Transversus Abdominis Plane Block Using Dexmedetomidine and Bupivacaine
Condition: Laparoscopic Orcheopexy
Study type: Interventional
Phase: Phase 2

Summary: 
      Pediatric laparoscopy has been first described in 1923 by Kelling but its use has increased
      since last decade. A laparoscopic approach offers several advantages over an open procedures;
      potentially reduces the surgical stress and fluid shifts that may accompany it; in addition
      there is less need for postoperative analgesia, reduction of postoperative respiratory and
      wound complications; shortens postoperative convalescence, including an intensive care unit
      stay; rapid return to normal diet and decreased overall hospital stay.

      Despite the minimally invasive nature, pain can be moderate to severe in the immediate
      postoperative period.

      Inadequate control of post-operative pain leads to several unwanted adverse events ranging
      from patients' discomfort and prolonged immobilization to thromboembolic phenomenon and
      pulmonary complications.

      Analgesic multimodalities were recommended to relieve the post-operative pain. Opioids
      although provide satisfactory analgesia, they are associated with unwanted side-effects.

      Transversus abdominis plane (TAP) block is a type of peripheral nerve block that involves
      innervations of the anterolateral abdominal wall. It provides adequate post-operative pain
      relieve following various abdominal surgeries.

      With the aid of ultrasound or anatomical landmark guidance, local anesthetic (LA) is injected
      into the transversus abdominis fascial plane, where the nerves from T6 to L1 are located.

      Ultrasound TAP block is also accompanied by a good pain relief and reduced intraoperative and
      postoperative opioids requirements after laparoscopic surgery. In this case a bilateral TAP
      block is necessary because the abdominal skin incisions for the ports of laparoscopic
      procedure are performed on both sides.

      Unfortunately, TAP block duration is limited to the effect of administered LA. Recently,
      adjuvant medications were added to LA to prolong the effect of TAP block. Dexmedetomidine is
      a selective alpha 2 (α2) adrenergic agonist with both analgesic and sedative properties. Its
      use with bupivacaine either epidurally or intrathecally is associated with prolongation of
      the LA effect.
    

Detailed description: 
      Preoperative assessment:

      The day prior to surgery, all patients will undergo pre-anesthetic checkup including detailed
      history, thorough general, physical, systemic examination and weight of the patient. All
      children will be kept nil per mouth for 8 h for solids and 2 h for clear liquids.

      Preparation of the patient:

        -  Written consent, coagulation profile, emergency resuscitation equipments including
           airway devices, pediatric advanced life support drugs for LA toxicity will be available.

        -  All patients will be premedicated with oral midazolam of 0.5 mg/kg about 20 minutes
           before induction of anesthesia.

      Intraoperative management:

      Intraoperative monitoring will include ECG, pulse oximetry, noninvasive blood pressure,
      capnography and temperature probe.

      All patients in this study will be anesthetized by the same team of anesthesiologists and
      operated upon by the same surgeon who will be unaware of the study medications.

      General anesthesia will be standardized for all patients in both groups using 8 MAC
      sevoflurane in 100% O2 with appropriate size face mask. After intravenous access securing,
      atropine 0.02 mg/kg and fluid bolus of 20 ml/kg will be given to offset hemodynamic effects
      when pneumoperitoneum is created. Endotracheal intubation with appropriate size to the
      patient's age will be performed after administration of 2 mg/kg propofol and 0.5 mg/kg of
      atracurium. After tracheal intubation, the stomach is suctioned with an orogastric tube and
      bladder catheterization is done in order to decrease the risk of visceral injury during
      trocar insertion. Controlled mechanical ventilation will be used to maintain end-tidal carbon
      dioxide at 35±5 mmHg. Minute ventilation will need to be increased by 20% or more to maintain
      normocapnia. General anesthesia will be maintained with 2-3 MAC sevoflurane delivered in 100%
      O2.

      Patients will be placed in the supine position and TAP block will be performed under
      ultrasound guidance. After skin preparation, the linear ultrasound probe (high frequency
      probe 7-12 MHz) connected to a portable ultrasound unit( MANDRAY ) will be placed in the
      axial plane across the mid-axillary line midway between the costal margin and the highest
      point of iliac crest. A 22 G × 50 mm PAJUNK needle attached with tubing system to a syringe
      filled with the LA solution will be inserted in plane with the ultrasound probe and advanced
      until it reaches the plane between the internal oblique and transversus abdominis muscles.
      After careful aspiration to exclude vascular puncture, injection of the study medication will
      be performed leading to separation between the internal oblique and the transversus abdominis
      muscles which will appear as a hypoechoic space on ultrasound. This procedure will be
      repeated on the opposite side of the midline.

      MAP, HR, SpO2 and ETCO2 will be recorded before induction of anesthesia, before block, after
      the block and every 10 minutes till end of surgery. Skin incision will be made 15-20 min
      after TAP block (Rozen et al, 2008). An increase in HR and MAP above 20% of baseline values
      with skin incision will be considered signs of inadequate analgesia. In these cases, fentanyl
      1 μg/kg will be given intravenously, and the case will be excluded from the study.

      The table position itself may need to be changed repeatedly during the operation; both the
      trendelenburg and the reverse trendelenburg positions are often used. Children may be placed
      near the foot end of the table. Accordingly, care must be taken to secure the patient to the
      table (e.g., using rolls of gauze and tape). Well padding of extremities should be ensured.

      Restriction of the intraabdominal pressure to 6-12 mmHg in children will be recommended.
      These pressures have minimal effects on cardiac index. Intraoperative hypotension defined as
      fall in MAP by 20% from the baseline requiring a fluid bolus and bradycardia defined as a
      decrease in HR by 20% from the baseline value requiring atropine will be recorded.
      Perioperative blood loss will be replaced using crystalloids and blood as indicated.

      After completion of the surgical procedure, reversal of neuromuscular blockade effect and
      extubation will be done after ensuring adequate orogastric suction and empting of
      pneumoperitonem. Bilateral air entry should be checked at the end of anesthesia. Patients
      will be transferred to the postanesthesia care unit (PACU).

      In PACU: MAP, HR, modified CHEOPS and nausea & vomiting score will be recorded on admission
      to PACU, 1, 4, 8, 12, 18, 24 h postoperatively by an observer who will be unaware of the
      study protocol.

      Postoperative pain will be measured using a modified Children's Hospital of Eastern Ontario
      Pain Scale (CHEOPS).

      Patients with modified CHEOPS > 6 will be given rescue analgesia with 15 mg/kg paracetamol
      intravenously. Those with modified CHEOPS of 4-5 will be given paracetamol 15 mg/kg as
      suppository. Pain scores will be recorded every 10 minutes after administration of rescue
      analgesia to evaluate pain relief or need for further rescue analgesia. The number of
      children who will need postoperative rescue analgesics and the duration of analgesia that
      will be taken at the time when an analgesic is required will be recorded.

      Patients will be discharged from the hospital when they are pain free and there is no other
      medical reason to admit them to a surgical ward. The parents who will be involved in the
      clinical trial will be invited to complete a postoperative chart with a simple pain scale (0
      = no pain/child calm; 1 = minimum pain/child irritable; 2 = mild pain/child consolable; and 3
      = severe pain/child inconsolable). Parents will be instructed to give their children oral
      ibuprofen 10 mg/kg when pain scores 2 or 3, and not more frequently than every 8 hours.

      Postoperative vomiting episodes will be recorded and treated with intravenous Metoclopramide
      0.5 mg/kg. Postoperative sedation will be assessed using sedation score described by Culebras
      et al, 2001 (1. Awake and alert. 2. Sleeping but easily arouses to voice or light touch. 3.
      Arouses to loud voice or shaking. 4. Arouses with painful stimuli only. 5. Unrousable).

      Other postoperative complications as infection or hematoma formation will be recorded.

      The parents will be asked to evaluate their satisfaction regarding pain control at the end of
      24 h postoperatively through 5-point Likert scale (1 = very satisfied, 2 = satisfied, 3 =
      neither satisfied nor dissatisfied, 4 = dissatisfied, 5 = very dissatisfied).
    

Intervention name(s): Dexmedetomidine; Bupivacaine
Intervention type(s): Drug; Drug
Intervention description(s): patients will receive ultrasound guided TAP block using 0.3 ml/kg bupivacaine (0.125%) with a maximum volume of 20 ml + 0.25 mg/kg dexmedetomidine dissolved in 2 ml normal saline (0.9%); patients will receive ultrasound guided TAP block using 0.3 ml/kg bupivacaine (0.125%) with a maximum volume of 20 ml + 2 ml normal saline (0.9%)
Intervention MeSH terms: Dexmedetomidine; Bupivacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Prevention
Keywords: transversus abdominis plane block , Dexmedetomidine