Discussion
This prospective study demonstrates that ESP is a safe block that is a feasible analgesic and anesthetic method for SICD placement under monitored anesthesia care (MAC). There was a small, but significant decrease in intraoperative and POD zero opioid consumption in the ESP group. While decreased narcotic use was noted on POD0, both groups had similar opioid consumption on POD1, 0 vs 1.5, wound infiltration vs ESP block (p=0.211). This is most likely a reflection of the limitation of single shot ESP nerve block with plain bupivacaine. Use of catheters or liposomal bupivacaine could be studied in the future to test extension of this analgesic effect. The day to discharge was shorter in the ESP block group, possibility reflecting better pain control and faster recovery from anesthesia.
SICD insertion is a very stimulating procedure; general anesthesia (GA) with ETT may provide ideal surgical condition. However, in high-risk, cardiac-compromised patients who are undergoing SICD placement, avoiding GA can minimize hemodynamic instability and facilitate quick recovery. Monitored anesthesia care (MAC) is often safer for these high-risk patients. Nonetheless, deep sedation is often needed due to the stimulating nature of the procedure including parasternal tunnel and device insertion between muscle layers. The possibility of oversedation and transitioning to GA without a secured airway can in turn lead to increased mortality and morbidity.6,7,8
Previously, the authors have completed a study showing transversus thoracis plane (TTP) and serratus anterior plane (SAP) blocks as a safe and feasible analgesic adjunct for SICD.9 There was significant reduction in intraoperative fentanyl use, with a median of 45mcg vs 90mcg. Zhang et al. also showed TTP and SAP blocks significantly reduced intraoperative dexmedetomidine and remifentanil use in patients undergoing SICD placement.10Postoperatively, sufentanil use in the block group was half of the local infiltration group; ketorolac use in the block group was a quarter of the local infiltration group.10
These studies demonstrated an important role for truncal blocks to reduce intraoperative and postoperative pain medication use while performing SICD implantation safely under moderate sedation. However, there are higher risks of pneumothorax and internal mammary artery puncture with the TTP block due to anatomical proximity of the fascia plane to the pleura and internal mammary artery.11 For a patient who has had an internal mammary coronary arterial bypass, the fascial plane injectate may not spread adequately to result in coverage of multiple dermatomes.11 On the other hand, ESP is a single trunk block that has the potential to cover the entire anterior thorax except for the sternum.2 This could provide analgesia for all incisional and tunneling sites (Fig 1). The transverse process provides a safe landing zone for the needle tip to lower the risk of pneumothorax in case the needle tip cannot be well-visualized during the block.2 ESP is a relatively easy block to perform with a steep learning curve. To the authors’ best knowledge, there has been no prospective studies comparing pain medication requirements between patients who received wound infiltration and ESP block for SICD placement under sedation. One retrospective chart review case series by Koller et al. showed that children who received parasternal and ESP blocks before extubation after SICD placement had reduced narcotic requirement compared to the wound infiltration group.12
ESP blocks have been used successfully in many thoracic and cardiac surgeries. Studies have shown promising results. In video-assisted thoracic surgery, Ciftci et al. showed decreased total fentanyl consumption in the ESP group (176mcg vs 717mcg) compared to the control group and significantly lower pain scores (passive and active) in the ESP group, especially in the first 8 hours, via a prospective randomized study of 60 paitnets.13 Multiple studies showed decreased opioid use and speedier recovery in cardiac surgery patients who received ESP blocks.14,15 Krishna et al. showed bilateral single shot ESP blocks reduced the mechanical ventilation time from 102 minutes to 63 minutes. Total opioid use was 231 mcg to 935mcg. Most importantly, the time to ambulation was cut in half, from 62 hours to 36 hours. ICU stay was 42 hours instead of 70 hours.14 Macaire et al. utilized bilateral ESP catheters in open cardiac surgery and demonstrated decreased total morphine consumption, PONV, time to first mobilization, and pain scores at rest one month after surgery.15
Although these patients can also receive paravertebral or epidural blocks for intraoperative and postoperative pain control with the possibility of dense analgesia precluding GA or deep sedation, the loss of sympathetic tone can result in profound hypotension and bradycardia. Many of the patients requiring SICD have compromised cardiovascular systems and may develop hemodynamic instability, especially when combined with sedation. Furthermore, many patients are on anticoagulation; due to concerns for epidural hematoma, paravertebral and epidural blocks would require the patient to hold anticoagulation ahead of time, which may not always be feasible.16,17These factors have contributed to the limited use of such techniques in cardiac procedures. Novel truncal blocks, such as ESP at the T4 level can provide analgesia to the T1 to T7 thorax by local anesthetic spreading cranial-caudally and towards the paravertebral space.
The use of local anesthetic infiltration with sedation is safe and effective in most patients and is still the preferred method of management in many centers.18 Even though an ESP block is relatively safe and easy to perform, there is still risk of pneumothorax and unintended epidural or intrathecal injection and it may not reliably block the parasternal incision and tunneling site. However, the benefit of decreasing even a small amount of opioid use intraoperatively and postoperatively can be beneficial in certain patient populations, such as the morbidly obese and patients with significant cardiac and pulmonary comorbidities, and the addition of an ESP block may provide larger benefits than in the average patient.19 While many hospitals are experiencing nursing shortages in the post-covid world, the ability to discharge patients early and safely with non-opioid pain management will benefit the entire healthcare system.
The use of ESP block did not increase the overall anesthesia time likely because it is a relatively easy to perform block and it is one injection whereas local infiltration requires injection of the entire tunneling sites which is large area. Furthermore, even under moderate sedation, patients likely move more due to the stimulation of the local injection in very densely innervated parasternal and inframammary sites. This often can prolong the procedural time, and hence the overall anesthesia time.
Recent studies have shown that even small reduction in intraoperative opioid use can have a significant decrease in postoperative complications, particularly in high-risk patients,20,21 although large studies are needed to determine this effect. The limitations of this study include the anesthesia provider and patient were not blinded to the block; these could have been sources of bias. Furthermore, the study population was small and a well powered study with a larger number of patients would be needed to determine outcomes and validate the use of this block as a standard of care for SICD placements. Additionally, larger volume and/or higher concentration of bupivacaine may potentially provide a denser block and prolong the analgesic effect. Some recent have shown that 0.375% and 0.5% bupivacaine compared to 0.25% and 30cc of volume compared to 20cc may provide better pain control.22-24