Distribution of injectate administered through a catheter inserted by three different approaches to ultrasound-guided thoracic paravertebral block: a prospective observational study

Abstract

BackgroundDespite the popularity of continuous thoracic paravertebral block (TPVB), there is a paucity of information on catheter tip position and distribution of injectate through the catheter. We observed, in real time, the spread of dye, the catheter tip position and sensory block levels produced with three different (intercostal (IC), transverse process sagittal (TS) and paralaminar (PL)) approaches to ultrasound-guided TPVB in patients undergoing video-assisted thoracoscopic surgery.MethodsAfter the induction of general anesthesia, ultrasound-guided TPVB was conducted with a patient in the lateral decubitus position. During surgery, 10 mL of dye was injected through a catheter to observe the catheter tip and the dye distribution under thoracoscopy. Dermatomal sensory block levels were measured postoperatively.ResultsTen patients for each of three different approaches completed the study. There were a variety of dye spreading patterns. The median (range) number of segmental levels stained with dye was 1.5 (1–4), 3 (1–4) and 3 (1–5) with the IC, TS and PL approaches, respectively. We observed that a catheter tip was present at the same segmental paravertebral space as intended in 50%–90% of patients using these approaches. The median (range) number of dermatomes with sensory blockade at 6 hours after block was 2.5 (1–4), 3 (2–8) and 3 (1–8) with the IC, TS and PL approaches, respectively.ConclusionsAlthough a bolus injection through a catheter for ultrasound-guided TPVB produced multiple levels of spread and sensory blockade in more than half the patients, considerable differences existed in the spread regardless of approach.