Oct 30, 2019, 11:27 AM by Jackson M. Condrey, MD; Robert Harvey, MD; Wesley Doty, MD; Eric Bolin, MD

Implantable cardioverter defibrillators (ICDs) are useful in the prevention of sudden cardiac death. The subcutaneous ICD (S-ICD) is a relatively recent innovation, having received Food and Drug Administration approval in the United States in 2012. S-ICD may be superior to the more familiar transvenous ICD (TV-ICD) in patients who have abnormalities of their central venous circulation, patients who have experienced complications from TV-ICD therapy, and patients at increased risk for lead infection.^[1],[2]

S-ICD generators are larger than TV-ICD generators; the incision site for a TV-ICD generator is usually in the subclavicular region, as opposed to the midaxillary line at the level of the fifth or sixth intercostal space for an S-ICD. (See Figure 1.) An electrode is tunneled subcutaneously from the generator to the xiphoid process and then superiorly along the sternal border to the second intercostal space. Tunneling a subcutaneous lead results in more periprocedural pain than transvenous lead placement, and local anesthetic infiltration is usually inadequate.^[1],[2]

Optimal anesthetic management for placement of these devices is evolving.^[3] Patients presenting for S-ICD placement often have significant comorbidities in addition to cardiac disease, including obesity, obstructive sleep apnea, anticoagulation, or renal failure. Interventions to reduce opioid requirements, such as multimodal analgesics and regional anesthesia, should be incorporated in patients’ periprocedural management.

Regional anesthesia for S-ICD placement requires coverage of the anterior chest wall, including the lateral border of the sternum, and laterally to the midaxillary line where the generator is placed, typically at the T4–T6 dermatomal level.^[3] Cranial-caudad distribution from roughly T2–T6 is needed. Innervation of the chest wall originates at the anterior primary rami of spinal nerves T1–T11, which travel in the costal groove of the corresponding rib between the innermost intercostal and the internal intercostal muscles. At the level of the midaxillary line, the intercostal nerves split into anterior and lateral cutaneous branches. The anterior cutaneous branches innervate the sternum, skin, and subcutaneous tissues of the anteromedial chest wall. The lateral cutaneous branches innervate the skin and subcutaneous tissues of the anterolateral portions of the chest wall. The pectoral muscles are innervated by the lateral and medial pectoral nerves, which arise from the brachiaI plexus. The lateral pectoral nerve lies in a plane between pectoralis major and minor. The medial pectoral nerve courses under the pectoralis minor before piercing it to also lie in the plane between pectoralis major and minor. The long thoracic nerve arises from the ventral rami of C5–C7 and travels to innervate the serratus anterior. The thoracodorsal nerve arises from the posterior cord of the brachiaI plexus and innervates the latissimus dorsi.

Regional anesthesia techniques and combinations for S-ICD placement include transversus thoracic block, paravertebral block, and serratus plane block. The serratus plane block anesthetizes the lateral cutaneous branches of T2–T9, the long thoracic nerve, and the thoracodorsal nerve. The block is performed by placing a linear ultrasound probe in the midaxillary line at the level between the fourth and fifth rib, and injecting in the plane between the latissimus dorsi and serratus anterior. Alternatively, an injection in the plane deep to serratus between the serratus anterior and ribs may be performed if the plane between latissimus and serratus is difficult to identify.^[4] Of note, results from a 2018 cadaveric study showed that using a higher volume of local anesthetic was more important for block spread than the plane selected for the block.^[5]

Transversus thoracic plane blocks can anesthetize the parasternal area; they are performed by injecting local anesthetic in the plane between the internal intercostal muscle and transversus thoracic muscle, as described by Ueshima et al.^[6] The anterior cutaneous branches of nerves T2–T6 can be anesthetized with this technique, which should provide coverage for the tunneling of the parasternal subcutaneous leads of an S-ICD. An alternative is the pectointercostal plane block, initially described by de la Torre et al., which anesthetizes the anterior cutaneous branches by injecting local anesthetic in the plane between the pectoralis major muscle and the external intercostal muscle.^[7]

PEC blocks may also anesthetize the anterolateral chest wall. The PEC I block places local anesthetic in the plane between the pectoralis major and minor muscles to anesthetize the lateral and medial branches of the pectoral nerves, providing coverage over the anterior chest wall. PEC II is sited between the pectoralis major and serratus anterior muscles, which blocks the third through fifth intercostal nerves along with the intercostobrachial and long thoracic nerve. This provides a more extensive area of coverage of the anterior chest wall when combined with the PEC I block.^[8],[9] Thoracic paravertebral blocks may also be used for chest wall and parasternal coverage, but anticoagulation can be an issue. Also, the precise location of parasternal tunneling is somewhat variable. The distance between the lateral border of the sternum to the lead varies, and occasionally the lead may be placed on the opposite side of the sternum.

The S-ICD is a relatively new device, and the body of literature supporting the use of regional anesthesia for its placement is limited. (See Table 1 for a summary.) Ueshima and colleagues have described several case reports in which S-ICDs have been implanted under transversus thoracic muscle plane blocks, thoracic paravertebral blocks, and serratus plane blocks. In one successful case report, an ultrasound-guided paravertebral block was performed with 20 cc of 0.375% levobupivacaine at the left T5 level, followed by transversus thoracic muscle plane block with another 20 cc of 0.375% levobupivacaine.^[10] In two other cases, serratus plane block was performed with 30 cc of 0.25% levobupivacaine superficial to the serratus anterior muscle, followed by a transversus thoracic plane block between the third and fourth ribs with 20 cc of 0.25% levobupivacaine.^[11]

Table 1: Studies supporting use of subcutaneous implantable cardioverter defibrillators.

Authors	Publication Type	Block Performed	Outcome	Comments
Ueshima et al.10	Case report	Thoracic paravertebral, transversus thoracic plane	Patients avoided general anesthesia.	Paravertebral block performed at left T5 with 20 mL of 0.375% levobupivacaine; transversus thoracic plane block performed between third and fourth ribs at sternum with 20 mL 0.375% levobupivacaine
Ueshima et al.11	Case report	Transversus thoracic plane, serratus plane	Patients avoided general anesthesia.	Technique successful with two patients
Miller et al.12	Retrospective analysis	Transversus thoracic plane, serratus anterior plane	Deep sedation group’s opioid consumption was significantly lower.	Both groups received transversus thoracic and serratus plane block; 10 patients received deep sedation and 10 patients received general anesthesia
Droghetti et al.13	Retrospective analysis	Serratus anterior plane	11 of 12 patients avoided general anesthesia.	30 mL of 0.75% ropivacaine used in block

A feasibility study investigated S-ICD placement with the use of regional anesthesia and deep sedation. Patients received general anesthesia or deep sedation with nonopioid analgesics for S-ICD placement. Both groups received serratus anterior plane blocks and transversus thoracic plane blocks. The deep sedation group used no opioids and reported better pain scores than the general anesthesia group, demonstrating that the use of regional anesthesia is feasible for S-ICD placement.^[12]

A subsequent study evaluated 12 patients undergoing S-ICD placement with a serratus anterior plane block using 30 cc of 0.75% ropivacaine injected between the latissimus dorsi and serratus anterior. Patients underwent S-ICD placement and received sedation only immediately prior to defibrillation testing. One patient required conversion to general anesthesia because of pain during the procedure. Of note, the S-ICD was placed using a two-incision technique, which omitted a superior sternal incision and placed the generator between latissimus and serratus.^[13]

At our institution, preoperative PEC I and serratus plane blocks serve as an adjunct to general anesthesia to improve pain control, reduce opioid requirements, and facilitate hospital discharge. Additional parasternal coverage may be needed for S-ICD placement in the absence of general anesthesia. Although our patients are currently hospitalized for pain management following S-ICD placement, improved postoperative pain management may allow these cases to be performed on an ambulatory basis and may ultimately significantly decrease the cost of care.

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Additional parasternal coverage may be needed for S-ICD placement in the absence of general anesthesia.

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In summary, regional anesthesia may provide useful opioid-sparing analgesia or anesthesia during S-ICD placement. The selected regional anesthesia technique should provide coverage to the anterolateral chest wall and parasternal area. Use of regional anesthesia has the potential to avoid general anesthesia in a patient population that may be particularly sensitive to hemodynamic changes. More data are needed to solidify the optimal regional anesthetic technique for S-ICD placement, but initial data support a beneficial role for regional anesthesia for S-ICD placement.

References