Serratus Posterior Superior Intercostal Plane Block for Analgesia in Off-Pump Minimally Invasive CABG

Overview

Postoperative pain after cardiac surgery is commonly moderate to severe due to sternotomy, thoracotomy, internal mammary artery harvesting, and chest tube placement, and may contribute to adverse systemic and pulmonary outcomes if inadequately managed. Enhanced Recovery After Surgery (ERAS) protocols emphasize opioid-sparing strategies to reduce opioid-related side effects and complications. Ultrasound-guided fascial plane blocks have increasingly been incorporated into perioperative analgesia protocols for cardiac surgery. The serratus posterior superior intercostal plane block (SPSIPB), a recently described technique, provides wide dermatomal sensory coverage and may offer effective analgesia in thoracic and cardiac surgical procedures. This prospective, randomized controlled study aims to evaluate the analgesic efficacy of SPSIPB in adult patients undergoing off-pump minimally invasive coronary artery bypass grafting (CABG). A total of 60 ASA III patients aged 18 years or older will be randomized into two groups: SPSIPB group and control group. The SPSIPB will be performed preoperatively under ultrasound guidance using 0.25% bupivacaine, while the control group will receive standard general anesthesia without any plane block. All patients will receive standardized general anesthesia and postoperative patient-controlled analgesia with tramadol. The primary outcome of the study is postoperative recovery quality assessed using the Quality of Recovery-15 (QoR-15) questionnaire. Secondary outcomes include intraoperative remifentanil consumption, postoperative opioid requirements, time to first rescue analgesia, numerical rating scale (NRS) pain scores at rest and during coughing, extubation time, intensive care unit and hospital length of stay, and postoperative complications such as nausea, vomiting, and atelectasis. This study aims to determine whether SPSIPB can improve postoperative recovery quality and reduce opioid consumption in patients undergoing off-pump minimally invasive CABG.

Introduction Pain after cardiac surgery is commonly moderate to severe due to sternotomy, sternal retraction, internal mammary artery harvesting, thoracotomy/thoracoscopy in minimally invasive approaches, and chest tube placement. Adequate pain management reduces pain-related systemic and pulmonary complications. Tachycardia and hypertension secondary to pain increase myocardial oxygen consumption and predispose patients to hemodynamic instability. Enhanced Recovery After Surgery (ERAS) protocols aim to reduce opioid consumption and eliminate opioid-related adverse effects. With increasing awareness of opioid overuse, tolerance, and opioid-induced hyperalgesia, opioid-sparing analgesic strategies have gained importance. The most critical component of opioid-sparing analgesia is the use of regional anesthesia techniques. Procedure-Specific Postoperative Pain Management (PROSPECT) guidelines recommend plane blocks as part of analgesic management in thoracic surgeries. The incidence of severe chronic pain within the first year after sternotomy has been reported to be approximately 35%. Various regional anesthesia techniques, including thoracic epidural anesthesia, thoracic paravertebral block, and parasternal intercostal block, have been used for postoperative analgesia in cardiac surgery. However, coagulation disorders limit the application of central neuraxial blocks. Ultrasound-guided fascial plane blocks have therefore been increasingly adopted in cardiac surgery. These include erector spinae plane block (ESPB), serratus anterior plane block, parasternal block, paravertebral block (PVB), pectoral nerve blocks (PECS I-II), and serratus posterior superior intercostal plane block (SPSIPB). Ultrasound-guided SPSIPB was first described by Tulgar et al. in 2023 through cadaveric studies and a case series of five patients. Due to its wide local anesthetic spread and extensive sensory dermatomal coverage (C3-T10), SPSIPB has been increasingly used in cervical and thoracic surgical procedures. In our clinic, coronary artery bypass grafting (CABG) procedures are performed on the beating heart, with the aim of accelerating postoperative recovery. Effective intraoperative and postoperative analgesia facilitates optimal surgical conditions and postoperative management. Therefore, regional anesthesia techniques are frequently employed to enhance analgesic efficacy. In this study, we aimed to evaluate the effectiveness of serratus posterior superior intercostal plane block (SPSIPB) in postoperative analgesia management for off-pump CABG surgery. Materials and Methods This prospective study is planned to be conducted between June 2025 and June 2026 at Kartal Koşuyolu High Specialization Training and Research Hospital and will include 60 patients aged 18 years or older, classified as ASA III, scheduled for off-pump minimally invasive coronary artery bypass surgery. Exclusion criteria include age under 18 years, ASA classification other than III, pregnancy, emergency surgery, history of trauma within the previous 24 hours, neurological diseases affecting consciousness or decision-making capacity, psychiatric disorders impairing decision-making ability, allergy to local anesthetics, skin infection at the puncture site, body mass index \>35 kg/m², body weight \<42 kg, and coagulation disorders (prothrombin time-international normalized ratio \>1.25, activated partial thromboplastin time \>35 s, or platelet count \<100,000/μL). Sixty eligible patients will be randomized into two equal groups using a sealed-envelope method: the SPSIPB group (n = 30) and the control group (n = 30). All patients will be informed about the study, and written informed consent will be obtained after providing detailed information regarding the plane block procedure. Before any intervention, all patients will complete the Quality of Recovery-15 (QoR-15) questionnaire. Premedication will be administered in the preoperative preparation area after standard monitoring and intravenous access with a 20-gauge cannula, consisting of intravenous midazolam 0.03 mg/kg and fentanyl 1 µg/kg. All blocks will be performed under strict aseptic conditions while patients are monitored and receiving supplemental oxygen via face mask. No plane block will be performed in the control group. In the SPSIPB group, patients will be positioned laterally with the surgical side up and the upper extremity extended over the head. After aseptic preparation, a high-frequency linear ultrasound probe will be placed over the scapula to identify the scapular spine. The third rib will be visualized medial to the scapula. After identifying the rib, pleura, and overlying serratus posterior superior muscle, the needle will be advanced until contact with the third rib is achieved. Following hydrodissection with 5 mL isotonic saline, 30 mL of 0.25% bupivacaine (1 mg/kg) will be injected between the serratus posterior superior muscle and the third rib, with cranio-caudal spread confirmed under ultrasound guidance. Standard intraoperative monitoring, including ECG, peripheral oxygen saturation, invasive arterial blood pressure, near-infrared spectroscopy (NIRS), and bispectral index (BIS), will be applied. Anesthesia induction will be achieved with propofol 2-2.5 mg/kg and rocuronium 1 mg/kg. Patients will be intubated with a double-lumen endotracheal tube, with correct placement confirmed by bronchoscopy. Anesthesia maintenance will consist of sevoflurane (0.8-1 MAC) in a 50% oxygen-air mixture and remifentanil infusion (0.01-0.1 µg/kg/min), with BIS maintained between 40 and 60. Remifentanil dosage will be increased to 0.1-2 µg/kg/min if heart rate or arterial blood pressure increases by more than 20% from baseline. Lung-protective ventilation with single-lung ventilation will be applied as required. Thirty minutes before the end of surgery, all patients will receive intravenous tramadol 1 mg/kg and paracetamol 1000 mg. Intraoperative remifentanil consumption, operative duration, hemodynamic parameters, and time to extubation will be recorded. Postoperatively, patient-controlled analgesia (PCA) with tramadol will be initiated, prepared at a concentration of 4 mg/mL in a total volume of 100 mL, with a 2 mL bolus dose, 15-minute lockout interval, and a 4-hour maximum dose of 100 mg. Pain scores using the numerical rating scale (NRS; 0 = no pain, 10 = worst pain imaginable) will be assessed at postoperative 30 minutes and at 1, 6, 12, 18, and 24 hours, both at rest and during coughing. Time to first rescue analgesia, incidence of postoperative nausea and vomiting, and other adverse effects will be recorded. Patients with NRS ≥4 despite PCA will receive intravenous paracetamol 1000 mg as rescue analgesia. The QoR-15 questionnaire will be repeated at postoperative 24 hours. Length of stay in the intensive care unit and hospital will be documented. Sample Size and Statistical Analysis Sample size calculation was performed using G\*Power v3.1.9.2 software. Based on a similar plane block study reported in the literature, postoperative 24-hour total opioid (morphine) consumption was significantly lower in the erector spinae plane block group (3.13 ± 1.44 mg) compared with the serratus anterior plane block group (4.33 ± 1.69 mg). With a significance level of 5% (α = 0.05) and a power of 85% (1-β = 0.85), a minimum of 26 patients per group was required. Considering a potential 20% data loss, 30 patients per group (total n = 60) will be enrolled. Statistical analyses will be performed using SPSS version 27.0. Continuous variables will be expressed as mean ± standard deviation, median, minimum, and maximum values, while categorical variables will be presented as frequencies and percentages. Normality will be assessed using the Shapiro-Wilk test and box plots. Comparisons between normally distributed variables will be conducted using Student's t-test, while non-normally distributed variables will be analyzed using the Mann-Whitney U test. Categorical variables will be compared using the chi-square test, Fisher's exact test, or Fisher-Freeman-Halton test as appropriate. A p-value \<0.05 will be considered statistically significant. Outcome Measures Primary Outcome: Comparison of Quality of Recovery-15 (QoR-15) scores. Secondary Outcomes: Intraoperative remifentanil consumption, postoperative opioid consumption, time to first analgesic request, NRS pain scores, time to extubation, length of intensive care unit stay, length of hospital stay, and incidence of postoperative complications (nausea, vomiting, atelectasis).