Ultrasound-Guided Pectoserratus Plane Block and Superficial Serratus Anterior Plane Block for Subcutaneous Implantable Cardioverter-Defibrillator Implantation: A Comparative Study

Background

The first implantation of the classic cardioverter-defibrillator was conducted in 1980, and the procedure has become the standard electrotherapy for dangerous arrhythmias in thousands of patients worldwide [1–5]. The device consists of a defibrillating electrode in the right ventricle connected to a battery and an electronic system, which includes a capacitor, implanted under the skin of the left subclavicular region [6,7]. In the past decades, the world has seen a dynamic development of electrophysiological capabilities in the field of stimulation, defibrillation, and long-term electrotherapy. Among other things, the dynamic miniaturization of electronics and the improvement of electrode design have led to progress [8].

The long-term presence of electrodes in the venous system and heart chambers can be associated with numerous complications, including acute complications, such as pneumothorax, vascular bleeding, and perforation; subacute complications, such as vein thrombosis and lead dislodgement; and chronic complications, such as lead infection, endocarditis, chronic venous occlusion, mechanical lead failure, inappropriate shocks due to lead failure, lead-related tricuspid regurgitation, and need for extraction [8–20]. Therefore, the subcutaneous cardioverter-defibrillator (S-ICD) has been developed to reduce the risk associated with implanting electrodes into the venous system. It consists exclusively of batteries, an electronic system monitoring the electrical work of the heart, and a subcutaneous electrode, which does not require the implantation of electrodes into the heart chamber. Su et al, in their meta-analysis, showed lower long-term complications with S-ICD than with transvenous ICD [21–26].

In 2014, the first implantation of the S-ICD was performed in Poland; from then until 2021, approximately 450 S-ICD implantations were performed in Poland, and a few thousand worldwide [27–29]. Patients with contraindications to transvenous electrode implantation are qualified for implantation of the S-ICD. A significant limitation of S-ICD implantation is higher perioperative risk associated with general anesthesia or deep sedation. The growing population of patients with American Society of Anesthesiologists (ASA) risk classification of III or IV and who are qualified for S-ICD implantation, especially the group with reduced ejection fraction, poses a challenge to performing safe anesthesia in this group of patients [30–32].

Dynamically developing regional anesthesia techniques performed under the control of ultrasound within the chest to reduce the risk associated with general anesthesia and deep sedation for S-ICD implantation procedures encouraged anesthesiologists in the Department of Anesthesiology and Intensive Care in 4th Clinical Military Hospital to begin to anesthetize these patients using primarily regional fascial blocks. As a result, the anesthesia formula has been established in the form of a modified combination of fascial regional blocks, namely the pectoserratus plane block (PSP) and superficial serratus anterior plane block (S-SAP) [33–37].

The PSP block was formerly known as pectoral nerves plane block II (PECS II), but in 2021, the ASRA-ESRA Delphi international consensus standardized the naming of chest blocks, giving the PECS II block a new name [35,38].

The PSP block is a modification of the interpectoral plane block, formerly known as the pectoral nerves plane block I (PECS I); after the local anesthetic deposition between the pectoral muscles, an additional dose of a local anesthetic is administered to the fascial compartment between the pectoralis minor muscle and the serratus anterior muscle, blocking the lateral branches of the intercostal nerves Th2–Th6, the intercostobrachial nerve, and the long thoracic nerve. The PSP block can be used for the procedures described above and for more extensive breast surgery procedures (mastectomy, quadrantectomy, portacath implantation) [34,39,40].

The naming of the serratus anterior plane (SAP) block was unified in 2021 (ASRA-ESRA Delphi consensus) [38]. The original SAP block was divided into 2 separate blocks depending on the technique and anatomical place of anesthetic deposit: the S-SAP and the deep serratus anterior plane block. SAP blocks the lateral cutaneous branches of intercostal nerves located below the serratus anterior muscle within the region of Th3–Th9. The superficial variant of the block also includes the long thoracic and thoracodorsal nerve. Local anesthetics are administered in the fourth and fifth rib regions into the fascial space between the serratus anterior muscle and the latissimus dorsi muscle [38,40].

For S-ICD implantation, the use of other fascial blockades has been described: the deep parasternal intercostal plane block, formerly known as the transversus thoracis plane block, and the superficial parasternal intercostal plane block, formerly known as the parasternal block [41,42].

Therefore, in this study, we aimed to compare outcomes from ultrasound-guided PSP block and S-SAP block in 16 patients requiring a subcutaneous S-ICD, at a single center in Poland.

Material and Methods

ETHICAL CONSIDERATIONS:

This study was approved by the the Bioethical Committee of the Military Medical Chamber (approval No.: KB 2/21 180/21, date of approval: January 26, 2021). Written informed consent was obtained from all patients participating in the trial as a part of enrollment for research. The trial was registered prior to patient enrollment at the Australian New Zealand Clinical Trials Registry platform (ACTRN12621001386820, registration date: October 14, 2021). The study was conducted in accordance with the guidelines of the Declaration of Helsinki and Good Clinical Practice. The study was a non-randomized, uncontrolled, open label trial and did not meet the CONSORT criteria.

DESIGN AND SELECTION CRITERIA:

This single-center, prospective, and interventional pilot study initially involved 22 patients. Finally, the analysis was conducted on consecutive procedures of a group of 16 patients (Figure 1). The study included patients of both sexes aged 23 to 71 years with ASA grade III or IV anesthesia risk assessment [43] who were qualified for S-ICD at the Cardiology Department of the 4th Clinical Military Clinical Hospital in Wrocław in the period from October 2021 to June 2022, and qualified for planned S-ICD implantation for tachyarrhythmia treatment.

The exclusion criteria were as follows: patient under 18 years, lack of patient consent, coagulation disorder, known allergy to the study drugs, inflammation at the site of the planned block, missing data in the research protocol, or technical difficulties in the implementation of the block. The study was conducted without a control group, since patients who qualified for general anesthesia or deep sedation were deemed unsuitable by the anesthesiologist due to their high-risk profile. Although patients who only required local anesthesia could have been considered, there was a potential risk of exceeding the maximum local anesthesia dosage, ultimately leading to the exclusion of such patients from the study.

REGIONAL BLOCS APPLICATION:

In all patients, the procedure was performed on the anterolateral chest wall on the left side in order to maintain a short distance between the S-ICD subcutaneous electrode and the heart.

PREPARING THE PATIENTS FOR ANESTHESIA AND SURGERY:

For premedication, patients with a body weight >50 kg received 150 mg of pregabalin orally 30 min before the procedure. For patients with a body weight <50 kg, the dose of pregabalin was reduced to 75 mg. Anesthesia was performed by an anesthesiology resident with over 3 years of experience in performing regional blocks under the expert supervision of an anesthesiology and intensive care specialist. The S-ICD implantation procedure was performed by a team of 2 cardiologists: an operator with 20 years of experience in electrophysiology implantations who had performed the S-ICD procedure independently several times, and an attending physician with 2 years of experience in electrophysiology implantations who had assisted in the S-ICD implantation procedure several times.

The anesthesia protocol for the procedure was performed immediately before the surgery. The patients were placed on their back with slight support under the left shoulder and left thoracic region achieving a 10° to 15° tilt of the torso to the right side, with the abduction of the left limb in the shoulder joint by an angle of 90^o.

PSP APPLICATION:

For PSP application, after aseptic preparation of the injection site, a linear ultrasound probe (GE Vivid I with a 5–12 MHz linear probe) was placed parallel to the clavicle in the midclavicular line in the sagittal plane, locating the subclavian vessels. The probe was then moved toward the axillary fossa with a gradual rotation of approximately 90°. As the probe was moved laterally, successive ribs were counted down (the landmark being the axillary artery at the height of the second rib). After placing the probe at the height of the third rib, slightly medially from the anterior axillary line, individual anatomical structures were identified: pectoralis major and minor muscles, serratus anterior muscle, and intercostal muscles. After ultrasound identification of the anatomical structures at the level of the third rib, a guide needle (Vygon Echoplex with a diameter of 22 Ga and a length of 85 mm) was inserted using the in-plane technique, parallel to the deltoid-thoracic sulcus toward the lower pole of the axillary fossa at an angle of 30° to 45° (Figure 2A). After confirming that the intended space between the pectoralis major and pectoralis minor muscles had been reached, a local analgesic was deposited, achieving the delamination of fascial planes over a length of 6 cm and a width of at least 1 cm. The needle was then inserted deeper, and after identifying the space between the pectoralis minor muscle and the serratus anterior muscle, a local analgesic was deposited, thus anesthetizing the nerve structures located there: the lateral branches of the Th2–Th4 intercostal nerves, the medial and lateral pectoral nerve, and partially the long thoracic nerve (Figure 2C) [34,37,39–41].

S-SAP APPLICATION:

For S-SAP application, the probe was then moved caudally in a sagittal line halfway between the midclavicular line and the anterior axillary line, identifying the fifth rib. In a further step, the probe was moved in the direction of the axillary fossa in a parallel line between the mid axillary line and the posterior axillary line. The interfascial compartment between the latissimus dorsi and serratus anterior muscles was identified. The anatomical point that facilitates the identification of structures is the thoracodorsal artery, located in this space. The fourth intercostal space and the fourth and fifth ribs should be visible in the ultrasound image. After identifying the structures, a guide needle (Vygon Echoplex with a diameter of 22 Ga and a length of 85 mm) was inserted using the in-plane technique, parallel to the posterior axillary line from the axillary fossa in the caudal direction at an angle of 45° to 60° (Figure 2B), reaching the fascial compartment between the latissimus dorsi muscle and the serratus anterior muscle. A local anesthetic was deposited in the space in an amount sufficient to delaminate fascial planes over a length of 10 cm, and a width of at least 1 cm; on ultrasound images, delamination of the fascia at the level of the fourth and fifth ribs was achieved (Figure 2D). The extent of the block includes the Th3–Th9 intercostal nerves, as well as the thoracic-dorsal nerve and partially the long thoracic nerve. The maximum volume of the anesthetic mixture per both blocks was 60 mL [34,37,39,41,44–47].

In the case of insufficient skin anesthesia, before the skin incision in the mid axillary line, linear infiltration anesthesia was performed using 0.5% lidocaine with 0.005% epinephrine in a volume of 5 mL. In addition, in the case of insufficient skin anesthesia, separate local anesthesia was administered to the skin incisions in the left parasternal line and, if performed, in the region of the parallel incision to the manubrium of sternum 2/3 cm cephalad from the xiphoid process in a volume of 5 mL each of 0.5% lidocaine (Figure 3).

S-ICD IMPLANTATION:

After the start of the procedure, the patients remained in direct contact with the anesthesiologist. During this time, the implant team prepared the skin, subcutaneous tissue, and fascia, successively reaching the muscle layer at the level of the sixth intercostal space in the anterior axillary line. Then a pocket under the latissimus dorsi muscle measuring 5×5 cm was created “bluntly”. Using a bayonet guidewire, an electrode was implanted along the parasternal line, and at the level of the fifth intercostal space, a gentle subcutaneous arc tunnel was created into the pocket under the axillary fossa (Figure 4A) [24,26,44,48].

The procedure was performed using a 3-incision technique: the pocket and 2 incisions in the parasternal line. The subcutaneous ICD electrode (Q-TRAK, Boston Scientific, Marlborough, MA, USA) was then connected to the pulse generator (A209 EMBLEM model, Boston Scientific, Marlborough, MA, USA), attaching the system to the fascia (Figure 4B). The last part of the procedure was a test of the implanted device. After the device pocket was closed, defibrillation threshold testing was performed by induction of ventricular fibrillation and delivery of at least 1 shock from the S-ICD [45]. Before the test, all the patients received propofol intravenously (i.v.) at a dose of 1 to 2 mg/kg of body weight in a titrated bolus. Propofol dose for defibrillation threshold testing was not included to the list of i.v. anesthetics used for regional block before defibrillation threshold testing and is not shown in Table 1.

ANALGESIA PROTOCOL:

In the case of significant discomfort of a non-specific nature: squishing, pressure, or stretching, single doses of propofol at a dose of 0.1 to 0.5 mg/kg i.v. or ketamine at a dose of 0.1 to 0.5 mg i.v. were administered. In addition, for pain rated at more than 5 points on the NRS scale, a bolus of fentanyl at a dose of 0.5 to 1 μg/kg i.v. was administered.

OUTCOMES ASSESSMENT:

Pain was assessed during and after the procedure using the 11-point NRS scale [46]. In addition, after 24 h, the patient’s comfort was assessed using the QoR-15 questionnaire [47,49]. During the procedure, every 15 min, the patients assessed their pain comfort on the NRS scale, and the operator assessed the comfort of the procedure on the proprietary Operator’s Comfort Scale. This scale assesses 3 domains: (1) patient reaction to commands, (2) cooperation with the patient/stability of the surgical field, and (3) pain management/quality of anesthesia of deep tissues. Scoring is as follows: 3, good; 2, moderately good; and 1, unacceptable. Total score ranges are as follows: 9–8 points, indicating comfortable conditions for performing the procedure for the operator; 7–6 points, indicating difficult conditions for performing the procedure; and <6 points, indicating conditions categorically unacceptable.

POSTOPERATIVE CARE:

After the procedure, the patients were transferred to the Cardiac Intensive Care Unit for 24 h. On postoperative day 1, i.v. analgesics were routinely administered: paracetamol 1 g every 6 h, metamizole 1 g every 6 h, and ketoprofen 100 mg every 12 h, and oral pregabalin 75 mg in the evening. At discharge from the Cardiac Intensive Care Unit, the patients were evaluated with the Aldrete score, which consists of assessing 5 clinical criteria performed every 30 min. If a patient scored at least 9 points twice, no more than 30 min apart, they were discharged from the unit. On day 2 and day 3 after the procedure, oral analgesics were used: paracetamol and metamizole, at a dose of 1 g every 8 h.

STUDY ENDPOINTS:

The study protocol recorded the time of the procedure, time to the start of the procedure, duration of the procedure, volume of analgesics used in each block, total volume of local analgesics, mean arterial pressure, heart rate, respiratory rate, and total dose of anesthetics and i.v. analgesics until the device implantation was completed (Figure 5). Additionally, any adverse reactions and events within 24 h after the procedure were recorded. After the procedure, patients were asked to subjectively evaluate the technique when answering whether they would recommend it to a family member.

STATISTICAL ANALYSIS:

The statistical analysis was performed using Statistica 13 (TIBCO Software Inc., USA). The research is a preliminary report. The sample size will be estimated for future studies based on the results. Arithmetic means, medians, standard deviations, quartiles, and the range of variability (extreme values) were calculated for measurable variables. The frequency of their occurrence (percentage) was calculated for qualitative variables.

Results

PATIENT CHARACTERISTICS:

The analysis was conducted on a group of 16 patients. The basic anthropometric data and data on anesthesia, surgery, complications, and analgesic use after the procedure are shown in Table 2. The median age of the patients was 42.5 years; 81% were men.

LOCAL ANESTHESIA TYPE AND DOSAGE:

The use of local anesthesia, analgesics, anesthetics during the procedure, and adverse events during and 24 h after the procedure are shown in Table 1. Ropivacaine and lidocaine were used as the basic anesthetic mixture in the following concentrations for PSP: ropivacaine 0.25% + lidocaine 0.5% (n=16, 100%) as well as for S-SAP: ropivacaine 0.25% + lidocaine 0.5% (n=6, 37%) and ropivacaine 0.125% + lidocaine 0.25% (n=10, 63%). The mixture of ropivacaine and lidocaine in the concentrations used gave a rapid onset of anesthesia (lidocaine) and effective and long period of action (ropivacaine). In 8 patients (50%), non-opioid analgesics were additionally administered during the procedure. In 11 patients (69%), intraoperative fentanyl bolus was administered, in a dose not exceeding 200 μg. All patients received a single bolus of anesthetics in moments of significant discomfort (pocket preparation, implantation of the subcutaneous electrode). Three adverse effects were observed during the procedure: 2 episodes of moderate hypoglycemia with the patient’s agitation during the block, and 1 episode of hypertension above 180/110 mmHg.

The mean volume of the local anesthetics mixture for PSP was 19.4 mL, and the mean volume of the local anesthesia mixture for S-SAP was 34.7 mL. The mean total volume of local anesthesia for both blocks was 54.1 mL.

PERFORMANCE TIME OF ANESTHESIA AND SURGERY:

Performance time for the block for the PSP block was 21.3 min. The time interval between block completion and start of surgery was 49.7 min; the mean time of the S-ICD implantation alone (surgery) was 108.4 min. Neither circulatory nor respiratory instability was observed during the procedure. The operator’s assessment of the procedure’s comfort was high (Q3 was 9 points); 94% of patients asked whether they would recommend the technique to their family members answered yes.

The value of the Aldrete score, indicating the possibility of safe transfer of the patient from the Cardiac Intensive Care Unit to the general ward 24 h after the procedure was high, and the upper quartile was 10 (maximum value).

PATIENT EVALUATION AND ADVERSE EFFECTS:

Results of patient pain assessment on the NRS scale and patient satisfaction during the first 24 h after the surgery on the QoR-15 score, including subsequent domains, are shown in Table 3. The intraoperative NRS score was very low (Q3=1 point, max=2 points), which indicated a very good analgesic effect of the block. Similarly, the pain assessment 24 h after the procedure was good (Q3=2 points, max=4 points). The mean postoperative patient satisfaction score on the QoR-15 was 133.9 points. Two adverse events were observed 24 h after the procedure: confusion with short-term memory disorders after implantation lasting <1 h, and nausea without vomiting until 2 h after the procedure.

Discussion

STUDY LIMITATIONS:

This study had several potential limitations, such as the lack of randomization and the small sample size of the study group. The primary endpoint of the study was the pain intensity reported by the patient in the different phases of the procedure and the postoperative period, as measured on a verbal rating scale. Pain intensity is a subjective parameter, and its assessment was not blinded.

Conclusions

The results of this pilot study confirm the feasibility and safety of using a combination of S-SAP and PSP blocks to provide anesthesia and analgesia during S-ICD implantation in patients with high operative risk (ASA grade III or IV). This technique eliminates the need for general anesthesia or deep sedation and has shown good efficacy. However, further large-population randomized studies are required to validate these findings. If the results are confirmed, the combined SAP and PSP blocks may represent a valuable alternative to general anesthesia or deep sedation for optimal anesthesia and analgesia during S-ICD implantation.