Weaker Lidocaine Provides Equal Pain Relief for Mohs

VANCOUVER — Compared with the lidocaine concentration typically used for local anesthesia during Mohs surgery, a lower concentration achieved equivalent pain relief with a 53% reduction in the total dose administered in a randomized, double-blind trial of 149 patients.

"We found in our clinic that 10%-15% of our patients were actually exceeding the recommended lidocaine dose of 7 mg/kg when we used 1% lidocaine with 1:100,000 epinephrine, which is the most common concentration of lidocaine used for Mohs surgery," explained Pamela Morganroth, noting that the patients nonetheless did not experience any symptoms.

"These patients often have large tumors, multiple sites, and extensive reconstructions," she said at the annual meeting of the American College of Mohs Surgery.

Minimizing lidocaine dose is important because symptoms of lidocaine toxicity occur in a dose-dependent manner; moreover, exceeding the recommended limit—even if symptoms do not occur or occur as a result of other conditions—exposes surgeons to medicolegal risk, observed Ms. Morganroth, a medical student at the University of Pennsylvania, Philadelphia.

"Unfortunately, multiple factors influence lidocaine dose," including older age; pregnancy; and renal, cardiac, and hepatic impairment, she added, "so it's virtually impossible to set a uniform maximum recommended lidocaine dose."

In the study, patients undergoing Mohs surgery were randomly assigned to local anesthesia consisting of 1.0% lidocaine with 1:100,000 epinephrine or 0.5% lidocaine with 1:200,000 epinephrine. Surgery was performed by a single physician who was unaware of the patient's assignment. The surgical field was infiltrated immediately before each Mohs layer and the reconstruction, with use of local infiltration and field blocks instead of regional nerve blocks. Excision began as soon as the patient reported no pain to a pinprick stimulus.

Outcomes included the total lidocaine dose administered (including all stages of Mohs surgery and the reconstruction) and patient comfort, which was measured subjectively with a 100-mm visual analog scale and objectively according to the volume of "rescue" lidocaine administered during the surgery. Analyses were based on 74 patients (with 83 tumors) in the 1.0% lidocaine group and 75 patients (with 85 tumors) in the 0.5% lidocaine group.

The mean total dose of lidocaine administered to patients in the 0.5% group was significantly lower, by 53%, than that administered to patients in the 1.0% group (139 mg vs. 297 mg). Mean scores for patient-rated pain (3.88 vs. 3.11 mm, respectively) or mean volume of rescue lidocaine administered (0.85 vs. 0.33 cc) did not differ significantly, Ms. Morganroth reported.

It appears that "0.5% lidocaine provides equivalent patient comfort at half the total dose of lidocaine as compared to 1.0% lidocaine," she said, while also acknowledging that the study did not measure blood levels of the drug.

"Our study demonstrates that 0.5% lidocaine decreases the risk of dose-dependent lidocaine toxicity without compromising patient comfort during Mohs surgery," said Ms. Morganroth, who reported having no conflicts of interest.

VANCOUVER — Compared with the lidocaine concentration typically used for local anesthesia during Mohs surgery, a lower concentration achieved equivalent pain relief with a 53% reduction in the total dose administered in a randomized, double-blind trial of 149 patients.

"We found in our clinic that 10%-15% of our patients were actually exceeding the recommended lidocaine dose of 7 mg/kg when we used 1% lidocaine with 1:100,000 epinephrine, which is the most common concentration of lidocaine used for Mohs surgery," explained Pamela Morganroth, noting that the patients nonetheless did not experience any symptoms.

"These patients often have large tumors, multiple sites, and extensive reconstructions," she said at the annual meeting of the American College of Mohs Surgery.

Minimizing lidocaine dose is important because symptoms of lidocaine toxicity occur in a dose-dependent manner; moreover, exceeding the recommended limit—even if symptoms do not occur or occur as a result of other conditions—exposes surgeons to medicolegal risk, observed Ms. Morganroth, a medical student at the University of Pennsylvania, Philadelphia.

"Unfortunately, multiple factors influence lidocaine dose," including older age; pregnancy; and renal, cardiac, and hepatic impairment, she added, "so it's virtually impossible to set a uniform maximum recommended lidocaine dose."

In the study, patients undergoing Mohs surgery were randomly assigned to local anesthesia consisting of 1.0% lidocaine with 1:100,000 epinephrine or 0.5% lidocaine with 1:200,000 epinephrine. Surgery was performed by a single physician who was unaware of the patient's assignment. The surgical field was infiltrated immediately before each Mohs layer and the reconstruction, with use of local infiltration and field blocks instead of regional nerve blocks. Excision began as soon as the patient reported no pain to a pinprick stimulus.

Outcomes included the total lidocaine dose administered (including all stages of Mohs surgery and the reconstruction) and patient comfort, which was measured subjectively with a 100-mm visual analog scale and objectively according to the volume of "rescue" lidocaine administered during the surgery. Analyses were based on 74 patients (with 83 tumors) in the 1.0% lidocaine group and 75 patients (with 85 tumors) in the 0.5% lidocaine group.

The mean total dose of lidocaine administered to patients in the 0.5% group was significantly lower, by 53%, than that administered to patients in the 1.0% group (139 mg vs. 297 mg). Mean scores for patient-rated pain (3.88 vs. 3.11 mm, respectively) or mean volume of rescue lidocaine administered (0.85 vs. 0.33 cc) did not differ significantly, Ms. Morganroth reported.

It appears that "0.5% lidocaine provides equivalent patient comfort at half the total dose of lidocaine as compared to 1.0% lidocaine," she said, while also acknowledging that the study did not measure blood levels of the drug.

"Our study demonstrates that 0.5% lidocaine decreases the risk of dose-dependent lidocaine toxicity without compromising patient comfort during Mohs surgery," said Ms. Morganroth, who reported having no conflicts of interest.

VANCOUVER — Compared with the lidocaine concentration typically used for local anesthesia during Mohs surgery, a lower concentration achieved equivalent pain relief with a 53% reduction in the total dose administered in a randomized, double-blind trial of 149 patients.

"We found in our clinic that 10%-15% of our patients were actually exceeding the recommended lidocaine dose of 7 mg/kg when we used 1% lidocaine with 1:100,000 epinephrine, which is the most common concentration of lidocaine used for Mohs surgery," explained Pamela Morganroth, noting that the patients nonetheless did not experience any symptoms.

"These patients often have large tumors, multiple sites, and extensive reconstructions," she said at the annual meeting of the American College of Mohs Surgery.

Minimizing lidocaine dose is important because symptoms of lidocaine toxicity occur in a dose-dependent manner; moreover, exceeding the recommended limit—even if symptoms do not occur or occur as a result of other conditions—exposes surgeons to medicolegal risk, observed Ms. Morganroth, a medical student at the University of Pennsylvania, Philadelphia.

"Unfortunately, multiple factors influence lidocaine dose," including older age; pregnancy; and renal, cardiac, and hepatic impairment, she added, "so it's virtually impossible to set a uniform maximum recommended lidocaine dose."

In the study, patients undergoing Mohs surgery were randomly assigned to local anesthesia consisting of 1.0% lidocaine with 1:100,000 epinephrine or 0.5% lidocaine with 1:200,000 epinephrine. Surgery was performed by a single physician who was unaware of the patient's assignment. The surgical field was infiltrated immediately before each Mohs layer and the reconstruction, with use of local infiltration and field blocks instead of regional nerve blocks. Excision began as soon as the patient reported no pain to a pinprick stimulus.

Outcomes included the total lidocaine dose administered (including all stages of Mohs surgery and the reconstruction) and patient comfort, which was measured subjectively with a 100-mm visual analog scale and objectively according to the volume of "rescue" lidocaine administered during the surgery. Analyses were based on 74 patients (with 83 tumors) in the 1.0% lidocaine group and 75 patients (with 85 tumors) in the 0.5% lidocaine group.

The mean total dose of lidocaine administered to patients in the 0.5% group was significantly lower, by 53%, than that administered to patients in the 1.0% group (139 mg vs. 297 mg). Mean scores for patient-rated pain (3.88 vs. 3.11 mm, respectively) or mean volume of rescue lidocaine administered (0.85 vs. 0.33 cc) did not differ significantly, Ms. Morganroth reported.

It appears that "0.5% lidocaine provides equivalent patient comfort at half the total dose of lidocaine as compared to 1.0% lidocaine," she said, while also acknowledging that the study did not measure blood levels of the drug.

"Our study demonstrates that 0.5% lidocaine decreases the risk of dose-dependent lidocaine toxicity without compromising patient comfort during Mohs surgery," said Ms. Morganroth, who reported having no conflicts of interest.