SPSIP Block in Shoulder Artroscopy

Background The interscalene block, the analgesic gold standard for shoulder arthroscopy, causes hemidiaphragmatic paresis in nearly all patients and significant upper-limb motor block. The serratus posterior superior intercostal plane (SPSIP) block targets the upper thoracic spinal nerves (T2-T5) deep to the serratus posterior superior muscle, far from the brachial plexus and phrenic nerve, and may therefore provide analgesia with less motor and diaphragmatic involvement. Its sensory distribution and diaphragmatic effects have not yet been systematically described.

Design Prospective, single-center, exploratory observational study at Piove di Sacco Hospital (ULSS6 Euganea, Italy). Only patients in whom the attending anesthesiologist has already chosen the SPSIP block are enrolled; all assessments are part of routine care and the study does not modify anesthetic management.

Procedures At the time of the block, age, sex, weight, height, and type, volume and dose of local anesthetic are recorded.

* Sensory block (30 min after the block): a swab cooled with ice spray is applied from the acromion in 1-cm steps along lateral, anterior and posterior lines (15 cm each). Each point is scored 1 (absent or reduced cold sensation vs. the contralateral side) or 0 (preserved), producing a sensory map.
* Upper-limb motor function (before and 30 min after the block): shoulder abduction (axillary nerve) and external rotation (suprascapular nerve), elbow at 90°, measured in degrees with a goniometer.
* Diaphragmatic function (before and 30 min after the block): M-mode ultrasound excursion during deep inspiration. Reduction from baseline is graded 0 (< 25%), 1 (25-75%, partial paresis) or 2 (> 75% or paradoxical movement, complete paralysis).

Surgery is then performed under general anesthesia; no intraoperative or postoperative data are collected.

Statistical analysis A pragmatic sample of 20 patients was chosen, as no formal sample size calculation was possible. Data will be analyzed descriptively; pre- and post-block diaphragmatic excursion will be compared with the paired t-test or Wilcoxon signed-rank test. Results will inform a future confirmatory study.

• SPSIPB block (Procedure), also known as serratus posterior superior intercostal plane block: It will be performed the serratus posterior superior intercostal plane block (SPSIP block) before shoulder arthroscopy surgery.

Primary outcomes

• Sensory blockade at 30 minutes [30 min after SPSIP block]: A cold cotton ball will be applied in the sensory territory of the shoulder in order to describe the loss of sensation by the SPSIP block across in this region

Secondary outcomes

• Motor sparing (shoulder abduction) [30 minutes post-SPSIP block]: Motor sparing will also be quantified by assessing shoulder abduction (axillary nerve). The movement will be assessed in degrees using a goniometer
• Motor sparing (external rotation) [30 minutes post-SPSIP block]: Motor sparing will also be quantified by assessing external rotation (suprascapular nerve). It will be assessed in degrees using a goniometer.
• Diaphragmatic Excursion [30 minutes post-SPSIP block]: The diaphramg excursion during normal breath will be evalauted by using an ultrasound machine (M-Mode) and measured in millimiters

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Patients scheduled for shoulder arthroscopy receiving an SPSIP block as the analgesic technique.
* Age ≥ 18 years.
* Patients able to provide informed consent to study participation and to the processing of personal data.

Exclusion Criteria:

* Refusal to provide consent to study participation.
* Pre-existing central or peripheral sensory neuropathy.
* Estimated time between block performance and entry into the operating room of less than 30 minutes.