Safety and Efficacy of Magnesium Sulphate as an Adjuvant to Levobupivacaine in Ultra-sound Guided Transversus Abdominis Plan Block in Pediatric Abdominal Cancer Surgery

In this double blinded randomized study, patients with American society of anesthesiology (ASA) Ӏ and ӀӀ physical status, aged from 1 to 7 years old and their weight 10 to 30 Kg of both sex will undergo abdominal cancer surgery will be enrolled.

A written informed consent from all parents or guardians of all participating children will be obtained and they've the right to roll-out at any time from the study.

Children with local infection, hemorrhagic disorders, drug hypersensitivity or allergy to the studied drugs, muscular disorders, central and peripheral neuropathy, significant organ dysfunction, cardiac dysrrhythmia, congenital heart diseases and unconscious or mentally retarded patients will be excluded from this study.

The participating children will be randomly allocated using computer generated randomization program (http://www.randomizer.org) into two groups:

Group A (control group): patients will receive 0.6 ml/ Kg levobupivacaine 0.25% divided into two doses, half the dose will be given in each side.

Group B (magnesium sulphate group): patients will receive 0.6 ml/ Kg levobupivacaine 0.25% + 2 mg/Kg MgSo4 divided into two doses, half the dose will be given in each side.

The patients and their parents or guardians, the anesthesiologist who administered the drugs, the independent investigator who prepare the drugs and the data collector will be blinded to the study drugs.

Preoperative and operative procedure:

No premedication will be given, after completing fasting hours, after applying standard monitors (non invasive blood pressure, pulse oximetery, electrocardiograph, temperature and capnography); general anesthesia will be induced with inhalation of sevoflurane 8% in oxygen via face mask. An intravenous cannula will be placed and secured. Fentanyl 1µg/ Kg, propofol 1mg/kg and appropriate antibiotic will be given then endotracheal tube will be inserted and secured. Two anestheologist expert in TAP block will do the ultrasound guided oblique subcostal TAP block throughout the study using SonoSite M Turbo (USA) with linear multi-frequency 6-13 MHz transducer (L25x6-13 MHz linear array) scanning probe and sonoplex stim 21 gauge cannula needle will be used, with the patient in the supine position, the site of the ultrasound and needle entry will be sterilized, the ultrasound probe is placed parallel to the subcostal margin near the xiphoid process and oblique respect to the sagittal plane. The transversus abdominis muscle is identified as the more hypoechoic muscle layer just beneath the rectus abdominis muscle near the xiphoid between the lateral edge of the rectus and the medial edges of the internal and external oblique muscles, the aponeurosis above the transversus abdominis is the first layer below the subcutaneous tissue. With the probe near the xiphoid, the needle is advanced in-plane, passing just below the rectus to the TAP, local anesthetic is deposited with intermittent aspiration and visualized as a hypoechoic layer transecting the TAP, 15 minutes after the block skin incision will be allowed, anesthesia will be maintained with sevoflurane in oxygen, the inhaled concentration of sevoflurane will be adjusted to achieve hemodynamic changes < 30% of the baseline values. During surgery, children will receive lactated Ringer's solution 6 mL/kg/h, whereas dextrose 50 mg/mL in NaCl 4.5 mg/mL will be infused at 4mL/kg/h in the postoperative period. No other narcotics, analgesics, nor sedatives will be administered intra-operatively. Standard monitoring (mean arterial blood pressure, heart rate, oxygen saturation and capnography) will be observed and recorded every 10 minutes till the end of surgery. The occurrence of intra-operative hypotension (hypotension was defined as systolic arterial pressure < 70 plus twice the age in years and associated with altered peripheral perfusion) requiring a fluid bolus and bradycardia (bradycardia was defined as HR below 60 beats/min) requiring atropine will be recorded. At the end of surgery, the patient will be extubated, after recovery assessment of 3 point emergency agitation scale will be assessed as follow (1 = calm; 2 = restless but calms to verbal instructions; and 3 = combative and disoriented) (23).

Postoperative:

Then the patient will be transferred to the post-anesthesia care unit (PACU) and will be monitored for vital signs (heart rate, noninvasive blood pressure, and saturation of peripheral oxygen). The Face, Legs, Activity, Cry, Consolability (FLACC) pain score (table 1) with its 0 - 10 score range will be used to assess pain immediately postoperative and then at 2, 4, 6, 8, 12, 18 and 24 hours in the postoperative period. Intravenous acetaminophen HCL (perfelgan) 15mg/kg/6hr will be given when the FLACC score ≥ 4 or 0.5-1 µg/Kg fentanyl if pain not controlled. The time to first request for analgesia, type, frequency and the total analgesic consumption in the first 24 hours will be recorded. sedation will be assessed using modified observer's assessment of alertness/ sedation scale (Table (2)). Side effects of the studied drugs as (hypotension, sedation, respiratory depression and vomiting), and complications of the block as (visceral damage due to inadvertent peritoneal puncture, hematoma, seizure, ventricular arrhythmia, transient femoral nerve palsy) will be observed and recorded for the first 24 hours postoperative.

Degree of satisfaction of the patients' parents assessed on a 5-point scale (completely dissatisfied, dissatisfied, not satisfied nor dissatisfied, satisfied or completely satisfied). (24)

Statistical analysis:

Data will be analyzed using IBM SPSS Advanced Statistics version 20.0 (SPSS Inc., Chicago, IL). Numerical data will be expressed as mean and standard deviation or median and range as appropriate. Qualitative data will be expressed as frequency and percentage. Chi-square test (Fisher's exact test) will be used to examine the relation between qualitative variables. For quantitative data, comparison between two groups will be done using independent sample t-test or Mann-Whitney test. A p-value <0.05 was considered significant.