High Versus Low Dose Serratus Anterior Plane Block After Minimally Invasive Valve Surgery.

Inclusion Criteria: * Scheduled for elective aortic valve surgery or elective mitral valve surgery via right anterolateral thoracotomy * Adult patients (minimally 18 years old) * Bodyweight \> 50kg * EuroScore ii \< 3% Exclusion Criteria: * Refusal to participate * Inability to communicate due to language or neurologic barriers * Inability to control and self-administer opioids with PCIA or to comprehend the NRS pain score due to confusion or learning difficulties * Chronic use of opioids * Chronic use of analgesic antidepressants and/or antiepileptics * Use of prohibited medication which possibly interacts with bupivacaine-epinephrine or opioids (mexiletine, ketoconazole, theophylline, IMAO, Digitalis and cimetidine) * History of major trauma or surgery to right chest wall * History of chronic pain at right chest wall * Allergy to opioids and/or local anesthetics * Allergy to paracetamol * Class 3 obesity (BMI 40 or more) * Pregnancy * Intraoperative events compromising early postoperative recovery (aortic dissection, systolic anterior motion of the mitral valve, cardiac tamponade, brady-arrhytmias requiring external pacing,...)