Over the past decade, poisonings and deaths related to the use of local anesthetics have declined. However, poisonings from a commonly used anesthetic, lidocaine, have increased in the U.S., according to two new studies from the University of Illinois Chicago.
By analyzing data from reports to national poison control centers and the Food and Drug Administration from 2010 to 2020, UIC researchers found that the total number of poisoning reports decreased by 50% during that period. However, poisonings from lidocaine increased by more than 50% in less than half that time, between 2016 and 2020. The findings were published in Regional Anesthesia & Pain Medicine and the British Journal of Anesthesia .
Local anesthetics, including lidocaine, are commonly used in medicine to relieve pain before, during, and after surgical procedures. General anesthesia affects the entire body, putting patients into a sleep-like state. Local anesthesia relieves pain and immobilizes a specific region of the body while the patient remains awake.
Local anesthetics numb a part of the body by blocking nerve signals, explains Dr. Michael Fettiplace, an assistant professor in the anesthesiology department at the College of Medicine. “They are incredibly useful drugs and are the second most important pain relievers we have, after opioids.”
Today, lidocaine is “undoubtedly the most commonly used local anesthetic,” according to Fettiplace. Its uses are varied: to numb a patch of skin before stitches, to prevent irregular heart rhythms, or to numb the throat before an upper endoscopy. Lidocaine is also available over-the-counter in patches and creams that are used to relieve back pain and hemorrhoid pain, for example.
Like all medications, lidocaine and other local anesthetics carry both benefits and risks. After administration, local anesthetics are absorbed by blood vessels and transported to the liver, where they are processed and detoxified. However, if a patient receives too much of the drug, extreme blockage of nerve pathways can lead to seizures, fatal arrhythmias, or cardiac arrest — a phenomenon known as local anesthetic systemic toxicity.
In 1998, anesthesiologist and professor Dr. Guy Weinberg of the University of California discovered that intravenous treatment with a lipid emulsion could fix the problem. "It was a revolution in anesthesia," said Fettiplace. "Suddenly, patients who had died from systemic toxicity of a local anesthetic had a treatment available that rapidly relieved toxic symptoms in many individual cases and prevented deaths."
In 2010, several professional societies in the US and UK developed recommendations for the detection, prevention, and treatment of local anesthetic poisoning. The focus was on the use of lipid emulsions. Ten years later, Fettiplace and his colleagues investigated how these recommendations affected the number of reported poisonings and deaths related to the drugs.
The researchers analyzed reports submitted to the National Poison Data System , the database of all 53 poison control centers in the United States, and the FDA Adverse Event Reporting System , a database of similar reports from the U.S. Food and Drug Administration. Through their analyses, they found that deaths mainly occur when lidocaine is administered intravenously or as a throat spray, and almost always at extremely high doses, sometimes up to four times the maximum, said Fettiplace.
This problem is exacerbated by the availability of high-dose administration methods and the risk of accidental overdose by emergency medical personnel. The authors suggest that improved education and updated recommendations could mitigate these risks, as the recommendations have already led to a reduction in the overall number of anesthetic poisonings and deaths.
The local anesthesia recommendations and the associated scientific changes have had a decisive impact, said Fettiplace. "The data suggest that the number of incidents or the number of adverse outcomes has decreased by about 50% over the last 15 years," he said.
Nevertheless, the increase in lidocaine-related poisonings suggests that current safety precautions may not be sufficient. Fettiplace and his colleagues are convinced that new, more targeted recommendations could further reduce harm.
