When a patient is to undergo heart surgery with a sternotomy, a transthoracic block is performed. The thoracic block is an analgesic technique which consists of injecting anesthetic product into the nerves, in order to avoid significant pain. The common technique is to make injections in the sternum by the surgeon. A new, increasingly widespread method is performed by the anesthetist who performs the block under ultrasound.

This research project aims to determine if performing this transthoracic block under ultrasound is more effective than injections performed by the surgeon without ultrasound.

Cardiac surgery, and more specifically associated sternotomy, leads to severe pain in the postoperative period. Adequate analgesia is therefore challenging, but of paramount importance to reduce associated side effects such as pulmonary hypertensive crisis, tachyarrhythmia, systemic hypertension, hypoxia, and increased morbidity and length of stay. Actual opioid crisis and risks associated with intravenous analgesics raises the question of having an alternative and better approach to relieve severe pain. Currently in the postoperative suites opiates are also used for sedative purposes. This strategy of sedation has to change. Recent advances in regional anaesthesia could be the answer.

Thoracic epidural or paravertebral blocks provide effective analgesia for open cardiac surgery in paediatric patients. However, the major risk of epidural hematomas caused by heparinization, hemodynamic instability, technical difficulties and pneumothorax has limited the application of these two techniques in open cardiac surgery, and promoted the development of new approaches with safe, reliable, and cost-effective techniques, such as ultrasound-guided peripheral nerve blocks. This might be the most effective method for pain management in paediatric patients undergoing cardiac surgery according to recent studies. Superficial Thoracic Transversus Muscle Plane Block has been recently described and evaluated for pain management in adult cardiac surgery. It works through the blockade of multiple anterior branches of the intercostal nerves (Th2-6) in the internal mammary region. It has also been described in children in a few papers: Zhang and al. in a randomized controlled trial in 100 children, Abdelbaser and al. conducted a randomized double blind study including 80 children. In these studies, the injection of local anaesthetics was made between the intercostal and transversus thoracis muscles. But in very small children, the risk of pleura or internal mammary artery puncture associated with this injection is relatively important. Superficial TTMPB (located between the intercostal and pectoralis major muscles) seems to have the same analgesic potency without the aforementioned risks.That is to say that TTMPB is better than nothing but, to our knowledge, there is no study comparing infiltration by surgeon and TTMPB.

The risks of the procedure are the same with all regional anaesthesia, which are vascular or nerves punction, hematoma and failure of anaesthesia.

This study is set up to test the hypothesis that analgesia performed by TTMPB may have a better antalgic effect than blocks made by surgeons, in patients who undergo cardiac sternotomy. At first, the standard in CHUV was injections made by surgeon. Nowadays the decision of technic used is made with a discussion between anesthesist and surgeon during operative time. The investigators want to bring an evidence based decision with this study.

Inclusion Criteria:

• All patients undergoing sternotomy for a cardiac surgery in CHUV, which is an academic hospital in Switzerland.

Participants fulfilling all of the following inclusion criteria are eligible for the study :

• Informed Consent as documented by signature.
• Age from 0 to 16 years old.
• Undergoing cardiac surgery with sternotomy in CHUV, Lausanne.

Exclusion Criteria:

• • Patients older than 16 years.

  • Pregnancy.
  • Sternotomy for operation other than cardiac surgery.
  • Contraindication to local anesthesic, e.g. known hypersensitivity or allergy to Bupivacaine.
  • Infection at the site of injection.
  • Not having consented for this procedure/ refusal of participation. Reoperation during the same hospitalisation.