Ultrasound-guided thoracic paravertebral block by the paralaminar in-plane approach using a microconvex array transducer: methodological utility based on anatomical structures

Abstract

Objective

We evaluated the analgesic feasibility of paralaminar in-plane (PL) approach for ultrasound-guided thoracic paravertebral block (USG-TPVB). As the needle trajectory was expected to be closely affected by the distance from the skin to the lamina-transverse process junction (LTPJ), we examined the correlativity between them on computed tomography (CT) or ultrasonography.

Methods

Thirty-two patients undergoing thoracotomy were recruited. We measured the distances between the skin and LTPJ using preoperative CT (S-L) and procedural ultrasonography (US-L). At the beginning and the end of the surgery, 20 ml of 0.5% ropivacaine was injected. The level of sensory block and postoperative numerical pain rating scale (NRS) was assessed. Relationships among the measured parameters and the agreement of the needle depth (ND) with S-L and US-L were evaluated using Pearson's correlation coefficient and Bland–Altman analysis.

Results

S-L and US-L were strongly correlated with ND (r = 0.72 and r = 0.81, respectively) but not with BMI. The Bland–Altman analysis showed that the mean percent differences between the ND and S-L or ND and US-L were −9.6 and 20.1%, respectively. Catheters were inserted 18.6 mm lateral from the midline on average. Analgesia extended to 3–5 dermatomes in 29 patients, and the median NRS was 2 at 1, 6, 12, and 24 h after surgery, respectively.

Conclusions

We demonstrated that PL approach provided feasible analgesia for thoracotomy and the ND was significantly correlated with the morphometric values. This technique allowed for inner catheter insertion route targeting longer anteroposterior thoracic paravertebral space length; this may reduce potential risk of pleural puncture for USG-TPVB.

Trial registry number This study was registered in the UMIN Clinical Trials Registry (UMIN-CTR). (URL:http://umin.ac.jp/ctr/, ID:UMIN000014821).

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