Transverse vs. parasagittal in-plane approaches in ultrasound-guided paravertebral block using a microconvex probe: A randomised controlled trial.

BACKGROUND: Several approaches have been proposed for ultrasound-guided thoracic paravertebral block, but the best approach remains unclear. OBJECTIVE: We compared two ultrasound-guided in-plane approaches using a microconvex probe, transverse and parasagittal. We assessed whether either approach would facilitate successful catheter placement in the paravertebral space. DESIGN: Randomised controlled trial. SETTING: University hospital, July 2015 to March 2016. PATIENTS: Sixty patients scheduled to undergo thoracotomy were randomly allocated into two groups. INTERVENTIONS: A microconvex probe was placed transversely between adjacent ribs (transverse) or sagittally between adjacent transverse processes (parasagittal). When the Tuohy needle reached the paravertebral space, a catheter was inserted to a depth of 4 cm. Then, 0.5-ml radiocontrast was injected through the catheter under fluoroscopy. MAIN OUTCOME MEASURES: The primary outcome was successful catheter placement in the paravertebral space; secondary outcomes were 0 to 100 mm visual analogue scale pain score and morphine consumption in the first 24 h. RESULTS: All patients received the allocated paravertebral block. Correct catheter placement occurred in 23 (77%) and 24 patients (80%) using the transverse (n=30) and parasagittal approaches (n=30), respectively (P = 1.00). Five patients were excluded due to changes in surgical procedure. Postoperative pain, represented by median [IQR] visual analogue scale score, was 19.5 [12 to 25] at rest and 55 [44 to 77] on movement with the transverse approach (n=28) vs. 22 [12 to 33.5] at rest and 59 [41.5 to 75] on movement with the parasagittal approach (n=27) (P = 0.57 at rest, P = 0.76 on movement). Median morphine consumption was 11.5 [5 to 21] and 11 [5 to 18] mg in the transverse and parasagittal approaches, respectively (P = 0.99). CONCLUSION: There were no clinically significant differences between approaches for continuous ultrasound-guided thoracic paravertebral block using a microconvex probe, and both approaches achieved a high rate of correct catheter placement. TRIAL REGISTRATION: UMIN Clinical Trials Registry identifier: UMIN000015988.