Objectives: A wide range of insertion points lateral to the midline are recommended for paravertebral blockade. The authors hypothesized that in a given subject, using an insertion point at the tip of the transverse process has a superficial but consistent depth to the pleura. The authors also hypothesized that for a given insertion point, depths to the pleura are related directly to the patient's anthropomorphic indices.
Design: Retrospective observational study.
Setting: Adult tertiary teaching hospital.
Participants: Forty-two adult patients.
Interventions n/a measurements and main results: The authors reviewed the computerized tomography scans of 42 adult patients and correlated patients' body mass index, weight, height, and body surface area with skin and transverse process-to-pleura depths at the level of T4, 25 mm from the midline and from the tip of the transverse process. The authors found that the depth to the pleura from the transverse process was significantly deeper at 25 mm lateral to the midline than at the tip of the transverse process (21 mm [4.2mm] v 12 mm [2.7 mm], p<0.0001), and its variability was significantly larger (p = 0.005). The authors found significant correlation between anthropomorphic indices and depths to pleura and transverse process (r>0.8, p<0.0001); however, the prediction bands around their regression lines proved too broad to be clinically useful.
Conclusions: The authors concluded that an insertion point at the tip of the transverse process may provide effective and safer paravertebral blockade and that depth to the pleura cannot be predicted reliably by patients' morphometric profiles.
Keywords: computerized tomography; correlation; paravertebral block; paravertebral space; pleura; pneumothorax; thoracic; transverse process.
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