Superficial Parasternal Intercostal Plane Block in Cardiac Surgery Trial

The goal of this clinical trial is to assess whether the use of intermittent superficial parasternal intercostal plane blocks reduces opioid usage in patients undergoing cardiac surgery with median sternotomy. Participants randomized to the intervention group will receive the blocks with 0.2% ropivacaine administered via catheters placed in the superficial parasternal intercostal plane bilaterally under ultrasound guidance. Researchers will compare this group with a control group given 0.9% saline through similarly placed catheters. The primary outcome will be cumulative postoperative opioid use (measured as Milligram Morphine Equivalent (MME)) up to 72 hours following catheter insertion.