Effectiveness of Four Versus Ten Local Anesthetic Injections for Post-submucosal Resection Pain Relief: a Randomized, Double Blinded Clinical Trial

Informed consent will be obtained from patients (ASA I and II) scheduled to undergo elective submucosal resection of the nasal septum between May and November 2015.

The sealed envelope technique is used to randomly assign patients into two groups. The anesthetists, surgeons, and nurses who collected the will be blinded to the study groups. Patients in both groups will receive general anesthesia and six injections on each side of the face at the following points: suprazygomatic maxillary (V2) area, infra-orbital area, supratrochlear area, medial to the medial canthus, nasal still and anterior septum. Group II patients will receive local anesthetic infiltration in two injections on each side of the face at the maxillary and infra-orbital areas and the remaining injections are placebo (saline). Group V patients will receive local anesthesia in five injections on each side of the face at the infra-orbital area, supratrochlear area, medial to the medial canthus, nasal still and anterior septum. The remaining maxillary injection is placebo.

To maintain double-blindness, three syringes (one 5 ml and two 10 ml) will be used for the six injections. They are prepared by a nurse who is not involved in the study. The 5 ml syringe (Becton Dickinson, Franklin Lakes New Jersey, USA) is labeled "F" indicating that it should be used at the infra-orbital area for both groups. The total injected solution is about 2 ml. One of the 10 ml syringes (Becton Dickinson, Franklin Lakes New Jersey, USA) is labeled "I" indicating that it should be used for infiltration at the supratrochlear area, medial to the medial canthus, nasal still and anterior septum. The total injected solution is 6 ml. The second 10 ml syringe is labeled "Z" to be used for the suprazygomatic maxillary nerve block.

The syringe labeled "F" always contains the local anesthetic solution. When syringe "I" contains the anesthetic mixture (group V), then syringe "Z" is placebo. In contrary, when syringe "Z" contains the anesthetic solution (group II), syringe "I" is placebo. The local anesthetic mixture is composed of 3 ml lidocaine 2%, 3 ml bupivacaine 0.5%, and 1 ml fentanyl 50 µg/ml. In addition, syringe "F" contains 50 µg clonidine while syringes "I" and "Z" have 100 µg clonidine (when they contain the anesthetic solution).

• Suprazygomatic maxillary nerve block technique: