Transversus Abdominis Plane (TAP) Block for Cesarean Section

Official Title: “Transversus Abdominis Plane (TAP) Block for Cesarean Section”

The purpose of this study is to determine whether a transversus abdominis plane (TAP) block with Clonidine added to the injectate (Clo-TAP) performed approximately 2hrs after the cesarean section (CS) will decrease the amount of postoperative hyperalgesia and ultimately reduce post-CS chronic pain.

Acute severe pain after cesarean section (CS) occurs more often than is thought and 10-15% of the women having a cesarean section develop chronic pain (Kehlet et al. 2006). With over 1.3 million cesarean deliveries per year in the US, this is bound to create a significant health problem. One way to address this health burden is to refine techniques that may help control the pain women experience after CS and ultimately reduce the potential to develop chronic pain.

The purpose of this randomized, double-blinded study is to evaluate the ability of an established anesthetic technique called the transversus abdominis plane (TAP) block to reduce the amount of hyperalgesia women develop around their incision after CS. Measuring the amount of punctuate mechanical hyperalgesia is used as a tool to assess postoperative central sensitization (Lavand'homme et al. 2005), which contributes to postoperative acute pain. Since postoperative acute pain has been shown to be predictive of developing postoperative chronic pain (Eisenach et al. 2008; Yarnitsky et al. 2008), an effective TAP block could help diminish the incidence of chronic pain after CS. In addition, blood samples will be collected for future genetic analysis and we will test preoperatively for mechanical temporal summation (mTS) to evaluate CNS sensitization and nociceptive system hyperexcitability and see if this correlates with the amount of hyperalgesia women develop around their incision after surgery.

The primary aim of this study is to evaluate the benefits of two different solutions injected by TAP block technique on postoperative peri-incisional hyperalgesia.

Intervention(s) in this Clinical Trial

• Procedure: TAP Block
  • 2x20mL 0.9% NaCl + 2x1mL of 0.9% NaCl
• Procedure: TAP Block
  • 2x20mL 0.375% Bupivacaine + 2x1mL of 0.9% NaCl = 150mg Bupivacaine
• Procedure: TAP Block
  • 2x20mL 0.375% Bupivacaine + 2x1mL Clonidine = 150mg Bupivacaine + 150µg Clonidine

Arms, Groups and Cohorts in this Clinical Trial

• Placebo Comparator: Placebo
  • Sterile Saline used for TAP block
• Active Comparator: TAP (150mg Bupivacaine)
  • 2x20mL 0.375% Bupivacaine + 2x1mL of 0.9% NaCl = 150mg Bupivacaine
• Active Comparator: Clo-TAP (150mg Bupivacaine + 150µg Clonidine)
  • 2x20mL 0.375% Bupivacaine + 2x1mL Clonidine = 150mg Bupivacaine + 150µg Clonidine

Primary Measures

• To determine which of three different TAP formulations (Placebo, TAP, Clo-TAP) has the most beneficial effect on the postoperative area of hyperalgesia 48hrs after the start of the cesarean section.
  • Time Frame: 48hrs after CS
    Safety Issue?: No

Secondary Measures

• To determine which of three different TAP formulations has the most beneficial effect on the postoperative area of hyperalgesia 24 hrs after the start of the CS
  • Time Frame: 24 hrs after CS
    Safety Issue?: No
• To determine which of the three different TAP groups has the most beneficial effect on the postoperative amount of static hyperalgesia 24 and 48hrs after the start of the CS
  • Time Frame: 48 hrs after CS
    Safety Issue?: No
• To evaluate pain scores at rest and during movement at 6, 12, 18, 24, 36 and 48hrs after the surgery
  • Time Frame: 48 hrs after CS
    Safety Issue?: No
• To evaluate the time it takes for a woman to ask for the first analgesic medication after the surgery
  • Time Frame: 48 hrs after CS
    Safety Issue?: No
• To evaluate postoperative morphine consumption (or equivalent of morphine) during the first 48hrs after the surgery
  • Time Frame: 48 hrs after CS
    Safety Issue?: No
• To evaluate the correlation between preoperative mechanical temporal summation (mTS) and amount of hyperalgesia and postoperative pain
  • Time Frame: 48 hrs after CS
    Safety Issue?: No
• To evaluate postoperative side effects such as postoperative nausea and vomiting (PONV), constipation, urinary retention, de-ambulation and motricity
  • Time Frame: 48 hrs after CS
    Safety Issue?: No
• To evaluate chronic pain at 3, 6 and 12 months post-surgery by phone with the Short-Form McGill Pain Questionnaire 2 (SF-MPQ-2)
  • Time Frame: 1 year after CS
    Safety Issue?: No
• To study selected candidate genes related to postoperative pain and analgesics
  • Time Frame: 1 year after CS
    Safety Issue?: No

Inclusion Criteria:

• non-laboring women who will benefit from and have clinically consented to a scheduled or non-scheduled cesarean delivery under spinal anesthesia
• English speaking
• aged between 18 and 45 years
• BMI < 40
• ASA physical status class I or II

Exclusion Criteria:

• laboring women undergoing a non-scheduled cesarean delivery
• non-English speaking
• previous spinal surgery
• contraindications for neuraxial anesthesia
• allergy to local anesthetic, ultrasound conduction gel, or Clonidine
• history of chronic pain
• inability to receive intraoperative Toradol

Gender Eligibility for this Clinical Trial: Female

Minimum Age for this Clinical Trial: 18 Years

Maximum Age for this Clinical Trial: 45 Years

Are Healthy Volunteers Accepted for this Clinical Trial?: No

Lead Investigator: University of Washington Other

Overall Clinical Trial Officials and Contacts

Ruth Landau, MD Study Chair University of Washington  

Information obtained from ClinicalTrials.gov on February 09, 2012

Link to the current ClinicalTrials.gov record. http://clinicaltrials.gov/show/NCT01015807

Study ID Number: 36707-K

ClinicalTrials.gov Identifier: NCT01015807

Health Authority: United States: Institutional Review Board