Figure 1: Pyramid of evidence-based medicine.
Illustration: HLWIKI International

The Case

A 49-year-old man presents to the emergency department with the chief complaint of left lumbar back pain that radiates down his leg. He had been doing yard work at home all week to get ready for a Labor Day weekend barbecue. He tried acetaminophen and ibuprofen, but it didn’t touch the pain. There are no “red flags” in his history or physical examination. The last time he hurt his back, they gave him morphine in the emergency department. The morphine worked, but it made him drowsy and nauseated, and he could not drive himself home. He asks if his pain could be taken away without an opioid.

Background

There are about 2.7 million annual ED visits for low back pain in the United States. They can be frustrating for both patients and physicians. Physicians have many pharmacological agents available to treat painful conditions in the emergency department with variable success depending on the cause (nonsteroidal anti-inflammatory drugs [NSAIDs], acetaminophen, opioids, muscle relaxants, and benzodiazepines).

Anesthetic agents, like lidocaine, that target sodium channels are widely used in the emergency department for topical and local anesthesia. Lidocaine is a local anesthetic agent with analgesic, anti-hyperalgesic, and anti-inflammatory properties. It has a short half-life (60 to 120 minutes) with often predictable adverse effects.

It has been suggested that IV lidocaine could be an alternative for pain control instead of opioids or NSAIDs when these other treatment modalities have been ineffective or associated with adverse effects.

IV lidocaine for the treatment of renal colic was covered in a recent “Skeptics’ Guide to Emergency Medicine” column (May 2018). The bottom line from that was that the study reviewed “does not provide good evidence for using lidocaine to treat patients presenting to the emergency department with renal colic.”

Clinical Question

In patients presenting to the emergency department with acute or chronic pain, is the administration of IV lidocaine safe and effective?

Reference

E Silva LOJ, Scherber K, Cabrera D, et al. Safety and efficacy of intravenous lidocaine for pain management in the emergency department: a systematic review. Ann Emerg Med. 2018;72(2):135-144.e3.

• Population: Adult patients presenting to the emergency department for the management of acute or chronic pain.
  • Exclusions: Studies in which patients received IV lidocaine in a setting outside the emergency department or for indications other than analgesia. Studies that used lidocaine for regional anesthesia were also not included.
• Intervention: At least one dose of IV lidocaine given in the emergency department.
• Comparison: Active controls, such as opioids and NSAIDs, or placebo controls.
• Outcomes:
  • Efficacy Outcomes: Reduction in pain score and need for rescue analgesia.
  • Safety Outcomes: Adverse drug reactions.
  • Risk of Bias:  Cochrane Collaboration bias appraisal tool for the randomized controlled trials (RCTs) and a modified Newcastle-Ottawa Scale tool for observational studies.
  • Certainty: The certainty for each outcome was evaluated with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methods.

Authors’ Conclusions

“There is limited current evidence to define the role of intravenous lidocaine as an analgesic for patients with acute renal colic and critical limb ischemia pain in the ED. Its efficacy for other indications has not been adequately tested. The safety of lidocaine for ED pain management has not been adequately examined.”

Key Results

Risk of Bias

Eight studies met inclusion/exclusion criteria, six RCTs and two case series, for a total of 536 patients. The causes of pain included radicular low back pain, renal colic, critical limb ischemia, and migraine headaches.

• Efficacy: There were six RCTs included and two case series for efficacy. Among the six RCTs, IV lidocaine had efficacy equivalent to that of active controls in two studies and was better than active controls in two other studies. In particular, IV lidocaine had pain score reduction comparable to or higher than that of IV morphine for pain associated with renal colic and critical limb ischemia. Lidocaine did not appear to be effective for migraine headache in two studies.
• Safety: There were 20 adverse events reported by six studies among 225 patients who received IV lidocaine in the emergency department, 19 non-serious events and one serious event related to an accidental overdose of lidocaine (rate 8.9 percent, 95 percent confidence interval 5.5 to 13.4 percent for any adverse event; and 0.4 percent, 95 percent confidence interval 0 to 2.5 percent for serious adverse events).

(click for larger image) Certainty in the Evidence

Evidence-Based Medicine Commentary

1. Search Strategy: This was an excellent example of how to do a good search.
2. Quality of Evidence: The quality of evidence was low due to methodological problems, risk of bias, inconsistency, small studies, and imprecision. There was so much heterogeneity that they correctly did not perform a meta-analysis.
3. Hierarchy of Evidence: There is a pyramid of evidence for evidence-based medicine (see Figure 1). On the bottom is background information and expert opinion and at the top is the systematic review. However, in this case, when the quality of evidence is so poor, I would suggest a well-done RCT gets us closer to the truth than a number of low-quality RCTs and observational studies.

There is limited current evidence to define the role of intravenous lidocaine as an analgesic for patients with acute renal colic and critical limb ischemia pain in the ED.

Bottom Line

The routine use of IV lidocaine for analgesia in the emergency department cannot be supported based on the current strength of available evidence.

Case Resolution

The patient is advised that physicians have tried lidocaine as a non-opioid analgesic, but that the research really does not support its effectiveness or safety at this time. The physician recommends IV morphine again, and the patient arranges another way home.

Thank you to Dr. Sergey Motov, an emergency physician in the department of emergency medicine at Maimonides Medical Center in New York City.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.