Continuous TAP Blocks: Relative Effects of a Basal Infusion vs. Repeated Bolus Doses
Condition: Postoperative Pain
MeSH terms: Pain, Postoperative
Intervention: Bolus; Basal
Intervention description: A transversus abdominis catheter was inserted and ropivacaine 0.2% administered as two separate bolus doses of 24 mL each: one at time point zero and one 3 hours later.; A transversus abdominis catheter was inserted and ropivacaine 0.2% administered as a continuous basal infusion (8 mL/h) from time point zero for the following 6 hours.
Phase: Phase 4
Study type: Interventional
Primary purpose: Treatment
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: This is a split-body study in which each study subject receives both treatments: one on each side of the body. Which treatment is applied to which side of the body is randomized (and masked).
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Masking description: The only individual aware of the treatment group assignments is the investigational pharmacist who has no interaction with the study subjects. Treatment group assignments were released by the investigational pharmacy only after completion of data collection.
Enrollment: 24.0
Sex: All
Minimum age: 18 Years
Healthy volunteers: Accepts Healthy Volunteers
Keywords: Healthy Human Volunteers

Summary:

      Single-injection transversus abdominis plane (TAP) blocks have been used to treat
      postoperative pain, and are become very popular within the United States because of their
      high analgesic potency and relative ease of placement. Unfortunately, the longest local
      anesthetic available lasts only 8-12 hours. Continuous TAP blocks-also termed "perineural
      infusion"-involve bathing the multiple nerves of the abdominal wall in local anesthetic using
      a percutaneously-inserted perineural catheter inserted just anterior (ventral) and cephalad
      to the anterior superior iliac spine. For most catheter locations, an infusion is preferred
      to a single-injection nerve block because the duration of analgesia may be extended to better
      match the duration of surgical pain. But, unlike brachial plexus, femoral, and sciatic nerve
      perineural infusion, a continuous basal infusion of local anesthetic does not provide
      adequate analgesia for TAP catheters. This may be due to the fact that the TAP is a
      relatively tight space, so it might require a bolus of fluid to adequately spread the
      perineural local anesthetic to the multiple required nerves (as evidence of this,
      single-injection TAP blocks are very effective, although with a limited duration). The result
      is that while single-injection TAP blocks are widely used, TAP catheters have not been
      adopted. This scenario leaves surgical pain untreated following the resolution of the
      single-injection TAP block. The recent development of an infusion pump that can automatically
      deliver repeated bolus doses may allow the spread of local anesthetic to the multiple sensory
      nerves necessary to provide adequate analgesia, with a duration that better matches
      postoperative requirements. The investigators therefore propose a randomized, double-masked,
      controlled trial to determine if delivering local anesthetic as a repeated bolus dose results
      in improved local anesthetic spread/effects compared with a continuous basal infusion for TAP
      catheters.
    

Eligibility criteria:

        Inclusion Criteria:

          1. healthy volunteers weighing more than 45 kg;

          2. must be willing to have bilateral transverses abdominis plane nerve block catheters be
             placed with subsequent ropivacaine administration and sensory testing for 6 hours

        Exclusion Criteria:

          1. BMI greater than 40 (BMI=weight in kg/ [height in meters];

          2. regular opioid use within the previous 2 months;

          3. previous participation within the same study;

          4. allergy to study medications;

          5. known renal insufficiency (creatinine > 1.5 mg/dL);

          6. pregnancy;

          7. incarceration; and

          8. any known neuro-muscular deficit of either abdominal wall.