Which ultrasound-guided parasternal intercostal nerve block for post-sternotomy pain? Results from a prospective observational study

Background: Parasternal intercostal blocks (PSB) have been proposed for postoperative analgesia in patients undergoing median sternotomy. PSB can be achieved using two different approaches, the superficial parasternal intercostal plane block (SPIP) and deep parasternal intercostal plane block (DPIP) respectively. Methods: We designed the present prospective, observational cohort study to compare the analgesic efficacy of the two approaches. Cardiac surgical patients who underwent full sternotomy from January to September 2022 were enrolled and divided into three groups, according to pain control strategy: morphine, SPIP, and DPIP group. Primary outcomes were was postoperative pain evaluated as absolute value of NRS at 12 h. Secondary outcomes were the NRS at 24 and 48 h, the need for salvage analgesia (both opioids and NSAIDs), incidence of postoperative nausea and vomiting, time to extubation, mechanical ventilation duration, and bowel disfunction. Results: Ninety-six were enrolled. There was no significant difference in terms of median Numeric Pain Rating Scale at 24 h and at 48 h between the study groups. Total postoperative morphine consumption was 1.00 (0.00-3.00), 2.00 (0.00-5.50), and 15.60 mg (9.60-30.00) in the SPIP, DPIP, and morphine group, respectively (SPIP and DPIP vs morphine: p < 0.001). Metoclopramide consumption was lower in SPIP and DPIP group compared with morphine group (p = 0.01). There was no difference in terms of duration of mechanical ventilation and of bowel activity between the study groups. Two pneumothorax occurred in the DPIP group. Conclusions: Both SPIP and DPIP seem able to guarantee an effective pain management in the postoperative phase of cardiac surgeries via full median sternotomy while ensuring a reduced consumption of opioids and antiemetic drugs.