Chapter 1 Atlas of Images of Local Anesthetic Diffusion Anatomy



10.1055/b-0037-142172

Chapter 1 Atlas of Images of Local Anesthetic Diffusion Anatomy

Donald H. Lalonde

In this atlas, the images you will see are drawn from photographs of live human volunteers injected with tumescent local anesthesia to determine where the solution naturally diffuses when you inject it under the skin in the hand, wrist, and forearm.


Producing tumescing local anesthesia requires injecting enough volume of anesthetic solution—lidocaine (also called lignocaine) with epinephrine—under the skin so that you can see its swelling, and you can feel it when you palpate the area (see Chapter 4). It is a form of extravascular Bier block injected only where you intend to operate.


In addition to anatomic maps of where the local anesthetic diffuses when you inject it in one place in the forearm, wrist, and hand, this chapter also describes the natural barriers to local anesthetic diffusion formed by creases and glabrous/nonglabrous skin boundaries.



GUIDE TO THE ATLAS




  • Each image answers the following question: Where does the local anesthetic diffuse and have its numbing effect when you inject it under the skin without moving the needle in the red injection point of the illustrated area?



  • The blue areas show the diffusion of visible and palpable lidocaine with epinephrine that usually takes place within 30 minutes after injection in most patients. These blue areas will be both numbed and vasoconstricted.



  • The green areas are blocked by nerve block. They may take up to an hour or longer after injection to achieve the peak nerve block. These green areas will not be vasoconstricted. Bleeding in the green areas may be more than in normal skin because of the sympathectomy effect of the nerve blocks. To avoid bleeding in the green areas, simply inject more local anesthetic where you will dissect, as described in Chapter 4.



  • Note that the ligaments at the glabrous/nonglabrous skin junction act as a diffusion barrier to distribution of the local anesthetic. This is where the volar skin meets the dorsal skin of the hand. This also is the embryologic boundary/border of many nerve distributions.



  • Ligaments that create creases in the hand and fingers also act as a natural diffusion barrier to local anesthetic. You will usually have to inject on both sides of the creases.



  • Preexisting scars and lacerations create natural diffusion barriers to local anesthetic. You will usually have to inject on both sides of preexisting scars and lacerations.



  • As in all anatomy, different patients will have small differences. Not all patients will get the green distal nerve blocks.



MIDLINE DORSAL FOREARM

When you inject 20 ml of 1% lidocaine with 1:100,000 epinephrine (buffered at a ratio of 10 ml of lidocaine/epinephrine to 1 ml of 8.4% sodium bicarbonate) 10 cm proximal to the wrist crease in the dorsal forearm midline in the red injection point just under the skin without moving the needle, local anesthetic can be seen and palpated to diffuse in the blue area in an unscarred patient. You numb the green area by nerve block, but this area has no epinephrine vasoconstriction and may bleed more because of the sympathectomy of the nerve block.


MIDLINE VOLAR FOREARM

When you inject 20 ml of 1% lidocaine with 1:100,000 epinephrine (buffered at a ratio of 10 ml of lidocaine/epinephrine to 1 ml of 8.4% sodium bicarbonate) 10 cm proximal to the wrist crease in the volar forearm midline in the red injection point just under the skin without moving the needle, local anesthetic can be seen and palpated to diffuse in the blue area in an unscarred patient. You numb the green area by nerve block, but this area has no epinephrine vasoconstriction and may bleed more because of the sympathectomy of the nerve block. The median and ulnar nerves may not be blocked unless the needle gets beneath the deep forearm fascia, since this can act as a natural barrier to local anesthetic diffusion.


MIDLINE RADIAL FOREARM

When you inject 20 ml of 1% lidocaine with 1:100,000 epinephrine (buffered at a ratio of 10 ml of lidocaine/epinephrine to 1 ml of 8.4% sodium bicarbonate) 10 cm proximal to the wrist crease in the radial forearm midline in the red injection point just under the skin without moving the needle, local anesthetic can be seen and palpated to diffuse in the blue area in an unscarred patient. You numb the green area by nerve block, but this area has no epinephrine vasoconstriction and may bleed more because of the sympathectomy of the nerve block.


MIDLINE ULNAR FOREARM

When you inject 20 ml of 1% lidocaine with 1:100,000 epinephrine (buffered at a ratio of 10 ml of lidocaine/epinephrine to 1 ml of 8.4% sodium bicarbonate) 10 cm proximal to the wrist crease in the ulnar forearm midline in the red injection point just under the skin without moving the needle, local anesthetic can be seen and palpated to diffuse in the blue area in an unscarred patient.


MIDLINE VOLAR WRIST

When you inject 10 ml of 1% lidocaine with 1:100,000 epinephrine (buffered at a ratio of 10 ml of lidocaine/epinephrine to 1 ml of 8.4% sodium bicarbonate) in the midvolar wrist in the red injection point just under the skin without moving the needle, local anesthetic can be seen and palpated to diffuse in the blue area in an unscarred patient. When the injection is under the skin and not below the forearm fascia, you may not achieve a median or ulnar nerve block, since the deep forearm fascia can act as a natural diffusion barrier to local anesthetic diffusion. You do get a palmar cutaneous and a dorsal sensory block, as shown in green. More of the local anesthetic tracks proximally, because the wrist crease acts as a natural barrier to local anesthetic diffusion into the palm. You numb the green area by nerve block, but this area has no epinephrine vasoconstriction and may bleed more because of the sympathectomy of the nerve block.

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Related posts:

SECTION I ATLAS OF TUMESCENT LOCAL ANESTHESIA ELBOW, FOREARM, WRIST, HAND, AND FINGER INJECTIONS Chapter 3 Safe Epinephrine in the Finger Means No Tourniquet Chapter 16 Minor Procedure Room Setup Chapter 23 Dupuytren′s Contracture Chapter 28 Thumb Metacarpophalangeal Joint Fusion and Ulnar Collateral Ligament Repair Chapter 35 Extensor Tendon Repair of the Finger

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May 29, 2020 | Posted by in ORTHOPEDIC | Comments Off on Chapter 1 Atlas of Images of Local Anesthetic Diffusion Anatomy

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