Anatomic Site Affects Ropivacaine Duration During Mohs Surgery Anatomic Site Affects Ropivacaine Duration During Mohs Surgery

DENVER – Use of subcutaneous ropivacaine for Mohs surgery in highly vascularized anatomical regions such as the nose results in significantly shorter duration of anesthesia compared with less vascularized regions such as the shin, results from a single-center study showed.

Dr Kira Minkis

Ropivacaine is a long-acting anesthetic that may be used as a substitute for the more commonly local anesthetics such as lidocaine or bupivacaine in dermatologic surgery, lead study author Kira Minkis, MD, PhD, told this news organization following the annual meeting of the American Society for Dermatologic Surgery, where the study results were presented during an oral abstract session. By comparison, ropivacaine has been reported to have a faster onset, similar duration in the range of 6-14 hours, less pain upon injection, and inherent vasoconstrictive properties.

“With tumescent anesthesia, studies have previously shown that the rate and absorption of anesthetics is influenced by the site of administration,” said Minkis, director of Mohs and dermatologic surgery at Weill Cornell Medicine, New York. “In studies comparing absorption of local anesthetics in tumescent anesthesia by regions that differ in vascularity, peak serum concentrations are greater and rise more rapidly after use in the head and neck compared to the trunk and extremities. However, no studies to date have compared the duration of ropivacaine in highly vascularized tissue or compared duration between regions that differ in vascularity.” The aim of the study, she noted, was to characterize the difference in duration of ropivacaine’s effects between anatomic regions of rich and comparably poor vascularity, such as the face and extremities, respectively.

Minkis and her colleagues recruited 17 women and 12 men with a mean age of 72 years who underwent Mohs surgery on the nose or the shin at Weill Cornell Medicine. Patients were anesthetized at each site with a subcutaneous injection of 0.5 mL of ropivacaine, 0.2%. Sensation was determined by pinprick prior to injection, at baseline, and every 15 minutes until sensation returned or surgery concluded. The primary endpoint was time to return of pinprick sensation.

The researchers found that the duration of ropivacaine was significantly shorter on the nose (a median of 60 minutes) than on the shin (a median of 210 minutes). In fact, the upper limit of the range of duration at the shin was not determinable because 22 of the 29 (76%) of participants did not regain sensation on the shin prior to leaving the surgical suite and concluding the study. The proportion of study participants who regained sensation within 1 hour was 76% among those who were treated on the nose vs. 3% of those who were treated on the shin (P < .0001).

“With durations of up to 6-14 hours reported, our results indicate a strikingly shorter duration of local anesthesia in highly vascularized tissue,” Minkis said. “The brevity of local anesthesia is even more surprising given the intrinsic vasoconstrictive properties of ropivacaine. Often, we co-administer epinephrine to achieve vasoconstriction and reduce local blood flow, thus prolonging local concentrations of the anesthetic with the added benefit of reducing bleeding during surgery. The short duration we’ve observed in our study is emphasized in using a potent, long-acting local anesthetic with vasoconstrictive properties that otherwise should attenuate the effects of high local vascularity.”

In other findings, patients with history of hypertension were more likely to regain sensation on the nose by 60 minutes but this did not reach statistical significance (P = .079). Other comorbidities including underlying anxiety/depression, diabetes, and kidney disease did not significantly impact duration of ropivacaine action on the nose. The same held true for patients who were treated on the shin.

“We highlight an inconsistency between the reported duration of a long-lasting local anesthetic and the short-lived anesthesia experienced by our patients in a highly vascularized region,” Minkis said. “In practice, adjunctive use of a long-acting anesthetic to prolong anesthesia is common, which may provide relief from multiple injections of shorter-acting lidocaine. However, the duration of Mohs surgery can be unpredictable. Extended wait times between stages may exceed the duration we’ve observed in this study.”

In addition, she continued, “pain is frequently reported on postoperative days 0 to 3, leading some to recommend the use of long-acting local anesthetics to prevent overprescription or a gap in pain coverage. This emphasizes a gap in effective pain control, but also an opportunity to improve our patients’ surgical and recovery experiences.”

Impact on Practice

Keith L. Duffy, MD, associate professor of dermatology at the University of Utah, Salt Lake City, who was asked to comment on the study, said that in light of current local anesthetic shortages and back orders, “we dermatologic surgeons have been experimenting with different anesthetics and concentrations that we can use in our patients. Ropivacaine may become the anesthetic of choice for many of our practices given its inherent properties.”

The duration of anesthetic effects by anatomic location in this study is “actually more impressive than I would have suspected as a practicing Mohs surgeon. The results of this study will immediately impact my Mohs surgery clinic,” he said, adding that he hoped that Minkis and others “will expand on this study to include more patients, different anesthetics, and more anatomic locations.”

Minkis acknowledged certain limitations of the study, including its single-center design and the fact that there were too few observations of medical and clinical characteristics for subgroup analysis.

She and Duffy reported having no financial disclosures.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.