though typically transient—reductions in pulmonary function, most notably HDP. Hemidiaphragmatic paralysis occurred in approximately 53% of patients, with average reductions of 27% in FEV¹, and 25% in FVC, respectively. These impairments are primarily attributable to unintended blockade of the phrenic nerve given its anatomic proximity to the C5–C6 nerve roots. Notably, patient age greater than 50 years was associated with a significantly higher incidence of hemidiaphragmatic paralysis (P = .029). However, no study stratified outcomes by other important patient-specific variables such as BMI, American Society of Anesthesiologists classification, or baseline pulmonary disease, representing a critical gap in the literature.

Our findings are in keeping with similar investigations. Across the literature base, ISB has a widespread association with a decrease in pulmonary function.5, 6, 7^,42,50 The benefits of ISB—high patient satisfaction, improved pain control, and reduced opioid consumption—have been well documented.^46,51 Systematic reviews and meta-analyses from Abdallah et al,¹ Yan et al,⁴⁸ and Hussain et al²¹ demonstrated significantly reduced pain with ISB use. Yan et al⁴⁸ also noted a shorter extubation time and a lower incidence of adverse events compared with general anesthesia alone.^1,21,40,48 As a result, ISB firmly maintains a role in multimodal analgesia following shoulder surgery. On a case-by-case basis, analgesic benefits must be weighed against the pulmonary risks.

Patient selection can play a critical role in mitigating risk associated with ISB as the transient HDP is typically well-tolerated in otherwise healthy patients. However, older patients and patients with decreased cardiopulmonary reserve are at higher risk of pulmonary complications—including severe hypoxia and respiratory failure.^9,13,33,47 Our findings further support this assertion as patients greater than age 50 years were at a higher risk of hemidiaphragmatic paralysis. Cohort data indicate that asthma, congestive heart failure, and BMI can all contribute to pulmonary complication following ISB.^30,37,47 Yet, most randomized trials have not stratified outcomes by BMI, baseline pulmonary disease, or American Society of Anesthesiologists class, limiting insight into which patients are most vulnerable to clinically significant respiratory compromise. Future randomized controlled trials can help quantify risk increases for each comorbidity.

Given the increased risk of pulmonary complications observed in older patients, alternative diaphragm-sparing regional techniques may be preferable including extrafascial injection. Approaches such as suprascapular nerve block, with or without axillary nerve block, have been explored as potential alternatives that may better preserve pulmonary function.^8,40 However, evidence remains variable, and our findings did not demonstrate an association between anesthetic parameters and pulmonary outcomes. As such, the role of these alternative strategies in reducing pulmonary complications remains uncertain.

In addition to patient selection, anesthetic parameters may be modified to minimize pulmonary risk. Oliver-Fornies et al³² investigated anesthetic-related factors and their effect on HDP and found a significant decrease in HDP rates when following a low-volume technique of ISB—marking the first identified anesthetic parameter with a direct relationship to HDP incidence. Likewise, Riazi et al³⁶ found that decreasing anesthetic volume from 20 mL to 5 mL reduced the incidence of hemidiaphragmatic paralysis from 100% to 45% and mitigated declines in FEV₁, FVC, and oxygen saturation. However, our findings stand in stark contrast to these findings. Given the pooled analysis of our analysis, it is currently unclear if pulmonary outcomes can be effectively improved by modifying anesthetic parameters. Collectively, these findings highlight the interplay of how patient demographics and anesthetic technique conjointly influence the pulmonary impact of ISB.

This systematic review features a robust review of Level I evidence studies, consisting of randomized controlled trials. However, it does have limitations. As a systematic review, this study is limited by variability across included studies, including differences in patient populations, anesthetic agents, dosing, data collection methods, and outcome assessment. This variability makes direct comparisons challenging and may influence the observed findings. Additionally, many studies had relatively small sample sizes, which may limit generalizability. As such, reported values should be interpreted as descriptive trends rather than pooled effect estimates. Furthermore, our ability to identify specific patient-related risk factors was limited as most studies did not stratify patients by cardiopulmonary risk factors, such as obesity, asthma, or chronic obstructive pulmonary disease. Although a RoB assessment was performed, heterogeneity was not formally quantified, and publication bias was not assessed. Lastly, our study was limited to papers written in English or with English translation, which may limit generalizability.

In summary, although ISB predictably reduces pulmonary function through transient phrenic nerve involvement, the clinical impact is often minimal in healthy patients and outweighed by its analgesic benefits. Care can be personalized according to risks and benefits as determined by patient characteristics. However, the lack of standardized criteria for risk stratification and the absence of comorbidity-stratified data limit patient selection.

Conclusion

Interscalene block remains a highly effective technique for perioperative pain control in shoulder surgery, with well-established benefits in minimizing opioid use and improving early recovery. However, it is consistently associated with reductions in objective pulmonary function. Advanced patient age was associated with increased risk of diaphragmatic impairment, while anesthetic parameters did not demonstrate consistent associations with pulmonary outcomes. These findings highlight the importance of patient selection and suggest that further investigation into comorbidity-specific risk stratification may help guide anesthetic decision-making, particularly as surgical indications expand to include more medically complex populations.

Disclaimers:

Funding: No funding was disclosed by the authors.

Conflicts of interest: The authors, their immediate family, and any research foundation with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.