- Single-injection nerve blocks provide up to 16 hours of postoperative analgesia.
- Portable infusion pumps allow outpatients to receive continuous nerve blocks.
More than 40% of ambulatory patients experience moderate to severe postoperative pain at home following orthopedic procedures.1 Up to 16 hours of analgesia may be provided by single-injection peripheral nerve blocks with long-acting local anesthetics. However, following block resolution, ambulatory patients must usually rely on oral opioids to control pain. Unfortunately, opioids are associated with undesirable side effects, such as pruritus, nausea and vomiting, sedation, and constipation. To improve postoperative analgesia following ambulatory surgery, there has been an increasing interest in providing "perineural local anesthetic infusions," also called, "continuous peripheral nerve blocks," to outpatients. This technique involves the percutaneous insertion of a catheter directly adjacent to the peripheral nerve(s) supplying the surgical site. Local anesthetic is then infused via the catheter providing potent, site-specific analgesia. Outpatients may theoretically experience the same level of analgesia previously afforded only to those remaining hospitalized by combining the perineural catheter with a portable infusion pump.
In 1946, Ansbro first described continuous regional blockade using a cork to stabilize a needle placed adjacent to the brachial plexus divisions to provide a "continuous" supraclavicular block.2 However, for decades patients were required to remain hospitalized because the available pumps used to infuse local anesthetic were large, heavy, and technically sophisticated. It was not until 52 years later that Rawal described outpatient perineural infusion using a percutaneous catheter and a small lightweight, portable infusion pump.3
- Significant decreases in postoperative pain and opioid side effects are possible.
- Earlier home discharge is possible for a select subset of hospitalized patients.
Following Rawal's article, case reports or series of ambulatory perineural infusion were described via catheters in various anatomic locations, including paravertebral,4 interscalene,5–7 intersternocleidomastoid,8 infraclavicular,6 axillary,9 psoas compartment,9,10 femoral,9,11 fascia iliaca,5 sciatic/Labat,9,10 sciatic/popliteal,6,12 and tibial nerve.6 Ambulatory continuous peripheral nerve blocks in pediatric patients have also been reported in patients as young as 8 years of age.13 However, Klein et al provided the first prospective evidence quantifying infusion benefits in 2000.14
This randomized, double-masked, placebo-controlled investigation by Klein et al involved subjects undergoing open rotator cuff repair who received an interscalene block and perineural catheter preoperatively, and they were randomized to receive either perineural ropivacaine 0.2% or normal saline postoperatively (10 mL/h). Patients receiving perineural placebo averaged a 3 on a visual analog pain scale of 0 to 10, compared with a 1 for subjects receiving ropivacaine. Although a portable pump was used, patients remained hospitalized during local anesthetic infusion <24 hours, and catheters were removed by investigators prior to home discharge. Patients had access to intravenous morphine via patient-controlled opioid analgesia because the investigators "felt compelled to provide more than oral analgesics," since patients remained hospitalized.14 As a result, patients receiving normal saline theoretically received a greater degree of analgesia than that available to ambulatory patients who must rely on oral instead of intravenous opioids. Consequently, although these data suggested perineural infusion may improve postoperative analgesia following ...