Continuous paravertebral block is an accepted technique for postoperative pain control after surgery of the abdomen,1 thorax,2 breast,3 and fractured ribs.4
The pain relief achieved with paravertebral block is comparable with epidural analgesia, and paravertebral block appears to have fewer complications.5,6 The original approach7 relied on anatomical landmarks and a blind approach in which the needle is advanced a fixed distance deep to the transverse process.7 Other approaches have been described based on neurostimulation,8 loss of resistance,9 pressure transduction,10 or the use of ultrasound to measure the depth from the skin to the transverse process before a blind technique.11 Recently, we published an alternative approach to the paravertebral space using a blind subcostal approach.12 This technique relies on the blind cannulation of the space between the internal and innermost intercostal muscles to facilitate placement of a catheter in the paravertebral space. The space cannulated by this technique is close to the pleura and also includes the intercostal artery and nerve. To potentially minimize the risk of vascular puncture, nerve injury, and pneumothorax, we investigated the feasibility of performing such a block using an ultrasound-guided technique. Initially, we studied the gross and sonographic anatomy in a fresh cadaver and a model (Figs. 1–3). A GE Logic e platform (Fairfield, CT) with a 12L probe oscillating at 13 MHz was used for this study portion. Subsequently, we applied this technique to 12 patients using a linear ultrasound transducer (SonoSite MicroMaxx, L25 probe, SonoSite, Bothell, WA).
This study was initially approved by the committee for quality assurance. The IRB subsequently gave us approval to retrospectively review the database for 12 patients. These patients underwent elective placement of bilateral paravertebral catheters for postoperative pain management after elective abdominal surgery. Patients were included in the study if they had a lean body habitus and if they arrived in the preanesthesia area 1–2 h before their scheduled surgery. These 12 patients were interspersed among several hundred other patients who received paravertebral blocks using a blind technique.
After the application of standard monitors, each patient was positioned prone and sedated with a combination of midazolam (0–2 mg) and fentanyl (0–100 μg). Nerve blocks were placed bilaterally between ribs 7 and 8, ribs 8 and 9, and ribs 9 and 10 based on palpation of the thoracic spine and the ultrasound scans. The corresponding intercostal space was scanned in the short axis (between T8 and T10), 8 cm lateral to the midline of the spine using a linear ultrasound transducer (Fig. 2). First, the ribs were identified and then the visceral and parietal pleura were identified by asking the patient to take a deep breath. The latter maneuver caused a visible movement of the visceral and parietal pleura over each other. Next, the probe was rotated so that it was oriented immediately over the long axis of the rib. By toggling (tilting) the probe (Figs. 2b and c), the intercostal muscles could be identified deep and inferior to the rib. The skin and subcutaneous tissues were anesthetized with lidocaine (10 mg/mL) using a 25-gauge needle. After skin anesthesia, a 17-gauge Tuohy needle (Arrow International, Reading, PA) was introduced in-plane at the lateral end of the probe. The Tuohy needle was advanced in increments aiming at the space between the internal and innermost intercostal muscles (Fig. 3a). After each advance, normal saline (1–2 mL) was injected until the fascial plane between the muscles was dilated and the pleura were displaced anteriorly (Fig. 3b). Once the space between the muscles was identified, the needle was disconnected from the normal saline syringe and the patient was asked to breathe deeply to exclude the possibility of accidental pleural puncture. After a negative blood and air aspiration test, 10 mL of ropivacaine (5 mg/mL) was injected and a 19-gauge wire-bound catheter was inserted 7 cm beyond the tip of the needle (Fig. 4). The same procedure was repeated on the contralateral side.
Each patient underwent general anesthesia using propofol, vecuronium, volatile anesthetics, and fentanyl or hydromorphone as well as endotracheal intubation. In the recovery room, each paravertebral catheter was bolused with 10 mL of lidocaine (15 mg/mL). Twenty minutes later, using a pinprick test with a 25-gauge needle, we determined the number of dermatomes completely anesthetized between T6 to T12. Each paravertebral catheter was connected to a CADD pump (Smith Medical MD, St. Paul, MN) set to infuse ropivacaine (2 mg/mL) at 10 mL/h. In addition, each patient was given free access to a patient-controlled analgesia pump set to administer IV hydromorphone (0.2 mg/dose) every 8 min on demand without a basal rate. Each patient was followed by the Acute Interventional Perioperative Pain Service. Verbal pain scores using an 11-point scale (0 = no pain to 10 = worst possible pain) were recorded over 3 days. Intravenous hydromorphone consumption for the first 24 h after surgery was also recorded. All catheters were removed within 72 h after the completion of surgery.
Patients’ demographic data are presented as mean ± sd and range. Because the pain scores and hydromorphone consumption were not normally distributed, these observations are reported as median and interquartile range (IQR).
The mean age of the patients was 56 ± 16 yr (range 19–86 yr). The mean weight was 81 ± 24 kg (range 50–141 kg). Twenty-four continuous paravertebral blocks were performed in 12 patients. The patient characteristics and extent of the block produced by the paravertebral injections are shown in Table 1. The median number of dermatomes blocked using a pinprick technique was 5 (IQR 4–6). Over the first 24 h, the median dose of hydromorphone consumed was 1.9 mg (IQR 0.7–5.05) (range 0.0–9.6 mg), and the median verbal pain score on postoperative day 1 was 5.5 (IQR 3.5–6) (range 1–10). We were able to demonstrate dermatomal block to pinprick in 23 of 24 blocks performed.
Our data indicate that we were able to approach the paravertebral space via the intercostal space relying on sonographic landmarks. With this approach, we achieved satisfactory dermatomal spread in 23 of 24 catheters placed under ultrasound guidance. Of the patients studied, only one patient asked for additional analgesia on postoperative day 1. This patient was given a bolus of dilaudid (0.4 mg), and both of his catheters were bolused with 6 mL of local anesthetic from his CADD pump. In one patient, we failed to demonstrate any block on one side. In this patient, it is likely that the local anesthetic was injected into a plane between more superficial muscles or into one of the intercostal muscles itself.
The key to a successful paravertebral block under ultrasound guidance is the ability to identify the plane between the internal and the innermost intercostal muscles. Factors that compromise successful performance include an ultrasound device with low resolution, blood or fracture in the intercostal space, as well as morbidly obese patients or air in the subcutaneous tissue after a pneumothorax. The practitioner must also keep the tip of the needle in view at all times during this procedure to minimize the risk of pneumothorax. Injection of local anesthetic or saline as the needle is advanced may help the practitioner to accomplish this task.
This series supports the premise that ultrasound guidance is a technique that allows the practitioner to cannulate the paravertebral space and to achieve a sensory block. Further study comparing this ultrasound-guided technique with other techniques is merited.
1. Rudkin GE, Gardiner SE, Cooter RD. Bilateral thoracic paravertebral block for abdominoplasty. J Clin Anesth 2008;20:54–6
2. Kaya FN, Turker G, Basagan-Mogol E, Goren S, Bayram S, Gebitekin C. Preoperative multiple-injection thoracic paravertebral blocks reduce postoperative pain and analgesic requirements after video-assisted thoracic surgery. J Cardiothorac Vasc Anesth 2006;20:639–43
3. Moller JF, Nikolajsen L, Rodt SA, Ronning H, Carlsson PS. Thoracic paravertebral block for breast cancer surgery: a randomized double-blind study. Anesth Analg 2007;105:1848–51
4. Karmakar MK, Critchley LA, Ho AM, Gin T, Lee TW, Yim AP. Continuous thoracic paravertebral infusion of bupivacaine for pain management in patients with multiple fractured ribs. Chest 2003;123:424–31
5. Davies RG, Myles PS, Graham JM. A comparison of the analgesic efficacy and side-effects of paravertebral vs epidural blockade for thoracotomy—a systematic review and meta-analysis of randomized trials. Br J Anaesth 2006;96:418–26
6. Lonnqvist PA, Mackenzie J, Soni AK, Conacher ID. Paravertebral blockade—failure rate and complications. Anaesthesia 1995;50:813–5
7. Eason MJ, Wyatt R. Paravertebral thoracic block—a reappraisal. Anaesthesia 1979;34:638–42
8. Naja MZ, Ziade MF, Lönnqvist PA. Nerve-stimulator guided paravertebral blockade vs. general anaesthesia for breast surgery: a prospective randomized trial. Eur J Anaesth 2003;20:897–903
9. Mehta Y, Arora D, Sharma KK, Mishra Y, Wasir H, Trehan N. Comparison of continuous thoracic epidural and paravertebral block for postoperative analgesia after robotic-assisted coronary artery bypass surgery. Ann Card Anaesth 2008;11:91–6
10. Richardson J, Cheema SPS, Hawkins J, Sababathan S. Thoracic paravertebral location: a new method using pressure measurement. Anaesthesia 1996;51:137–9
11. Pusch F, Wilding E, Klimscha W, Weinsable C. Sonographic measurement of needle insertion depth in paravertebral blocks in women. Br J Anaesth 2000;85:841–3
12. Burns DA, Ben-David B, Chelly JE, Greensmith JE. Intercostally placed paravertebral catheterization: an alternative approach to continuous paravertebral blockade. Anesth Analg 2008;107:339–41