Medical imaging & patient care

Ease the pain

In October 2013, a study presented at the American Society of Anesthesiologists gave new hope to fibromyalgia suffers: an intravenous lidocaine infusion. This treatment could help patients who are otherwise resistant to medication. But with the infusion so difficult to administer, what are the clinical implications? We ask Dr Billy Huh, lead researcher, whether the benefits outweigh the costs. 

Fibromyalgia is a notoriously tricky condition to manage. A central nervous system disorder, characterised by widespread pain and fatigue, its symptoms are extensive and somewhat mysterious. With the exact causes unknown, diagnosis can be difficult and treatment more perplexing still.

Unlike, say, postoperative soreness, it is not simply a matter of administering painkillers and waiting for the aches to ebb away. Rather, it’s about tackling the disorder on the individual’s own terms – while all experience pain of varying intensities, they may also contend with insomnia, headaches, irritable bowel syndrome and depression.

Although it is estimated that 5% of the world’s population are sufferers (with women affected more frequently than men), the condition has not been on clinicians’ radar for long. Indeed, it was only formally recognised in 1990, when the American College of Rheumatology set out its diagnostic criteria. Back then, the checklist included pain in all four quadrants of the body, including at least 11 of 18 designated pressure points.

While this definition was revised in 2010 to take into account other cognitive and somatic issues, the disorder still isn’t widely understood. After all, there are no blood tests or X-rays that can reliably show up fibromyalgia; no specific abnormalities that come to light on a routine scan. Nor can any given treatment be considered a magic bullet.

“Fibromyalgia is a difficult disease in terms of pain,” says Dr Billy Huh, a specialist in the field. “There are medications the FDA has approved for patients, but some people respond more and some respond less. For patients with no response, there are no good options.”

Huh is well placed to comment, having worked within pain medicine for nearly 20 years. He has published dozens of papers and book chapters, and sits on numerous committees. At present, his role stands as professor and medical director of the Department of Pain Medicine at the University of Texas MD Anderson Cancer Centre, and adjunct professor of the Department of Anaesthesiology at Duke University Medical Centre.

Of all the conditions he researches, fibromyalgia is one of the most problematic. “It’s a combination of so many things,” Huh says. “Because it’s multifactorial, it’s difficult to work to target. A lot of patients need to have a multidisciplinary, multimodal therapy just to get some benefit.”

Treatment and remedies

Typical remedies range from the pharmaceutical to the psychological, with antidepressants, anticonvulsants, pain relievers and sleep aids having been shown to help. Increasingly, the condition is seen as the province of neurologists as much as rheumatologists; today’s medications are largely designed to regulate the body’s neurotransmitters. Lifestyle changes are also recommended. In Huh’s words, it’s a “package deal”.

Unfortunately, certain patients remain unresponsive to conventional therapies. It was for this reason that Huh conducted his latest study, which was presented at the American Society of Anesthesiologists’ annual meeting in October 2013. The study concerned an unusual medication: intravenous lidocaine infusion, and asked how efficacious might this be where nothing else has worked.

“With conventional medication you take a pill, but lidocaine infusions are taken intravenously in the clinic,” explains Huh. “The patients received anything from 4–5mg/kg over a one-hour period under strict monitoring. On average they received about a 10% reduction in pain for about three weeks.”

In total, the study involved 55 patients, with statistics collected for sex, race and body weight. Their pain levels were assessed via several questionnaires, both before and after the lidocaine infusion. Also measured were the duration of pain and the duration of pain relief.

Before the infusion, subjects registered an average of 83.18 on the brief pain inventory scale, which then dipped to 73.68. Similarly, their average pain interference score (a measure of how much pain impeded their everyday functioning) dropped from 7.73 to 6.88. The infusion was not a cure by any stretch, but it did make a real difference.

This study provides further insight into a contentious area of medicine. According to a 2010 meta-analysis entitled ‘Intravenous lidocaine for chronic pain: a systematic review’, “IV lidocaine is efficacious for very temporary relief of chronic pain”, but “there is a dearth of studies on the benefit of IV lidocaine beyond 24 hours post-treatment”. Huh’s results suggest that, in the case of fibromyalgia patients, effects can typically be felt for some weeks.

Further findings

The study also brought to light a certain discrepancy between the subjects. While lidocaine worked well for many patients, it showed limited efficacy for smokers and African Americans. In fact, the smokers’ average brief pain inventory score after lidocaine was as high as 89.98, skewing the average for the rest.

Huh believes that, in the case of African American patients, the poor results can be attributed to a particular genetic makeup.

“It’s well-known that certain drugs work for African Americans and certain drugs work well for Caucasians,” he says. “There is a lot of genetic variability in the response to medication.”

With smokers, the reason is more likely due to vascular damage impairing blood circulation. While lidocaine is normally used as a local anaesthetic, here it is administered intravenously as opposed to topically. This means its function relies upon healthy blood flow.

“To put it simply, fibromyalgia sufferers have pain almost everywhere – there is no specific target area we can inject,” says Huh. “The lidocaine is a numbing medicine, so it will be circulated through the nerve fibres and blocks the sodium channels there. Chronic smokers have poor blood flow, so the circulation of lidocaine to the target nerve is diminished.”

Study challenges

Further studies will undoubtedly be of use, to clarify these areas and others. Huh’s study was a retrospective review, meaning medical records were analysed after the treatments took place. This gives it certain limitations not associated with prospective studies, a lack of randomisation being one. Typically speaking, retrospective studies are more prone to error than their prospective equivalents, and rank lower on the hierarchy of evidence.

Perhaps more problematically, the study lacked any kind of control group. Ideally speaking, a trial of this kind would involve another set of patients receiving a saline solution. Unfortunately, this would place one in murky ethical territory, especially bearing in mind the realities of the IV procedure.

With one hour required to administer the drug, and another hour to monitor the patient afterwards, infusion is a time-consuming and labour-intensive process. It’s a big ask for patient and clinician alike. And while giving subjects a dud sugar pill is one thing, hooking them up to a dud saline drip is quite another.

“With chronic pain patients like this, it’s challenging because it’s unethical to give a placebo to patients,” says Huh. “It’s difficult to get approval to give nothing to the patients who are suffering.”

Unfortunately, Huh believes that the practical challenges of lidocaine infusion may stand in the way of its widespread adoption. Although it helped many of his patients, it is unlikely to revolutionise the therapeutic picture for other fibromyalgia sufferers. Given its inconvenience, its expense and the possible side effects, the benefits may not justify the costs.

“It’s not a cost-effective way to deliver care,” says Huh. “Because it takes such a long time, it’s only in academic centres like ours that we can afford to do this. It has to be given in the clinic with blood pressure and heart rate monitored, so if something happens, like seizures or arrhythmia, we are ready to intervene. I don’t know how widely it can be implemented.”

For the time being, there is no easy way of helping out these sufferers, and the condition continues to diminish their quality of life. But with research underway into all aspects of fibromyalgia, it is likely that treatments will continue to improve as the aetiology is more thoroughly understood.

As for Huh’s original patients, IV lidocaine infusions have thrown them a lifeline. “A lot of them come back every month to get a lidocaine infusion, because they find it to be more efficacious than anything else,” he says.

Dr Billy Huh
Dr Billy Huh specialises in anaesthesiology and is currently professor and medical director of the Department of Pain Medicine at the University of Texas MD Anderson Cancer Center, and adjunct professor of the Department of Anaesthesiology at Duke University Medical Center.

Fibromyalgia – symptoms & possible causes

Fibromyalgia (meaning “pain in the fibrous tissues”) is a common and debilitating condition, in which the body aches all over. It shows up in people of all ages, 80–90% of whom are women, and costs around $20 billion each year to the US healthcare system.

Like many chronic conditions, symptoms tend to wax and wane, but generally it is severe enough to have a significant impact on the sufferer’s quality of life. Diagnosis is confirmed by a physical test in conjunction with self-reported symptoms.

The characteristic pain is highly variable, and can range from aches and stiffness to burning or stabbing sensations. It is combined with tiredness and reduced quality of sleep, which may lead to a state of mental fatigue known as fibro fog. Many sufferers also deal with irritable bowel syndrome, chronic headaches, facial tenderness and chemical sensitivity, as well as numbness and memory impairment.

Much like a related condition, chronic fatigue syndrome, the causes are unknown. Many researchers theorise that it is sparked by a triggering event (an infection or accident, for example) that awakens an existing physiological abnormality. This may be a hormonal issue, an immune system disturbance or a problem with neurotransmitter regulation. Older theories, which were based on psychiatric models, have now been largely dismissed.

 Panel 2. How does lidocaine work?

Generally used as a local anaesthetic in minor surgery, there is mounting evidence that an intravenous lidocaine infusion can help with chronic pain. In this case, the lidocaine is delivered directly into the vein, circulating in the blood, eventually reaching the nerve fibres.

Here, it works to prevent the conduction of sodium ions through sodium channels, which are gates in the membrane surrounding the nerve cell. Normally, when faced with a cause of pain, the gates open and let in a flood of sodium ions. These cause a signal to travel up the spinal cord and into the brain, causing the person to realise they’re in pain. When lidocaine is administered, these channels are blocked, reducing the transmission of painful stimuli.

While lidocaine is a relatively safe drug when properly administered, overdose can cause seizures and arrhythmia, so it is essentially that dosage is properly monitored in a clinical setting.

This feature appears in the latest edition of Practical Patient Care

 

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