Comparison of three different types of injection methods for supraclavicular block and their effects on diaphragm muscle function evaluated with diaphragm thickening fraction: a prospective, randomized, double-blind study.

Background: The aim of the study was to compare the effects of three different types of injection methods used in supraclavicular blocks on levels of phrenic nerve blocking with diaphragm thickening fraction (DTF).

Methods: The study was designed as prospective, randomized, controlled, and double-blind. Patients presenting for elective upper extremity surgery were divided into three groups according to the injection method for the supraclavicular block (The multi-injected GM group (N.=28), the GD group given two equal injections intracluster and the corner pocket (N.=29), and the GC group (N.=28), who were given local anesthetic only to the corner pocket). The primary outcome was to demonstrate the DTF differences. The secondary outcomes included sensory block level, block success, and additional procedures during the operation.

Results: In terms of the DTF difference before and after the block (ΔDTF), a statistically significant difference was observed (P=0.001). Median ΔDTF was found to be 62% (IQR: 47%) in the GM group, 38% (IQR: 61%) in the GD group, and 20% (IQR: 47%) in the GC group. A successful block was detected in 100% of the GM group, 97% in the GD group, and 82% in the GC group, with a statistically significant difference (P=0.022).

Conclusions: The method with two equal injections intracluster and the corner pocket shows a more acceptable diaphragm involvement rate compared to the multi-injection method and a high block success rate close to the multi-injection method.