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Anesthesia Alert
When Nerve Blocks Wear Off
John Dilger
Publish Date: October 27, 2008   |  Tags:   Anesthesia

We now regularly perform rotator cuff repair, ankle arthrodesis and other procedures once restricted to hospitals. This pushing of the envelope puts anesthesia specialists under more pressure to control the considerable post-operative pain associated with these cases.

We do our best to control the pain while the patient is under our care, but there's not much we can do when the single-injection nerve blocks wear off the next day. Inpatient facilities control this with a multimodal regimen. With a few adaptations, we can make this approach work for us.

Going to hurt tomorrow
First, some background: Peripheral nerve blocks offer site-specific action and potentially let you avoid using opioids or general anesthesia. They give superior analgesia and lower rates of nausea and vomiting, but the effects of such blocks may not carry over into the recovery period. Placing a nerve block with a long-acting local anesthetic such as bupivacaine gives up to 14 hours of analgesia, but about 30 percent of patients may experience the return of moderate to severe pain when the block resolves, according to a study. The study also found that nearly one in five orthopedic patients needed opioids after a week because even long-acting blocks didn't last long enough.

Applying continuous peripheral nerve blocks lets you match the duration of the analgesia with the duration of the pain state. When continuous nerve blocks are part of a multimodal treatment regimen, the pain state is of shorter duration and is less intense. This is a common approach in inpatient orthopedic settings, where the nerve blocks in the lower extremities have proven as effective as epidurals for analgesia but with fewer catheter issues such as urinary retention and injection site concerns. When the blocks are a part of a multimodal analgesia approach that includes using acetaminophen, celecoxib and oxycodone, lower extremity arthroplasty patients report lower pain scores.

You can apply this same strategy in the outpatient setting with the same benefits. After you administer local anesthetics such as bupivacaine or ropivacaine at the level of the peripheral or cutaneous nerves, deliver a continuous infusion in the peripheral nerve or wound. This has been proven safe and effective once the patient goes home. Two studies indicate that this method may even be better than oral analgesics for orthopedic patients.

Placing continuous catheters in the wound during incisional closure can provide pain relief after discharge. A study of inguinal herniorrhaphy patients found that continuous local anesthesia infused into the wound resulted in significantly less pain and fewer analgesic interventions than a course of opioid treatments.

Controlling the pain
To apply this strategy, I recommend having:

  • An induction room for block placement. This lets you place the blocks in advance, which saves operating room time.
  • A properly functioning catheter. Check the nerve block to ensure the post-op analgesia is effective for the prescribed time interval.
  • continued...

  • A pump with a large local anesthetic reservoir. We prefer instruments with a fixed rate (10cc/hr for peripheral nerve blocks) with no bolus for maximum analgesia (higher basal rate) and an elastometric system for easy use.
  • Staff training. Staffers should know how to administer analgesics (acetaminophen, celecoxib and oxycodone) so that they may teach the patient and their families.
  • Written instructions for patients. No driving and no standing without assistance. Keep the anesthetized limb protected and elevated. Also tell patients that the catheter could leak local anesthetic around the wound dressing.
  • A handout describing local anesthesia toxicity. Give patients a list of the symptoms and explain when they should be concerned.
  • A way to stay in touch. Make sure the patients have your facility's contact number and give them a follow-up call the next day to see if the analgesia was effective.

As tricky as PONV
Pain management is a lot like treating post-op nausea and vomiting in that there doesn't seem to be a magic combination that will always work. As the pain's intensity increases, patients may need additional analgesics that complement each other but work by different mechanisms. You can use these in combination with nerve blocks.

Maintaining post-op nerve blocks inhibits the transmission of noxious afferent stimuli from the operative site to the spinal cord and brain; other interventions would control the local tissue inflammation and pain. This will also reduce the risks of hyperalgesia, allodynia and worsening pain. As a result, patients with a multimodal pain control regimen will have less pain over a shorter duration, which should allow for earlier recovery and rehabilitation.

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