Author: Michael Vlessides
Anesthesiology News
Opioids may be the preferred therapy for treating cancer-related pain, but as a French study has demonstrated, continuous peripheral nerve blocks also may have a place. The study found that in carefully selected cancer patients, continuous peripheral nerve blocks represent a safe and surprisingly effective alternative analgesic modality, sometimes lasting many months.
“As we know, opioids remain the gold standard approach in cancer-related pain,” said RÉgis Fuzier, MD, PhD, a staff anesthesiologist at the Cancer University Institute of Toulouse Oncopole, in Toulouse, France. “But in our experience, many patients prefer to avoid these kinds of drugs because of their side effects.
“On the other hand, we know that continuous peripheral nerve blocks have many advantages compared to opioids,” Dr. Fuzier continued. “But the main risk of this kind of technique is the risk of infection, which is why in our normal practice—such as for postoperative analgesia—the use of these kinds of catheters is typically limited to the first three or four days. Nevertheless, for this study we decided to use these kinds of catheters for longer periods of time.”
“We used 0.2% ropivacaine,” he said. “The patients were sent home a few hours after the insertion of the catheter, and it’s very important that a network of nurses could visit and follow the patients once they got home.”
Breast cancer with metastasis (n=10) and sarcoma (n=5) were the most frequently observed cancers in the cohort. Among the various pain sites, the most common were the brachial plexus (n=13), arm (n=4) and femur (n=4). A variety of continuous catheters were used, including interscalene (n=17), femoral (n=7), sciatic (n=2), median (n=1), radial (n=1) and supraclavicular (n=1) blocks.
“When inserting these catheters, our objective is always to find the area of innervation of the pain and limit the block to the more distal innervation,” Dr. Fuzier explained. “For example, for a patient with an ischemic thrombosis in the extremity of the second finger secondary to myelodysplasia, we decided to perform a block of the median nerve at the forearm.”
As Dr. Fuzier reported at the 2018 Joint World Congress on Regional Anesthesia and Pain Medicine and annual meeting of the American Society of Regional Anesthesia and Pain Medicine (abstract 5353), the analysis revealed that opioids were stopped or decreased in the majority of patients in whom they were used before the introduction of the catheter. Catheters were kept in place for a median of 24 days, ranging from one to 201 days. Five patients had their catheters for at least 60 days.
The study also yielded some surprising results, as Dr. Fuzier discussed. “We noted that in several patients when we removed the catheter after 30 to 45 days of treatment, the cancer pain did not reappear at all, even if the cancer is still very much there,” he said.
Although the results were promising, the therapy was not without its side effects. Inflammation/infection was the most prevalent adverse event noted, occurring in five patients after 15, 24, 25, 43 and 80 days. Three patients—all of whom reported complete pain relief—suffered unbearable sensory blocks that prompted catheter withdrawal.
Other adverse events included a lack of efficacy (one patient), as well as a case of pulmonary failure related to an interscalene block. “This was likely due to poor patient selection,” Dr. Fuzier explained.
Three patients required opioids immediately after catheter removal. Of note, one patient presented with withdrawal symptoms a few days after insertion of the catheter and acute cessation of opioids. “Now we have to take into account this very important possibility,” Dr. Fuzier said. “In the future, when we insert this kind of catheter into a patient who is currently being treated with opioids, we must maintain some opioids. This is not for pain therapy but to avoid the withdrawal-related side effects.”
Adverse events aside, the researchers were pleased with their findings, which they said may open the door to future alternative analgesic modalities in cancer patients. “We are convinced that this therapy is a viable option in carefully selected patients,” he said. “It allows us to avoid the risk of opioids, which we all know presents its own problems.
“But we have to perform careful selection of the patients.”
Session moderator Christopher L. Wu, MD, a professor of anesthesiology and critical care medicine at the Johns Hopkins University, in Baltimore, was intrigued by the findings. “I find it very interesting that you didn’t have any pain after removal of the catheters in several patients,” Dr. Wu said. “With cancers, there may be recurrent pain, regardless of the level of analgesia attained during the block.”
“It could be something related to their memory,” Dr. Fuzier replied, “though I don’t really have an explanation for that.”
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