EXPERT ANALYSIS FROM WCD 2015
VANCOUVER (FRONTLINE MEDICAL NEWS) – Achieving effective local anesthesia is the critical first step in successful nail surgery, Dr. Chris G. Adigun said at the World Congress of Dermatology.
“Always remember: Nail surgery hurts. Your patients will applaud you enthusiastically when they’re back home for your having used a long-acting anesthetic,” said Dr. Adigun, a dermatologist in group practice in Chapel Hill, N.C.
The three most widely used anesthetic agents in nail surgery are lidocaine (Xylocaine), bupivacaine (Marcaine), and ropivacaine (Naropin). Dr. Adigun said she strongly prefers ropivacaine. It combines the best features of the other two: lidocaine’s rapid onset along with a duration of action that’s even longer than bupivacaine’s, she noted. Ropivacaine’s duration of action is 8-12 hours – and it comes without bupivacaine’s potential for cardiotoxicity. Moreover, ropivacaine has a vasoconstrictive effect, which improves hemostasis and enhances visualization during the surgery.
She provided numerous additional tips on how to predictably achieve effective anesthesia for nail surgery:
• Buffer with sodium bicarbonate. The idea is to bring the anesthetic solution close to physiologic pH, which makes for a far less painful experience than injecting the acidic unbuffered solution.
• Warm it. Investigators have shown that warming anesthetic fluid reduces pain upon injection of both nonbuffered and buffered local anesthetics ( Ann Emerg Med. 2011 Jul;58(1):86-98 ).
• Stick to a small-gauge needle. Dr. Adigan said she favors 30 gauge. It makes for a smaller, less painful puncture and limits the rate of flow of anesthetic fluid into the digital space.
• Inject in a perpendicular plane. This will disrupt fewer nerve endings than when going in at an angle.
“I think this is something that’s not frequently taught to residents in dermatology. I think we almost always go in at an angle, but if you go in at a perpendicular plane, you’re going to cause less pain,” according to Dr. Adigun.
• Inject just below the dermis. The dermis is nociceptor rich, and stretching those tissues by injecting a volume of fluid there will cause intense, continuous pain until the local anesthetic has time to take effect.
• Use distraction techniques liberally. Dr. Adigun said she likes to tell stories and jokes, which she calls “talkesthesia.” She also utilizes a battery-powered massager.
“Put the massager as close to your surgical field as you’re comfortable with. Under the gate theory of pain, you want to create as much sensory ‘noise’ as possible with your distraction techniques so that gate is filled with your sensory noise rather than pain,” the dermatologist explained.
There are three solid, time-tested completely acceptable techniques for getting the target digit numb: the wing block, the traditional digital block, and the transthecal digital block.
Dr. Adigun said she generally relies upon the wing block unless she is concerned that the associated blanching might cause her to lose her digital landmarks during surgery addressing a subtle abnormality. In that situation she turns mainly to the traditional digital block, which doesn’t interfere with digital landmarks and effectively anesthetizes both the paired digital and volar nerves.
The downside of the traditional digital block is it entails a 15- to 20-minute wait for the anesthetic to diffuse. So does the transthecal digital block, which has the additional shortcoming of achieving predictable results only when applied for surgery on the second, third, or fourth digits.
The wing block is an efficient infiltrative technique targeting the distal digit. It offers immediate anesthesia of the total nail unit. To achieve an excellent wing block, initially inject just 0.1-0.2 mL of anesthetic fluid subcutaneously into the proximal nail fold midway between the cuticle and the distal interphalangeal joint. Wait for a wheal to form; then wait an additional 45-60 seconds. At that point, inject obliquely along the lateral edge of the nail fold in the direction of the digital tip. The needle should be advanced while maintaining a gentle fluid bolus ahead of the needle tip in order to minimize the patient’s sensation of the moving needle. The process is then repeated on the opposite side of the digit.
“You want to keep that needle in the dermal plane and avoid filling the pulp with anesthetic fluid. If you do this correctly, only one prick is felt by the patient. I very rarely have to use a full cc of anesthetic fluid when I use a wing block,” Dr. Adigun said.
If any additional needle insertions are needed, make sure they’re placed into tissue that’s already been anesthetized, she added.
Dr. Adigun reported having no financial conflicts of interest.