The aim of this study is to assess and compare the efficacy of a serratus anterior plane (SAP) block and our current pain protocol (Patient Controlled Intravenous Analgesia with opioids) in the prevention and treatment of acute postoperative pain after totally endoscopic aortic valve replacement (AVR) surgery.

During the last two decades, cardiac surgical techniques changed dramatically. Evidence for good short and long-term outcome after endovascular and minimally invasive procedures is rising. The goal of avoiding sternotomy is earlier patient recovery without compromising safety. Therefore, enhanced recovery after surgery (ERAS) protocols have been implemented to aim for early extubation and ambulation. Analgesic regimens after cardiac surgery did not change significant however. Opioids remain the cornerstone of analgesia in the postoperative cardiac surgical care units, despite known side effects as nausea, constipation and risk for addiction. Neuraxial anesthetic techniques after cardiac surgery have been studied and validated to reduce opioid consumption. Their implementation in clinical practice however remains limited for two reasons. First, heparinization is required for cardiac surgery, which increases the risk neuraxial hematoma after neuraxial anesthesia, leading to deleterious complications as paraplegia. Secondly, neuraxial anesthesia induces orthosympathicolysis, enhancing vasoplegia after cardiac surgery. However, fascial plane blocks in cardiac surgery since peripheral blocks do not induce sympathicolysis and consequences of chest wall hematoma are limited.

In 2013, Blanco described the serratus anterior plane (SAP) block as an analgesic option for chest wall surgery. In this fascial plane block, local anesthetics are injected in the plane beneath the anterior serratus muscle and in the plane between latissimus dorsi and serratus anterior in an ultrasound guided manner. SAP block provides analgesia in dermatomes T2-T9. Recently, successful analgesia after SAP block has been demonstrated for soft tissue chest wall surgery, thoracotomy and rib fractures. No major side effects were reported. More specifically, no sympatholytic effects or chest wall hematoma were observed. However, up to now no prospective studies assessing the analgesic efficacy of SAP block after cardiac surgery are published. Two retrospective studies show conflicting results. Berthoud et al. retrospectively compared SAP block to continuous wound infusion after different types of minimally invasive cardiac surgery (MICS) and found reduced morphine consumption as well as shorter intensive care and hospital length of stay after SAP block. In contrast, Moll et al. found no difference in opioid consumption between SAP block and no block in patients after robotic coronary artery bypass grafting (rCABG). The authors comment they only performed the deep component of the SAP block, and some surgical entry points were outside dermatomes T2-T7.

Totally endoscopic aortic valve replacement (AVR) is a novel minimally invasive cardiosurgical technique. Surgical incision is made anteriorly in intercostal space two on the right hemithorax. Since intercostal space two is innervated by dermatomes T2-T3, somatic analgesia can be obtained with SAP block. In addition with a favorable safety profile and a minimal/non-existent risk of evoking sympatholytic effects, a SAP block may be a suitable analgesic technique to prevent/minimize postoperative pain after totally endoscopic AVR surgery.

Inclusion Criteria:

• Scheduled for elective aortic valve replacement surgery via right anterolateral thoracotomy
• Adult patients (minimally 18 years old)
• EuroScore ii < 3%
• Bodyweight > 50 kg

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
• 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 acetaminophen
• Morbid obesity (BMI > 35)
• Pregnancy
• Peroperative events compromising early postoperative recovery (aortic dissection, systolic anterior motion of the mitral valve, cardiac tamponade, ..)