Superficial Parasternal Intercostal Plane Blocks (SPIB) With Buprenorphine, Magnesium, and Bupivacaine for Management of Pain in Coronary Artery Bypass Grafting

Abstract

Introduction Management of post-operative pain after cardiac surgery continues to be a challenge; inadequate management of pain can lead to increased morbidity, impaired physical function with potential delay in recovery, increased perioperative and chronic opioid consumption, increased cost of care, and a decreased quality of life. This study aimed to evaluate the effect of adding buprenorphine and magnesium to bupivacaine for superficial parasternal intercostal plane blocks (SPIB) on pain and opioid consumption in the first 24 hours after coronary artery bypass grafting (CABG). Methods Patients undergoing CABG were divided into the following four groups: saline SPIB, SPIB with bupivacaine (BPVC), SPIB with bupivacaine and buprenorphine (BPVC+BPRN), and SPIB with bupivacaine, buprenorphine, and magnesium (BPVC+BPRN+MG). The primary outcomes were pain scores and opioid consumption after SPIB; the secondary outcomes were post-operative nausea and vomiting, time to extubation, and length of stay (LOS) in the intensive care unit and hospital. Results One hundred thirty-four eligible patients undergoing CABG were randomized to either the saline (n=27), BPVC (n=20), BPVC+BPRN (n=24), or BPVC+BPRN+MG (n=29) group. All of the intervention groups combined (BPVC, BPVC+BPRN, and BPVC+BPRN+MG) had decreased pain scores and decreased opioid consumption when compared to the saline group; although not statistically significant, visual analog scale (VAS) scores trended downward at most time points with BPVC versus saline, BPVC+BPRN versus BPVC, and BPVC+BPRN+MG versus BPVC+BPRN. There was no difference among the study groups in the incidence of post-operative nausea and/or vomiting (PONV), time to extubation, hospital LOS, and ICU LOS. Conclusion In this prospective, double-blind, placebo-controlled trial, we found that SPIB with local anesthetic is effective at reducing VAS scores and opioid consumption after CABG. Further study is needed to determine whether the addition of adjuvants can further improve pain control and opioid consumption.

Keywords: buprenorphine; coronary artery bypass grafting; magnesium; post-operative opioid consumption; post-operative pain management; superficial parasternal intercostal block.

Figure 1. Injection of local anesthetic below ribs 2-6 during SPIB prior to chest closure.

SPIB: superficial parasternal intercostal plane blocks

Figure 2. Consolidated Standards of Reporting Trials (CONSORT) diagram.

BPVC: bupivacaine; BPRN: buprenorphine; MG: magnesium

Figure 3. Patient characteristics for all four groups of the study.

Boxplots of (a) age (year), (b) weight (kg), and (c) BMI (body mass index) (kg/m²). The solid line in the middle of the box represents the median. The box represents the middle 50%, and the whiskers represent the top and bottom 25%. Mild outliers are represented by circles and extreme outliers by stars. There was no significant difference between the mean values of the four groups of all three variables. BPVC: bupivacaine; BPRN: buprenorphine; MG: magnesium

Figure 4. Boxplots of (a) duration of the surgery (hours), (b) time to extubation after surgery (hours), (c) length of ICU stay (days), and (d) length of hospital stay (days).

The solid line in the middle of the box represents the median. The box represents the middle 50%, and the whiskers represent the top and bottom 25%. Mild outliers are represented by circles and extreme outliers by stars. BPVC: bupivacaine; BPRN: buprenorphine; MG: magnesium

Figure 5. Comparison of saline (n=27) group and the three (BPVC, BPVC+BPRN, and BPVC+BPRN+MG) SPIB groups with bupivacaine combined (n=73).

The pain scores and the total post-operative 24-hour opioid OME (mg) are significantly lower for the three SPIB groups with bupivacaine combined in comparison to the saline group. The p-values are as the following: (a) 0.011, (b) 0.007, (c) 0.010, (d) 0.001, (e) 0.030, and (f) 0.000. BPVC: bupivacaine; BPRN: buprenorphine; MG: magnesium; SPIB: superficial parasternal intercostal plane blocks

Figure 6. Boxplots (a) pain score at extubation, (b) pain score at 6 hours, (c) pain score at 12 hours, (d) pain score at 18 hours, and (e) pain score at 24 hours.

The solid line in the middle of the box represents the median. The box represents the middle 50%, and the whiskers represent the top and bottom 25%. Mild outliers are represented by circles and extreme outliers by stars. BPVC: bupivacaine; BPRN: buprenorphine; MG: magnesium

Figure 7. Bar charts for the pain scores at (a) extubation, (b) 6 hours, (c) 12 hours, (d) 18 hours, (e) 24 hours, and (f) the total post-operative 24-hour opioid consumption (OME) (mg) for all four groups.

At extubation (a) pain scores for the BPVC+BPRN (p=0.046) and BPVC+BPRN+Mg (p=0.001) groups were significantly lower than the saline group. Pain scores for the BPVC+BPRN+Mg (p=0.005) group were significantly lower than the BPVC group. At 6 hours (b) pain scores for the BPVC+BPRN+Mg (p=0.003) group were significantly lower than saline group. At 12 hours (c) pain scores for the BPVC+BPRN (p=0.019) and BPVC+BPRN+Mg (p=0.005) groups were significantly lower than the saline group. At 18 hours (d) pain scores for the BPVC (p=0.008) and BPVC+BPRN+Mg (p=0.000) groups were significantly lower than the saline group. Pain scores for the BPVC+BPRN+Mg (p=0.003) group were also significantly lower than BPVC+BPRN group. At 24 hours (e) pain scores for the BPVC+BPRN (p=0.040) and BPVC+BPRN+Mg (p=0.023) groups were significantly lower than the saline group. The total post-operative 24-hour opioid consumption (f) for the BPVC (p=0.000), BPVC+BPRN (p=0.002), and BPVC+BPRN+Mg (p=0.000) groups were significantly lower when compared to the saline group. Error bars are ±1 x SEM (standard error mean). BPVC: bupivacaine; BPRN: buprenorphine; MG: magnesium

Figure 8. Boxplots (a) total intra-operative opioid oral morphine equivalent (mg), (b) total post-operative 24-hour opioid oral morphine equivalent (mg), (c) total opioid consumption oral morphine equivalent (mg), and (d) percent of the patients with PONV in the first 24-hours after surgery for the four groups.

The solid line in the middle of the box represents the median. The box represents the middle 50%, and the whiskers represent the top, and bottom 25%. Mild outliers are represented by circles and extreme outliers by stars. BPVC: bupivacaine; BPRN: buprenorphine; MG: magnesium; PONV: post-operative nausea and/or vomiting