The Effect of Perineural Adjuvants on Superficial Parasternal Intercostal Plane Blocks in Cardiac Surgery: A Triple-Blinded Randomized Controlled Feasibility Trial

Background and aim The study aimed to investigate the effect of adding perineural adjuvants, clonidine and dexamethasone, to local anesthetic in Superficial Parasternal Intercostal Plane (SPIP) blocks. It was designed as a prospective, randomized, triple-blinded, feasibility trial, conducted at a single-center university hospital. The participants included adult patients who were undergoing cardiac surgery via median sternotomy. Methodology Following skin closure, patients were randomized to receive either SPIP with 0.25% bupivacaine and 2.5 mcg/mL epinephrine (control group, <i>n </i>= 12) or SPIP with 0.25% bupivacaine, 2.5 mcg/mL epinephrine, 1.67 mcg/mL clonidine, and 0.1 mg/mL preservative-free dexamethasone (adjuvant group, <i>n </i>= 8). Results No significant difference was found between the adjuvant and control groups for the primary outcome of the area under the curve of longitudinal pain scores with incentive spirometry use measured at four timepoints during the first 24 hours following surgery (96.5 ± 58.4 vs. 94.3 ± 39.6, <i>P </i>= 0.93, respectively). Additionally, no difference was found for secondary outcomes, including opioid consumption in morphine milligram equivalents (120, interquartile range [IQR] 93-150 vs. 120, IQR 82-158; <i>P </i>= 0.88), time to extubation (232.02 ± 68.69 vs. 276.82 ± 78.61 min, <i>P </i>= 0.25), intensive care unit length of stay (31.4 vs. 38.2 hours, <i>P </i>= 0.64), or pain satisfaction scores between the adjuvant and control groups (<i>P </i>= 0.46), respectively. The adjuvant group demonstrated higher incentive spirometry volumes at the six-hour postoperative timepoint (1333.33 ± 857.97 mL vs. 525.00 ± 338.56 mL, <i>P </i>= 0.003), with a trend toward a difference at 12 and 18 hours (<i>P </i>= 0.24 and <i>P </i>= 0.10, respectively). Conclusions The addition of perineural adjuvants to SPIP was not associated with any difference in pain scores within the first 24 hours after cardiac surgery. Given the small nature of this feasibility study, further investigation is warranted.