Fascial plane regional anaesthesia techniques

Peri-operative pain management and a reduction in stress response to cardiac surgery has traditionally been accomplished with opioids, but these agents also have a negative effect on enhanced recovery after surgery (ERAS). Techniques based on reducing opioid use is associated with fewer side effects and earlier patient recovery. Increasing pressure to provide efficient patient care while improving patient outcomes has led to a recent surge in administering regional techniques for cardiac surgery as part of a multimodal pain management concept, with the overall goal to provide effective and safe patient care during cardiac surgery procedures.^1,2

Inadequate control of surgical pain can lead to chronic pain in up to 20% of post-sternotomy and 25 to 60% of postthoracotomy patients. Regional techniques may help to reduce acute postoperative pain, including opioid-induced hyperalgesia and the development of chronic pain by reducing noxious sensitisation.

Poorly controlled pain is associated with sympathetic nervous system activation and an increased hormonal stress response. This response may contribute to multiple adverse postoperative events, including myocardial ischaemia, cardiac arrhythmias, hypercoagulability, pulmonary complications and increased rates of delirium and wound infection.³

Huang et al. reviewed the incidence of pain at two months after cardiac surgery and found that out of 244 patients, 30% had persistent sternal pain, 29% had continued chest pain after mini-thoracotomy, 17% had shoulder pain and 15.9% had back pain after cardiac surgery.⁴

Fascial plane blocks involve the deposition of local anaesthetic (LA) between the fascial layers, thereby blocking sensory nerve fibres that pass through the fascial planes and pierce different muscle layers to finally supply cutaneous sensory innervation. The nerve often gives off sensory and motor branches to the muscle layers along its course. With ultrasound guidance, the procedure is relatively simple with a low risk profile.

Neuraxial regional anaesthesia, like spinals or epidurals, carries an uncomfortably high perceived risk in terms of nerve injury due to compressive haematoma in a fully heparinised patient. With these techniques, there is also the risk of potential haemodynamic instability at the spinal analgesia level, which is required.

Pectoral blocks (PECS I and PECS II) have been used in breast surgery, as described by Blanco, and more recently introduced to cardiac surgery (Fig. 1).⁵

Fig. 1.

Transverse chest anatomy.

The medial (C8–T1) and lateral (C5–C7) pectoral, long thoracic (C5–C7) and thoracodorsal (C6–C8) nerves originate from the brachial plexus and provide primarily motor innervation to the muscles of the chest wall, but also carry sensory nerve fibres.

Segmental thoracic sensory innervation of the chest wall extends from the spinal nerve root level T1 to T11. The spinal nerve exits the intervertebral foramen and divides into a dorsal and ventral ramus within the paravertebral space, which communicate with the sympathetic trunc via the white and gray rami communicantes. Dorsal rami supply the muscles, bone, joints and skin of the midback. Ventral rami travel alongside blood vessels between pleura and endothoracic fascia, then between internal and innermost intercostal muscles, supplying the lateral and anterior chest wall.

At the mid-axillary level, a branch pierces the internal and external intercostal muscles and serratus anterior muscle (SAM), becoming the lateral cutaneous branches providing sensory innervation to the lateral chest wall. The rest of the nerve courses anteriorly towards the sternum and pierces the internal intercostal muscle, external intercostal membrane and pectoralis major muscle, providing sensory innervation for the anterior chest wall. The intercostal nerves provide segmental innervation with an overlap between the adjacent nerves, requiring blockade of at least the nerve above and below.

The PECS I block is performed by injecting LA between the pectoralis major and minor muscle at Morheim’s pouch. The ultrasound probe is first placed below the mid-clavicle and moved inferolaterally to the level of the third rib. The thoraco-acromial artery may be seen between the pectoralis major and minor muscles. Tilting the probe helps to identify fascial planes. The needle is inserted in the plane, in a craniocaudal direction. The shaded area (Fig. 2) illustrates approximate interfascial LA spread between the pectoralis major and pectoralis minor muscles.

Fig. 2.

Pectoral I block anatomy.

The PECS II block is performed by injecting LA between the pectoralis minor muscle and SAM. PECS I and II blocks are frequently performed with a single skin puncture site by first injecting the LA in the PECS II plane, followed by needle withdrawal and injection into the PECS I plane.

The site of PECS I injection affects the distribution of the block, with a more lateral injection spreading towards the axilla and blocking the intercostobrachial nerve, and a more medial injection spreading toward the midline, potentially blocking the anterior intercostal nerve branches. The PECS II blocks the long thoracic and thoracodorsal nerves and lateral cutaneous branches of the intercostal nerves, providing innervation to the SAM and lateral chest wall (Fig. 3). A recent case report discusses the use of PECS II with a continuous catheter for two patients undergoing trans-apical aortic valve implantations (TAVI).⁶

Fig. 3.

Pectoral II block anatomy.

Randomised studies in breast surgery patients comparing PECS I/II blocks to placebo consistently demonstrate improved analgesia with the blocks. Randomised studies comparing PECS I/II blocks to the paravertebral blocks in similar patient populations show conflicting results, which differ in terms of analgesia duration and quality. This may be due to differences in the extent of surgical dissection, techniques used when performing the blocks, and the type and amount of LA injected. PECS II will block the thoracodorsal and long thoracic nerves, but spare the anterior branches of the intercostal nerves.

The serratus anterior plane (SAP) block anaesthetises primarily the thoracic intercostal nerves and provides analgesia of the lateral thorax. The SAP block can be considered an extension of the PECS II block, with a more inferolateral level of injection and a wider spread. It can block the spinal nerve root at level T2 to T9, including the anterior, lateral and posterior chest wall. The efficacy is partly influenced by the volume of LA injected, as well as the injection site being deep or superficial to the SAM. Better anterior spread of the block occurs with deep injection, while the superficial injection may be preferred for a more posterior spread. Anaesthetising T1 to T8 requires a LA volume greater than 40 ml (Fig. 4).

Fig. 4.

Serratus anterior block anatomy.

The efficacy and duration of an SAP block, PECS II block and intercostal nerve block (ICNB) for the management of postthoracotomy pain was examined in paediatric cardiac surgery patients and was found to be equally efficacious, but longest lasting with the SAP block (more than 12 hours), followed by the PECS II block (8–12 hours) and then the ICNB (4–6 hours).7 While their use is relatively safe, we must be cognisant of their potential complications, which include infection, thoraco-acromial artery injury, haematoma, pneumothorax and intravenous injection with subsequent LA toxicity.

Anterior cutaneous branches can be anaesthetised by injecting LA in the fascial planes of the anterior chest wall. The intercostal nerves run between the innermost and inner intercostal muscles. As they reach the most anterior part of the chest wall, they run between the transverse thoracic (deeper) and internal intercostal (superficial) muscles in the same plane as the internal mammary artery. They then pierce through the internal intercostal muscle and external intercostal membrane anteriorly to give medial and lateral cutaneous branches, innervating superficial tissues in the parasternal area. The target anterior branches of the intercostal nerves are from T2 to T6.

An ultrasound-guided pecto-intercostal fascial (PIF) block was introduced as an adjunct to PECS blocks, providing analgesia to the anterior chest wall with an injection placed 2 cm lateral from the sternum between the pectoralis major and (internal) intercostal muscles (Fig. 5). With a transverse thoracic muscle plane (TTMP) block, the injection is performed between the internal intercostal and transverse thoracic muscles (Fig. 6). However, the transverse thoracic muscle is a very thin structure lying posterior to the sternum and can be difficult to visualise with ultrasound.

Fig. 5.

Pecto-intercostal fascial block (PIF).

Fig. 6.

Transverse thoracic muscle plane block (TTMP).

The TTMP and PIF blocks are useful for patients undergoing median sternotomies and patients with anterior chest wall trauma.^8,9 Potential complications include infection, haematoma, pneumothorax and internal mammary artery injury. The PIF, compared to the TTMP block, avoids the plane of the internal mammary artery.

In a prospective, randomised study, 108 patients undergoing open cardiac surgery received either bilateral PIF blocks or nothing. The primary endpoint was postoperative pain, with secondary endpoints being analgesia consumption, time to extubation, the presence of ileus, intensive care unit (ICU) length of stay, insulin resistance and interleukin-6 (IL-6) levels.

The PIF block group consumed less sufentanil and parecoxib than the control group. Compared to the PIF block group, the control group had higher numerical rating scale (NRS) pain scores at 24 hours after operation, both at rest and during coughing. The time to extubation, length of stay in ICU and length of hospital stay were significantly decreased in the PIF block group compared with the control group. The PIF block group had lower insulin, glucose, IL-6 and HOMA-IR levels than the control group at three days after surgery. This study demonstrates that bilateral PIF blocks provide effective analgesia and accelerate recovery in patients undergoing open cardiac surgery.¹⁰

In a prospective, double-blind, randomised study investigating TTMP blocks, Aydin et al.¹¹ showed good efficacy and a reduction in opioid requirements. They investigated 48 adult patients having cardiac surgery with median sternotomy. Patients were randomly assigned to receive pre-operative ultrasoundguided TTMP block with either 20 ml of 0.25% bupivacaine or saline bilaterally. Postoperative analgesia was administered intravenously in the two groups four times a day with 1 000 mg of paracetamol and patient-controlled analgesia with fentanyl. They demonstrated a reduction in postoperative 24-hour opioid consumption (p < 0.001).

Pain scores were significantly lower in the TTMP group compared with the control group up to 12 hours after surgery, both at rest and during active movement (p < 0.001). Compared with the TTMP group, the proportion of postoperative nausea and pruritus was statistically higher in the control group (p < 0.001). Interestingly, the median fentanyl use in the control group was 465 μg, while it was only 255 μg in the TTMP group.

A recent prospective, randomised, placebo-controlled trial investigated by Khera et al.¹² determined the effect of PIF block on postoperative opioid requirements, pain scores, lengths of ICU and hospital stays, as well as the incidence of postoperative delirium in cardiac surgical patients at a single tertiary centre. The study investigated 80 adult cardiac surgical patients (age > 18 years) requiring median sternotomy. Patients were randomly assigned to receive ultrasound-guided PIF block, with either 0.25% bupivacaine or placebo.

On postoperative days zero and one, patients receiving PIF block with 0.25% bupivacaine showed a statistically significant reduction in visual analog scale (VAS) scores (4.8 ± 2.7 vs 5.1 ± 2.6; p < 0.001) and 48-hour cumulative opioid requirement. A low incidence of complications and an improvement in VAS pain scores suggested that PIF block can be performed safely in this population and it warrants additional studies.¹²

The erector spinae plane (ESP) block was initially described for the treatment of chronic thoracic neuropathic pain. It can be used for acute postoperative analgesia involving chest, thoracic, cardiac and abdominal surgeries.

LA is injected ventral to the erector spine muscle along thoracic levels 5–9, within the costotransverse foramen region, providing analgesia to the ventral and dorsal rami of the spinal nerves. The erector spinae muscle is the main component of the paraspinal muscles that stabilise the torso, but there is also and immediately adjacent to the bony vertebrae, and includes multifidus, rotators and intertransverse muscles. The rotators and intertransverse muscles, together with several ligamentous structures, such as the superior costotransverse ligament, span the gap between adjacent vertebral transverse processes. This ‘intertransverse tissue complex’ is a permeable posterior boundary of the paravertebral space (Fig. 7).

Fig. 7.

Erector spinae plane block anatomy.

The ESP block is performed under ultrasound guidance with the patient sitting, prone or in the lateral decubitus position. Using an aseptic technique, a high-frequency (12–15 MHz) linear-array transducer is placed in the parasagittal plane and moved from a lateral to medial direction until the ribs are no longer visualised and the transverse processes of T3 to T5 with overlying trapezius, rhomboid major and erector spine muscles are identified. The most caudal vertebral attachment of the rhomboid major muscle is the T5 spinous process, and tapering out of the rhomboid at this level may be useful confirmation of the desired probe position. An in-plane needle is inserted in the craniocaudal direction and advanced below the erector spine muscle, with the tip contacting the T5 transverse process. This block can be used with rib fractures, chest wall surgery and cardiac surgery (Fig. 8).

Fig. 8.

Erector spinae plane block anatomy.

Significant variations among cadaver studies have been found regarding injectate spread into the ventral rami after magnetic resonance imaging and dissection assessment, but all studies report significant distribution along the craniocaudal plane and the lateral cutaneous branches of the intercostal nerves. Schwarzmann et al.¹³ report radiological confirmation of notable craniocaudal spread with a single ESP injection.

Athar et al.¹⁴ conducted a randomised, double-blind, controlled trial assessing the efficacy of an ESP block in cardiac surgery. Their study included 30 patients aged 18 to 60 years, body mass index ranging between 19 and 30 kg/m², undergoing elective on-pump, single-vessel coronary artery bypass grafting or valve replacement under general anaesthesia. Patients were randomly categorised into two groups of 15 patients each receiving bilateral ESP blocks with 20 ml of 0.25% levobupivacaine per side, or placebo blocks with 20 ml of normal saline per side. Endpoints included total opioid dose in 24 hours, time-to-rescue analgesia, duration of mechanical ventilation, Ramsay sedation score (one of the most commonly used measures of sedation) six-hour post-extubation, postoperative nausea and vomiting, pruritus and the incidence of pneumothorax.

According to their study, a single-shot ESP block provided superior analgesia compared with a placebo block. It decreased the first 24-hour postoperative analgesic consumption by 64.5% and risk of pain by five times in the authors’ population. It also reduced the duration of mechanical ventilation (88 vs 103 hours) in their postcardiac surgery patients.¹⁴

In this edition of the journal, Turkmen and Mutlu¹⁵ (page 153) compared the efficacy of ultrasound-guided PECS II block with a parasternal (PS) block in 100 patients undergoing open-heart surgery through midline sternotomy. This is the first study comparing two blocks between two groups after openheart surgery via sternotomy. For postoperative analgesia, 50 patients received a PECS II block and 50 a PS block at the end of surgery. They were then compared in terms of sedation scores, ventilation duration, and pain scores at rest after extubation as first endpoints. Block duration and cumulative morphine consumption were secondary endpoints, while complications such as postoperative nausea and vomiting were also compared.

Interestingly in this study, the VAS scores at rest, a tool widely used to measure pain, were higher in the PECS II block group over the first six hours than in the PS group (p < 0.01). This was associated with a block duration that lasted longer in the PS block group. The cumulative morphine consumption (p < 0.01) and the Richmond agitation–sedation scale scores (RASS, a medical scale used to measure the agitation or sedation level of a person) (p < 0.01) were also higher in the PECS II block group than in the PS block group over the first four hours. There was no difference in the ventilation duration, block durations, pain and sedation scores over the first two hours. The final conclusion from the authors was that a PS block provides longer block duration with lower postoperative pain and sedation scores, as well as lower cumulative morphine consumption than a PECS II block for patients receiving a heart operation via median sternotomy.

We must keep in mind that there is a strong trend towards performing cardiac surgery via a minimally invasive and minimal-access approach. This is usually performed through a mini-thoracotomy, which makes these procedures also amenable to other thoracic plane blocks. The discussion about analgesia for thoracotomy procedures is however not comprehensively covered in this editorial.

The relatively low risk of complications, with the potential beneficial effects on opioid consumption, duration of ventilation and ICU length of stay, make fascial plane analgesia techniques an exciting field of research. More research is necessary to validate fascial plane blocks. We expect them to become part of our daily cardiac anaesthesia techniques and part of any cardiac ERAS programme.