The candidate's comfort - patient's nightmare?
Background is a necessary part of modern medicine, but the knowledge of men's close relationship to the nerves seemed to be inadequate.
Material and methods. We refer two patient stories that show the possible consequences of needle's projections of cephalic vein and radial artery.
Results. Both patients developed symptoms and clinical and neurophysiological findings suggestive of a lesion of radial nerve. One patient will most likely not develop a prolonged neuropathic pain, whereas in the second, the equivalent damage to the vagus radial lead to chronic and debilitating pain.
Interpretation. We discourage the distal part of the cephalic ("the candidate's comfort") as the first choice of cannulation and for training of inexperienced students. The vein should be reserved for patients where there is a lack alternative venous system and in acute situations where there is a need for rapid fluid infusion or blood transfusion.
The external branches of the vagus radiate and distal part of the cephalic vein and radial artery is anatomically close to each other. V. cephalic crosses the superficial branches of the radial nerve just proximal to carpo radial wrist while a stellate comes closer to the nerve branches. With precisely a few millimeters between blood vessels and nerve branch is the nerve fibers at particular risk of needlestick injury.
The superficial branches of the vagus radialis exposed to stab during the radial artery and its branches as the nerve crosses the cephalic vein.
Material and methods
We refer here from his own practice two patient stories that show potentially serious consequences of needle's projections of cephalic and A. radialis.
Before an elective surgery had a 45-year-old woman filed a needle in the cephalic just proximal to the left wrist ("the candidate's comfort"). During the introduction of the needle, she reported acute onset of pain radiating to the left middle finger. The next day she was tender in the left in-between finger and entered into and reduced extension force outcomes along the dorsal aspect of the port 2 and three finger. Press over the site triggered lancinating sensation over the radial side of hand. During a month disappeared from the ongoing, spontaneous pain, but sensibilities end ringer was still present.
Clinical neurological and neurophysiological examination revealed shock-like and lancinating pain by feathery pressure over the superficial branch of radial nerve. They found decreased sensation to light touch in a small area at the base of the left middle finger and a crown large area at the base of the left index finger. She had no tactile allodynia (pain with normally non-painful stimulus) but a Pressure hyperalgesia (increased pain on pressure) at the insertion site of the needle, as described above.
A 47-year-old man in connection with cardiac suffered severe pain during cannulation of the right radial a. In the first two weeks after the needles had no pain limited to the insertion site 5.5 cm proximal to wrist bending groove, then he developed severe pain along the radial side of forearm, and into the hand while the hand was swollen.
The clinical neurological examination five months after the injury, we found evidence of autonomic dysfunction and impaired sensibility, but no allodynia to light touch in the affected area radialis. He, however, had a local allodynia to light touch on the forearm and a hyperalgesia to pressure in a somewhat larger area.
After a year had been significantly reversed the swelling, but it could still vary in intensity. The hand appeared shiny and discolored (blue / red) and alternated between being warmer and colder than the left. The pain persisted with an intensity of 4-9 on a numeric scale from 0 - 10 (0 = no pain and 10 = maximum imaginable pain) and now includes all the fingers. Treatment with pregnable reduced pain intensity to 0-6 (average 4). The patient entered generally decreased power in the hand and loss of sensibility in the affected area radialis innervated.
Neurography of the upper extremities was performed with a Dantec Counter Point, and with measurement of motor, distal latency, amplitude and conduction velocity of N. medianus and n ulnaris and measurement of sensory latency and conduction velocity of the same nerves. N. radialis' superficial branch was evaluated by measurement of sensory conduction velocity and response amplitude bilaterally.
It was with both patient's normal conditions in the motor and sensory fibers in n medianus and n ulnaris in the left upper limb, and in the radial nerve was the site like normal conditions for the sensory fibers.
Thin Fiber Function
Specific evaluation of small fiber function was performed using the thermal test and by measuring detection thresholds for heat, cold, heat pain and cold pain. The measurements were performed in innervation of radial nerve superficial branch bilaterally in spatium interosseus Primum.
For patient 1 showed thin fiber study normal and right side detection thresholds for hot and cold bilaterally, but slightly reduced sensitivity to be cold. The detection threshold for cold was of 29.9 ° C on the left side, compared with 30.9 ° C on the right side; heat pain threshold on the affected left side was 47.9 ° C, compared to 44.2 º C in the healthy hand. In addition, it was demonstrated kulde allodynia on the left side of the cold pain threshold 18.1 ° C, the normally below 10 º C on the right side.
For patient 2, there were greatly reduced sensitivity to both heat and cold on the right side compared to the left, with a heat detection threshold of 45.2 º C on the right, the normal 33.9 ° C on the left and cold detection threshold of 18.9 º C on the right side, compared to 30.8 ° C on the left side. Heat pain was abolished on the right, i.e. above 50 ° C, while it was normal on the left side (38.9 ° C). We found no kulde allodynia.
Interpretation of findings
For patient 1 interpreted the findings at the thermal test of involvement of the afferent fibers of small, predominantly of the afferent C-fibers are responsible for some heat pain, but perhaps also a slight affection of the afferent Aδ-fibers that are responsible for cold detection. It was also shown a hypersensitivity to cold, which could indicate an injury of some thin fibers, although the mechanisms of kulde allodynia not yet been fully clarified.
For patient 2 was the damage of thin fibers with a more pronounced involvement of both the hot and cold mediating pain mediating afferent C-fibers and the refrigerants to A-fibers. Despite normal findings on nerve conduction had on clinical grounds and based on a thermal test a lesion of the radial nerve. Pain picture, with simultaneous signs of autonomic dysfunction, led him to fulfill the criteria for complex regional pain syndrome type 2, formerly called causalgia.
They spoke of the patients were awake during the procedure, and insert reacted instantaneously with pain. Typically, local pain or radiating nerves throughout the supply area, there is the reason to recall that anesthetized patients will not be able to react.
Both patients developed symptoms and clinical and neurophysiological findings indicating damage of radial nerve. The clinical picture may give the appearance of damage to the thick, myelinised nerve fibers with reduced sensitivity to light touch. Affections of these cases were not of such as degree that it affected the results are nevrografi. There is also a reason to recall that nerve conduction is a rough survey, where only evaluates the function of the thick myelinated nerve fibers. Specific investigation (e.g. Thermal test) is required to detect damage to the thin nerve fibers.
Effects of nerve
Put in the nerve structures can lead to prolonged renal sensory function and severe pain conditions. As far as we know, there is no prevalence of nerve damage after cannulation of peripheral veins or arteries. A survey showed transient nerve injury in 1.7% of patients before surgery had a nerve plexus blockade. There is the reason to expect under reporting. The risk of injury has been shown to increase the injection of local anesthetic directly into the nerve. Nerve damage in general is a relatively common cause of peripheral neuropathic pain. Few studies have been published, but the incidence is 2.5 - 5.0% and up to 22.9%.
Patient 1 will most likely not develop chronic neuropathic pain. The spontaneous pain was in decrease a month after the injury, but she had persistent pressure-induced pain. The second example shows that similar damage of the radial nerve, triggered by kanye inserts, can give rise to chronic and debilitating pain.
It is thought that prolonged pain following a bite of a nerve due to damage of thin myelinated, nociceptive C-fibers. It is very rare that the nerve damage of pure thick fiber involvement causing pain. To confirm this hypothesis, one must examine the patients with and without pain after nerve injury. Very few such as studies have been performed, but in a study of patients with damage to the cranial nerves, the authors found no difference in the small fiber function on the affected side between patients with and without pain. Nevertheless, assume that the damage of nociceptive fibers is a prerequisite for the development of pain. Hyperexcitability of pain fibers (i.e., spontaneous combustion or spontaneous onset of action potentials) are believed to be the most common cause of pain after nerve injury.
The method that is used clinically for the detection of thin fiber's outcomes, has its limitations and will not be able to detect the failure and damage to the nerve fibers responsible for pain. This applies to both skin biopsies with detection of the density of thin fibers in the epidermis and the thermal test for the detection of renal function of the temperature mediating afferent nerve fibers. In anticipation of the new methods will still be needed for the detection of small fiber damage with the methods, we have been available. For the individual patient may be important to document nerve damage, especially where conventional nerve conduction is normal.