SPSIPB Versus SAPB for Postoperative Analgesia After Minimally Invasive Repair of Pectus Excavatum

Pectus excavatum is the most common chest wall deformity in pediatric and adolescent patients and is characterized by posterior depression of the sternum and anterior chest wall. Although many patients are asymptomatic, corrective surgery is frequently performed during adolescence or young adulthood for cosmetic reasons and to improve body image and quality of life.

Minimally invasive repair of pectus excavatum involves the placement of a curved metal bar beneath the sternum. The bar is then rotated to elevate the sternum and correct the chest wall deformity. Despite favorable cosmetic and quality-of-life outcomes, postoperative pain remains a major clinical challenge after this procedure. Pain is mainly related to sternal elevation, pressure exerted by the bar, and repositioning of the ribs. Inadequate pain control may increase opioid consumption and prolong hospitalization. Higher opioid exposure may also lead to adverse effects such as nausea, vomiting, constipation, pruritus, and urinary retention.

Regional anesthesia techniques have become important components of multimodal postoperative analgesia in thoracic surgery. Thoracic paravertebral block, erector spinae plane block, and serratus anterior plane block are among the regional techniques commonly used for thoracic analgesia. Serratus anterior plane block has also been used for postoperative pain management after minimally invasive repair of pectus excavatum.

Serratus posterior superior intercostal plane block is a recently described ultrasound-guided interfascial plane block. The technique involves injection of local anesthetic between the serratus posterior superior muscle and the rib, usually at the level of the second or third rib. This block has been reported to provide analgesia in various thoracic and scapular pain conditions and has shown promising results in thoracic surgery.

The aim of this study is to compare the postoperative analgesic outcomes of serratus posterior superior intercostal plane block and serratus anterior plane block in patients undergoing minimally invasive repair of pectus excavatum. Because this is an observational study, the choice of regional analgesia technique will not be determined by the study protocol. The block technique will be selected by the attending anesthesiologist according to routine clinical practice. No randomization or protocol-driven assignment will be performed.

• Postoperative Analgesia Protocol (Drug): All participants will receive a standardized multimodal postoperative analgesia protocol. Patient-controlled analgesia with intravenous morphine will be used. The device will be programmed to administer 1 mg of intravenous morphine per demand, with a lockout interval of 10 minutes. Paracetamol will be administered as part of routine multimodal analgesia. If adequate analgesia cannot be achieved, 100 mg tramadol will be administered as rescue analgesia according to clinical need.
• Bispectral Index Monitoring (Device), also known as BIS, BIS Monitoring: Continuous intraoperative depth of anesthesia monitoring using the Bispectral Index (BIS) device. BIS values are recorded throughout the procedure to assist in titration of anesthetic agents and to standardize anesthesia depth across study cohorts. The BIS device is used for monitoring only, and no device-related investigational procedures are performed.
• Serratus Posterior Superior Intercostal Plane Block (Procedure), also known as SPSIP Block, SPSIPB: Bilateral ultrasound-guided serratus posterior superior intercostal plane block will be performed according to standard techniques described in the literature and routinely used in the clinic. Local anesthetic dosing will be determined according to institutional practice and safety limits. In bilateral applications, the total bupivacaine dose will not exceed 2.5 mg/kg.
• Serratus Anterior Plane Block (Procedure), also known as SAP Block, SAPB: Bilateral ultrasound-guided serratus anterior plane block will be performed according to standard techniques described in the literature and routinely used in the clinic. Local anesthetic dosing will be determined according to institutional practice and safety limits. In bilateral applications, the total bupivacaine dose will not exceed 2.5 mg/kg.

Primary outcomes

• Total postoperative opioid consumption during the first 24 hours [From the end of surgery to 24 hours postoperatively]: Total opioid consumption during the first 24 hours after surgery will be recorded and expressed as intravenous morphine equivalents in milligrams.

Secondary outcomes

• Intraoperative opioid consumption [From induction of anesthesia to the end of surgery]: Total intraoperative opioid consumption will be recorded.
• Postoperative pain scores [At arrival in the post-anesthesia care unit and at postoperative 6, 12, 24, and 48 hours]: Pain intensity will be assessed using the Numeric Rating Scale, where 0 indicates no pain and 10 indicates the worst imaginable pain.
• Patient satisfaction [At postoperative 6, 12, 24, and 48 hours]: Patient satisfaction with postoperative analgesia will be assessed using a 4-point Likert scale, where 0 indicates very dissatisfied and 3 indicates very satisfied.
• Incidence of Opioid-Related Adverse Effects [From the end of surgery to 48 hours postoperatively]: Presence of nausea, vomiting, pruritus, constipation, urinary retention, sedation, and respiratory depression. Adverse effects will be compared among the two groups.
• Duration of anesthesia [Intraoperative period]: The total duration of anesthesia will be recorded in minutes.
• Duration of surgery [Intraoperative period]: The total duration of surgery will be recorded in minutes.
• Time to mobilization [From the end of surgery until the first documented ambulation, assessed within the first 48 postoperative hours]: The time from the end of surgery to first mobilization will be recorded.
• Length of hospital stay [Length of postoperative hospital stay, defined as the time from the end of surgery to hospital discharge, assessed up to 30 days postoperatively]: The duration of postoperative hospitalization will be recorded.

Sex: All, ages: 15 Years to 25 Years

Inclusion Criteria:

* Patients aged 15 to 25 years
* Diagnosis of pectus excavatum
* Scheduled to undergo minimally invasive repair of pectus excavatum under general anesthesia
* Receipt of either bilateral serratus posterior superior intercostal plane block or bilateral serratus anterior plane block as part of routine perioperative analgesic care
* Written informed consent obtained from the patient or, for patients younger than 18 years, from a legal guardian

Exclusion Criteria:

* Refusal to participate in the study
* Contraindication to regional anesthesia
* Known allergy to local anesthetics or study analgesic medications
* Chronic opioid use
* Pre-existing chronic pain syndrome
* Coagulopathy or use of anticoagulant therapy that contraindicates regional block application
* Local infection at the block injection site
* Neurological or psychiatric condition that may interfere with pain assessment
* Incomplete perioperative or postoperative data
* Conversion to another surgical technique or major intraoperative complication requiring a change in the routine analgesic protocol

• Cem Özdemir, MD, Study chair, Marmara University
• Seniyye Ülgen Zengin, Associate Professor, MD, Principal investigator, Marmara University
• Meliha Orhon Ergün, Associate Professor, MD, Study director, Marmara University