Ultrasound-guided mid-point transverse process to pleura block versus thoracic paravertebral block in pediatric open-heart surgery: A randomized controlled non-inferiority study.

Study Objective: The mid-point transverse process to pleura block (MTPB) is a new variant of thoracic paravertebral block (TPVB). This study aimed to compare TPVB and MTPB with respect to intraoperative attenuation of the hemodynamic stress response to surgery and postoperative analgesia in pediatric open heart surgery with midline sternotomy.

Design: A single-center, randomized, controlled, double-blind, non-inferiority study.

Setting: Tertiary care children's university hospital.

Patients: We recruited 83 children aged 2-12 years of both sexes with American Society of Anesthesiologists (ASA) physical status class II who were scheduled for elective open cardiac surgeries with midline sternotomy for the repair of simple noncyanotic congenital heart defects.

Interventions: Eligible participants were randomized into either the TPVB or MTPB groups at a ratio of 1:1. In the TPVB group, patients were bilaterally injected with 0.4 ml/kg of 0.25% bupivacaine in the paravertebral space at T4 and T5. In the MTPB group, patients were bilaterally injected with 0.4 ml/kg of 0.25% bupivacaine mid-transverse process and pleura just posterior to superior costotransverse ligament at the level of T4 and T5.

Measurements: The primary outcome was the hemodynamic responses to sternotomy incision, including heart rate (HR) and invasive mean arterial pressure (MAP), recorded before and after the induction of anesthesia, after skin incision, after sternotomy, 15 min after cardiopulmonary bypass (CPB), and after the closure of the sternum. The secondary outcomes were time needed to perform the bilateral block, intraoperative fentanyl consumption, postoperative fentanyl consumption, modified objective pain score (MOPS) measured at 1, 2, 6, 12, 18, and 24 h after extubation, extubation time, intensive care unit (ICU) discharge time, and the incidence of non-surgical complications (postoperative pruritus, postoperative vomiting, pneumothorax, hematoma or local anesthetic toxicity).

Main Results: There were no significant differences in HR and MAP in the TPVB group compared with the MTPB group at the following time points: baseline, after induction, after skin incision, after sternotomy, 15 min after CPB, and after sternal closure. Intergroup comparisons of HR and MAP did not reveal significant differences between the groups. The median (IQR) time needed to perform bilateral MTPB (7[6-8] min) was significantly (p < 0.001) shorter than that of TPVB (12[10-13] min). Intraoperative fentanyl consumption and fentanyl consumption in the first postoperative 24 h after extubation were similar in the TPVB and MTPB groups (4[2-4] vs 4[2-4] and 4.66 ± 0.649 vs 4.88 ± 1.082 μg/kg), respectively. Extubation time and ICU discharge time were comparable in the TPVB and MTPB groups (2[1-3] vs 2[1-3] h and 21.2 ± 2.5 vs 20.8 ± 2.6 h), respectively. Measurements of MOPS pain scores at 1, 2, 6, 12, 18, and 24 h after extubation were similar in both groups. The incidence of nonsurgical complications was similar in both groups.

Conclusions: MTPB is non-inferior to TPVB in attenuating the intraoperative hemodynamic stress response to noxious surgical stimuli and in reducing perioperative opioid consumption, extubation time, and ICU discharge time. Moreover, MTPB is technically easier than TPVB and requires less time to perform. Clinical trial registration number The clinical trial registration was prospectively performed at the Pan African Clinical Trials Registry (PACTR202204901612169, approval date 01/04/2022, URL https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=22602).