Similar to peripheral nerve blocks of the upper or lower limb, truncal blocks provide excellent postoperative pain relief, avoid the risk for major complications associated with central nerve blockade such as epidural hematoma or abscess, and can be used as a sole anesthetic technique for some types of surgery. However, their use in daily practice has remained limited until recently. Because of the many advantages that they offer, truncal blocks should have a place in the armamentarium of every anesthesiologist involved in the management of postoperative analgesia, particularly in the outpatient setting. In this chapter, the following truncal blocks are discussed: paravertebral, intercostal, ilioinguinal, iliohypogastric, genitofemoral, transverse abdominal plane, and rectus sheath blocks.
Paravertebral Nerve Blockade
The renewed interest in paravertebral nerve blockade is related to many factors: the involvement of anesthesiologists in postoperative pain control, the development of ambulatory surgery, and the need to apply simpler and more reliable techniques to reduce postoperative stay in the intensive care unit. Paravertebral blockade consists of injecting local anesthetic close to the vertebra at the level where the spinal nerves exit the intervertebral foramina. Such injection induces an ipsilateral somatic and sympathetic blockade that extends, most of the time, longitudinally above and below the injected vertebral level. It is indicated for acute as well as unilateral chronic pain syndromes. Such blockade is associated with no major cardiovascular or respiratory effects.
Anatomy
The paravertebral space is triangular shaped. It is limited by the superior costotransverse ligament posteriorly, by the parietal pleura anterolaterally, and by the head and neck of the adjacent ribs superiorly and inferiorly. It is in continuity with the epidural space through the intervertebral foramen, with the intercostal space, and with the contralateral paravertebral space anteriorly. It contains the dorsal and ventral rami and the sympathetic chain. Hence, injection of local anesthetic into the area results in unilateral sensory, motor, and sympathetic blockade ( Fig. 55.1 ).
In the paravertebral space, the endothoracic fascia is firmly applied to the ribs and fuses medially on the vertebral body. It thus divides the paravertebral space into two compartments: the extrapleural space anteriorly and the subendothoracic space posteriorly. Naja and coworkers claim that longitudinal spread of local anesthetic is better when the injection is performed ventral to the endothoracic fascia whereas a dorsal injection results in localized spread. However, another author has questioned the significance of the endothoracic fascia.
Whether local anesthetic injected into the low paravertebral thoracic segments spreads to the lumbar levels remains controversial. Some authors question the anatomic barrier created by the psoas muscle. Others stress that local anesthetic can spread through the posterior insertion of the diaphragm when the solution is injected deeper to the endothoracic fascia or along the lateral border of the psoas muscle.
Technique
As for any regional technique, standard monitoring includes electrocardiography, pulse oximetry, and noninvasive blood pressure monitoring.
Positioning
The sitting position is usually preferred since it facilitates palpation of the landmarks. The lateral decubitus position is an alternative.
Approaches
Several approaches have been suggested for locating the paravertebral space.
Blind Approach
Once the transverse process is contacted (usually at a maximum distance of 4 to 5 cm from the skin), the needle is withdrawn to subcutaneous tissue, reoriented caudally (but sometimes cephalad when caudal insertion is impossible because of contact with bone), and advanced 1 to 1.5 cm deeper to the transverse process.
Loss-of-Resistance Approach
Loss of resistance (a syringe filled with saline, air, or both is connected to the needle) is felt once the paravertebral space is entered. This approach may be associated with the blind approach.
Nerve Stimulator Approach
Clinical studies have shown that use of a peripheral nerve stimulator may improve the position of the needle with respect to the nerve.
Effective intravenous sedation and local anesthetic infiltration of the puncture sites are mandatory. Indeed, needle insertion through the different muscular structures and bone contact are painful.
Single Injection Technique
The needle entry site is located 2.5 to 3 cm lateral to the cephalad border of each spinous process ipsilateral to the side to be operated on ( Fig. 55.2 ). The needle, attached via extension tubing to a syringe, is advanced anteriorly in the parasagittal plane until it contacts the transverse process. It is then withdrawn and reoriented caudally so that it can be walked off the caudad edge of the transverse process. The needle is then advanced anteriorly approximately 1 to 1.5 cm deeper to the transverse process. Note that Naja and colleagues have shown that the distance from the skin to the paravertebral space is greater at the upper and lower thoracic levels than at the midthoracic levels (T4-8). Their median needle insertion depth was 55 mm. They also determined that body mass index influences the depth at the upper and lower thoracic levels but not at the midthoracic ones. After negative aspiration, 4 to 5 mL of a long-acting local anesthetic (e.g., 0.5% ropivacaine or levobupivacaine) is injected at each level, with the total volume not to exceed 0.3 mL/kg. The onset of sensory loss and surgical anesthesia typically occurs 10 minutes and 20 to 30 minutes, respectively, after injection.
Some studies suggest that a single-injection technique is as effective as a multiple-injection one (average of five dermatomes blocked) as long as the total volume of 0.3 mL/kg is used. These results were confirmed in a thermographic study by Cheema and coworkers. However, it seems preferable to use a “multiple-injection” technique when extensive spread of local anesthetic is required because of the risk for bilateral or epidural spread associated with a single large-volume injection.
Catheter Technique
Once the paravertebral space has been identified, the catheter is threaded 2 to 3 cm through the needle. A bolus dose of 20 mL of long-acting local anesthetic is injected for surgery (an average of six to eight segments are blocked), followed by continuous infusion of a dilute solution (e.g., 0.125% levobupivacaine or 0.2% ropivacaine) at a rate of 5 to 10 mL/hr. The catheter technique has the advantage of providing surgical anesthesia and prolonged postoperative analgesia. Bilateral paravertebral block catheters have been shown to be effective after bilateral thoracotomy in children, after major abdominal vascular surgery, and in outpatient bilateral reduction mammaplasty.
Ultrasound Approach
Initially, ultrasound was used to visualize landmarks such as the transverse process and to measure the distance from the skin before inserting the needle. Pusch and coauthors reported good correlation between the depth of needle insertion, from the skin to the transverse process, and such distance when measured by the ultrasound machine. Presently, anesthesiologists are using ultrasound guidance to perform paravertebral blocks because it allows reliable identification of critical anatomic structures such as the pleura. Being able to preview the paravertebral anatomy and determine the depth of the transverse process and pleura helps in reducing the incidence of pleural puncture. Moreover, ultrasound guidance allows visualization of the spread of local anesthetic.
The thoracic paravertebral space can be scanned in two different anatomic planes:
- •
Transverse scan ( Fig. 55.3 ). Performed with a high-frequency probe, a transverse scan allows identification of the apex of the paravertebral space as a triangular hypoechoic area limited by the hyperechoic parietal pleura anteriorly and the internal intercostal membrane posteriorly.
Figure 55.3
Sonographic anatomy of the paravertebral space (arrow) via a transverse scan.
- •
Sagittal paramedian scan ( Fig. 55.4 ). This scan allows identification of the transverse processes, the intertransverse and costotransverse ligaments, and the hyperechoic pleura.
Figure 55.4
Sonographic anatomy of the paravertebral space (arrow) via a parasagittal scan.
Under ultrasound guidance, the needle approach can be either in plane or out of plane. Thus, four different techniques to approach the thoracic paravertebral space are described.
- •
Transverse scan with an “in-plane” approach. The transverse process is identified as an acoustic shadow hiding the visibility of the paravertebral space. The block needle is inserted in the plane of the ultrasound beam in a lateral-to-medial direction. Note that as the needle is advanced medially in the direction of the intervertebral foramen, there is a risk for central spread of local anesthetic or catheter placement. Moreover, such an approach seems to be less comfortable for the patient because the needle path is long and a 100-mm needle is usually required to reach the paravertebral space.
- •
Transverse scan with an “out-of-plane” approach. When compared with the previous one, this approach has the advantage of significantly reducing the distance between the skin and the paravertebral space, thus making it more comfortable for the patient. In addition, because the direction of the needle remains in the paramedian plane, the risk for central spread of the local anesthetic solution should be lower than with the previous approach.
- •
Sagittal scan with an “out-of-plane” approach. Once the pleura has been carefully identified between two adjacent transverse processes, the needle is advanced until it crosses the costotransverse ligament. Two to 3 mL of local anesthetic is injected into the paravertebral space. Such injection displaces the parietal pleura anteriorly. This approach appears to be the easiest one for the single-shot technique because the path of the needle is very short (3 to 4 cm) and the pleura is easily visible.
- •
Sagittal scan with an “in-plane” approach. With this approach it is often difficult to visualize the complete path of the needle because the angle of needle insertion is very steep. Nevertheless, it is the authors’ preferred approach for catheter insertion.
With all these approaches, hydrolocation with very small amounts of either local anesthetic or saline during needle insertion is helpful to accurately check the location of the needle tip. As soon as the paravertebral space is entered and injected, the parietal pleura is displaced anteriorly by the injected solution.
Equipment
An 8- to 10-cm needle is required to perform this block. It can be a 22-gauge spinal, a 19-gauge Tuohy epidural, or an insulated stimulating needle.
Puncture Site
The puncture site is determined by the type of surgery. At the thoracic level, breast surgery requires blockade of the T1-6 dermatomes, whereas thoracotomy requires lower dermatomal blockade (T4-10). At the lumbar level, an extensive block (T10-L2) is required.
Drugs and Additives
A bolus dose of 2 mg/kg of ropivacaine can be used safely as demonstrated in a recent pharmacokinetic study. The authors recommended the addition of epinephrine (1:200,000) to ropivacaine to decrease C max and delay T max and the rapid absorption phase. The measured venous plasma ropivacaine concentration (2.83 ± 1.31 µg/mL) did not exceed the toxic threshold when a continuous infusion rate of 0.1 mL/kg/hr of a 0.5% solution was used.
Indications
A paravertebral block is associated with excellent analgesia after many types of chest surgery and a reduction in the incidence and severity of chronic pain syndromes ( Box 55.1 ).
Major breast surgery
Thoracic surgery
Laparoscopic cholecystectomy
Inguinal hernia repair
Renal surgery
Percutaneous transhepatic biliary drainage
Labor pain, first stage
Rib fractures
Intercostal neuralgia
Pleuritic pain
Coronary syndromes
Major Breast Surgery
In addition to postoperative pain, a high incidence of nausea and vomiting has been reported after general anesthesia during the first 24 hours following breast cancer surgery. Paravertebral blockade results in effective anesthesia for operative procedures on the breast and axilla, reduces postoperative nausea and vomiting, and provides prolonged postoperative analgesia, thereby minimizing narcotic requirements. When compared with the standard analgesic regimen, which usually requires an overnight hospital stay, a paravertebral block allows discharge of the patient on the same day, for a total cost savings of up to 22%.
When performed as a multiple-injection technique, paravertebral blockade has been shown to be effective for breast surgery. Moreover, the unilateral sympathetic blockade that it induces improves oxygenation of the flap tissue after breast reconstruction with the latissimus dorsi, thus potentially improving healing of the flap.
Breast surgery may result in a “postmastectomy pain syndrome.” Its incidence varies between 20% and 50%. Risk factors include the severity of postoperative pain, anxiety, and young age. Interestingly, preincisional paravertebral blockade has been shown to reduce the prevalence of motion-related and chronic pain 1 year after such surgery. It should be kept in mind that because of potential complications such as pneumothorax or epidural spread, the risk-benefit ratio does not favor its use for minor breast surgery. Moreover, the relatively low pain scores and the very low incidence of postoperative nausea and vomiting after minor breast surgery do not warrant the use of a paravertebral block in these situations.
Thoracic Surgery
Although thoracic epidural analgesia is still considered the “gold standard” for postoperative analgesia after thoracic surgery, continuous paravertebral analgesia has been shown to be as effective as epidural analgesia. Such efficacy occurs whether the catheter is inserted blindly by the anesthesiologist or under direct vision by the surgeon before wound closure. Moreover, a paravertebral catheter avoids the potential risks observed with epidural analgesia, including epidural hematoma, infection, and spinal cord injury. Chronic pain after thoracotomy occurs in 20% to 50% of patients. The occurrence of this syndrome is significantly reduced when early and effective postoperative pain treatment (e.g., epidural analgesia, paravertebral block) is provided.
Cardiac Surgery
A unilateral continuous paravertebral block has been shown to be effective in managing pain after major unilateral thoracic surgery, such as minimally invasive coronary artery bypass surgery.
Inguinal Hernia Repair
The effectiveness of a paravertebral block in providing adequate and long-lasting postoperative relief of pain after herniorrhaphy is well documented in the literature. In this setting, a paravertebral block should be performed between the T10 and L2 levels. In pediatric surgery, a paravertebral block with a mixture of 2% lidocaine, epinephrine, and clonidine provided better postoperative analgesia during the first 48 hours than did standard general anesthesia. In adults, Hadzic and associates showed that a paravertebral block (T9-L1) using 20 mL of 0.75% ropivacaine was more effective than the combination of general anesthesia and wound infiltration. This was supported by more patients bypassing the postanesthesia care unit, less need for supplemental analgesics, and earlier discharge home.
Multiple Rib Fractures
A paravertebral block provides effective pain relief after multiple rib fractures. It can be performed either as a single shot (bolus of 15 to 20 mL of a long-acting local anesthetic) or as a continuous technique. It has been shown to improve both ventilatory and arterial blood gas parameters.
Neuralgia and Pleuritic Pain
Paravertebral blocks have been used to treat chronic pain after thoracotomy or mastectomy.
Contraindications
Contraindications to paravertebral blockade include infection (local, empyema), allergy to local anesthetics, major chest deformity, previous ipsilateral thoracic surgery, and coagulation abnormalities.
Failure Rate
A paravertebral block is an easy technique to learn. Even in inexperienced hands, it rapidly provides a high success rate. Indeed, it has been shown that the success rate is significantly improved after a cutoff of 15 blind paravertebral blocks. The failure rate with the blind technique varies between 6% and 15%, depending on the experience of the operator. Recently, ultrasound assistance has made this block much easier and more popular than in the past.
Complications
The incidence of complications after paravertebral blocks varies between 2% and 5% ( Box 55.2 ). The incidence of hypotension requiring a low dose of vasopressors (e.g., ephedrine) is 4%. The hypotension may be due to either sympathetic blockade (unilateral or bilateral) or a vasovagal event during the procedure. Horner’s syndrome is due to cephalad spread of the local anesthetic after a high thoracic paravertebral block. With regard to epidural spread, dye injection studies have shown the incidence of unilateral epidural spread to be up to 70% when using the blind approach. However, its clinical effects are negligible because of the small amount of local anesthetic injected.
Pneumothorax (0.5% to 1.5%)
Hypotension
Vascular puncture (6%)
Intrathecal spread (1%)
Toxic seizures
Horner’s syndrome
Epidural spread
Intercostal Nerve Blockade
Anatomy
The intercostal nerves are the anterior divisions of the thoracic spinal nerve from T1 to T11. They are distributed mainly to the thoracic pleura and abdominal peritoneum. The first two nerves supply fibers to the upper limb in addition to their thoracic branches, the next four are limited in their distribution to the parietal pleura of the thorax, and the lower five supply the parietal pleura of the thorax and abdomen. The 7th intercostal nerve terminates at the xiphoid process, the 10th intercostal nerve terminates at the umbilicus, and the 12th (subcostal) thoracic nerve is distributed to the abdominal wall and the groin.
Technique and Drugs
An intercostal block (ICB) is usually performed at the level of the posterior axillary line ( Fig. 55.5 ). The needle is inserted until it contacts the rib. It is then partially withdrawn, reoriented caudally, and advanced less than 0.5 cm deeper than the bone contact. Use of a stimulating needle connected to a peripheral nerve stimulator may be helpful. Elicitation of intercostal muscle contractions indicates adequate needle location. It is preferable to block the two proximal and two distal adjacent nerves from the selected level to cover all the areas affected by the surgical incision.
During thoracotomy, the block may be performed by the surgeon under direct vision either at the beginning or at the end of the operation before skin closure.
Ultrasound-Guided Technique
With direct visualization of the ribs and pleura ( Fig. 55.6 ), ultrasound guidance allows the anesthesiologist to perform an ICB proximal to the scapula, where the intercostal nerve can be blocked before its division to ensure adequate anesthesia of the pleura. In addition, ultrasound guidance allows visualization of injection of the local anesthetic into the intercostal space, thereby enabling the provider to adjust the trajectory and depth of the needle to ensure adequate spread of anesthetic and avoid pleural puncture. The patient is positioned prone, and the spinous processes of the thoracic vertebra are identified by palpation. The chest wall is best imaged in a parasagittal plane. The intercostal space is visualized with a high-frequency linear probe. The ribs appear as an oval structure with a bright surface (periosteum). A dark shadow is seen deep to the rib secondary to echo shadowing. The pleura and lungs are visualized deep to the intercostal space between the echo shadows. The needle target is the internal intercostal muscle.
After subcutaneous infiltration of local anesthetic, a 22-gauge needle is inserted either in plane or out of plane toward the plane just deep to the internal intercostal muscle. Then, 3 mL of a long-acting local anesthetic with epinephrine is injected into the intercostal space.
With continuous techniques, the infusion rate is 5 to 7 mL/hr for an average-sized adult. Many studies have shown that C max occurs rapidly within 3 to 20 minutes after the block. Administration of 16 mL of either 0.5% plain bupivacaine or 1.5% lidocaine with epinephrine results in an acceptable range of local anesthetic plasma concentrations (1.44 ± 0.2 µg/mL for bupivacaine and 2.78 ± 0.2 µg/mL for lidocaine).
Indications
Indications for ICB include relief of postoperative pain after breast surgery, thoracotomy, video-assisted thoracic surgery, and coronary artery bypass surgery. It has been used for the relief of pain after rib fractures and with chronic pain syndromes involving the chest.
For minor breast surgery, multiple ICBs (T3-6) result in a significantly better quality and duration of postoperative analgesia than afforded by general anesthesia alone.
Many studies have confirmed the effectiveness of ICB in relieving pain after thoracic surgery. It has been noted that when performed at five levels, ICB results in effective analgesia during the first 6 hours after thoracotomy, similar to thoracic epidural analgesia. In contrast, interpleural analgesia was ineffective in providing adequate pain relief.
Video-assisted thoracic surgery is less invasive than open thoracotomy but is still followed by postoperative pain and impairment of lung function. Bilateral ICB of the second, third, and fourth intercostal nerves, under direct vision during surgery, has been shown to be safe and effective in reducing postoperative pain and analgesic requirements. However, another study was unable to show any difference between ICB, intrapleural analgesia, and opioid analgesia.
The efficacy of ICB in relieving pain and improving ventilatory parameters after multiple rib fractures has clearly been demonstrated.
For minimally invasive coronary bypass surgery, it has been shown that when compared with opioid analgesia, ICB (four levels, 5 mL of 0.1% ropivacaine per level) provides better pain relief in the early postoperative period and allows earlier patient discharge to the intermediate care ward.
Contraindications and Complications
Contraindications to ICB include local infection and contralateral pneumothorax. Its major complication is pneumothorax, the incidence of which is estimated to be 1.4% for each intercostal nerve blocked.
Intercostal Nerve Blockade
Anatomy
The intercostal nerves are the anterior divisions of the thoracic spinal nerve from T1 to T11. They are distributed mainly to the thoracic pleura and abdominal peritoneum. The first two nerves supply fibers to the upper limb in addition to their thoracic branches, the next four are limited in their distribution to the parietal pleura of the thorax, and the lower five supply the parietal pleura of the thorax and abdomen. The 7th intercostal nerve terminates at the xiphoid process, the 10th intercostal nerve terminates at the umbilicus, and the 12th (subcostal) thoracic nerve is distributed to the abdominal wall and the groin.
Technique and Drugs
An intercostal block (ICB) is usually performed at the level of the posterior axillary line ( Fig. 55.5 ). The needle is inserted until it contacts the rib. It is then partially withdrawn, reoriented caudally, and advanced less than 0.5 cm deeper than the bone contact. Use of a stimulating needle connected to a peripheral nerve stimulator may be helpful. Elicitation of intercostal muscle contractions indicates adequate needle location. It is preferable to block the two proximal and two distal adjacent nerves from the selected level to cover all the areas affected by the surgical incision.
