Numbing nuances for nail surgery

September 1, 2007

There are several factors involved in achieving complete anesthesia before performing nail surgery. One expert in the field, speaks about topical anesthesia, the use of epinephrine, as well as the different injection techniques – their pros and cons, and which methods he believes are most successful for a smooth, painless procedure.

Providence, R.I. - Nail surgery, whether on the fingers or toes, can be a frightening, painful experience, and can be the source of significant anxiety to the patient. Therefore, achieving total anesthesia with minimal discomfort and approaching the surgery with confidence is the aim.

"What I stress (about nail surgery) is that there are many parameters that you can control. I always go through a thorough informed consent process preoperatively and review reasonable expectations with the patient. They have to know that the anesthesia may involve some discomfort, but that it is possible to minimize their discomfort using several techniques," says Nathaniel J. Jellinek, M.D., assistant professor of the department of dermatology at Brown Medical School, Providence, R.I.

Just prior to injecting the anesthesia, Dr. Jellinek uses a cryogen freeze spray, which is a mixture of ethyl chloride and dichlorotetrafluoroethane, to freeze the skin locally.

This way the patients will feel the cold rather than the needle stick.

Another topical anesthesia is a eutectic mixture of lidocaine and prilocaine, which can be applied to and occluded over the injection site up to two hours before procedure. Dr. Jellinek cites two studies that analyzed the effects of this cream before digital blocks in toenail surgery. He says that although the studies came to two different conclusions, one can still take away an important message.

One study showed that there was no difference in pain experienced by the patient when comparing nail surgeries with topical anesthetic vs. those without topical anesthetic. Yet another study showed that there was an approximate 40 percent reduction in pain when topical anesthetic was applied prior to injection.

"I believe that a topical anesthetic can work in certain situations to alleviate the pain on injection. Certainly if someone is very anxious, and with the thought of 'do no harm,' topical anesthetics are a reasonable option. Furthermore, using a topical anesthetic will not interfere with the procedure. I tell patients its efficacy is not guaranteed," Dr. Jellinek tells Dermatology Times.

Epinephrine use

Dr. Jellinek says the traditional teaching in most books is that it is an absolute contraindication to use any concentration of epinephrine when performing traditional digital blocks (a common technique used in nail anesthesia), because of the risk of digital ischemia and necrosis.

Dr. Jellinek took a closer look at the data collected by Dr. Krunic, et al. (J Am Acad Dermatol. 2004;51:755-759) on digital ischemia and necrosis following digital block, and found several interesting points that may support the safe use of epinephrine in this procedure. He says that of the 50 cases of digital necrosis identified and associated with digital blocks, only 21 were associated with epinephrine use. Among those associated cases, the concentration of epinephrine was not known or was not reported in the majority of them.

"In some cases, inappropriately high concentrations of epinephrine may have been used. The data also showed that tourniquets were inappropriately used, too much anesthetic was infused and postop infections occurred. All were associated with cases of digital infarction. Therefore, the data does not support that the use of low concentrations of epinephrine in digital blocks is necessarily dangerous. Certainly, it is not an absolute contraindication, as traditionally taught," Dr. Jellinek says.

If a physician would like to perform a digital block with epinephrine, Dr. Jellinek suggests using only a low concentration (1:200,000) of epinephrine, using a minimal volume and avoiding use of a proximal ring block. He also recommends buffering the anesthetic, because premixed lidocaine with epinephrine is acidic.

"When you decrease blood flow to a digit (as occurs during anesthesia and surgery on the nail unit), acidosis develops in the ischemic area. If you inject an acidic anesthetic, it worsens the situation and may increase tissue damage. Buffering it to a neutral solution reduces pain and is a safer alternative," Dr. Jellinek explains.