Nalgesic Effect of Nulbuphine-bupivacaine Combination in Ultrasound Guided Transversus Abdominis Plane Block in Patients Undergoing Major Abdominal Cancer Surgeries .

The ultrasound-guided TAP block will be performed before the induction of general anesthesia. Upon arrival at the operating room, the patients will be place in the supine position and an 18-gauge intravenous (IV) cannula will be inserted for IV fluid and drug administration. Basic monitoring probes (electrocardiography, non-invasive blood pressure, oxygen saturation, and temperature) will be applied, and their baseline vital signs will be recorded. Lactated Ringer's solution 10mL/ kg will be infused intravenously over 10 minutes before the initiation of the TAP block.

The TAP block will be performed with the use of ultrasound, under complete aseptic technique. A broadband linear array probe will be used with an imaging depth of 4 - 6 cm. The ultrasound probe will be placed transversely to the abdomen (horizontal plane) in the midaxillary line between the costal margin and the iliac crest. Three muscle layers are clearly seen in the image. The needle (22-gauge x 80 mm SonoPlex stim cannula, Pajunk®, Geisingen, Germany) will be inserted in a sagittal plane approximately 3 - 4 cm medial to the ultrasound probe. The point of needle insertion will be closer to the probe. For optimal imaging of the needle, it will be held parallel to the long axis of the probe (in-line view). The needle tip will be directed into the plane below the internal oblique and above the transversus abdominis muscle. A small volume of local anesthetic (2 mL) was seen to open the plane between the 2 muscles and was followed by insertion of the full dose of local anesthetic. If the 2 mL dose appears to be within the muscle rather than between them, then needle adjustment will be required. The local anesthetic injected appeared hypoechoic (black compared to the muscle layers) on ultrasound image.

The TAP block will be performed with the use of ultrasound under complete aseptic technique. A broadband linear array probe will be used with an imaging depth of 4 - 6 cm using a 22-gauge × 80 mm SonoPlex stim cannula (Pajunk®, Geisingen, Germany). Twenty minutes after the TAP block, the extent of sensory blockade will be evaluated by using the pin prick test (0 = no block, 1 = hyposthesia, and 2 = anesthesia) by another blinded attending anesthetist. Any patients with a failed block will be excluded from the studied groups.

Anesthetic Technique:

The anesthetic technique will be standardized in the 3 groups. No preoperative analgesics will be given. After a successful TAP block, ?? general anesthesia will be induced intravenously (propofol 1 - 2 mg/kg, lidocaine 1.5 mg/ kg) and fentanyl 1 μg/kg. Endotracheal intubation will be facilitated by neuromuscular blockade with cisatracurium 0.3 mg/kg. Anesthesia and muscle relaxation will be maintained with isoflurane in an air/oxygen mixture and cisatracurium 0.15 mg/kg. The patients will be mechanically ventilated in parameters that maintain the end-tidal CO2 (ETCO2) between 33 and 36 mmHg. The patients' heart rate, oxygen saturation, ETCO2, and systolic and diastolic blood pressures will be measured and recorded. Hypotension will be defined as a 15% decrease in systolic blood pressure from the base line, bradycardia as a heart rate slower than 50 beats per minute, and hypoxia as an oxygen saturation less than 90%. Hypotension will be treated with intravenous boluses of ephedrine 0.1 mg/kg, repeated as required. Bradycardia will be treated with intravenous atropine 0.01 mg/kg.