Exparel vs. Marcaine ESP Block for Post-cardiac Surgical Pain

Inclusion Criteria: * Adults (18 years-no upper age limit) * Scheduled for mini thoracotomy (i.e. valve repair) or open sternotomy (i.e. bypass graft) at single academic medical center (in and out-patients). Exclusion Criteria: Patients will be excluded if they: * Are currently on pain medication or pain regimen for chronic pain condition * Convert to sternotomy (for thoracotomies) * Require, upon intraoperative discovery and surgeon's decision, the need for an unplanned secondary procedure other than the originally scheduled index operation * Undergo emergent surgery * Are non-English speaking (The majority of the PI's patient population speak English. As a pilot study the investigators cannot afford to enroll non-English speaking subjects due to time, personnel, and financial constraints.) * Mechanical circulatory support (MCS) * Vasoactive medications * Intubated * Active infection * Patients otherwise deemed ineligible for ESP block by the investigators due to safety concerns.