Transversus Abdominis Plane (TAP) Block in Laparoscopic Gastric-bypass Surgery

• Pain scores [ Time Frame: 48 hours ] [ Designated as safety issue: No ]
  Measured with a visual analogue scale (VAS, from 0 to 10), in the postoperative care unit, at rest and on movement (coughing).
• Opioid consumption at 48 hours [ Time Frame: 48 Hours ] [ Designated as safety issue: No ]
  Opioid consumption expressed as milligram doses of PO morphine in the postoperative care unit and at 48 hours.If other opioids are used, doses will be converted to the equivalent PO morphine dose using standard opioid dosage conversion tables
• Duration of block [ Time Frame: 48 hours ] [ Designated as safety issue: No ]
  starting after block administration till drop in sensory block injection
• Block procedure time [ Time Frame: 30 minutes ] [ Designated as safety issue: No ]
  the time from placement of the ultrasound probe on the patient on one side to withdrawal of the needle on the other side;
• TAP block complications [ Time Frame: 48 hours ] [ Designated as safety issue: Yes ]
  vascular puncture, intravascular local anesthetic injection and local hematoma;
• incidence of nausea and vomiting, and number of antiemetic medication administrations [ Time Frame: during hospital stay average of 2 - 3 days ] [ Designated as safety issue: No ]
• incidence of itching, and number of antipruritic medication administrations [ Time Frame: 48 hours ] [ Designated as safety issue: No ]

Laparoscopic gastric-bypass surgery (LGBS) is one of the surgical treatments for morbid obesity, which is performed under general anesthesia. TAP block is an analgesic strategy covering the dermatomes from T6 to L1 and consists of injecting local anesthetic in the TAP between the costal margin and the iliac crest, where the thoracolumbar nerves (T6-L1) are located. As far as the investigators know, this analgesic technique has never been studied in LGBS. The investigators objective is to determine whether an ultrasound (US)-guided TAP block provides improved analgesia during the first 24 hours after laparoscopic gastric-bypass surgery, compared to conventional therapy only.

• Gastric-bypass Surgery
• Opioid Consumption
• Obesity

• Procedure: TAP-Block
  Block needle will be inserted out-of-plane to the ultrasound beam, perpendicular to the skin surface, until the tip lies deep between the fascia of the transversus abdominis muscle and the internal oblique muscle. 30 ml of the study solution in each side will be injected at this location and should be observed to spread in an anterior-posterior direction between two muscles. Each patient will receive a total dose of 60 ml of 0.25% bupivacaine (150 mg) + 1:200,000 epinephrine.
• Other: Conventional Managment
  For these group.no TAP block administration. just conventional management for post operative pain.

• Active Comparator: Conventional management
  On the ward, patients will be prescribed acetaminophen 1 g every 6 hours. If additional analgesia is required, patients will take oxycodone 5-10 mg up to every 2 hours or iv morphine. Patients with contraindications to oxycodone will be prescribed oral hydromorphone 1-2 mg instead. This is the current standard of care at Toronto Western Hospital.
  Intervention: Other: Conventional Managment
• Experimental: TAP Block+Conventional Management
  The TAP block will be performed after the induction, before the surgery, by an anesthesiologist with experience of at least 10 successful TAP blocks.Also patients will be prescribed acetaminophen 1 g every 6 hours. If additional analgesia is required, patients will take oxycodone 5-10 mg(oral hydromorphone 1-2 mg) up to every 2 hours or iv morphine.
  Intervention: Procedure: TAP-Block

Inclusion Criteria:

• ASA physical status I-III
• 18-70 years of age, inclusive
• scheduled for elective laparoscopic gastric-bypass surgery.

Exclusion Criteria:

• contraindications to regional blockade (e.g., allergy to local anesthetics, coagulopathy, malignancy or infection in the area)
• pregnancy
• history of alcohol or drug dependence/abuse
• history of long term opioid intake or chronic pain disorder
• history of significant psychiatric conditions that may affect patient assessment
• inability to understand the informed consent and demands of the study