Learning points.
By reading this article, you should be able to:
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Describe the indications for paravertebral blocks.
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Discuss the different techniques used to perform a paravertebral block.
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Review the safety, complications and failure rates of landmark and ultrasound-guided techniques.
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Compare paravertebral blocks with the newer paraspinal blocks.
Key points.
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Paravertebral blocks provide good intra- and postoperative analgesia.
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They may be used as the sole anaesthetic technique for breast surgery.
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Uni- or bilateral blocks can be performed for thoracic and abdominal surgery.
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Ultrasound-guided techniques reduce failure rates and complications.
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Novel alternative techniques are promising but more research is required to verify their effectiveness.
The paravertebral block (PVB) was first described by Sellheim in 1905 and has been used widely since 1978 to treat both acute and chronic pain.1 The PVB may be placed uni- or bilaterally, and either single-shot or continuous catheter techniques are possible. The advent of ultrasound has increased interest in PVB but also led to alternative paraspinal techniques including the erector spinae plane (ESP), retrolaminar, midpoint transverse process to pleura (MTP) and intercostal paraspinal blocks, all of which are purported to achieve blockade of thoracic nerve roots without entering the paravertebral space.2,3 This article reviews the evidence base, and the different techniques for PVB. The newer paraspinal blocks are also discussed briefly.
Anatomy of paravertebral blockade
The thoracic paravertebral space (TPVS) is a wedge-shaped space adjacent to the thoracic spine on either side of the vertebral column. The boundaries of the TPVS are the parietal pleura anterolaterally, the superior costotransverse ligament (SCTL) posteriorly, the vertebrae and intervertebral foramina medially and the heads of the ribs superiorly and inferiorly (Fig. 1).
Figure 1.
(a) Thoracic paravertebral space. (b) Sagittal section of the thoracic paravertebral space with needle.
Between the parietal pleura and the SCTL is the endothoracic fascia, a fibroelastic structure which lines the inside of the thoracic cage and divides the TPVS into anterior and posterior fascial compartments. The subserous fascia is found between the parietal pleura and the endothoracic fascia. The SCTL, which can be seen with ultrasound, is continuous with the internal intercostal membrane. This is of anatomical importance because the needle tip must penetrate this ligament for a successful PVB. However, the SCTL is thought to be porous in nature, either via gaps at the medial or lateral aspects, or through fenestrations in the ligament itself, which may partly explain the mechanism of some of the newer paraspinal blocks.
The TPVS space contains fatty tissue, intercostal spinal nerves, dorsal rami, intercostal vessels, rami communicantes and the sympathetic chain. The spinal nerves lie freely in the TPVS, the intercostal nerves and vessels are posterior to the endothoracic fascia and the sympathetic trunk is anterior. The cranial limit of the space is not yet defined, but radiocontrast media has been observed to spread to the cervical region after injection. The caudal boundary is marked by the origin of the psoas muscle. The TPVS communicates with the epidural space medially and the intercostal space laterally.
Description of techniques
Various landmark and ultrasound-guided techniques exist. All can be used for either single-shot injections or catheter placement.
Landmark technique
With the patient in a sitting or lateral position, a mark is made 2.5–3 cm lateral to the spinous process at the appropriate vertebral level. A Tuohy needle is typically used, and a catheter can be placed through this if required. The needle is advanced perpendicular to the skin in all planes until it contacts the transverse process (TP): this depth is greatest in higher thoracic levels (T1–T2) and shallowest in the midthoracic area (T5–T10). This depth is about 4 cm in the thoracic region, meaning needle insertion beyond this point without bony contact necessitates caution as the needle may be between TPs and deeper insertion risks pneumothorax. The TP contacted should be that of the thoracic vertebrae below given the angulation of the spinous process, that is the T5 spinous process is at the level of T6 TP. Once the needle contacts the TP, it is walked off either superiorly or inferiorly, using a loss of resistance to air or saline technique. Alternatively, the needle may be advanced no more than 1–1.5 cm past the TP—a pop is typically felt as the needle passes through the SCTL.4 Unlike epidural block, the loss of resistance or a pop in TPVB is very subjective. Local anaesthetic can be injected after gentle aspiration. If required, a catheter is advanced until 2–3 cm remains in the TPV space.5
Several modifications of this landmark technique have been suggested, aiming to reduce failure rates and complications. Sonographic measurements of the distances from skin to TP and parietal pleura can help calculate the depth of needle insertion to avoid unintentional pleural puncture.5 Nerve stimulation techniques have been used, aiming for twitching of intercostal or abdominal muscles (the ventral ramus of the spinal nerve) at a current intensity of approximately 0.4 mA. Loss of contraction with injection of the local anaesthetic is the endpoint for a successful block.6 Fluoroscopy or chest radiography after injection of contrast can also be used to assess the needle position, but this may be neither readily available nor practical in most settings.
Surgical insertion of prevertebral catheter
A Tuohy or nerve block needle is placed under direct vision by the surgeon. Injection of local anaesthetic can be seen to cause tenting of the parietal pleura and a catheter is left in situ. Video-assisted placement of a paravertebral catheter during thoracoscopic surgery has also been described.
Ultrasound-guided technique
The two most commonly used approaches are described below. Other approaches beyond the scope of this article are detailed elsewhere.7
Longitudinal oblique, in-plane technique
The ultrasound probe is placed in a caudocranial orientation approximately 5 cm from the midline, where the ribs and pleura are identified. The probe is moved medially until the transition of ribs (convex) to TP (more squared and superficial) is seen. The probe is then rotated slightly anticlockwise, so that the cranial end is now medial and caudal end is lateral. Finally, the probe is then tilted slightly laterally to improve the image (Fig. 2). Needle advancement is in the caudal to cranial direction, in plane with the ultrasound beam. When the SCTL is pierced, the needle tip is in the paravertebral space and local anaesthetic, when injected, will push the pleura downward.
Figure 2.
Ultrasound image of thoracic paravertebral space. TP, transverse process; SCTL, superior costotransverse ligament; TPVS, thoracic paravertebral space; ESM, erector spinae muscle; RM, rhomboid major; TM, trapezius muscle.
Transverse, in-plane technique
The ultrasound probe is placed transversely (axially), just lateral to the midline, aiming to identify the rib. The probe is then manoeuvred caudally to visualise the intercostal space. The pleura should be seen along with the internal intercostal membrane which is continuous with the SCTL. The needle is advanced in a lateral to medial direction towards the TP until it breaches the internal intercostal membrane. Local anaesthetic is injected after negative aspiration, and the pleura should again be visualised moving downwards.
Potential advantages of ultrasound-guided TPV block compared to blind techniques include visualisation of the anatomical structures, needle shaft, needle tip, local anaesthetic spread and catheter placement.8 The use of ultrasound results in a shorter onset time, longer block duration, lower local anaesthetic volume requirements, lower failure and complication rates and less patient discomfort.
Clinical performance of block
As with any regional nerve block technique, a PVB should be performed under strict aseptic conditions and requires informed consent, i.v. access, standard monitoring and the availability of resuscitation equipment. Although PVB can be undertaken at the cervical and lumbar regions, the most common technique is the thoracic PVB. Current guidance is that blocks are performed in patients who are awake.9 PVB can be uncomfortable, and both a small amount of sedation and analgesia are generally required. The level of needle insertion should be chosen based upon the surgical procedure, generally aiming for injection at the mid-dermatomal level with reference to the procedure.
Needle choice
A 16G Tuohy needle is usually recommended for thoracic PVB. An 18G needle is recommended if catheter placement is planned. The shaft of the needle should have depth markings to gauge placement. When performing ultrasound-guided PVB, echogenic needles may be advantageous given the needle trajectory (which is sometimes steep) and the risk of pneumothorax.
Local anaesthetic choice and volume
Long-acting local anaesthetics are mostly used given that long-lasting analgesia is generally desired. Bupivacaine or levobupivacaine 0.25% and ropivacaine 0.25% may be used for analgesia, and 0.5% levobupivacaine used for anaesthesia. Overall, 20–25 ml local anaesthetic is generally injected as a single shot to cover approximately four to five dermatomes, or 4–5 ml can be used for each level in the multiple injection technique. However, a single ultrasound-guided injection results in equivalent dermatomal coverage, takes less time to perform, may cause less discomfort and has a similar analgesic profile. For larger coverage, multiple injections are required.
The maximum dose of local anaesthetic must be adjusted in older, poorly nourished and frail patients. The TPV space is highly vascular, leading to rapid absorption of local anaesthetic into the systemic circulation. An infusion either of bupivacaine or levobupivacaine 0.25% or ropivacaine 0.2%, running at a rate of 0.1–0.2 ml kg−1 h−1, can be started after the initial bolus injection if required and can be continued for 3–4 days.
Single-shot vs catheter technique
A single-shot PVB can provide pain relief for up to 18 h. When more prolonged analgesia is desirable, an indwelling catheter may be inserted.10 The same steps for a single-shot PVB are followed, using a Tuohy needle and full asepsis. Then, 3–5 ml of local anaesthetic is deposited deep to SCTL to facilitate threading of the catheter. The catheter is inserted through the 18G Tuohy needle and 2–3 cm threaded beyond the needle tip. The catheter is safely secured after removing the Tuohy needle. Anterior displacement of the pleura should again be seen after injection through the catheter. Local anaesthetic solution can be administered via continuous infusion, patient-controlled boluses or repeated operator boluses.
Indications and evidence base for PVB
Paravertebral blocks can provide both analgesia and anaesthesia, especially where unilateral nociceptor afferents from the chest or abdomen are involved. However, the technique can also be used bilaterally.8 Common indications for and contraindications to PVB are outlined in Table 1.
Table 1.
Indications and contraindications for paravertebral blocks
| Indications (level of block) | Contraindications |
|---|---|
Postoperative analgesia
|
Absolute
|
Evidence base for analgesia and anaesthesia
Breast surgery
Two systematic reviews demonstrated significantly lower resting, dynamic and worst pain scores in patients receiving PVB alone, or with GA, compared with other modalities of pain relief. Opioid requirements were reduced, as were postoperative nausea and vomiting (PONV) and other opioid-related adverse effects.11 Hospital stay was shortened (although to a clinically irrelevant degree), and the incidence of chronic postsurgical pain (CPSP) at 6 months was less. In one systematic review, postoperative pain control (but during movement only) was better with multilevel PVB injection compared to single injection.12 An RCT comparing the anatomical landmark PVB technique to an ultrasound-guided technique for breast surgery showed that more patients had successful blocks with ultrasound.13 Pain control, both at rest and movement, was superior and catheter top-ups were less frequent in the ultrasound group.
Thoracic surgery
A Cochrane meta-analysis comparing TPV block with thoracic epidural analgesia for post-thoracotomy pain concluded that TPV block reduced the risk of developing hypotension, pruritus, urinary retention and PONV compared with thoracic epidural analgesia but was as effective in controlling pain. There were no differences in 30-day mortality, major complications (pneumothorax) or hospital length of stay.14 Another systematic review and metaregression examined the efficacy and safety of PVB, and variables such as administration technique (continuous infusion or intermittent boluses, choice of LA agent and dose of LA) for analgesia after thoracotomy. It concluded that higher doses of local anaesthetic agents appear to offer better analgesia whereas continuous infusions were shown to be better than intermittent boluses, although no single technique was found to be superior to any other.15
Cardiac surgery
Similar to thoracic surgery, a meta-analysis has demonstrated that continuous PVB reduced the incidence of nausea and vomiting, hypotension and urinary retention compared with epidural analgesia whilst providing equivalent analgesia.16
Rib fractures
PVB provides effective pain relief in patients with unilateral multiple rib fractures. It has also been shown to improve respiratory function and gas exchange.17
Chronic pain management
Breast surgery is associated with a 22–53% incidence of CPSP, whereas thoracotomy is also an operation associated with significant CPSP.8 Two meta-analyses evaluated the effects of a single thoracic paravertebral injection of 15–20 ml bupivacaine 0.5% on post-thoracotomy and postmastectomy pain.12,18 Although initial results were good in 99% of blocks, long-term pain relief in the post-thoracotomy group was better than in the postmastectomy group. A more recent study investigated PVB for the prevention of chronic pain after breast cancer surgery.19 There was no difference from control in preventing CPSP at 3 months. However, PVB was protective at 6 months, with a relative risk (RR) reduction of 54%. Metaregression suggested that the RR of CPSP was lower when both single injection and multilevel PVB were used, although there were methodological limitations. Interestingly, the findings also suggested that multilevel single injection TPV block may be protective against CPSP at 6 months compared to a continuous infusion TPV block. Larger trials are required to confirm this finding.
Cancer recurrence and PVB
There are conflicting opinions in the literature on PVB and breast cancer recurrence. A recent systematic review and meta-analysis showed that perioperative regional anaesthesia was found to be associated with improved overall survival but not with reduced cancer recurrence.20 A Cochrane review concluded that the evidence for regional anaesthesia on overall survival and time to tumour progression and recurrence is not adequate.21 A recent narrative review on perioperative intervention on oncological outcomes concluded that there still remains insufficient data to change current clinical practice.22 A recently published multicentre trial comparing regional anaesthesia–analgesia (PVB and propofol) with general (volatile) anaesthesia and opioids found no difference between the groups.23
Inguinal herniorrhaphy
PVB can be used both for postoperative analgesia and as the sole anaesthetic technique for inguinal hernia repair.24 When used as a primary anaesthetic technique compared to general anaesthesia (GA), the PVB group had lower resting and dynamic pain scores, less PONV and a small reduction in analgesic requirements. In a different study where PVB was compared with transversus abdominis plane (TAP) block and spinal anaesthesia, the PVB patients reported lower pain scores in the first 12 h, and decreased diclofenac consumption.24
Laparoscopic cholecystectomy
In a comparison of bilateral PVB with systemic analgesia for patients undergoing laparoscopic cholecystectomy under GA, pain scores were reduced in the PVB group in PACU only, although analgesic requirements were reduced in the PVB group for 24 h.24 In contrast, a prospective RCT comparing GA and PVB with GA alone demonstrated lower pain scores at rest and movement for the first 72 h, with reduced analgesia requirements for 36 h.24 PONV was reduced in the PVB group in both trials. Another RCT, which compared PVB with thoracic epidural analgesia, reported higher pain scores and opioid consumption in the PVB group.24
Renal/urological surgery
When comparing PVB with either GA and systemic analgesia or single-shot thoracic epidural for percutaneous nephrolithotomy (PCNL) pain scores, morphine consumption and PONV are all reduced in the PVB group.24 TPV block was compared with systemic analgesia in patients having open nephrectomy under GA, and this study showed pain scores and opioid requirements were significantly lower in the PVB group for up to 24 h.24
Block failure and complications
‘Block failure’ definitions vary from higher than expected pain scores, no block on dermatomal testing, inability to access the TPV space or as a general term for failure of surgical anaesthesia.12,21,25 The failure rate when using landmark techniques appears to be higher than that under ultrasound guidance, with quoted rates between 1.98% and 5.6%.12,21 Of the various landmark techniques, the loss of resistance approach has a higher failure rate (5.2%) than when using the predetermined distance approach (2.3%).21 Failure rates with ultrasound-guided approaches are lower (0–2.3%), but the number of studies available for analysis is small.12,21 These lower rates could be explained by good needle visualisation and the ability to see the spread of local anaesthetic in the appropriate and intended location.
Reported complication rates in both landmark and ultrasound-guided techniques are low. Hypotension, vascular puncture, pneumothorax and nerve damage have an incidence of less than 1%.14 Epidural spread is seen in 2.1%.12 A retrospective analysis of 1500 ultrasound-guided blocks showed no cases of pneumothorax, but there are no prospective data to substantiate this finding.25 Postoperative outcomes such as respiratory complications, readmission rates to intensive care units or length of stay are similar in TPV block and thoracic epidural analgesia for thoracic surgery. The incidence of vascular puncture is increased with multi-injection techniques.
Bilateral PVB may be considered as an alternative to an epidural in some surgical settings. It confers the advantage of less profound sympathetic blockade, which results in better cardiovascular stability. In a study of patients undergoing thoracotomy, bilateral continuous thoracic PVB provided similar pain control with reduced colloid and vasopressor requirements compared with epidural analgesia, but increased the risk of pneumothorax and pleural puncture from 0.4% to 3%; whereas the risk of vascular puncture risk was increased from 5% to 9%.25
Novel paraspinal blocks
Several novel paraspinal blocks have been described where blockade of the thoracic nerve roots in the paravertebral space is purported to be possible without the block needle entering the TPVS (Fig. 3). These are all ultrasound guided and described below.
Figure 3.
Newer paraspinal blocks. ESP, erector spinae plane; PVB, paravertebral block; RLB, retrolaminar block; MTP, midpoint transverse process to pleura.
ESP block
With the patient either sitting or in the lateral decubitus position, the target TP is identified by placing the ultrasound transducer approximately 3 cm lateral to the spinous process in a sagittal orientation. This allows visualisation of the adjacent TPs as flat, squared-off acoustic shadows with only a very faint image of the pleura visible. An 18G echogenic needle is inserted using an in-plane approach, cranial-to-caudal (or vice versa) to contact the TP with the tip of the needle deep to the fascia of the erector spinae muscle. The injection of 1–2 ml of local anaesthetic and observing its linear spread lifting the erector spinae muscle off the TP confirms the correct position of the needle (Fig. 4). A catheter can be inserted through the needle once the fascial plane is recognised and opened. Cranial and caudal spread of local anaesthetic can be seen after the injection of a bolus of local anaesthetic through the catheter.2 It has been suggested that ESP block is easy and safe, but more randomised controlled studies are required to assess complications and efficacy of this promising block.26
Figure 4.
Erector spinae block with needle. ESM, erector spinae muscle; TP, transverse process; TV, thoracic vertebrae; RM, rhomboid muscle; TM, trapezius muscle; LA, local anaesthetic. Arrowheads denote the needle.
Retrolaminar
The vertebral laminae are identified by moving the ultrasound transducer from lateral to medial by sequentially visualising the pleura and ribs, TPs and the corresponding laminae. The block needle is guided in plane to contact the lamina, and the local anaesthetic is injected on the lamina. Spread is visualised from cranial to caudal under real-time imaging. A catheter can be inserted and used for continuous analgesia.3
Mid-point transverse process to pleura
A linear ultrasound probe is placed in the paramedian plane to identify the TP and pleura. The needle is directed in plane caudal to cephalad towards the TPV space. The local anaesthetic is injected at the midpoint of the posterior border of TP and the pleura.3
Intercostal paraspinal
The ultrasound probe is placed more laterally over the ribs in a paramedian plane to identify the rhomboid major and intercostal muscles. The needle is directed in plane in a cephalad to caudal direction to reach the fascial plane between the rhomboid major and intercostal muscle, where the local anaesthetic is injected.3
Single-level injection in these planes appears to produce multilevel dermatomal effects. These novel blocks are arguably easier for the less experienced anaesthetist to perform and are potentially safer because the needle endpoint is further from the pleura or, compared to an epidural, the spinal cord. However, further studies are required to establish their clinical efficacy in terms of ability to provide both anaesthesia and analgesia, the degree of sympathetic blockade caused and overall safety and to determine how these novel blocks compare to epidural and TPV blocks.
Conclusion
Thoracic PVB is an effective analgesic technique for thoracic and abdominal surgery, with prolonged analgesia achievable with catheter placement and local anaesthetic infusion. Ultrasound-guided approaches improve success and may potentially reduce complication rates. Newer paraspinal blocks also show promise, but more studies are required to evaluate their effectiveness.
Declaration of interests
The authors declare that they have no conflicts of interest.
Acknowledgements
The authors thank Dr Eoin Kelleher for the illustrations of the TPV space.
MCQs
The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.
Biographies
Shrijit Nair FCAI FJICMI is a fellow in hepatopancreatic biliary and transplant anaesthesia.
Hugh Gallagher FCARCSI DABPM DPMed FFPMCAI is a consultant in anaesthesia and pain medicine at St Vincent's Hospital and vice dean of the Faculty of Pain Medicine of the College of Anaesthesiologists of Ireland.
Niamh Conlon MSc FCAI FJICMI is a consultant anaesthetist with special interests in liver transplantation, thoracic anaesthesia, regional anaesthesia and acute pain. She developed a pathway for pain management and early referral for patients with rib fractures in St Vincent's Hospital, has taught on national courses in regional anaesthesia and has published previously on paravertebral blocks.
Matrix codes: 1D02, 2E01, 3A09
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