Thoracic Paravertebral Block

Anatomy and Physiology

The triangle-shaped area between the head and neck of the rib. The paravertebral space is delineated anterolaterally by the parietal pleura, posteriorly by the costotransverse ligament, medially by the vertebrae, and intervertebral foramina, inferior and superior by the ribs. The vertebral root divides in this anatomical space after emerging from the intervertebral foramen to give the dorsal and ventral branches. Thus the content of this space includes adipose tissue, anterior ramus of the spinal (intercostal) nerves, posterior ramus of the spinal (intercostal) nerves, sympathetic chain, and rami communicantes. The sympathetic chain communicates with the intercostal nerves via the rami communicantes. 

Thoracic paravertebral space communicates with:

• Medially: Epidural space via the intervertebral foramen[9]
• Laterally: Intercostal space[10]
• Superiorly: Cervical paravertebral space
• Inferiorly: The origins of the Psoas Major muscle

The nerves in this space are devoid of the fascial sheath, making them particularly sensitive to local anesthetics injected. This injection of local anesthetic will cause unilateral, segmental, somatic, and sympathetic anesthesia, including the posterior branch in several thoracic dermatomes.[11]

This extensive dissemination of the local anesthetic has been demonstrated by several authors, notably Cheema et al. (1995), using a thermographic imaging technique.[8]

Other authors have described a diffusion in the epidural space of this nerve block or even on the contralateral side of the block reported by Karmakar et al. (2000) after injection of contrast medium through a thoracic paravertebral catheter.[12]

Indications

The TPVB is indicated to provide anesthesia and analgesia of any hemithorax surgical procedure and when the associated pain is mainly unilateral of the chest and abdomen. Perioperative bilateral TPVB uses have also been described during the thoracic phase of major abdominal surgeries.[13]

It is often used as an adjunct to multimodal postoperative analgesia in thoracic surgery, breast surgery, renal surgery, video-assisted thoracoscopic surgery,  minimally invasive cardiac surgery, and more frequently indicated recently in breast reconstruction surgery in combination with general anesthesia.[14][15]

The TPVB can be used as an alternative anesthesia technique for breast surgery in patients who may have a high risk of perioperative and postoperative complications after general anesthesia, especially elderly patients with low vital capacity and low lung reserve or patients with cardiac morbidity.[16]

For major breast surgeries, recent studies have demonstrated the efficacy of TPVB with minimal complications and a low conversion rate to general anesthesia, considerably improving the quality of postoperative recovery.[17]

Contraindications

The main contraindications for TPVB include:

• Patient refusal
• Hypersensitivity reaction or allergy to local anesthetics
• Coagulopathy or systemic anticoagulation (INR> 1.4 or insufficient time since stopping anticoagulant according to ASRA guidelines)
• Infection at the injection site
• Tumor occupying the region
• Respiratory infection, or persistent pleural enlargement: due to the risks of pneumothorax. 
• According to some authors, a deformity of the rib cage may predispose to a pleural or intrathecal puncture.

Equipment

The TPVB is currently performed in the majority of hospital institutions under ultrasound guidance to minimize the risk of nerve and/or pleural damage which can lead to pneumothorax. To perform the procedure we need the following equipment:

• Ultrasound guidance with the high-frequency probe or low-frequency curvilinear probe depending on the patient's body
• Sterile sleeve and gel
• One 23 to 25 gauge needle for skin infiltration
• 25 mL of local anesthetic
• Needle size: 80mm B-bevel nerve block needle
• 1 pack of gauze 4-inch x 4-inch
• Chlorhexidine gluconate solution for skin asepsis
• Sterile gloves
• Marking pen for anatomical landmarks

Personnel

Staff qualified in regional anesthesia is recommended for this kind of procedure as they must manage the complications related to the nerve block.

Before performing the procedure, administration of an anxiolytic may be necessary to reduce stress for some patients.

A nurse trained in regional anesthesia should accompany the physician during his procedure and help them manage sedation if necessary.

Preparation

Before any regional anesthetic procedure, a complete checklist assessment should be performed. An assessment of the patient's comorbidities should be performed beforehand, including medical history, physical examination with assessment of the respiratory tract, and analysis of preoperative tests.

Before obtaining informed consent from the patient, the anesthesiologist is required to inform them of the risks and benefits of TPVB and the potential complications.

A clinic specializing in regional anesthesia is recommended to perform the nerve block to ensure optimal monitoring of the patients' vitals. This monitoring includes pulse oximetry, electrocardiography, and blood pressure, as described in the standards of the American Society of Anesthesiologists.

Technique or Treatment

The authors have described several techniques to perform this procedure. The patient can be in a seated, lateral, or prone position. The sitting position offers more comfort for the awake patient.

The classical and conventional technique, which was the most commonly used and described by former practitioners, is based on the loss of resistance as published by Eason and Wyatt (1979).[4] This loss of resistance allowed the anesthesiologist to locate the paravertebral space after passing the needle through the superior costotransverse ligament to end in the desired space. After asepsis, the needle is inserted 2.5 to 3 cm laterally to the spinous process and advanced perpendicular to the skin to contact the lower vertebra's transverse process. Once passed over of the transverse process, the needle is gradually advanced until a loss of resistance to air. The needle then passes through the costotransverse ligament, and after gentle aspiration, the local anesthetic is injected.

This technique is much less practiced by centers specializing in regional anesthesia today because it represents a significant failure rate. The complications related to lesions of the parietal pleura can lead to pneumothorax, which has forced the authors to modify their technique and rely on an ultrasound-guided approach to verify the correct location of the needle in the paravertebral space.

In 2009 Luyet et al. described in a study based on cadaveric imaging a catheter placement in the paravertebral space under ultrasound guidance. Since then, many studies have demonstrated an interest in ultrasound guidance in the use of TPVB.[18][19]

After aseptic disinfection, which should include the cervicothoracic para-vertebral areas up to the lower edge of the scapula, the regional anesthesiologist performs a T2 to T6 ultrasound location of the paravertebral region at the surgical site. A 50 mm 15-6 MHz linear probe is used.[19]

The spinous process T1 to T8 is identified based on the C1 vertebra or from the lower edge of the scapula, which corresponds to T7, and the ultrasound probe is positioned on the spinous process in relation to the surgical site to be covered, the examiner visualizes the transverse process by lateral movement of the probe, and performing an oblique movement of the probe, three important anatomical structures are visualized: the typical double layer of the internal intercostal membrane, the transverse process and the respiratory movements of the parietal pleura. After skin anesthesia with 2% lidocaine (1 ml), the needle-guided out of the plane is positioned 1 cm caudal from the ultrasound probe. When the needle reaches the space between the internal intercostal membrane and the pleura, a local anesthetic is then administered over a period of 30 seconds.

Complications

Apart from the classic complications observed during regional anesthetic techniques such as puncture site infections, hematomas at the puncture site, nerve damage, and toxicity linked to an overdose of local anesthetics. The paravertebral block presents specific complications such as the risk of pneumothorax, hemothorax, or intrathecal injection as described by certain authors ( Lekhak and colleagues ).[20]

Pulmonary hemorrhage has been described in patients who have undergone paravertebral block during thoracic surgery.[21]

Other complications such as Ipsilateral brachial plexus block and hemidiaphragmatic paresis were observed by Steven H Renes et al. (2011).[22]

Burlacu et al. (2005) and Crawley S M (2006) also reported diffusion to the ipsilateral stellate ganglion during TPVB leading to ipsilateral Horner syndrome.[23][24]

Nowadays, these complications are becoming less frequent thanks to the existence and technological progress of ultrasound devices.

Clinical Significance

The TPVB is a regional anesthetic procedure associated with a low overall incidence of complications thanks to ultrasound. It suppresses the neuroendocrine response to surgical stress by its somatic and sympathetic nerve blockade, allowing major thoracic surgery to be performed with optimal intraoperative and postoperative analgesia. The thoracic epidural is presented as the gold standard for analgesia during a major thoracotomy, but the TPVB, compared to the thoracic epidural in terms of analgesia, also provides effective pain relief with few side effects and should be seen as a safe alternative in case of contraindication to the thoracic epidural.[25]

In the current literature, we can discover the publication of a whole series of studies on the impact of TPVB and its beneficial effects on the optimization of intraoperative and postoperative analgesia. These investigations include randomized controlled trials (RCTs), observational trials, and numerous case reports.

In a recent study including patients with non-small cell lung cancer (NSCLC) undergoing lobectomy surgery, ultrasound-guided thoracic paravertebral block (UG-TPVB) demonstrated effectiveness in reducing postoperative pain, quality of life, and improving recovery for early revalidation.[14]

A single thoracic paravertebral injection is effective for acute pain control in the emergency room in patients with multiple post-traumatic rib fractures.

To assess the analgesic efficacy of TPVB in patients scheduled for modified radical mastectomy, a prospective randomized trial was published recently, including 90 females.  Postoperative morphine consumption during the first 48 hours has been recorded. The author concludes that the TPVB allowed a significant reduction in postoperative opioid consumption than the control group and without an increase in adverse effects.[5]

In a recent meta-analysis (2/2020), the authors have compared the analgesic efficacy of pectoral block versus TPVB at 2 postoperative hours in patients who had undergone breast surgery. Eight trials, including 388 patients, were identified, and the authors concluded that compared to paravertebral block, there is low-quality evidence that a pectoral block provides marginal postoperative analgesic benefit after a radical mastectomy.[26]

In another recent study, the authors evaluated retrospectively opioid consumption in patients who underwent video-assisted thoracic surgery after placing a paravertebral catheter.[27] A total of 269 patients were enrolled in this study, and conclude that TPVB appears to be a safe and effective analgesic technique for reducing postoperative pain and improving patient satisfaction.

In a prospective randomized and controlled study, H Hu et al. (9/2020) included 60 patients receiving single-port video-assisted pulmonary lobectomy with a paravertebral block guided by thoracoscopy at the end of the operation. The VAS (visual analog score) score of the TPVB group was significantly lower than that of the control group at all time points. The author concludes that the regional analgesic procedure chosen for these patients can effectively reduce postoperative pain while ensuring patient safety.[28]

Enhancing Healthcare Team Outcomes

Major thoracic surgery involves interprofessional and multidisciplinary teams for the perioperative and postoperative management of pain. The TPVB should be performed by an anesthesiologist specialized in regional anesthesia with the assistance of a qualified nurse. Communication in this context is essential to provide optimal patient care. A thorough checklist of the patient's medical history is mandatory. Time-out should be performed by confirming patient identification, the surgical procedure to be performed, and the surgical site marked before starting the procedure.

The medical and surgical team involved must manage any complications that may arise during these procedures and help in an emergency.

A nursing and medical team capable of managing pain and establishing optimal pain control strategies is essential for the patient's post-operative recovery.

Nursing, Allied Health, and Interprofessional Team Interventions

A qualified nursing team for the operating room is recommended when performing the TPVB, and the management of postoperative pain by the regional anesthesiologist.

Nursing, Allied Health, and Interprofessional Team Monitoring

The TPVB should be performed in a university hospital center equipped with cardiovascular and respiratory monitoring equipment to ensure optimal monitoring of vital parameters to predict and manage the occurrence of complications as safely as possible.

Although the safety in performing nerve blocks has increased under ultrasound guidance, complications may still arise, and a qualified anesthesiologist should be well equipped to manage them.