Electron microscopy evaluation of block needle‐related trauma to the tibial nerve

Background: Direct puncture by a needle is a risk factor for nerve damage. This investigation used scanning electron microscopy (SEM) to attempt to visualize the damage caused by different needles. Method: A 15 cm section of the tibial nerve was removed from the ankle of a patient undergoing below‐the‐knee amputation. The nerve specimen was punctured perpendicular to the fibers once by each of four needles: an insulated 22 G short‐beveled (30°), a 25 G long‐beveled Quincke spinal needle, an 18 G Tuohy, and a 25 G Whitacre pencil point. The distal and proximal ends on either side of the needles were marked and the nerve was sectioned into 0.5 cm pieces. Each sample was preserved and then prepared for SEM. The needle tract was observed for evidence of mechanical damage at magnifications between × 47 and × 102 using SEM. Results: The epineurium, perineurium, fascicles, endoneurium, and vessels were identified in each sample. In both the short‐beveled and the Whitacre samples, all fascicles along with the surrounding perineurium were intact. In both the Tuohy and the Quincke samples, obvious transection of fascicles and disruption of the perineurium were observed. Conclusions: This investigation suggests that both the Tuohy and the Quincke needles may be more likely to cause trauma to the tibial nerve than either the short‐beveled or the Whitacre needles.     

PERIPHERAL NERVE INJURY CAUSED BY INJECTION NEEDLES USED IN REGIONAL ANAESTHESIA: INFLUENCE OF BEVEL CONFIGURATION, STUDIED IN A RAT MODEL

We have studied the immediate and long term (up to 28 days)effects of short and long bevelled needle impalement of therat sciatic nerve. Three techniques were used to assess neuraltrauma and its consequences: stained longitudinal nerve sectionswere assessed by light microscopy and scored for injury; theextravasation of Evan's Blue dye, after antidromic electricalnerve stimulation, was used as a test of unmye/inated fibrefunction; the flexion withdrawal times from a noxious stimuluswere measured. The results of all three experiments suggestedthat, should a nerve fascicle become accidentally impaled duringregional anaesthesia, the lesions induced by short bevelledneedles are more severe, more frequent and take longer to repairthan those induced by long bevelled needles. Nerve injury inducedby short bevelled needles was associated with persisting signsof injury 28 days after the injury. These results suggest thatthe current practice of using short bevelled needles to preventnerve injury complicating regional anaesthesia be reassessed.(Br. J. Anaesth. 1992; 69: 433–438). ^* Present address: Nuffield Department of Anaesthetics, JohnRadcliffe Hospital, Headley Way, Headington, Oxford OX3 9DU.     

Spinal needle design and size affect the incidence of postdural puncture headache in children

Background: In adults, pencil point spinal needles are known to be less traumatic and hence to be superior compared with cutting point needles in respect of postpuncture complications. In children, only a few trials have evaluated the difference in the incidence of postdural puncture headache (PDPH) using spinal needles with different tip designs. The aim of this study was to evaluate the success rate and the incidence of PDPH and backache following spinal anesthesia (SA) with the two types of needles currently in use for children. Methods: This is a retrospective study of prospectively collected data. The success rate and postpuncture complications of 26G cutting point (Atraucan^®) spinal needle were compared with 27G pencil point (Pencan^®) spinal needle in 414 children aged 2–17 years undergoing surgery with SA. Results: Both needles had similar first‐attempt success rates: 87% in the cutting point group and 91% in the pencil point group (P = 0.16). Pencil point needles caused less PDPH compared to cutting point needles; 0.4% vs 4.5%, respectively (P = 0.005). Both needles caused similar backache (P = 0.08). No severe neurologic symptom was reported for both needles. Conclusion: The data suggest that 27G pencil point spinal needles lead to less PDPH compared to 26G cutting point spinal needles in children.     

Possibility of nerve lesions related to peripheral nerve blocks. A study of the human sciatic nerve using different needles

When a needle tip comes too close to a nerve axon, the mechanical effect over the nerve membrane produces paresthesia. We examined the hypothetical mechanical damage of short bevel and long bevel needles over sciatic nerve bundles under scanning electron microscopy. METHODS: We obtained samples of sciatic nerve from three patients of 68, 74 and 76 years old. These samples were fixed, dehydrated and coated with gold microfilm for their observation under scanning electron microscopy. Ten short bevel needles and ten long bevel needles were studied under the same microscopic technique. We interpolated microscopic images from sciatic nerve samples and different needle bevels at various angles to study the mechanical damage of these needles to nerve axons. RESULTS: Sciatic nerve bundles were found 0.1 to 0.2 mm deep in the samples; information was given about the bevel length and angle of needles. The damage is perceptible under scanning electron microscopy, when the needle bevel is introduced 0.3-0.4 mm deep into the nerve bundle; here, the needle tip cuts through the perineurum, piercing the nerve bundle. At a depth of 1 mm, the lesion caused by short bevel needles is greater than that caused by long bevel needles. The type of epineural lesions caused by short bevel needles is also different from the ones caused by long bevel needles. CONCLUSIONS: Lesions that affect superficially the epineurum can cause paresthesia by compression of nerve fascicles without damaging the axons. If the perineurm is damaged, the lession will also affect the blood-nerve barrier, leading probably to posterior sequels.     

The effect of needle size and type in paediatric caudal analgesia

A randomized prospective study compared three types of needle for caudal analgesia in 623 children. Inadvertent vascular puncture (bloody tap) was more likely if a child weighed more than 15 kg. There were no significant differences in respect to success or complication rate between the needle types (21 g and 23 g standard bevelled intramuscular (IM) needles and 22 g short bevelled «regional block>> needle).     

Collagen nerve protector in rat sciatic nerve repair: A morphometric and histological analysis

Peripheral nerve repair is often complicated by fibroblastic scar formation, nerve dysfunction, and traumatic neuroma formation. Use of bio‐absorbable protective wraps may improve outcomes of these repairs. This study histologically compared the incidence of neuroma formation, connective tissue proliferation, and axonal regrowth in transected rat sciatic nerves repaired with and without tubular collagen nerve sleeves. Twenty Sprague‐Dawley rats underwent unilateral sharp sciatic nerve transection and microscopic nerve repair with four epineural sutures and were randomly treated with or without an encircling collagen nerve sleeve. Normal nerves from the contralateral sciatic nerve were also examined. At sacrifice three months later, the nerves were evaluated for traumatic neuroma formation, perineural scar formation, and morphometric analysis. Histological examination of normal and repaired nerves by a neuropathologist demonstrated healing, minimal Wallerian degeneration and no traumatic neuroma formation. Distal section analysis (nine nonwrapped, 10 wrapped), revealed no significant differences in total fascicular area, myelinated fibers per nerve, fiber density, myelin area per nerve, myelinated fiber diameter, axon diameter, myelin thickness, or G‐ratio. Significantly greater (P = 0.005) inner epineural connective tissue formation was observed in nonwrapped nerves (0.62 mm² ± 0.2) versus wrapped nerves (0.35 mm² ± 0.16). The ratio of connective tissue to fascicular area was larger in nonwrapped (1.08 ± 0.26) versus wrapped nerves (0.63 ± 0.22) (P < 0.001). This study demonstrated decreased inner epineural connective tissue formation with use of a collagen nerve wrap during primary repair of peripheral nerve transection in a rat sciatic nerve model. © 2010 Wiley‐Liss, Inc. Microsurgery 30:392–396, 2010.     

Pencil point spinal needles and neurological damage

Editor—The editorial by Fettes and Wildsmith¹ discussesthe important issue of neurological damage after spinal anaesthesiawith pencil point needles. They mention several factors aboutthese needles and how these may predispose to neurological damage.I would like to comment on three of the four points they makein the section on equipment. Their first point is that pencil point needles require to beinserted for a greater length because the needle orifice issituated approximately 1 mm proximal from the tip. Whilst thelatter is true, there is no evidence of the former. We performeda pilot trial, which did not support this     

Possibility of cauda equina nerve root damage from lumbar punctures performed with 25-gauge Quincke and Whitacre needles

OBJECTIVE: To assess the possibility of puncturing nerve roots in the cauda equina with spinal needles with different point designs and to quantify the number of axons affected. MATERIAL AND METHODS: We performed in vitro punctures of human nerve roots taken from 3 fresh cadavers. Twenty punctures were performed with 25-gauge Whitacre needles and 40 with 25-gauge Quincke needles; half the Quincke needle punctures were carried out with the point perpendicular to the root and the other half with the point parallel to it. The samples were studied by optical and scanning electron microscopy. The possibility of finding the needle orifece inserted inside the nerve was assessed. On a photographic montage, we counted the number of axons during a hypothetical nerve puncture. RESULTS: Nerve roots used in this study were between 1 and 2.3 mm thick, allowing the needle to penetrate the root in the 52 samples studied. The needle orifice was never fully located inside the nerve in any of the samples. The numbers of myelinized axons affected during nerve punctures 0.2 mm deep were 95, 154, and 81 for Whitacre needles, Quincke needles with the point held perpendicular, or the same needle type held parallel, respectively. During punctures 0.5 mm deep, 472, 602, and 279 were affected for each puncture group, respectively. The differences in all cases were statistically significant. CONCLUSIONS: It is possible to achieve intraneural puncture with 25-gauge needles. However, full intraneural placement of the orifice of the needle is unlikely. In case of nerve trauma, the damage could be greater if puncture is carried out with a Quincke needle with the point inserted perpendicular to the nerve root.     

Postdural puncture headache and transient neurologic symptoms in children after spinal anaesthesia using cutting and pencil point paediatric spinal needles

Background: In the last decade the use of spinal anaesthesia (SA) in paediatric anaesthesia has increased. In adults, pencil point spinal needles are supposed to be less traumatic and hence to be superior compared with cutting point needles in respect of postpuncture complaints. In children, the use of spinal needles with a special tip design have not been compared. The aim of this study was to study the clinical utility and postpuncture characteristics of four newly designed spinal needles in paediatric surgery. Methods: In this open-randomised, parallel groups, prospective study we compared the puncture quality, success rate and post-puncture characteristics in 200 children aged 2 to 128 months. Two cutting point needles; a 50-mm-long 25G Quincke and a 25-mm-long 26G Atraucan were compared with two pencil point needles; a 37-mm-long 27G Whitacre and a 35-mm-long 24G Sprotte. The children were premedicated with oral diazepam and those anxious or uncomfortable after premedication were sedated with i.v. thiopentone or propofol. Bupivacaine 5 mg ml^?1 0.3–0.5 mg kg^?1 was used for the SA. Results: The spinal puncture was successful with one or two skin punctures in 96% of children. The cutting point needles were easier to insert through the skin and ligaments (P=0.001) but the pencil point needles gave a better (P=0.001) indication of the dural passage. The success rate of the SA was 91% without differences between the needles. Five patients were given general anaesthesia and 13 children a single dose of i.v. fentanyl/sedative. The spinal block was completed in less than 3 min in 96% of the cases without differences between the needles. Seventeen children developed a headache, 10 of which were classified as a postdural puncture headache (PDPH), 3 with the Sprotte, 3 with the Quincke and 4 with the Atraucan needles. The youngest child developing PDPH was a 12-month-old boy. Eight of the PDPH were mild and 2 moderate. Ten children developed a low back pain, 2–3 in each study group. Three children in the pencil point groups developed signs of transient radicular irritation. Conclusion: SA using bupivacaine and the study needles produced smooth and safe anaesthesia for paediatric surgery with a high success rate. PDPH after SA is as common in children (5%) as in adults although most often mild and short lasting. SA using bupivacaine can cause transient radicular irritation.     

Assessment of a new disposable introducer for spinal needles

The compatibility between spinal needles and their introducers varies between manufacturers and can significantly influence the usable length of the spinal needle available resulting in failure to locate CSF in larger patients. The usable length of 90‐mm pencil point spinal needles from four manufacturers ranged from 68 to 79 mm when the needle was used in combination with its introducer. A new purpose‐built introducer needle is described which, when used with a 25 g or finer spinal needle, maximises the usable length of the needle. Using this new introducer the usable needle length of a 90‐mm Whitacre needle was increased by a further 7 to 86 mm resulting in only a 4 mm loss of total needle length. The new introducer was well received by users.     

A randomised,single‐blind technical study comparing the ultrasonic visibility of smooth‐surfaced and textured needles in a soft embalmed cadaver model

Visibility of the needle tip and shaft is important during ultrasound‐guided regional anaesthesia in order to prevent nerve trauma. Tip and shaft visibility is reduced when needles are inserted in‐plane at wide angles and out‐of‐plane at narrow angles to the ultrasound probe. Although textured needles are more reflective than smooth needles, we hypothesised that poor visibility of the tip and shaft still remained using the above angle‐probe combinations. In a single‐blind study, we compared the visibility of a textured Tuohy needle, a textured single‐shot needle and a conventional smooth‐surfaced Tuohy needle when inserted into the biceps and deltoid muscles of a soft embalmed cadaver. One hundred and forty‐four needles were block‐randomised to in‐plane and out‐of‐plane insertions at 30°, 45°, 60° and 75° to the ultrasound beam. Two blinded raters assessed needle tip visibility on video recordings of the insertions using a binary scale (0 = not visible, 1 = visible) and shaft visibility using a 5‐point Likert scale. The median (IQR [range]) proportions of visible needle tips were 83% (67–83 [50–100]%) for the textured Tuohy, 75% (67–83 [33–83]%) for the textured single‐shot needle and 33% (33–46 [0–50]%) for the smooth‐surfaced Tuohy (p = 0.0007). Median (IQR [range]) needle shaft visibility was rated as 4.0 (3.5–4.7 [3.0–4.9]) for the textured Tuohy, 4.0 (3.8–4.5 [2.7–4.9]) for the textured single‐shot needle and 3.0 (2.4–3.3 [2.3–3.5]) for the smooth‐surfaced Tuohy (p = 0.015). Nevertheless, visibility was reduced at wide angles in‐plane and narrow angles out‐of‐plane both for needle tips (p = 0.004) and shafts (p = 0.005).     

Sonographic visualization and ultrasound-guided block of the third occipital nerve: prospective for a new method to diagnose C2-C3 zygapophysial joint pain

BACKGROUND: Chronic neck pain after whiplash injury is caused by cervical zygapophysial joints in 50% of patients. Diagnostic blocks of nerves supplying the joints are performed using fluoroscopy. The authors' hypothesis was that the third occipital nerve can be visualized and blocked with use of an ultrasound-guided technique. METHODS: In 14 volunteers, the authors placed a needle ultrasound-guided to the third occipital nerve on both sides of the neck. They punctured caudal and perpendicular to the 14-MHz transducer. In 11 volunteers, 0.9 ml of either local anesthetic or normal saline was applied in a randomized, double-blind, crossover manner. Anesthesia was controlled in the corresponding skin area by pinprick and cold testing. The position of the needle was controlled by fluoroscopy. RESULTS: The third occipital nerve could be visualized in all subjects and showed a median diameter of 2.0 mm. Anesthesia was missing after local anesthetic in only one case. There was neither anesthesia nor hyposensitivity after any of the saline injections. The C2-C3 joint, in a transversal plane visualized as a convex density, was identified correctly by ultrasound in 27 of 28 cases, and 23 needles were placed correctly into the target zone. CONCLUSIONS: The third occipital nerve can be visualized and blocked with use of an ultrasound-guided technique. The needles were positioned accurately in 82% of cases as confirmed by fluoroscopy; the nerve was blocked in 90% of cases. Because ultrasound is the only available technique today to visualize this nerve, it seems to be a promising new method for block guidance instead of fluoroscopy.     

Incidence of postdural puncture headache and backache following diagnostic/therapeutic lumbar puncture using a 22G cutting spinal needle, and after introduction of a 25G pencil point spinal needle

BACKGROUND: Postdural puncture headache (PDPH) after lumbar puncture (LP) is as common in children as adults. 22G needles are routinely used in adults and children for diagnostic/therapeutic LP, in contrast to 25G or less as standard for spinal anesthesia. We sought to identify incidence of PDPH and backache in oncology children undergoing LP at Royal Marsden Hospital, and whether this could be reduced by a change from 22G to 25G pencil point needle. METHODS: Symptom questionnaires were given to parents for completion 7 days following LP, and incidence of side effects ascertained. The standard needle was a 22G Quincke. A 25G pencil point spinal needle was subsequently introduced and incidence of side effects reaudited. Number of attempts with the pencil point needle was documented. RESULTS: Fifty-six of 83 questionnaires were completed for the 22G Quincke (67%). Incidence of headache was 33%, with 11% classified as PDPH (6 children, 2 > 7 days). Nausea/vomiting occurred in 25% and backache in 11%; 43 of 79 questionnaires were completed for the 25G pencil point needle (54%). Incidence of headache was 30% with 7% classified as PDPH (3 children, none >7 days). Nausea/vomiting occurred in 23%, and backache in none. Seventy percentage of needle insertions by pediatricians were successful on first attempt, 89% on second, and 100% on third. CONCLUSIONS: We have confirmed a significant incidence of PDPH in oncology patients and suggest that a 25G pencil point needle can be used successfully for diagnostic/therapeutic LP, with significantly reduced incidence of back pain, and a small tendency towards a shorter duration of PDPH symptoms.     

Comparison of insulated and uninsulated needles for locating peripheral nerves with a peripheral nerve stimulator

This study was designed to compare the use of insulated and uninsulated needles with a peripheral nerve stimulator for locating a peripheral nerve in an anesthetized cat. The needles were mounted on a one-dimensional manipulator and both the saphenous and sciatic nerves were located. The tip of the insulated needle was consistently placed on the sciatic nerve. The tip of the uninsulated needle was placed 0.1-0.9 cm past the sciatic nerve. Injecting saline to assess the position of the tip of the needle relative to the sciatic nerve did not detect the needle being past the nerve. With the saphenous nerve preparation, both the needle and nerve were visible through the tissue. Using an insulated needle, the minimum current required to stimulate the nerve occurred when the tip of the needle touched the saphenous nerve. Using an uninsulated needle, the minimum current occurred when the tip was 0.1-0.8 cm past the nerve. The conclusion is that insulated needles more precisely locate the peripheral nerve than uninsulated needles.     

Sonographic Visualization and Ultrasound-guided Block of the Third Occipital Nerve: Prospective for a New Method to Diagnose C2-C3 Zygapophysial Joint Pain

Background: Chronic neck pain after whiplash injury is caused by cervical zygapophysial joints in 50% of patients. Diagnostic blocks of nerves supplying the joints are performed using fluoroscopy. The authors' hypothesis was that the third occipital nerve can be visualized and blocked with use of an ultrasound-guided technique.

Methods: In 14 volunteers, the authors placed a needle ultrasound-guided to the third occipital nerve on both sides of the neck. They punctured caudal and perpendicular to the 14-MHz transducer. In 11 volunteers, 0.9 ml of either local anesthetic or normal saline was applied in a randomized, double-blind, crossover manner. Anesthesia was controlled in the corresponding skin area by pinprick and cold testing. The position of the needle was controlled by fluoroscopy.

Results: The third occipital nerve could be visualized in all subjects and showed a median diameter of 2.0 mm. Anesthesia was missing after local anesthetic in only one case. There was neither anesthesia nor hyposensitivity after any of the saline injections. The C2-C3 joint, in a transversal plane visualized as a convex density, was identified correctly by ultrasound in 27 of 28 cases, and 23 needles were placed correctly into the target zone.     

An experimental model of an electrical injury to the peripheral nerve

OBJECTIVE: Injury to the peripheral nerves is a common complication found in patients suffering from electrical burns. At present, there are many kinds of experimental models for electrical injury, but no report describes an animal-based experimental model for a relatively simple electrical injury to the peripheral nerves. We have designed and constructed a specific device to generate increasingly severe electrical shocks of a known voltage for the experiment. This device can simulate injuries of different degrees (minor, medium and severe) caused by shock to the right sciatic nerve of rats. METHOD: Thirty Sprague-Dawley rats were randomly divided into Group I (3600 V, n=10), Group II (1000 V, n=10) and Group III (500 V, n=10). The voltage required for the electrical shock was generated by the above-mentioned device and was adjusted to deliver 3600, 1000 and 500 V, respectively. The specific voltage, as mentioned above, was delivered three times to the right sciatic nerve of the rats. The shock duration was set to last for 10 ms. The time interval between the shocks was 3 min. Three rats were randomly selected from each group to observe changes in the morphology, electric physiology of the nerve and their histology the first, second and fourth week after injury. RESULTS: All rats survived the injuries. Leg function was partially impaired and swellings occurred on the injured extremity. However, by the second week after the injury the rats had recovered. Digit ulcers were observed by the fourth week after injury in Groups I and II. Neural electric physiology showed that the recovery rate of the neural conduction velocity (RNCV) disappeared in part or in whole immediately after the injury in experimental rats. RNCV recovered up to 65% in Group III and to 7% in Group II by the fourth week after injury, however, RNCV did not recover in Group I at all. Histology showed that blood vessel embolism occurred within the injured nerve. A large number of nerve fibres experienced Waller degeneration while the myelin sheath was vacuolated. The neural plate disintegrated largely by the first week after injury and the myelin sheath disintegrated into a loose structure by the second week after injury in Group I. Group II displayed a similar situation as Group I, wherein some nerve fibres experienced Waller degeneration and disintegration. Regenerative myelin appeared in some rats at about the fourth week after injury. The following changes were seen in Group III: The degree of neural injuries was different. The point of entry of the electric currents showed obvious Waller degeneration and disintegration of the myelin sheath, while some nerves showed a regenerated myelin sheath by the second week after injury. The morphology (such as quantity and diameter) of the injured myelin was basically normal by the fourth week after injury. CONCLUSION: This device can produce controlled injuries to the sciatic nerve giving different degrees of severity (minor, medium and severe), by means of varying the electrical shock voltage and shock duration on the rats. It is a useful model for experimental studies of injuries to peripheral nerves.     

Clinical and user-friendly classification of traumatic digital nerve injuries of hand

INTRODUCTION: Surgical findings of traumatic neurapraxia and neurotmesis in digital nerve injuries of hand have significantly different prognosis and surgeons managing such injuries must be able to provide the expected incidence of these injuries along with decision on surgical exploration. There is a paucity of data in the literature defining the incidence of traumatic neurapraxia and neurotemesis in lacerated hand injuries with clinical features of digital nerve injury. MATERIALS AND METHODS: We carried out a study in an urban practice to understand this problem on 81 consecutive patients with 82 digital nerve injuries over 1.5 years. Seventy-two percent of the injuries were caused mainly in the domestic accidents by glass and knife. All patients had clinical features of digital nerve injury. RESULTS: Operative findings revealed nerve damage in 76 patients (confidence interval at 95% = 91-97). Seventy-one had severed nerves and underwent repair (CI at 95% = 80-95). There were 7% patients with operative findings of normal looking nerves and 6% of bruised but intact nerves. All of these 13% patients who did not require surgical repair were grouped as traumatic neurapraxia and showed complete clinical recovery. CONCLUSION: Traumatic neurapraxia in digital nerve injuries of the hand are not uncommon, as previously thought, following lacerated injuries to hand and have favourable prognosis. This information is important for clinicians in getting more informed consent and patient education. The classification of digital nerve injuries into traumatic neurapraxia and neurotemesis appears logical for its practical application in routine clinical practice.     

Needle perforation of the appendix

BACKGROUND/AIMS: Needles are among the most frequently swallowed foreign bodies. In most cases they are excreted per vias naturales, but in some cases needles can lead to perforation of the stomach or duodenum in adults. METHODS: We report a case of acute appendicitis after perforation of the appendix by a swallowed needle. An appendectomy was performed without any knowledge of the reason for perforation. RESULTS: Inspection of the resected appendix demonstrated a needle of 1.5 cm length inside the lumen of the appendix, which had caused a perforation of the distal end of the appendix. CONCLUSION: As seen in this case a longer-lasting nondiagnosed perforation can lead to extensive local inflammation which could have been avoided by early surgical treatment which should also be considered if the patient has very few symptoms, as in this case.     

Perineural Administration of Dexmedetomidine in Combination with Bupivacaine Enhances Sensory and Motor Blockade in Sciatic Nerve Block without Inducing Neurotoxicity in Rat

Background: The current study was designed to test the hypothesis that high-dose dexmedetomidine added to local anesthetic would increase the duration of sensory and motor blockade in a rat model of sciatic nerve blockade without causing nerve damage.

Methods: Thirty-one adult Sprague-Dawley rats received bilateral sciatic nerve blocks with either 0.2 ml bupivacaine, 0.5%, and 0.5% bupivacaine plus 0.005% dexmedetomidine in the contralateral extremity, or 0.2 ml dexmedetomidine, 0.005%, and normal saline in the contralateral extremity. Sensory and motor function were assessed by a blinded investigator every 30 min until the return of normal sensory and motor function. Sciatic nerves were harvested at either 24 h or 14 days after injection and analyzed for perineural inflammation and nerve damage.

Results: High-dose dexmedetomidine added to bupivacaine significantly enhanced the duration of sensory and motor blockade. Dexmedetomidine alone did not cause significant motor or sensory block. All of the nerves analyzed had normal axons and myelin at 24 h and 14 days. Bupivacaine plus dexmedetomidine showed less perineural inflammation at 24 h than the bupivacaine group when compared with the saline control.     

Comparative observations on effects of carbon dioxide laser-induced peripheral nerve lesions in the rat

This study was conducted to determine any changes that might occur in the associated cell bodies and proximal nerve stumps of sciatic nerves cut with carbon dioxide laser radiation. These changes were then compared with the changes that occur when performed with cutting cautery and scalpel. Both the proximal stump and the related dorsal root ganglia were examined with light and electron microscopy. The sciatic nerve was severed in 10 rats with the carbon dioxide laser, a cutting cautery, or a scalpel. Subsequent histopathologic examinations revealed: (a) both myelin and axonal degeneration in scalpel cuts; (b) less degeneration of proximal stump myelin in laser cuts compared with cautery cuts; and (c) no abnormalities in the associated dorsal root ganglia of nerves cut with the carbon dioxide laser. It was concluded that both the carbon dioxide laser and cutting cautery result in less damage and degeneration than a scalpel when used to sever peripheral nerves. The difference between the laser and cautery lesions was more quantitative than qualitative in that both impart thermal energy to the nerve. The carbon dioxide laser resulted in the least amount of injury.