Emergency room physicians in busy medical centers see and treat a lot of finger injuries each week.  From lacerations (cuts) to fractures, it is often difficult to fully evaluate and treat (suturing a cut or straightening a broken or displaced finger bone) without numbing the area.  Even cleaning blood or debris from an injury may be painful enough to require anesthesia.

Anesthetic creams would probably not be sufficient to provide pain relief. Local injectables such as Lidocaine (brand name Xylocaine), are necessary to provide anesthesia. Lidocaine may be placed around the actual wound superficially (local infiltration) or may be directed to “block” a specific nerve that serves the area to be treated.  This procedure is known as a nerve block.

How Nerve Blocks are Used

Each nerve block is intended to numb a portion of the course of a nerve as it travels through the body, so as to numb the injured area.  For a finger injury, numbing the entire finger gives superior anesthesia to just placing some Lidocaine around the injury itself (in most cases). There are various injectable local anesthetics on the market, such as Procaine (Novocain), Bupivacaine (Marcaine), and Mepivacaine (Carbocaine).  Lidocaine (Xylocaine) is, however, the most widely used these days, due to the rapidity and effectiveness of its anesthetic action.

1% or 2% plain Lidocaine is acceptable; for areas like fingers, which have limited circulation, avoid Lidocaine with Epinephrine. Epinephrine constricts the blood vessels and may compromise blood flow, and even lead to gangrene and the loss of the digit.  Before you consider the use of local anesthetic, you should be aware of your patient’s medical history. Some, such as those with liver disease, cardiac disease, or the elderly, should receive less quantities of the drug. Veterinary Lidocaine is not exactly the same as human Lidocaine, by the way.  There are several ingredients in veterinary  Lidocaine that are called “inert” that cost money to remove, and have been extracted from human Lidocaine.

The Anatomy of a Finger

The anatomy of a finger includes bone, tendons, nerves, and blood vessels.  For our purposes today, let’s look at the nerve distribution of the distal hand and fingers.  The median and ulnar nerves travel up opposite sides of the wrist and branch out into “digital” nerves.  These run up opposite sides of the palmar aspect of the finger, and branch again to give sensation to the back of the fingers as well.

            Source of image:  www.nysora.com; designed by VisionExpo.design

Of course, you’ll need some equipment:  Sterile towels and gauze to create a sterile field in which to work,an antiseptic such as Betadine, at least one 6cc or 10cc syringe, and a thin gauge 1-1 ½ inch needle (25 or 27 gauge will do fine). Don’t forget gloves! You can decrease the “sting” of the injection by warming the local anesthetic somewhat and/or adding 1cc of sodium bicarbonate solution to 10cc of medication.

The procedure to give anesthesia to a finger is relatively simple.  Despite this, the following information is for your information and possible use only in a post-apocalyptic situation where modern medical care is inaccessible for the foreseeable future.  If there are doctors with experience in this procedure, seek them out.

Place the hand pronated on the sterile field (use more Betadine than I did in the photos).  With your small gauge needle and a Lidocaine syringe, place a small amount of local anesthesia on either side of the base of the finger, raising a wheal (a slight swelling) just under the skin.  This will make any later injections less painful.  After waiting a minute or so, insert the needle in the wheal and forward toward the base of the finger bone. Begin injecting the local anesthesia. Repeat on each side of the injured finger.  1-2 ml, injected as you slowly withdraw the needle, on each side should be sufficient.  Too much may cause compression of blood vessels.

An alternative to this approach, or perhaps an addition for more complete anesthesia, is the “transthecal” finger block.  The benefit is that this approach may numb the finger with a single injection, if done correctly.  To perform this type of block, turn the hand palm up, and follow the tendon of the finger down to the level of the first palmar crease line.  Inserting the needle at a 45 degree angle, go down to the tendon and inject 2 ml of Lidocaine.  If you notice resistance you are too close to the tendon and should pull back a little.  Some suggest rubbing the area to distribute the medication.

Wait about 10 minutes or so before assessing for completeness of anesthesia.  This may be done by lightly pricking with a safety pin or applying slight pressure to the area.  After any work on the finger injury, immobilize it with a finger splint or the “buddy method” of using an adjacent finger for support.  Cover with a generous wrapping.

Some important things to know:

• Don’t inject any area that is clearly infected (red, swollen, warm to the touch)
• Use small gauge needles to avoid hitting blood vessels and causing bleeding
• Don’t inject into any visible veins
• Pull back on the needle before you inject anesthesia; if you see blood in the syringe, abort and try again
• Avoid Epinephrine
• No more than 2 ml on each side of the finger
• If the injection is extremely painful, you may be hitting the nerve with the needle; abort and try again

There is always more to know about medical procedures that what can be written in one article.  Do your own research, and come to your own conclusions as to whether you should consider learning this type of medical technique.

Dr. Bones