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

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 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.