Ultrasound-guided intercostal nerve injection in rabbit cadavers: Technique description and comparison with blind approach.

Objective: To develop an ultrasound-guided technique for intercostal nerve blocks in rabbit cadavers and to compare the success rate and potential complications of this technique to blind injection.

Study design: Prospective, randomized, blinded, descriptive experimental cadaveric study.

Animals: A group of nine adult domestic rabbit cadavers (body mass 1.8-2.4 kg).

Methods: Anatomic landmarks were identified by dissection of one cadaver and used to develop the ultrasound-guided technique. Eight cadavers were administered blind injections on one hemithorax and ultrasound-guided injections on the opposite hemithorax. The side used for each treatment was randomly assigned. For both techniques, the third to ninth intercostal nerves were targeted and 0.1 mL of yellow dye solution was injected per site. Medial displacement of the parietal pleura was assessed during ultrasound-guided injections. Rabbits were dissected following injection, and injections were considered successful if the circumference of the intercostal nerve was stained with dye. Additionally, the internal aspect of the parietal pleura was assessed for the presence of free dye to determine whether perforation of the parietal pleura had occurred. The number of stained nerves and incidence of pleural perforations were compared between injection techniques using Fisher's exact test. Data were considered statistically different if p < 0.05.

Results: A total of 56 blind and 56 ultrasound-guided intercostal injections were performed. Success rates of the blind and ultrasound-guided techniques were 35.7 % and 66.0 %, respectively (p = 0.002). The internal aspect of the pleura was stained in 23.2 % of blind and 21.4 % of ultrasound-guided injections, with no significant difference between groups (p > 0.999).

Conclusions and clinical relevance: Ultrasound guidance improves the accuracy of intercostal nerve injections when compared with a blind technique; however, pleural puncture is a common complication when performing intercostal injections with both techniques studied.