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