Successful cutaneous sensory blockade following single-injection and double-injection techniques of ultrasound-guided superficial parasternal intercostal plane block: a randomized clinical trial

Background While superficial parasternal intercostal plane blocks can improve analgesia after cardiac surgery, the optimal site and the number of injections remain uncertain. This study aimed to compare the efficacy of single versus double injections of superficial parasternal blocks, hypothesizing that double injections would achieve superior cutaneous sensory blockade. Methods 70 cardiac patients undergoing median sternotomy were randomly assigned to receive either single or double injections of superficial parasternal blocks bilaterally. Each patient received 40 mL of 0.25% bupivacaine with epinephrine 5 µg/mL and dexamethasone 10 mg. The single-injection group received 20 mL/side at the third costal cartilage, while the double-injection group received 10 mL/injection at the second and fourth costal cartilages. The primary outcome was a successful block, defined as sensory loss in the T2–T6 dermatomes. Secondary outcomes included sensory block of T1, T7, and T8 dermatomes, block-related complications, intraoperative hemodynamics, postoperative pain intensity, opioid consumption, and recovery quality. Results Double injections achieved an overall higher success rate compared with the single-injection technique (81% vs 51%, relative risk 1.6; 95% CI 1.2, 2.0; p<0.001). Additionally, higher blockade percentages were observed in dermatomes T1 (83% vs 59%, p=0.003), T7 (67% vs 46%, p=0.017), and T8 (61% vs 39%, p=0.011) with double injections. Other secondary outcomes did not differ significantly between groups. Conclusions Compared with single injection, double injections of superficial parasternal blocks provided more reliable coverage of the T2–T6 dermatomes, crucial for median sternotomy. However, no differences were observed in intraoperative hemodynamic effects or postoperative pain control after cardiac surgery. Trial registration number TCTR20230408004.