Regional Anesthesia for Cardiac Surgery

Abstract

Cardiac surgery is associated with significant postoperative pain, regardless of surgical approach. Median sternotomy and thoracotomy are particularly traumatic, resulting in pain that typically lasts weeks and may lead to chronic pain syndromes. Even newer minimally invasive procedures involving mini-thoracotomy and other smaller incisions are not pain-free, while the presence of chest tubes also causes significant discomfort. Uncontrolled pain following cardiac surgery contributes to adverse outcomes, particularly pulmonary complications and prolonged lengths of stay. Intravenous opiates alone or in combination with other sedatives are imperfect solutions to this problem as they are associated with excess sedation, nausea, vomiting, pruritis, delirium, constipation, and dependence. In recent years, regional anesthesia techniques have increasingly been utilized for cardiac surgery as part of enhanced recovery after cardiac surgery pathways. In many cases, techniques that were developed for other surgical procedures, particularly breast surgery, have been applied to the cardiac surgical population with favorable results. However, many practicing cardiac anesthesiologists have limited experience with these regional anesthesia techniques, so implementing them into clinical practice effectively can be challenging. This chapter aims to address this gap by reviewing the evidence, techniques, and applicability of the regional anesthesia approaches appropriate for cardiac surgery patients.

1. Introduction

Effective pain management is crucial in cardiac surgery to optimize patient outcomes and reduce postoperative complications. Cardiac anesthesia has significantly changed over the last 50 years, evolving from earlier techniques that utilized high doses of opiates and other narcotics to a more balanced approach that incorporates the principles of enhanced recovery after cardiac surgery (ERACS). This review aims to provide a comprehensive overview of the regional anesthesia techniques currently in use for cardiac surgeries, including median sternotomy, thoracotomy, and minimally invasive approaches. The relevant anatomy, technique, and pharmacology for each regional technique will be described as well as their clinical applications, complications, and contraindications. The techniques will be described in anatomical order, centrally to peripherally, beginning with neuraxial approaches and ending with the most peripheral parasternal nerve blocks.

2. Neuraxial techniques

Spinal and epidural anesthesia and analgesia techniques involve administering local anesthetics, with or without adjuvant medications, into either the subarachnoid or epidural space, respectively, providing potent sensory, motor, and sympathetic depression in the region of the block. The use of neuraxial techniques in cardiac surgery has been controversial due to the potential for hemodynamic instability and the concern for spinal or epidural hematoma [1]. However, evidence suggests that appropriate use of these techniques has numerous advantages, including improved patient outcomes and healthcare cost savings [2].

2.1 Anatomical considerations

The spinal cord is protected by the cervical (C1-7), thoracic (T1-12), and lumbar vertebrae (L1-5) and is encased by three membranes: the dura, arachnoid, and pia mater. The dura encases the brain, spinal cord, and the spinal nerve roots, which are suspended in cerebrospinal fluid. The location of the caudal end of the spinal cord, or conus medullaris, is somewhat variable between individuals, usually terminating at the level of L1 or L2 in adults and L3 in children. Therefore, spinal anesthesia is usually performed at the level of L3/4 or L4/5 to avoid damage to the spinal cord. Intrathecally injected local anesthetics exert their effects directly on the spinal cord and the emerging spinal roots, providing potent nerve blockade with relatively small doses of local anesthetic [3].

The epidural space surrounds the dura from the foramen magnum to the sacrococcygeal ligament and is defined by the ligamentum flavum posteriorly, the vertebral pedicles laterally, and the posterior longitudinal ligament anteriorly. It contains fat, epidural blood vessels, lymphatics, and the spinal nerve roots. Local anesthetics injected into the epidural space exert their effects at these nerve roots and on the spinal cord itself via diffusion through the dura [4]. For this reason, much larger doses of local anesthetics must be administered to achieve the desired effect compared to intrathecally injected medications. However, this also allows epidural anesthesia to be more easily titrated to a desired level of sensory or motor blockade. Further, because epidural anesthesia does not involve puncture of the dura, there is little risk of direct spinal cord trauma, and the technique can be applied anywhere from the mid-thoracic to the lower lumbar regions [5].

2.2 Epidural anesthesia and analgesia

Thoracic epidural anesthesia has been used to augment general anesthesia and provide postoperative pain control in the cardiac surgery population for more than 20 years. A large meta-analysis of 51 randomized clinical trials found that compared to general anesthesia alone, thoracic epidural anesthesia decreased ICU length of stay (LOS), hospital LOS, and time to extubation. Statistically significant improvements in pain scores, pulmonary complications, arrhythmias, transfusion requirements, and delirium were also identified [6]. Other contemporary meta-analyses have yielded similar findings [7, 8], with one of these also finding a modest decrease in mortality [7].

Recently, neuraxial blockades have been gaining attention in pediatric cardiac surgery [9]. Compared to general anesthesia alone, caudal anesthesia may provide superior pain control [10]. Caudal anesthesia has also been shown to decrease intraoperative opioid usage [11], decrease the time to extubation, and reduce hospital LOS [12]. However, there have been conflicting reports in the literature regarding the potential for hemodynamic instability following caudal anesthesia in pediatric patients undergoing cardiac surgery [10, 13, 14].

2.2.1 Technique

Thoracic epidural catheters may be inserted using either a midline or paramedian approach. In the midline approach, the epidural needle (typically a 17 or 18G Touhy) is inserted into the middle of the patient’s back between two spinous processes. The needle is advanced through the supraspinous ligament and interspinous ligament. Once the needle has reached the interspinous ligament, the stylet is removed and a syringe is attached to enable the detection of loss of resistance to air, saline, or both, which represents penetration of the ligamentum flavum and identification of the epidural space.

For the paramedian approach, the epidural needle is introduced 1 centimeter lateral and 1 centimeter caudad to the inferior portion of the superior spinous process. The needle is advanced until the lamina of the vertebral body below is encountered. The needle is then directed 15–20° medially before advancing cephalad such that the needle “walks off” the lamina until the ligamentum flavum is encountered. A loss of resistance technique is then used as in the midline approach.

The paramedian approach may be a better option for patients who cannot flex their spine or when midline approaches are unsuccessful. For the midline approach in the thoracic region, the epidural needle must take a steeply angled trajectory parallel to the direction of the spinous processes. For this reason, some practitioners prefer the paramedian approach for thoracic epidurals [15]. The paramedian approach can also be facilitated by real-time ultrasound guidance [16] and may be associated with less procedure-related back pain compared to the midline approach [17].

The caudal approach to the epidural space is used frequently in pediatrics. The epidural space is accessed through the sacral hiatus, which is a foramen formed by the nonunion of the fifth sacral vertebral body. To perform a caudal block, the patient is positioned either lateral or prone and the sacral hiatus is identified as the apex of an equilateral triangle formed together with the superior inferior iliac spines. The bony processes, called the sacral cornua, on either side can also be palpated to identify the space. The epidural needle is inserted at a 45° angle directed cephalad until a popping sensation is felt as the needle pierces the sacrococcygeal membrane. The needle is then flattened until it is nearly parallel to the plane of the skin and advanced into the sacral canal until loss of resistance is encountered [18].

2.2.2 Complications and contraindications

Any patient with a spinal cord injury, epidural or spinal cord hematoma, intracranial hypertension, or vertebral fracture is not a candidate for neuraxial anesthesia due to a high risk of neurological complications [1]. Patient refusal, bacteremia, and infection at the insertion site of the epidural needle are also absolute contraindications [19]. Patients with coagulopathic disorders such as hemophilia should not receive neuraxial anesthesia due to the increased risk of epidural or spinal hematoma. Generally, a platelet count of less than 50,000 per microliter or an INR greater than 1.5 is also considered absolute contraindications [1].

Because many cardiac surgery patients are maintained on anti-platelet and other anti-coagulant agents, it is important to observe the American Society of Regional Anesthesia and Pain Management guidelines regarding how long these drugs should be discontinued before neuraxial anesthesia and when it is safe for them to be resumed post-procedure [20]. Many cardiac anesthesiologists have been reluctant to incorporate epidural anesthesia into their practice because of a concern that systemic heparinization required for cardiopulmonary bypass increases the risk of epidural hematoma, a devastating complication that can lead to permanent paralysis. The literature is unclear regarding exactly how high this risk is in the cardiac population, with some authors finding that the rate may be as high as 1 in 3552 [7], while others have estimated the value as 1 in 12,000, a rate similar to that observed in the non-obstetric non-cardiac surgery population [21].

2.3 Spinal anesthesia and analgesia

The use of spinal anesthesia in cardiac surgery has been limited, however, authors from one center have reported using bupivacaine and opiates intrathecally to augment general anesthesia in over 10,000 cardiac surgery patients. They also reported no incidents of spinal hematoma and favorable pain control [1]. Another group found intrathecal morphine administered prior to minimally invasive cardiac surgery decreased visual analog pain scores and intravenous opiate usage post-operatively [22]. A meta-analysis of intrathecal morphine compared to general anesthesia alone in cardiac surgical patients also found decreases in pain scores and post-operative opiate use at the expense of increased pruritis [23].

2.3.1 Technique

The intrathecal space may be accessed using either a midline or paramedian approach, as described above for epidural anesthesia. Unlike the epidural technique, a much smaller needle (typically a 25-27G cutting or pencil point needle) is used to deliberately pierce the dura until free-flowing CSF is observed to exit the needle. After this, the desired amount of local anesthetic or adjuvant medication is injected into the subarachnoid space [3].

2.3.2 Complications and contraindications

Contraindications to spinal anesthesia are similar to those for epidural anesthesia, including patient refusal, coagulopathy, neurologic dysfunction, intracranial hypertension, local skin infection, and bacteremia. Unlike epidural anesthesia via a catheter, in which local anesthetic can be introduced gradually into the epidural space, spinal anesthesia requires that these agents be injected as a single shot. This can have more profound and abrupt changes in hemodynamics and may not be tolerated by patients who are dependent on the maintenance of preload or blood pressure, such as those with severe aortic stenosis.

While spinal anesthesia also confers a risk of neurologic damage from hematoma formation, this risk is substantially less than that for epidural anesthesia [24]. Because spinal anesthesia necessitates a puncture of the dura, there is also a risk for post-dural puncture headache of up to 25%, however, the incidence in the cardiac surgical population is not well established.

3. Posterior thoracic wall blocks

The thoracic paravertebral plane block (PVB) and erector spinae plane block (ESPB) with or without catheter placement have emerged as potential options for providing effective analgesia following cardiac surgery, particularly those performed via thoracotomy such as thoracic aneurysm repair, mitral valve procedures, and minimally invasive cardiac surgery procedures.

3.1 Anatomical considerations

The PVB involves the injection of local anesthetic into the paravertebral space (PVS), which is located just anterior to the transverse process and lateral to the vertebral bodies. It is a triangular space bounded by the superior costotransverse ligament, the vertebral body, and the pleura. This space contains the paravertebral sympathetic chain, intercostal nerve roots, and associated blood vessels (Figure 1). The block targets the spinal nerves as they emerge from the intervertebral foramina before they split into the ventral and dorsal rami, as well as the thoracic sympathetic nerves which mediate visceral pain. This makes the PVB more complete compared with other chest wall blocks with an area of analgesic distribution that makes it appropriate for a variety of thoracic procedures, including sternotomy. Just posterior to the paravertebral space is the retro-superior costotransverse space (RSCTS). This is bounded by the superior costotransverse ligament, the transverse process and the erector spinal muscle. There are communications between the RSCTS and the PVS, so injectate administered in the RSCTS will reach the PVS as well [25].

Figure 1.

The anatomy of the paravertebral space (green). PVS: paravertebral space; SCTL: superior costotransverse ligament; and DRG: dorsal root ganglion.

The ESPB, on the other hand, involves injection of local anesthetic into the erector spinae muscle plane which is located lateral to the transverse process of the vertebrae. The local anesthetic spreads along this fascial plane, acting on the dorsal and ventral rami, blocking the posterior and lateral cutaneous intercostal nerves. Some of the injectates may penetrate the paravertebral space, potentially blocking multiple levels of spinal nerves, although not as densely as the PVB. While a T2-10 block is possible with the ESPB, the distribution is highly variable in clinical practice [26].

3.2 Paravertebral block

Unilateral PVB has been shown to improve patient outcomes for a variety of thoracic procedures, including thoracic aneurysm repair. Bilateral PVB for sternotomy has also been shown to decrease the time to extubation and the need for intra- and post-operative intravenous opiates in both adults and children [27].

3.2.1 Technique

The PVB is typically performed at the level of the surgical incision or one or two vertebral levels above and below the surgical site, depending on the dermatomal distribution of the surgical field. Although originally described using a loss of resistance technique [28], real-time ultrasound guidance has now become the standard approach. The anatomy is best visualized using a linear or curvilinear ultrasound probe in the parasagittal orientation 2.5 cm lateral to the spinous process (Figure 2). The block may be performed with the patient in a sitting, lateral, or prone position. The injection is usually performed in-plane, and the needle may be directed either cranially or caudally [29].

Figure 2.

(A) Ultrasound image for ESPB or PVB. (B) Labeled ultrasound image showing proper needle trajectory and injection site for the ESPB (blue arrow) and PVB (red arrow). ESM: erector spinae muscle; TP: transverse process; SCTL: superior costotransverse ligament; PVS: paravertebral space; and ICM: intercostal muscle.

The PVB can also be performed with the ultrasound probe in the transverse orientation, and the PVS identified by identifying the transverse process and then scanning either cranially or caudally [30]. One cadaveric study found this approach was slightly less successful than the parasaggital approach [31]. With either technique, the needle should be placed anterior to the superior costotransverse ligament, and a 3 mL test dose administered demonstrating anterior displacement of the pleura [29]. The dosage of local anesthetic for a single injection is 20–25 mL or 4–5 mL per level, and for catheter placement, a continuous infusion of local anesthetic at 0.1–0.2 mL/kg/h is often used [32].

3.2.2 Complications and contraindications

Because of the proximity to the spine, rare complications of the PVB can include epidural or spinal hematoma or infection. If a catheter is placed, this is more likely if the catheter is advanced more than 3–4 cm beyond the needle tip. Pneumothorax is also possible, and the risk is minimized with proper use of ultrasound. More common reactions include hemodynamic instability due to sympathetic blockade, which is more likely to occur after a bolus of more concentrated preparations of local anesthetic. The overall risk of adverse effects is roughly 5% [33]. However, a recent meta-nalysis of PVB compared to thoracic epidural for open thoracotomy, found that while analgesia was similar between the two techniques, PVB was associated with less nausea, vomiting, urinary retention, and hypotension [34].

3.3 Erector spinae plane block

The ESPB can be used either as a single-shot or continuous catheter-based technique for either preemptive or rescue analgesia for patients undergoing thoracotomy or other thoracic surgery. Some studies, including those on cardiac surgery patients, have found equal analgesic benefits when compared to PVB, but with a lower risk of hypotension, bradycardia, and hematoma [35, 36].

3.3.1 Technique

The ESPB is typically performed at the level of the surgical site or one or two vertebral levels above or below the surgical field, depending on the spread of the local anesthetic needed. The ultrasound probe should be oriented in the parasagittal plane approximately 2.5 cm lateral to the spinous process similar to probe placement for the PVB (Figure 2). It may be possible to identify the three overlying muscle layers: the trapezius, rhomboid, and erector spinae. The needle should be directed in-plane either cranially or caudally with injectate directed just deep to the erector spinae muscles. If correctly placed, the injectate should demonstrate lifting of the erector spinae muscle off transverse process [37].

3.3.2 Complications and contraindications

The risk of complications with the ESPB is thought to be low, but pneumothorax, and motor blockade, have been reported [38, 39, 40]. Like the PVB, there is a rare but potential risk of neurologic complications, including epidural or spinal hematoma. However, this risk is less than with PVB because of the more lateral point of needle insertion away from the spinal cord. Sympathetic blockade may also be observed resulting in hypotension. While either the PVB or the ESPB can be expected to cover 4 dermatomes if 30 ml of local anesthetic is used, the distribution and degree of coverage are more variable and less complete with the ESPB.

4. Lateral chest wall blocks

The lateral chest wall blocks are relatively new techniques, only coming into use within the last decade. Although ineffective in providing analgesia for median sternotomy, these blocks can be useful for procedures involving incisions of the lateral chest, including thoracotomies and newer minimally invasive approaches to coronary bypass [41]. The pectoralis nerve block type I (PECS I), pectoralis nerve block type II (PECS II), and serratus anterior plane block (SAP) all achieve analgesia by blocking the intercostal and pectoral nerves at different points along the chest wall [42, 43, 44].

4.1 Anatomical considerations

The sensory innervation of the anterior and lateral chest wall is mainly carried by the intercostal nerves (T1–T11). After exiting the vertebral foramen, each thoracic spinal nerve travels anteriorly via ventral rami. Initially, the ventral rami travels between the innermost intercostal muscle and the internal intercostal muscle. As the intercostal nerve reaches the midaxillary line, the lateral cutaneous branch crosses the intercostal and serratus anterior muscles, providing sensory innervation to the lateral chest wall. The rest of intercostal nerve continues to course toward the sternum and pierces the internal and external intercostal muscles as well as the pectoralis major muscle, providing sensory innervation to the anterior chest wall via the anterior branch [45]. The sensory innervation to the lateral chest wall is also supplied by the branches of the brachial plexus, most notably the lateral pectoral nerve [46].

4.2 Pectoralis nerve block type I and II

The PECS I block was first described by Blanco in 2011 as an effective post-operative analgesia block for patients undergoing breast surgery [42]. It is an inter-fascial plane block in which local anesthetic is injected between the pectoralis major and pectoralis minor at the level of the third rib [45]. The PECS I aims to block the medial and lateral pectoral nerves which are branches of the brachial plexus. These two nerves mostly provide motor innervation; however, the lateral pectoral nerve also provides sensory innervation to the anterolateral chest wall. The distribution of analgesic coverage provided by PECS I depends on the location of the injection of local anesthetic. If injected more medially, the local anesthetic can spread toward the midline, providing anterior chest wall coverage by blocking the anterior intercostal nerve branches [47].

The PECS II block, introduced a year after PECS I, targets a deeper fascial plane between the pectoralis minor and serratus anterior, blocking the anterior divisions of the thoracic intercostal nerves from T2–T6, the long thoracic nerve, and the thoracodorsal nerve [43]. The coverage of the anterior cutaneous intercostal nerves provides more anterior chest wall coverage compared to PECS I [48]. As a result, PECS II is rarely performed in isolation and is instead used in addition to PECS I such that analgesic coverage is provided to the anterior and lateral portions of the chest wall.

The PECS I and II blocks are used widely for patients undergoing breast surgery and there is a limited body of evidence supporting their use in thoracotomies and video-assisted thoracic surgeries, often in combination with the SAP block [49]. One randomized controlled trial (RCT) of 100 adult patients undergoing cardiac surgery via thoracotomy demonstrated the superiority of both the PECS II and SAP blocks compared to intercostal nerve blocks in terms of reduced need for fentanyl rescue and improved visual analog scale (VAS) scores at 8, 10, and 12 hours [50]. These investigators also reported similar findings in a pediatric population undergoing thoracotomy for cardiac surgery [51]. There are also reports of the PECS II block being used either alone or in combination with general anesthesia for cardiac device implantation and transcatheter cardiac procedures [49]. While several groups have reported using PECS I and II blocks either alone [52] or in combination with parasternal blocks [53] for post-sternotomy analgesia, there is only one RCT of 40 adult patients showing superior analgesia and decreased opioid requirements compared to patients receiving systemic opioids [48].

4.2.1 Technique

The PECS I and II blocks are performed under ultrasound guidance. The patient is positioned supine with the ipsilateral arm either beside the chest or abducted at a 90° angle. With the probe in the parasagittal plane, the subclavian vessels are identified along with the second rib. The probe is then moved inferiorly to the level of the third rib where the pectoralis major and minor muscles are identified. Once the pane between the pectoralis major and minor is identified, the needle is inserted into the plane using an in-plane technique, and the local anesthetic is injected at the inter-fascial plane between the two muscles [42].

When performing both blocks, PECS II is usually performed first with the injection of local anesthetics between pectoralis minor and serratus anterior (Figure 3). The needle is, then, withdrawn to the fascial plane between pectoralis major and pectoralis minor for PECS I block [43].

Figure 3.

(A) Ultrasound image for PECS I and II block. (B) Labeled ultrasound image showing proper needle trajectory and injection site for the PEC I (blue arrow) and PEC II (red arrow). SAM: serratus anterior muscle; Pec Maj: pectoralis major muscle; and Pec Min: pectoralis minor muscle.

4.2.2 Complications and contraindications

PECS I & II are considered very safe blocks with the very low rate of complications. Possible complications associated with PECS I & II include injury to the thoracoacromial artery, hematoma, infection, pneumothorax, intravascular injection, and local anesthetic systemic toxicity (LAST) [41].

4.3 Serratus anterior nerve plane block

The SAP block was the third chest wall fascial block described by Blanco and colleagues in 2013. In comparison to PECS II, SAP block has more inferolateral level of injection and has a wider spread, which makes it a popular choice for patients undergoing breast surgery or thoracic surgeries. The SAP block provides coverage of the anterior, lateral, and posterior chest wall; however, it does not extend to the midline and is, therefore, inappropriate for median sternotomy [44].

Although the lack of anterior chest wall coverage limits its use for cardiac surgery with sternotomy, SAP block has a potential role in postoperative analgesia in cardiac surgery patients undergoing thoracotomy incisions. Currently, there is no study of SAP block on patients undergoing median sternotomy; however, given the wide use of SAP block for video-assisted thoracoscopic surgery, SAP block may have a role in patients undergoing minimally invasive cardiac surgeries that require mini thoracotomy incisions [49]. One limiting factor is that mini-thoracotomy incisions for minimally invasive cardiac surgery are usually located at the anterolateral chest, which may not be adequately covered by the SAP block alone. In this case, based on the expected coverage, PECS II block may be required to supplement the SAP block. Likewise, if SAP block is used for patients undergoing sternotomy, it is recommended that SAP be performed along with transversus thoracic muscle plane (TTP) or PECS II block [54].

4.3.1 Technique

There are two fascial targets for SAP: superficial and deep. For the superficial SAP, the local anesthetic is injected at the fascial plane between Latissimus dorsi muscle and serratus anterior muscle. For the deep SAP block, the local anesthetic is injected below the serratus anterior muscle (Figure 4). It is unclear whether one technique is better than the other; however, it has been suggested that deep SAP may have a more anterior spread of local anesthetic, thereby providing slightly more anterior coverage [44].

Figure 4.

(A) Ultrasound image for SAP block. (B) Labeled ultrasound image showing proper needle trajectory and injection site for the deep SAP block (blue arrow) and superficial SAP block (red arrow). SAM: serratus anterior muscle; Lat: latissimus dorsi muscle; and ICM: intercostal muscle.

As with all plane blocks, the spread is dependent on the volume of local anesthetics. It is recommended that 30–40 mL of long-acting local anesthetic be injected for adequate spread while staying under the maximum limit to prevent LAST [41].

4.3.2 Complications and contraindications

Like PECS I & II, SAP block also has a very low rate of complication. Potential complications of SAP are similar to the complications of PECS I & II, with an additional risk of winging of scapula from the blockade of long thoracic nerve for superficial SAP as the long thoracic nerve runs on top of the serratus anterior muscle [41].

5. Parasternal blocks

Parasternal blocks are emerging techniques that can provide targeted pain relief in the anterior thoracic wall, which is commonly incised during cardiac surgery. Among the various parasternal blocks, pecto-intercostal fascial plane block (PIFB) and transversus thoracic plane block (TTP) are commonly used for postoperative pain management following median sternotomy [55]. Additionally, the subcostal transverse abdominal plane block can be used for subxiphoid chest tube coverage in cardiac surgery. Both the PIFB and the TTP can be used as part of a multimodal analgesic approach in cardiac surgery to provide effective pain relief and reduce the need for systemic opioids. They are relatively simple to perform, provide effective analgesia and have a low risk of adverse effects. Subsequently, the European Society of Regional Anesthesia and Pain Therapy recently added parasternal blocks to their recommendations for managing post-sternotomy pain [56]. These blocks can be performed preoperatively, intraoperatively, or postoperatively and they can be used in combination with other regional anesthesia techniques, such as thoracic epidural analgesia or paravertebral block, to achieve optimal pain control.

5.1 Anatomical considerations

To understand the parasternal blocks, it is important to review the relevant anatomy. The thoracic wall is composed of intercostal muscles, nerves, blood vessels, and fascial planes. The intercostal nerves originate from the anterior rami of the thoracic spinal nerves and course around the lateral chest wall between the internal and innermost internal costal muscles. As the intercostal nerves approach the sternum, they lie between the transversus thoracic muscle and the internal intercostal muscle before piercing the external intercostal membrane as the anterior cutaneous branch [41]. This same facial plane also contains the internal mammary artery and vein which run on either side of the sternum. It is important to identify and avoid these structures when performing parasternal blocks [57]. The anterior cutaneous branch subsequently gives rise to a medial and lateral branch, providing sensory innervation of the skin, subcutaneous tissue, and periosteum of the sternum [41].

5.2 Pecto-intercostal fascial block

The PIFB, also known as pectoral nerve block or pectoral fascial plane block, involves injecting local anesthetic into the plane between the pectoralis major muscle and the intercostal muscles [58, 59]. This is a superficial block, that aims for a T2–T6 sensory blockade of the anterior cutaneous nerve as it makes it way anteriorly. The PIFB is commonly used for pain management in surgeries involving median sternotomy, such as coronary artery bypass grafting (CABG) or valve surgery. The PIFB has been shown to reduce postoperative intravenous opiate consumption, improve pain scores and may decrease the time to extubation following sternotomy [55, 59, 60]. One recent randomized controlled trial compared the TTP to the PIFB and found that they were equivalent in analgesic effectiveness [61].

5.2.1 Technique

Using the ultrasound probe in the parasagittal orientation immediately lateral to the sternum, the rib above and below the desired site of injection are identified. The needle is directed cephalad at an angle of approximately 45° relative to the skin. A popping sensation is often appreciable when the needle enters the facial plane between the pectoralis major muscle and the intercostal muscle. Some practitioners advocate aiming for the inferior surface of the superior rib and then backing the needle back slightly to access the space (Figure 3). A test injection of saline should result in an expansion of the space between the two muscle groups. Relatively large volumes of local anesthetic, such as 0.25% bupivacaine or 0.2% ropivacaine, are typically used (20–30 mL per side) to achieve a successful field block. The volume injected can be administered at one site or divided among different intercostal levels which may provide a better spread of local anesthetic [41, 57].

5.2.2 Complications and contraindications

The PIFB is considered a very safe block with a low rate of serious complications. However, care must be taken to avoid inadvertent puncture of the pleura or the pericardium with the block needle. Generally, the PIFB is considered lower risk compared to the TTP block as the facial plane targeted is more superficial and further from the pleura and pericardium [61, 62]. Sterile technique should be fastidiously maintained to avoid infection, particularly in the setting of sternotomy as this could contribute to sternal wound infections. However, a recent meta-analysis of 18 studies evaluating parasternal blocks found no difference in the rate of sternal wound infections compared to control [55]. Appropriate dosing of local anesthetic based on patient weight is also important given the high volumes utilized to avoid LAST [63].

5.3 Transversus thoracic plane block

The transversus thoracic plane (TTP) block is another parasternal block technique that targets the neurovascular plane between the intercostal muscles and the transversus thoracic muscle. The transversus thoracic muscle is very thin and often difficult to distinguish on ultrasound, such that the target area for the block usually appears as a potential space immediately above the pleura. The TTP block is used for post-operative pain management following median sternotomy.

5.3.1 Technique

The ultrasound is oriented in the parasagittal plane at a point somewhat more lateral to the sternum than for the PIFB, typically between the fourth and fifth ribs. The block needle is advanced in-plane at a steeper angle than that utilized for the PIFB until the needle tip traverses the intercostal muscle and enters the space (Figure 5). It is important to identify and avoid the internal mammary artery and vein. Local anesthetic dosing is like the PIFB and should be injected slowly under visualization with periodic aspiration to avoid intravascular injection.

Figure 5.

(A) Ultrasound image for PIFB or TTP block. (B) Labeled ultrasound image showing proper needle trajectory and injection site for the PIFB (blue arrow) and TTP block (red arrow). ICM: intercostal muscle; and TTM: transverse thoracic muscle.

5.3.2 Complications and contraindications

Because the TTP block is deeper than the PIFB, there is a greater risk of puncturing the pleura or pericardium with the block needle. It is important to visualize the internal mammary artery in the long axis to avoid inadvertent puncture of this vessel or unintended arterial injection. The technique is contraindicated following internal mammary artery harvest for coronary bypass surgery as the transversus thoracic muscle is deroofed and the injected local anesthetic will spill into the pleural space [57].

5.4 Transverse abdominal plane block

The transverse abdominal plane (TAP) block has gained popularity in recent years as a component of post-operative multimodal analgesia for abdominal surgeries. When performed in the subcostal region, the TAP block can provide coverage for the subxiphoid chest tube insertion sites typically used for cardiac surgery. The TAP block in this setting is typically used to augment other regional techniques, such as the PIFB and TTP that do not adequately cover chest tube insertion sites. The TAP block involves the injection of local anesthetic between the internal oblique and transverse abdominus muscle and blocks the anterior cutaneous nerves of the T6–T9 dermatome.

5.4.1 Technique

The ultrasound is positioned in the transverse plane immediately caudal to the costal margin on the anterior axillary line. The needle is inserted medial to the probe and is advanced laterally in plane through the rectus abdominus or the linea semilunaris until the space between the transverse abdominus and internal oblique is accessed. Like most other plane blocks, typically large volumes of local anesthetics are used for the subcostal TAP block to achieve adequate distribution. It is important select concentrations and dosages of local anesthetics that do not exceed established safety limits as the subcostal TAP block for cardiac surgery is usually performed in conjunction with the PIFB or TTP block.

5.4.2 Complications and contraindications

TAP blocks have been used widely for approximately 20 years and have an excellent safety record. Inadvertent puncture of abdominal viscera is possible but occurs infrequently if ultrasound guidance is used appropriately. Avoidance of LAST through careful consideration of drug dosages and concentrations is important if the block is performed in conjunction with other regional anesthesia techniques.

6. Conclusion

While the approaches to cardiac surgery were once limited to median sternotomy and thoracotomy, recently surgeons have expanded the use of minimally invasive and percutaneous approaches. However, cardiac surgery continues to be associated with significant postoperative pain which if left uncontrolled can be an impediment to patient recovery. The shortcomings of opiates in mitigating postoperative pain in cardiac surgery patients are many, and anesthesiologists are increasingly utilizing regional anesthesia techniques to reduce the use of these drugs. This review has described the major regional anesthesia techniques being implemented in cardiac surgery patients today, including the contemporary evidence supporting their use.

There is no “one-size-fits-all” approach to regional anesthesia in the cardiac patient, and the specific technique or techniques utilized should depend on the site of the surgical incision, patient factors, and the technical repertoire of the anesthesiologist in question. Institutional factors should also be considered. For example, implementing catheter-based techniques would be unwise if there is not a multidisciplinary team in place to manage the catheters postoperatively. Similarly, integrating regional anesthesia techniques into clinical workflow can be challenging, and should consider the institutional resources available. While some centers rely on cardiac anesthesiologists performing these blocks themselves in the operating room, others have found utilization of a “block team” and pre-operative or post-operative timing of the regional anesthesia procedure to be the most efficient option. Regardless of logistical hurdles, integrating regional anesthesia into the care of cardiac surgical patients has the potential to improve patient outcomes and achieve cost savings for the hospital by reducing length of stay and postoperative complications.

Conflict of interest

The authors declare no conflicts of interest.