We conducted a monocentric randomized single blinded controlled trial for six months starting from February 2015 until July 2015. Patients undergoing laparoscopic gynecologic procedures were included and randomly assigned in two groups receiving either an ultrasound guided TAP block (TAP group) or usual Neuromuscular blockade curare type: Atracurium (TRAC group). Randomization was simple and the allocation sequence was generated by a random number table via computer. The surgeon in charge was blinded about the performance of a TAP block.

Anesthesia protocol was almost the same in the two groups apart from the TAP block performance in the study group and the use of the neuromuscular blockade . No premedication was given to before the procedure. Monitoring was standard with a 5 leads electrocardioscope, non-invasive arterial pressure, pulsed oximetry (SpO2) and pressure of end tidal expired CO2 (PetCO2). Peripheral venous access was obtained and a 0.9 % saline vascular prefilling was done via an 18 or a 16 Gauges (G) percutaneous line in the non-dominant superior member. In the TRAC group, induction was given with 2.5 mg Propofol, 3 γ/kg Fentanyl and 0.6 mg/kg Atracurium. In The TAP group general anesthesia was induced, after a 3 minutes pre-oxygenation, with 3 γ/kg fentanyl, 2.5 mg/kg Propofol and 1mg/kg Suxamethonium. Thereafter the TAP block was performed under ultrasonography guidance with a Samsung (MySonoU6) transportable device and a linear high frequency 5-12 Megahertz transducer. The probe was oriented transversely on the antero-lateral abdominal wall and the image depth was set between 4 and 6 cm. Once anatomic structures were visualized and well distinct, the probe was moved posteriorly until the mid-axillary line between the 12th rib and the iliac crest. Operator should be able to identify from top to bottom: the subcutaneous fat tissue (hypo-echogenic), External Oblic Abdominal Muscle (EOAM), Internal Oblic Abdominal Muscle (IOAM), Transverse Abdominis Muscle (TAM) (heterogeneous), peritoneum (hyper-echogenic) and underneath intraabdominal organs both moving with respiration. The junction between the posterior fascia of the IOAM and the anterior fascia of the TAM is also hyper-echogenic and represent the region of interest as it is the local anesthetic injection site. The puncture was proceeded with 100 mm lenght needle 21 G (Vygon, France) needle witch progressed obliquely through the abdominal wall. Operator realized an in plane ultrasound guided approach. As soon as the tip of the needle was placed in the junction between the IOAM and TAM and the aspiration test negative, a priming of 3 ml local anesthetic injection was used in order to unsure a correct position of the needle. In this case the injectate would appear as a hypo-echogenic oval well-shaped volume spreading between the two muscle layers. An inaccurate injection was suspected by the absence of the described image. Intramuscular injection could appear as a poorly defined hyper-echogenic image within the muscle. Once the correct position verified, the rest of the 20 ml of the 2.5% bupivacaine is injected. The contralateral block was performed equally. Anesthesia was maintained by a total intravenous anesthesia in both groups. Fentanyl was systematically reinjected every 30 minutes and Propofol was infused at 8-10 mg/kg/h. In the TRAC group, Atracurium reinjections were guided by the monitoring of the NMB every 20 minute at a dose equal to 0.1mg/kg to be reevaluated after 5 minutes. In the TAP group, a rescue injection of NMB agent was indicated in case of diaphragmatic contractions, surgeons' complaint or patients' movement after optimization of narcosis by increasing propofol infusing speed to a maximum of 5 mg/kg/h beyond the baseline speed and checking analgesia. In both groups patients were ventilated on a volume assisted mode with 50 % of inspired fraction of Oxygen and 4-6 cmH2O of positive end expiratory pressure (PEEP) aiming to get an SpO2\>95%. Tidal volume and respiratory rate were set as to maintain a PetCO2 between 30 and 45 mmHg. A nasogastric tube was inserted before trocars introduction (T0). Patients from the two study groups had a postoperative analgesia prescription including acetaminophen (1g/6h), Ketoprofen (100 mg/12h) and Nefopam (20mg/4h). A 5 mg subcutaneous morphine injection was considered as rescue analgesia.