Case Report: Thoracic paravertebral catheter positioning for postoperative continuous analgesia

Introduction

The thoracic paravertebral block (PVTB) is a regional anesthesia technique that involves the injection of a local anesthetic into the paravertebral space, a virtual triangular space bordered anterolaterally by the parietal pleura, posteriorly by the costotransverse ligament, medially by the vertebra and intervertebral foramen, and inferiorly and superiorly by the ribs (Figure 1). PVTB is a unilateral, segmental, somatic, and sympathetic block of the dermatome at the level of the injection and contiguous dermatomes, affecting at least two levels both cranially and caudally (1).

The classic technique was described in 1979 by Eason and Wyatt (2), while in 2009, the placement of a catheter in the paravertebral space was described in a cadaveric study (3). Since then, there has been increasing interest in ultrasound-guided PVTB with significant clinical applications.

The ultrasound-guided block technique involves using a high-frequency linear probe placed transversely (perpendicular to the spinous process line) or longitudinally (parallel to the spinous process line). PVTB can be performed with the patient sitting, in lateral decubitus, or in the prone position. The needle approach can be in-plane or out-of-plane.

PVTB is effective for analgesia and anesthesia in thoracic surgery (4) and has been proposed as an alternative technique to thoracic epidural anesthesia for thoracotomy procedures (5). It is the technique of choice for postoperative pain management in minimally invasive thoracic surgery (6, 7). Pain management in video-assisted thoracic surgery (VATS ) has a high recommendation level, both for single-shot and continuous techniques (8).

The main limitation of this technique is its limited duration, which, despite enhancement with adjuvants, generally does not exceed 12 h. Therefore, continuous PVTB would be preferable (9, 10). However, placing a catheter in the paravertebral space for continuous PVTB is a non-routine technique and is subject to frequent failure (11). In some surgical settings, the catheter for continuous paravertebral block is even positioned directly by the surgeon, with results comparable to those of US-guided percutaneous catheterization (12).

In this case report, we describe our approach to ultrasound-guided placement of a thoracic paravertebral catheter for continuous operative analgesia in a left VATS pneumectomy. At the end of the procedure, the catheter tip is visualized by ultrasound using a bolus of air and saline. The video shows how the visualization obtained in this way is as reliable as using a dye such as methylene blue.

Case report

The 50-year-old patient was scheduled for a VATS 3P left pneumonectomy. Physical examination revealed a patient with Class I obesity (BMI of 30 kg/m²) and chronic obstructive pulmonary disease (COPD) due to smoking (pack-year of 48). Pulmonary auscultation showed reduced breath sounds on the left side, consistent with the clinical diagnosis. Cardiovascular status was stable, with a functional capacity estimated at >4 metabolic equivalents of task (METs). Relevant preoperative labs were within normal limits, though forced expiratory volume in the first second (FEV1) was 60% of predicted, diffusion lung carbon monoxide (DLCO) was 38%, and a volume oxygen maximum (VO₂ max) of 32% was calculated on perfusion lung scintigraphy, emphasizing the need for optimal regional analgesia to prevent postoperative respiratory complications. Once in the operating room, anesthesia was induced with the total intravenous anesthesia-target-controlled infusion (TIVA-TCI) technique using propofol and remifentanil according to bispectral index (BIS) monitoring. Muscular relaxation was obtained with rocuronium 0.6 mg/kg and a 39 Fr left double-lumen tube was placed. Once the patient was placed in the side position, chlorhexidine disinfection was performed and a sterile field was set. The ultrasound probe was covered with a sterile barrier and a sagittally oriented thoracic paravertebral space block (TPVB) space US scan was performed. Once the T4–T5 space was identified, a SonoLong Echo™ 20-G 50 mm Tuohy needle was used with an in-plane approach (Pajunk, 78187 Geisingen, Germany). Needle progression was checked using hydrodissection with saline solution. Once the superior costotransverse ligament was passed, a 5 mL bolus of 7.5 mg/mL ropivacaine was administered with pleural shift as feedback (Figure 2). Once the infusion line was disconnected from the needle, the spiral tail catheter was advanced to the tip of the needle using the centimeter markings as a reference. Once the desired insertion depth was reached, it was important to ensure that no retraction of the catheter occurred during needle withdrawal. To ensure correct positioning, a bubble test was performed with 4 mL of saline solution. The path of the catheter was clearly highlighted and allowed the surgeon to visualize the correct position of the device (Figure 3). At the end of surgery, a bolus of 10 mL of 0.5% ropivacaine with 2 mL of methylene blue was administered. At this point, the metameric spreading of the mixture in the TPVB spaces was evident, in agreement with the US data obtained at the beginning of the intervention. At the end of surgery, the patient was awakened and transferred for a short period of postoperative observation in the post-anesthesia care unit (PACU). The postoperative pain relief protocol includes a continuous PVTB infusion of 7 mL/h with 0.2% ropivacaine, 1 g of paracetamol, and 15 mg of ketorolac every 8 h. Furthermore, an 8 mL ropivacaine 0.2% bolus was used as rescue. The patient’s static and dynamic postoperative numerical rating scale (NRS) scores were constantly <3 during his hospital stay. No complications occurred and the patient was dismissed on the 8th postoperative day (Table 1).

Table 1. Clinical timeline: summary of the patient's care, detailing the preoperative evaluation, intraoperative ultrasound-guided continuous paravertebral block (PVTB) placement, postoperative pain management protocol, and clinical outcomes.

Discussion

The ultrasound-guided placement of a thoracic paravertebral catheter is considered to guarantee analgesia equivalent to that of epidural analgesia (5, 8, 13). Despite the efficacy widely described in the medical literature, the use of continuous PVTB is little used due to frequent malpositioning of the catheter in the first hours of the postoperative period (14). Likewise, especially in obese patients or in those with particularly deep paravertebral spaces, the retraction of the needle at the end of the procedure can cause a displacement of the catheter tip, which compromises the efficacy of the technique (15). This, in our opinion, may depend on the following three factors: the lack of a thick ligamentous structure, such as the ligamentum flavum; the need to not excessively advance the catheter outside the needle due to the risk of migration towards the intercostal space or the intervertebral foramen; and continuous changes in direction during the progression of the needle, which create tensions between the muscular planes that could exert tension on the catheter once the rigid structure of the needle is withdrawn. Therefore, at the end of the procedure, after having fixed the catheter at the exit point on the patient's skin with a transparent drape, we perform a new ultrasound examination to confirm the proper catheter position. It is often impossible to identify it, in which case we use a “bubble test” to highlight the course of the catheter by exploiting the physical effect of the air on the ultrasound. Once the correct position has been confirmed, surgery can begin; alternatively, the operator can correct any technical failures by repositioning the catheter. The primary strength of this technique lies in the real-time ultrasound guidance combined with a functional confirmation (bubble test), which ensures the catheter's tip remains in the paravertebral space after the needle is withdrawn. This is particularly crucial in patients with a high BMI, such as the patient described in this case report (BMI of 30), where deeper anatomical structures and tissue redundancy increase the risk of catheter displacement (16). However, a clear limitation is that this is a single case report; while the clinical outcome was excellent, large-scale randomized trials are needed to define its sensitivity and specificity. The saline bubble test is highly reproducible and requires no specialized equipment beyond a standard syringe. By visualizing the air–liquid interface (hyperechoic artifacts) moving within the PVTB space, the clinician receives immediate feedback. The validity of this test was confirmed in our case by the subsequent visualization of the methylene blue spread during the surgical phase, showing perfect concordance between the ultrasound “bubbles” and the dye distribution. While technically demanding, this method is generalizable to the majority of thoracic surgery settings, especially in obese patients, where traditional landmarks are obscured. From the patient's perspective, the procedure was well-tolerated, and the pain relief satisfaction was high, with NRS scores consistently below 3, allowing for early mobilization and effective respiratory physiotherapy.

Conclusion

Ultrasound-guided placement of a thoracic paravertebral catheter offers a reliable alternative to epidural analgesia for thoracic surgeries. Despite concerns about catheter malpositioning, particularly in obese patients, our experience demonstrates that the “bubble test” with saline can effectively confirm the catheter's position and ensure proper analgesia. This approach can provide excellent postoperative pain control, with minimal complications, making it a valuable technique for managing pain in VATS and other thoracic procedures. The placement of the paravertebral catheter also offers the possibility of an infusion of analgesic drugs in the postoperative period, increasing pain control and patient comfort.

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Footnotes

Edited by: Roger Royster, Wake Forest Baptist Medical Center, United States

Reviewed by: Manuel Granell, University of Valencia, Spain

Longbin Zheng, Affiliated Hospital of Jiangsu University, China

Abbreviations PVTB, thoracic paravertebral block; VATS, video-assisted thoracic surgery; COPD, chronic obstructive pulmonary disease; NRS, numerical rating scale; METs, metabolic equivalents of task; FEV1, forced expiratory volume in the first second; DLCO, diffusion lung carbon monoxide; VO₂ max, volume oxygen maximum; TIVA-TCI, total intravenous anesthesia-target-controlled infusion; US, ultrasound.