Lidocaine 2

A solution of 200 mL of lidocaine (Lidocaine 2%, B. Braun Melsungen AG, Melsungen, Germany) and 0.2 mL of methylene blue was prepared and 0.5 mL kg⁻¹ (LV) and 1 mL kg⁻¹ (HV) were loaded in two syringes for each of the eight canine cadavers. One of the two volumes was injected into the TTP in one side of the thorax and the other into the contralateral side, after a randomization performed using Microsoft Excel for Windows Version 2103 (Microsoft Corporation, Redmond, WA, USA). The investigator who performed the anatomical dissections (M.A.) was different from the one that injected the solution (C.L.), being the first one blinded to the injection side randomization.

The injectable solution consisted of a mixture of 200 mL lidocaine (lidocaine 2%, B. Braun Melsungen AG, Melsungen, Germany) and 0.2 mL of methylene blue. For the HV and LV injections, the total volume was equally divided into two syringes, with 0.5 mL kg⁻¹ and 0.25 mL kg⁻¹ of the injectable solution for each of the eight cadavers, respectively. The HV injections were performed into the TTP at the same hemithorax at the third and sixth intercostal spaces. The LV injections were performed at the contralateral hemithorax using the same procedure. Cadavers were randomized (Microsoft Excel for Windows Version 2013, Microsoft Corporation, Redmond, WA, USA) as to which hemithorax, right or left, and which volume of the solution, LV or HV, was injected. After all injections were performed in the same cadaver, the spread of the injectate and the staining of the intercostal nerves were evaluated by anatomical dissection. The injections and dissections of the cadavers were performed by different researchers (MA and CB, respectively), with second investigator blinded to the volume of solution injected at each hemithorax.