Median sternotomy is commonly used in cardiac surgery and is often associated with significant postoperative pain. Poor pain control after sternotomy may increase opioid use, delay mobilization, prolong extubation time, and contribute to respiratory complications and longer hospital stay. Regional analgesia techniques may help improve pain management and reduce opioid requirements after surgery.

This study is a prospective, randomized, single-center clinical trial that will compare two ultrasound-guided regional analgesia techniques in adult patients undergoing elective cardiac surgery through median sternotomy: thoracic paravertebral block and bilateral deep parasternal intercostal plane block. A total of 80 patients will be randomly assigned in a 1:1 ratio to receive one of these two blocks in addition to standard general anesthesia and routine multimodal analgesia.

The main objective of the study is to compare the effects of these two techniques on total opioid consumption during the first 24 hours after surgery. Secondary outcomes include postoperative pain scores, need for additional analgesics, analgesia-related side effects such as nausea, vomiting, or respiratory depression, and extubation time. Pain will be assessed using a visual analog scale at predefined time points during the first 24 postoperative hours.

The study hypothesis is that there will be a clinically meaningful difference in postoperative analgesic effectiveness between thoracic paravertebral block and bilateral deep parasternal intercostal plane block in patients undergoing cardiac surgery via median sternotomy. The results of this study may help guide the selection of the most appropriate regional analgesia technique for pain control after sternotomy.

Median sternotomy remains the most commonly used surgical approach in adult cardiac surgery and is associated with substantial postoperative pain. Inadequate pain control after sternotomy may lead to increased opioid consumption, delayed mobilization, prolonged extubation time, respiratory complications, and extended intensive care unit or hospital stay. Despite the routine use of multimodal analgesia, postoperative pain after sternotomy continues to be a significant clinical problem.

Ultrasound-guided regional analgesia techniques have increasingly been used as part of multimodal pain management strategies in cardiac surgery. Thoracic paravertebral block is one of the established regional techniques that can provide effective hemithoracic analgesia. However, its use may be limited by technical difficulty, dependence on operator experience, and the potential risk of complications. In contrast, deep parasternal intercostal plane block is a more superficial fascial plane block that targets the anterior cutaneous branches of the intercostal nerves, which play an important role in sternotomy-related pain. Although both techniques have shown potential benefit in previous studies, direct comparative data between thoracic paravertebral block and deep parasternal intercostal plane block are limited.

This study is designed as a prospective, randomized, controlled, single-center clinical trial in adult patients undergoing elective cardiac surgery via median sternotomy. A total of 80 patients aged 18 to 65 years with American Society of Anesthesiologists physical status II-III will be enrolled. Eligible participants who provide written informed consent will be randomly assigned in a 1:1 ratio to one of two groups: the thoracic paravertebral block group or the bilateral deep parasternal intercostal plane block group. Randomization will be performed using a computer-generated sequence, and group assignments will be concealed in sealed, opaque, sequentially numbered envelopes.

All patients will undergo surgery under standard general anesthesia and routine perioperative monitoring according to institutional practice. In addition to standard anesthesia and multimodal analgesia, patients in one group will receive ultrasound-guided thoracic paravertebral block, while patients in the other group will receive ultrasound-guided bilateral deep parasternal intercostal plane block before surgery. All block procedures will be performed by an experienced anesthesiologist. Surgical procedures will be carried out by the same cardiovascular surgical team using the standard median sternotomy technique in order to reduce procedural variability.

The primary outcome measure is total opioid consumption during the first 24 hours after surgery. Secondary outcome measures include postoperative pain scores assessed with the Visual Analog Scale at 0, 2, 4, 6, 12, and 24 hours, additional analgesic requirements, analgesia-related adverse effects such as nausea, vomiting, or respiratory depression, and extubation time. Demographic and clinical variables including age, sex, body mass index, ASA class, diabetes mellitus, comorbidities, internal mammary artery preparation, and duration of surgery will also be recorded.

The hypothesis of the study is that there will be a significant difference in postoperative analgesic effectiveness between thoracic paravertebral block and bilateral deep parasternal intercostal plane block in adult patients undergoing cardiac surgery through median sternotomy. The findings are expected to contribute to the evidence base regarding the comparative effectiveness and clinical applicability of these two active regional analgesia techniques in post-sternotomy pain management.

Inclusion Criteria:

Age 18 to 65 years Scheduled for elective cardiac surgery via median sternotomy American Society of Anesthesiologists physical status II or III Planned to undergo surgery under general anesthesia Able to comply with postoperative pain assessment using the Visual Analog Scale Able to provide written informed consent

Exclusion Criteria:

Emergency cardiac surgery Cardiac surgery performed through an approach other than median sternotomy Redo sternotomy Local infection or skin disruption at the planned block site Known allergy or hypersensitivity to amide local anesthetics Clinically significant coagulopathy or antiplatelet/anticoagulant treatment preventing safe regional block according to institutional protocol Clinically unstable condition or high risk for pleural complications that would make the block unsafe Chronic opioid use or chronic pain syndrome Advanced musculoskeletal disease or deformity that may interfere with pain assessment Neurological or psychiatric disorder causing inability to comply with postoperative pain assessment Cognitive impairment preventing reliable pain assessment Clinically significant peripheral neuropathy or other neurosensory condition affecting pain perception Pregnancy or breastfeeding Severe pulmonary disease, including advanced chronic obstructive pulmonary disease or severe restrictive lung disease Anticipated inability to comply with the study protocol

There is no plan to make individual participant data available to other researchers. Due to patient privacy considerations and institutional data protection policies, individual-level data will not be shared outside the study team.

Postoperative outcome assessments, including Visual Analog Scale pain scores, will be performed by research staff/nurses blinded to group allocation. The anesthesiologist performing the block procedure will not be blinded.