Comparative Study of Two Different Techniques to Perform TAP-blocks
Condition: POSTOPERATIVE PAIN
MeSH terms: Pain, Postoperative
Study type: Interventional
Phase: Phase 4

Summary: 
      The TAP is a space between the muscle layers of the abdominal wall that houses nerves
      supplying the abdominal skin. Injecting the local anesthetic ropivacaine into this space will
      block these nerves and prevent pain following c-section. The investigators will compare two
      different approaches to injecting the local anesthetic in this space. Conventionally, the
      block is done after surgery is completed and the abdomen is closed. The anesthesiologist
      introduces a needle through the abdominal wall skin under ultrasound guidance to reach the
      TAP space and the drug is injected. Since the TAP layer is one of the deeper layers of the
      abdominal (belly) wall and is closer to the inside of the abdomen than to the outside (skin),
      injecting from the inner aspect of the abdominal wall during the surgery is easier and
      quicker to perform than the conventional block and does not require ultrasound guidance as
      there is no risk of injury to abdominal organs like the liver.

      With this research the investigators attempt to prove that surgically administered TAP blocks
      take 25% less time to perform compared to the conventionally administered TAP block for post
      cesarean section pain relief. Surgical TAP blocks are also more cost-effective as in addition
      to reduced OR time, they are safer and do not require skilled operator and specialized
      equipment. Secondary outcomes will include total time spent in the Operating room, presence
      and severity of postoperative pain, time to first request for pain medication, total
      postoperative narcotic consumption in 48 hours after surgery and side effects.
    

Detailed description: 
      The investigators propose to perform a prospective randomized trial of the surgically
      administered TAP block as compared to the conventional TAP block. The investigators will
      recruit women undergoing scheduled cesarean delivery under neuraxial anesthesia. Participants
      will be recruited in the labor and delivery of Maimonides Medical Center. Written informed
      consent will be obtained from the patients in a standardized consent form which explains the
      voluntary nature of the study, benefits and risks of both procedures and alternatives.

      Sample size calculation: Estimates of time taken to perform the anesthetic block in our set
      up was an average of 10 minutes and standard deviation of 3.75 minutes (range 5-20min). The
      number of participants necessary to detect a 25% reduction in the time taken to perform the
      block with a power of 80% and α=0.05 was 36 patients in each group and a total of 72
      patients. Allowing for a 15% dropout rate will require 42 patients to be recruited in each
      group and a total of 84 patients. The investigators will initially conduct a pilot study with
      the first five patients. Patients will undergo stratified block randomization to control for
      BMI (BMI<40 and BMI> or =40), complexity of surgery based on number of previous uterine scars
      (< or = 2previous scars, 3 or more previous scars) Anesthetic regimen: Cesarean sections will
      be performed under neuraxial anesthesia- spinal, epidural and combined spinal-epidural.
      Standard dosing of local anesthetic will be used in all patients. Patients receiving
      supplemental short acting non-opioid medication (eg: ketamine) intraoperatively will be
      included but patients converted to general anesthesia will be excluded.

      TAP Block: The conventional TAP block is performed after the skin is closed at the completion
      of surgery and after the dressing is applied. The abdomen will be prepped and draped in a
      sterile fashion and the block performed under sonographic guidance at the level of the
      umbilicus in the anterior axillary line. A blunt tip 21G needle will be used to perform the
      block and 20ml of 0.5% ropivacaine will be injected after confirming the location of the
      needle on sonogram. Similar procedure will be repeated on the other side. The surgical TAP
      block will be performed by a technique adapted from the description by DJ Owen et al (Owen
      DJ, 2011). After uterine closure is completed and good hemostasis has been secured, the
      abdominal wall on the side away from the surgeon will be retracted superiorly by the surgical
      assistant and the surgeon will palpate the lateral border of the rectus muscle. The block
      will be performed lateral to the rectus muscle in order to avoid injury to the inferior
      epigastric vessels. Safe access to the TAP plane will be achieved by inserting a blunt needle
      through the parietal peritoneum and transverse abdominis muscle during which time there is an
      appreciable loss of resistance ('one pop'). The needle and local anesthetic drug used is
      identical to that of the conventional TAP block. After careful aspiration, to ensure no
      vascular injury has occurred, 1 ml of the anesthetic solution is introduced slowly. The
      presence of substantial resistance to injection or a bleb formation (at the peritoneal site)
      suggests incorrect needle tip position, resulting in needle repositioning by advancement or
      retraction as required. The surgeon will feel the expanse of this plane after a significant
      volume is injected with very little resistance. The surgical TAP block will then be performed
      on the other side in a similar manner except the surgeon will switch sides with the assistant
      for better visualization while performing the block. Following the block, the rectus sheath
      and skin will be closed in the usual manner.

      Blinding: The patient and the operator assessing postoperative outcomes measures (pain,
      analgesic requirements, side effects and patient satisfaction) will be blinded to the
      allocation. The investigator assessing primary outcome (time taken to perform the block)
      cannot be blinded due to the nature of the study but will be an independent observer and not
      the surgeon or anesthesiologist performing the procedures. The investigators will have two
      independent observers collecting data on time outcomes to reduce error and also have the
      procedure filmed on a random sample of 10% of patients to verify the times assigned by the
      study personnel.

      Postoperative: Each woman will be prescribed a standard analgesic regimen of toradol 30mg IV
      every 8 hours and IV Tylenol 1000mg every 6 hours as needed. Morphine PCA will also be
      available for pain not controlled with toradol and Tylenol. The presence and severity of
      postoperative pain, sedation, nausea/vomiting, and respiratory depression will be assessed
      postoperatively at 4, 8, 24 and 48 hours by an investigator blinded to group allocation. The
      time to first request for rescue analgesia and total consumption of opioid and non-opioid
      pain medication in 48 hours will also be recorded. The severity of pain at rest and on
      coughing will be as assessed using a 10-cm visual analog scale (0 no pain and 10 worst
      imaginable pain). Presence of side effects like nausea/vomiting, sedation and itching will be
      recorded.

      Outcomes: The primary outcome is the time taken to perform the block (conventional TAP block
      and the surgical TAP block). Secondary outcomes include time components (total time spent in
      the Operating room, time from uterine closure with hemostasis to exit from OR) and
      postoperative outcomes (presence and severity of postoperative pain, time to first request
      for rescue analgesic, total consumption of pain medication 48 hours after surgery, sedation,
      postoperative nausea/vomiting, itching).

      Statistical analysis: Standard descriptive statistics will be used and mean or median will be
      used to describe data depending on whether the assumptions of normality are violated. For the
      primary outcome which is time taken to perform the block, student t test or other appropriate
      nonparametric test to compare differences between the two groups will be performed. An
      intention to treat analysis will be performed. All calculations will be done using SPSS
      software. Senior biostatistician Dr Peter Homel will be performing the analysis.

      The study will be suspended on Fridays, Saturdays, Sundays, and observed religious holidays.
      Physicians and nursing staff from the Department of Anesthesiology and Obstetrics blinded to
      the dose of ropivacaine administered will collect data at 4, 8, 24, and 48 hours after
      cesarean section through verbal interaction of the staff with the patients. The patients'
      answers will be recorded on data collection sheets and placed in the chart for future
      analysis by the principal and co-investigators, and other physicians and nursing staff
      affiliated with the Departments of Anesthesiology and Obstetrics. For quality control there
      will be a bimonthly review of data collected to ensure the integrity and completeness of the
      information collected.
    

Intervention name(s): Surgical TAP block; Conventional TAP block; 0.5% ropivacaine
Intervention type(s): Procedure; Procedure; Drug
Intervention description(s): surgeon administered TAP block; Anesthesiologist administered TAP block; 20ml of 0.5% ropivacaine is used to perform the TAP block
Other intervention name(s): Naropin
Intervention MeSH terms: Ropivacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: TAP block, post-cesarean analgesia