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.

This trial is comparing the use of 0.2% ropivacaine and 0.9% saline through a parasternal intercostal plane block and to measure whether there are any tangible changes in:

1. The primary outcome will be cumulative postoperative opioid use (measured as Milligram Morphine Equivalent (MME)) up to 72 hours following catheter insertion.

   Secondary outcomes will be:

2. cumulative postoperative opioid use from catheter insertion up to hospital discharge - measured as MME

3. median pain score - measured at rest and with coughing using a standardized numerical rating scale - for 72 hours post catheter insertion

4. delirium - assessed twice daily using institutional scores up to 72 hours following catheter insertion.

5.) Quality of Recovery -15 (QoR-15) score 24-96 hours post-surgery

Tertiary outcomes will be:

6.) time from catheter insertion to extubation 7.) time from catheter insertion to first opioid analgesic provision following extubation 8.) time from catheter insertion to mobilization 9.) lengths of stay in the intensive care unit and the hospital 10.) postoperative nausea and vomiting - measured twice a day and antiemetic medication requirements for the 72 hours after catheter insertion 11.) opioid requirements following discharge from the hospital 12.) chronic post-sternotomy pain/disability (McGill Pain Questionnaire) 13.) participant-reported outcomes (PROMIS-29 survey) at 6 weeks and 3 months post surgery

Inclusion Criteria:

• Adult patients undergoing cardiac surgery via median sternotomy

Exclusion Criteria:

• Redo sternotomy, or cardiac surgery performed through non-sternotomy approaches (minimally invasive procedures, thoracotomies, mini-sternotomy, hemi-sternotomy, etc.)
• Emergency procedures (surgery within 2 hours)
• Clinical instability which in the judgement of the investigator precludes enrollment or participation in the study
• Weight < 50kg
• Active systemic bacterial infection including infective endocarditis or pre-existing sternal infections
• Surgery for infective endocarditis
• Pregnancy or nursing
• Chronic opioid/narcotic use > 6 weeks, active use of illicit drugs, long-term opioid exposure or chronic pain disorder/syndromes
• Allergies to amide anesthetic agents or any components of study interventions
• Inability to comply with, or participate in, protocol (i.e. cognitive impairment/altered mental status/neurological deficit or disorder, inability to provide informed consent, inability to complete pain rating scales, etc.)
• Receipt of an investigational drug or device within past 7 days

The patient, intervention appliers (i.e. the operating room staff), medical practitioners, and outcome assessors will all be blinded to the randomized treatment arm until the database is locked. Unblinding procedures will be made available for breaking codes if necessary for clinical treatment.