SAN FRANCISCO — Postmenopausal women who received a single injection of bupivacaine to the stellate ganglion reported half as many bothersome hot flashes in the 6 months after the nerve block than those who received sham therapy.
This finding comes from the first randomized controlled clinical trial to investigate the use of this chronic pain treatment for menopause-associated vasomotor symptoms.
"It's a very exciting finding with a surprisingly long duration of effect," said lead investigator David Walega, MD, from the Northwestern University Feinberg School of Medicine in Chicago.
The only nonhormonal treatment of menopausal vasomotor symptoms approved by the US Food and Drug Administration is the antidepressant paroxetine mesylate (Brisdelle, Noven Therapeutics).
Dr. Walega noted that the improvement in hot flashes seen with paroxetine is less than that seen in this study with bupivacaine. Stellate ganglion block is "the first meaningfully effective, nonhormonal treatment for hot flashes," he said.
This study is likely the first to include an objective measure of vasomotor symptoms after this treatment, and it had a control group, unlike previous studies, according to Dr. Walega.
The research — a hot topic here at the American Society of Anesthesiologists 2013 Annual Meeting — was presented by Dr. Walega.
The 6-month double-blind study involved 40 patients, 30 to 65 years of age, who had gone through natural or surgical menopause and had a history of moderate to severe vasomotor symptoms, defined as at least 25 hot flashes per week.
Subjects were randomly assigned to either stellate ganglion block (n = 20) or sham treatment (n = 20).
In the treatment group, fluoroscopic guidance was used to inject 0.5% bupivacaine 5 mL at the C6 vertebra on the right side. In the sham group, saline 5 mL was injected into the deep subcutaneous tissues over C6, rather than in the stellate ganglion.
All subjects in the treatment group developed Horner's syndrome for up to 8 hours after injection, demonstrating a successful block, Dr. Walega reported.
Eighteen women in the treatment group and 17 in the sham group wore a skin conductance monitor for 24 hours before the nerve block and for two 24-hour periods during the 3 months after injection. The monitor measured and recorded the patients' core temperature during a hot flash.
This objective monitoring showed a 29% decrease in the frequency of vasomotor symptoms in the 3 months after the nerve block; there was no reduction in the sham group.
The women kept a daily diary of the number and severity of their vasomotor symptoms for 2 weeks before the procedure and for 6 months after.
There was no statistically significant difference in the number of severe hot flashes between the groups in the first 3 months, and only a trend toward improvement with bupivacaine in months 4 to 6, the researchers report.
However, the number of moderate to severe hot flashes was significantly better in the treatment than in the sham group (relative risk, 0.50; confidence interval, 0.34 - 0.73; P < .001).
Table. Effects on Hot Flashes in the Treatment and Sham Groups
| Self-Reported Outcome | Bupivacaine, % (n = 20) | Sham, % (n = 20) | P Value |
| Change from baseline to 3 months | |||
| Depression | –30 | 0 | .07 |
| Change from baseline to 6 months | |||
| All hot flashes per day | –34 | –18 | .10 |
| Moderate to severe hot flashes per day | –52 | –4 | <.001 |
"In women with moderate to very severe vasomotor symptoms who have tried and failed to respond to medication therapies, it is reasonable to proceed with a stellate ganglion block," Dr. Walega said.
"The lack of a placebo effect in the sham-treatment group shows that there is a definitive effect of the stellate ganglion block," Dr. Walega told Medscape Medical News.
He noted, however, that many of the 260 prospective subjects screened for the study refused to participate because they were afraid of the injection. Dr. Walega stressed that stellate ganglion block is safe when performed by a physician with training in interventional pain medicine, especially when using fluoroscopic guidance.
"My concern if this becomes an accepted treatment of hot flashes is that inexperienced providers will perform stellate ganglion block, which will change the safety profile for women undergoing the procedure," Dr. Walega said.
These results offer hope to the many women who experience severe vasomotor symptoms and want nonhormonal treatment options, said John Simmons, MD, an anesthesiologist from the Aurora West Allis Medical Center in Wisconsin, who was asked by Medscape Medical News to comment.
"This is a huge issue," he said. Because long-term hormone replacement therapy was found to raise the risk for heart disease and cancer, "there are not many good treatments left for sufferers of hot flashes," said Dr. Simmons, who was not involved with the study.
Hot flashes affect 70% to 80% of menopausal women, the literature shows. Severe symptoms can include drenching sweats, anxiety, and disturbed sleep.
Advantages of the nerve block are the lack of systemic adverse effects and the fact that there is no known increased risk for breast cancer or stroke, according to Tom Guttuso Jr., MD, from the University at Buffalo in New York, who specializes in menopause disorders. A disadvantage, he told Medscape Medical News,is that it costs $1000 to $3000 per procedure.
After reviewing the abstract, Dr. Guttuso said he would have liked to see data that the researchers did not report.
"The results are encouraging," he said, "but there's a lot more information that would be vital to know, such as whether the severity of hot flashes improved and whether the patients were satisfied with therapy. Hopefully, the researchers will address those issues in a larger study."
The mechanism by which stellate ganglion block affects vasomotor symptoms is not clear. Dr. Walega explained that it might modulate norepinephrine and nerve growth factor, which can trigger vasomotor symptoms.
Previous research has suggested that the nerve block interrupts central nervous system connections with the sympathetic nervous system, resetting endogenous temperature-regulating mechanisms (Med Hypotheses. 2007;69:758-763).
This study was funded by Northwestern University's Department of Anesthesia. Dr. Walega and Dr. Simmons have disclosed no relevant financial relationships. Dr. Guttuso helped develop and patent gabapentin for the treatment of hot flashes; had the FDA approved this treatment, which it did not, he would have received royalties.
American Society of Anesthesiologists (ASA) 2013 Annual Meeting. Presented October 12, 2013.
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Cite this: Bupivacaine Injection Reduces Menopausal Hot Flashes by 50% - Medscape - Oct 16, 2013.
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