This trial demonstrated that PIFB combined with RSB can reduce intravenous opioid consumption until 48 h after cardiac surgery and did not reduce perioperative systemic inflammation.
Intravenous opioid consumption within 24 h after surgery was significantly decreased in the PIFB + RSB group (2.33 ± 1.77 mg vs 3.81 ± 2.24 mg, p = 0.010). Opioid consumption within 48 h was also significantly decreased (4.71 ± 2.71 mg vs 7.25 ± 3.76 mg, p = 0.006). The application of RSB reduced opioid consumption by nearly 35%. From the view of opioid consumption, we can conclude that combined PIFB with RSB could provide better analgesia, although pain scores were similar (at rest p = 0.287, 0.653, 0.449, at cough p = 0.097, 0.551,0.371) at 12, 24, 48 h between the two groups. As all participants were educated by professional staff on how to use analgesic devices according to their own pain intensity and demands. There was no significant difference in the incidence of pain at the chest tube within 48 h (14.8% vs 29.6%, p = 0.190), only a higher trend in the PIFB group. There was no difference in the adverse events with opioids, perhaps hydromorphone is a kind of improved opioid subtype with fewer adverse events.
Cardiac surgery is commonly performed via median sternotomy, which causes catastrophic pain, particularly sternal splitting. Full heparinization and hemodynamic instability make the use of epidural analgesia or paravertebral block controversial. Transverse thoracic muscle plane block and PIFB, aiming at the anterior chest wall innervated by branches of intercostal nerves, can achieve the same analgesia for sternotomy in cardiac surgery [9], but PIFB is more superficial, safer and simpler. [10] While pain after cardiac surgery is complicated, drainage insertion can cause skin incisions to rub. In addition, irritation of drainage to adjacent tissues and rectus abdominal muscle would result in persistent pain that cannot be covered by PIFB [8], so additional methods should be combined for better pain management. The most painful area related to chest tubes was mainly concentrated in the epigastric area [11]. RSB is widely used in laparoscopic surgery and targets upper abdominal postoperative analgesia [12]. We conducted a randomized controlled trial to prove that RSB combined with PIFB is a more optimized maneuver to provide adequate analgesia compared to single PIFB in cardiac sternotomy.
The duration of a single shot for regional anesthesia is limited, even for long-acting local anesthetics. Surprisingly, a single shot of PIFB combined with RSB in our trial decreased opioid consumption until 48 h after surgery. The long duration of combined regional techniques can be explained as follows. The addition of dexamethasone, as a safe and effective adjunct, can further prolong the duration of long-acting local anesthetics [13]. Its effect on sensory block duration is dose-independent between 4 and 10 mg [14]. In our study, patients in the PIFB + RSB group received 10 mg dexamethasone, which contributes to sustained analgesia.
There was no difference in time to drainage removal, ability to ambulate, or LOS in the ICU and hospital between the two groups. Although opioid consumption was decreased in our trial, the effect on early recovery was mild. Actually, the process of recovery is related to a series of programs, including adequate postoperative analgesia, surgeon-based preferences, and protocols for system perioperative care [15]. The implementation of enhanced recovery after surgery requires the participation and cooperation of all staff and patients. Perhaps continuous blocks would show more benefits than a single shot. Continuous bilateral erector spine plane block or infusion of local anesthetics at the median sternotomy site has been identified to reduce opioid consumption and LOS in hospitals after cardiac surgery [16, 17]. Continuous PIFB combined with RSB, covering T1-T10, has been attempted with good analgesia in cardiac surgery. [18] More research is needed to find the association between postoperative analgesia and early recovery in cardiac surgery in the future.
Sawing the sternum and cardiopulmonary bypass in cardiac surgery made patients experience severe systemic inflammation associated with poor outcomes. IL-6, IL-10 and TNF-α are important cytokines that are related to surgical trauma and the degree of tissue damage, and the levels of these cytokines reflect the systemic inflammatory response to some extent [19,20,21]. In our study, the combination of PIFB and RSB did not attenuate perioperative systemic inflammation. There was no difference in the level of these cytokines, which may be the basis for the same clinical outcome in the two groups.
Chest tube-related pain has been recognized gradually, and this pain is described as piercing and occurring upon breathing and coughing. In addition, the pain related to chest tubes is severe and persistent, and many protocols have been administered to address this problem. Injection of bupivacaine into the pleural and mediastinal drains has been concluded to relieve pain after cardiac surgery [22]. Intrapleural injection of lidocaine can also reduce drainage pain and improve pulmonary function after CABG [23], and even topically administered lidocaine could be useful [6, 24]. The safety of these methods is uncertain due to the probability of arrhythmia or wound infection caused by local anesthetics. RSB is an ultrasound-guided direct regional technique with safety and definite analgesia. Moreover, it has been combined with PIFB to manage subxiphoid drainage and sternal pain successfully in an awake patient undergoing cardiac surgery debridement [25]. Most researches in cardiac field merely solve partial postoperative pain with a single nerve block, while we combine regional techniques for better and adequate analgesia after cardiac median sternotomy.
There are some limitations in this trial. First, PIFB and RSB were conducted after anesthesia induction to maximize patient comfort, so we cannot check the spread range of regional blocks according to the patients’ sense. Successful nerve block was uncertain merely from total intraoperative opioid consumption and hemodynamics. However, all regional blocks were guided under ultrasound, and the spread of the drug was definitely observed. Second, our sample size was based on the primary outcome, and it was small to detect the differences in postoperative early outcomes. However, we conducted a randomized controlled trial to explore the efficacy of PIFB combined with RSB. Combined regional techniques could provide adequate analgesia for median sternotomy in cardiac surgery.
