Nerve puncture and apparent intraneural injection during ultrasound-guided axillary block does not invariably result in neurologic injury

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 degrees), 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 x 47 and x 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.

New trends in regional anesthesia for shoulder surgery: Avoiding devastating complications

Surgeons and patients are often reluctant to support regional anesthesia (RA) for shoulder and other orthopedic surgeries. This is because of the sometimes true but usually incorrectly perceived "slowing down" of operating room turnover time and the perceived potential for added morbidity. Recently, severe devastating and permanent nerve injury complications have surfaced, and this article attempts to clarify the modern place of RA for shoulder surgery and the prevention of these complications. A philosophical approach to anesthesiology and regional anesthesiology is offered, while a fresh appreciation for the well-described and often forgotten microanatomy of the brachial plexus is revisited to explain and avoid some of the devastating complications of RA for shoulder surgery.

Ultrasound-guided nerve blocks: efficacy and safety

The introduction of affordable, portable and high-resolution ultrasound machines has rejuvenated interest in regional anaesthesia. The inherent benefits of direct visualisation of nerves and surrounding anatomy, continual observation of the needle tip and spread of local anaesthetic make ultrasound-guided regional anaesthesia highly appealing. However, in the cost-conscious health-care setting and to convince sceptics, there also needs to be evidence of increased benefits and reduced complications. Ultrasound is a rapidly developing area of technology and some of the newer modalities are discussed. This article focusses on the recent growing evidence to support the benefits of its use in nerve and plexus blocks. Common complications of nerve blocks can be avoided with ultrasound but have still been reported. Anatomical variants have been demonstrated by ultrasound and it has proved to be useful in performing regional anaesthesia in difficult situations or where peripheral nerve stimulation is unsuccessful or inappropriate.

Neurological complication analysis of 1000 ultrasound guided peripheral nerve blocks for elective orthopaedic surgery: a prospective study

Little data exists regarding the frequency of neurological complications following ultrasound guided peripheral nerve blockade. Therefore, we studied single injection and continuous ultrasound guided interscalene, supraclavicular, infraclavicular, femoral and sciatic nerve blocks in patients undergoing orthopaedic extremity surgery. All patients were contacted during postoperative weeks 2-4 and questioned for numbness or altered sensation anywhere in the involved extremity, and pain or weakness unrelated to surgery. The presumed aetiology of symptoms was based on the collective agreement of principal investigator, primary surgeon and a neurologist. Multivariate analysis was performed for characteristics potentially important in the causation of neurological complications. Of 1010 consecutive blocks, successful follow up between weeks 2 and 4 occurred in 98.6%. New, all-cause, neurological symptoms were present in 56/690 blocks (8.2%) at day 10, 37/1010 (3.7%) at 1 month and 6/1010 (0.6%) at 6 months. Most symptoms were due to causes unrelated to the block. Of 452 patients directly questioned at the time of the block, new neurological symptoms were more common in patients who experienced procedure-induced paraesthesia (odds ratio = 1.7, p = 0.029). The postoperative neurological symptom rate in this series is very similar to those previously reported following traditional techniques.

Structural injury to the human sciatic nerve after intraneural needle insertion

BACKGROUND

Recent clinical reports suggest that intraneural needle placement may not always lead to neurologic injury. To explain the absence of neurologic complications in these reports, we studied the risk and extent of nerve injury after intentional needle-nerve placement in a cryopreserved human sciatic nerve.

METHODS

The sciatic nerve was dissected from a cryopreserved cadaver through partial exposure. Needles were inserted through the nerve, using blunt-tip (30 degrees beveled) (group A) and sharp-tip (15 degrees beveled) (group D) needles. Five needle insertions were made for each needle type. Subsequently, transverse nerve sections at 10 needle trajectories were processed. Nerve samples were stained with hematoxylin-eosin, Masson trichromic, and immunohistochemical stains. In each section, the following variables were quantified: total number of fascicles and vessels in the immediate vicinity of the needle trajectories and the number of injured fascicles and vessels.

RESULTS

A total of 520 fascicles were quantified, of which 134 were in contact with the needle trajectories. The numbers of fascicles and vessels per section were 65 +/- 8 and 14 +/- 7, respectively. A mean of 16 +/- 5 fascicles were found in contact with the needle trajectory (group A: 17+/- 3, group D: 15 +/- 6). Of these, 4 fascicles (3.2%) and 1 intraneural vessel were found damaged in group D. No fascicular or vascular injuries were found in group A.

CONCLUSIONS

Our findings suggest that intraneural needle insertion may more commonly result in interfascicular rather than intrafascicular needle placement.

Intraneural injection during nerve stimulator-guided sciatic nerve block at the popliteal fossa

BACKGROUND

Exact location of the needle tip during nerve stimulation-guided peripheral nerve blocks is unknown. Using high-frequency ultrasound imaging, we tested the hypothesis that intraneural injection is common with nerve stimulator-guided sciatic nerve (SN) block in popliteal fossa.

METHODS

Forty-two patients scheduled for hallux valgus repair were studied. Sciatic block at the popliteal fossa was accomplished using nerve stimulation. When a motor response was elicited at <0.5 mA (2 Hz, 0.1 ms), 40 ml of local anaesthetic (LA) was injected. Using ultrasound (Titan, Sonosite, 5-10 MHz), the diameters and area of the SN were measured before and after the injection. The presence of nerve swelling and proximal or distal diffusion of LA were also assessed. Intraneural injection was defined as nerve area (NA) increase of > OR =15% and one or more additional ultrasonographic markers (nerve swelling, proximal-distal diffusion within epineural tissue). Clinical neurological evaluation was performed 1 week after the block.

RESULTS

Post-injection NA increase > OR =15% was seen in 32 (76%) patients [0.54 (SD 0.19) cm(-2) vs 0.76 (0.24) cm(-2); P<0.05]. Nerve swelling with fascicular separation was observed in 37 (88%) patients; proximal and distal diffusion of LA were present in six (14%) and 14 (38%) patients, respectively. Intraneural injection criteria were met in 28 (66%) patients. Greater NA increase was present in patients with fast block onset [61 (45) vs 25 (33)%; (Dif 35% 95% CI 61-9%); P<0.05]. No patient developed neurological complications.

CONCLUSIONS

Intraneural (subepineural) injection is a common occurrence after nerve stimulator-guided SN block at the popliteal fossa, yet it may not inevitably lead to neurological complications.

Ultrasound-guided regional anesthesia and analgesia: a qualitative systematic review

Ultrasound guidance has become popular for performance of regional anesthesia and analgesia. This systematic review summarizes existing evidence for superior risk to benefit profiles for ultrasound versus other techniques. Medline was systematically searched for randomized controlled trials (RCTs) comparing ultrasound to another technique, and for large (n > 100) prospective case series describing experience with ultrasound-guided blocks. Fourteen RCTs and 2 case series were identified for peripheral nerve blocks. No RCTs or case series were identified for perineural catheters. Six RCTs and 1 case series were identified for epidural anesthesia. Overall, the RCTs and case series reported that use of ultrasound significantly reduced time or number of attempts to perform blocks and in some cases significantly improved the quality of sensory block. The included studies reported high incidence of efficacy of blocks with ultrasound (95%-100%) that was not significantly different than most other techniques. No serious complications were reported in included studies. Current evidence does not suggest that use of ultrasound improves success of regional anesthesia versus most other techniques. However, ultrasound was not inferior for efficacy, did not increase risk, and offers other potential patient-oriented benefits. All RCTs are rather small, thus completion of large RCTs and case series are encouraged to confirm findings.

Perforation of the median nerve with an acupuncture needle guided by ultrasound

In an experiment on one of the authors, we used ultrasound to visualise an acupuncture needle completely perforating the median nerve at the acupuncture point PC6. During this procedure only a slight sensation occurred, and no pain. We conclude that, in individual cases, the median nerve might be perforated without causing pain or neurological problems.

Lidocaine injection into the rat dorsal root ganglion causes neuroinflammation

BACKGROUND

Injury of a spinal nerve or dorsal root ganglion (DRG) during selective spinal nerve blocks is a potentially serious complication that has not been adequately investigated. Our hypothesis was that local anesthetic injection into these structures may result in an inflammatory response and hyperalgesia.

METHODS

We evaluated inflammatory and behavioral responses after injection of 4 microL lidocaine or saline into the L5 spinal nerve or DRG of rats after partial laminectomy. Behavioral testing was performed before and after surgery to examine hyperalgesia in response to nociceptive mechanical stimulation of the foot. DRGs were harvested and stained, and rings of immunoreactive glial cells around neurons were counted.

RESULTS

Animals demonstrated hyperalgesia on the ipsilateral paw up to 4 days after lidocaine injection into the DRG but not after injection into the spinal nerve. The number of glial fibrillary acid protein immunopositive glial cell rings, which represent activation of satellite cells, significantly increased in DRGs after injection of lidocaine into either the DRG or the spinal nerve. The number of glial fibrillary acid protein-positive cells in the lidocaine-injected group was significantly larger than in the saline-injected group. Sporadic OX-42 immunopositive cells, which represent activated microglia, were also seen in lidocaine-injected DRGs. Testing for Pan-T expression, which labels activated T lymphocytes, showed no positive cells.

CONCLUSIONS

Lidocaine injection into the DRG may produce hyperalgesia, possibly due to activation of resident satellite glial cells. In a clinical setting, local anesthetic injection into the DRG should be avoided during selective spinal nerve blocks.

Upper extremity regional anesthesia: essentials of our current understanding, 2008

Brachial plexus blockade is the cornerstone of the peripheral nerve regional anesthesia practice of most anesthesiologists. As part of the American Society of Regional Anesthesia and Pain Medicine's commitment to providing intensive evidence-based education related to regional anesthesia and analgesia, this article is a complete update of our 2002 comprehensive review of upper extremity anesthesia. The text of the review focuses on (1) pertinent anatomy, (2) approaches to the brachial plexus and techniques that optimize block quality, (4) local anesthetic and adjuvant pharmacology, (5) complications, (6) perioperative issues, and (6) challenges for future research.

[Complications after regional anesthesia]

In recent years, there has been a considerable increase in the number of procedures carried out under regional anesthesia. The techniques used can be associated with a number of complications, which should be understood so that they can be recognized and managed appropriately. The overall incidence of reported complications associated with these techniques is low and therefore, with currently available data, we can only have an approximate idea of their incidence. The objective of this study is to systematically describe the complications that may arise from the use of neuraxial and peripheral regional anesthesia techniques.

Guidance of block needle insertion by electrical nerve stimulation: a pilot study of the resulting distribution of injected solution in dogs

BACKGROUND

Little is known regarding the final needle tip location when various intensities of nerve stimulation are used to guide block needle insertion. Therefore, in control and hyperglycemic dogs, the authors examined whether lower-intensity stimulation results in injection closer to the sciatic nerve than higher-threshold stimulation.

METHODS

During anesthesia, the sciatic nerve was approached with an insulated nerve block needle emitting either 1 mA (high-current group, n = 9) or 0.5 mA (low-current group, n = 9 in control dogs and n = 6 in hyperglycemic dogs). After positioning to obtain a distal motor response, the lowest current producing a response was identified, and ink (0.5 ml) was injected. Frozen sections of the tissue revealed whether the ink was in contact with the epineurium of the nerve, distant to it, or within it.

RESULTS

In control dogs, the patterns of distribution using high-threshold (final current 0.99 +/- 0.03 mA, mean +/- SD) and low-threshold (final current 0.33 +/- 0.08 mA) stimulation equally showed ink that was in contact with the epineurium or distant to it. One needle placement in the high-threshold group resulted in intraneural injection. In hyperglycemic dogs, all needle insertions used a low-threshold technique (n = 6, final threshold 0.35 +/- 0.08 mA), and all resulted in intraneural injections.

CONCLUSIONS

In normal dogs, current stimulation levels in the range of 0.33-1.0 mA result in needle placement comparably close to the sciatic nerve but do not correlate with distance from the target nerve. In this experimental design, low-threshold electrical stimulation does not offer satisfactory protection against intraneural injection in the presence of hyperglycemia.

Ultrasound-guided peripheral nerve blocks: what are the benefits?

BACKGROUND

Use of ultrasound by anaesthesiologists performing regional blocks is rapidly gaining popularity. The aims of this review were to summarize and update accumulating evidence on ultrasound-guided nerve blocks, with an emphasis on the clinical relevance of the results and to critically appraise changing standards in regional anaesthesia.

METHODS

A search of MEDLINE and EMBASE (1966 to 31 December 2007) was conducted using the following free terms: 'ultrasound and regional anesthesia', 'ultrasound and peripheral block' and 'ultrasound and nerve and block'. These were combined with the MESH terms 'nerve block' and 'ultrasonography'. The following limits were applied: studies with abstracts, only in humans, published in core clinical journals. Trial type: meta-analysis, randomized-controlled trial and clinical trial.

RESULTS

When peripheral nerves are adequately imaged by ultrasound, the concomitant use of nerve stimulation offers no further advantage. However, several studies reported problems with obtaining satisfactory images in some patients. Ultrasound guidance significantly shortened the block performance time and/or reduced the number of needle passes to reach the target in all comparative studies. The occurrence of paraesthesia during block performance was also reduced, but not the incidence of short-lasting post-operative neuropraxia. The frequency of accidental vascular punctures may be lower, but the data are contradictory. Block onset time was significantly shortened. Block duration was longer in children, but not in adults. Ultrasound also allowed dose reduction of the local anaesthetic (LA).

CONCLUSIONS

Ultrasound guidance shortens the block performance time, reduces the number of needle passes and shortens the block onset time. Blocks may be performed using lower LA doses.

[Portable ultrasound devices in regional anesthesia: the brachial plexus block]

Ultrasonography has received increasing attention in regional anesthesia in recent years because it allows visualization of the nerves, the needle, and the surrounding structures and makes it possible to monitor distribution of the local anesthetic. Ultrasound technology is unfamiliar to most anesthesiologists, unless they work with transesophageal echocardiography. Ultrasound-guided regional anesthesia relies entirely on the expertise of the person performing the technique and how that person interprets the images, though the latest portable ultrasound devices are ergonomically designed for fast, easy use, even by less experienced personnel. The high-frequency probes can identify the brachial plexus and produce excellent images of considerable educational value that differ only slightly from those provided by larger, more expensive equipment. Ultrasonography makes it possible to identify the brachial plexus, from the roots to the peripheral nerves of the arm. We describe the main approaches used in providing an ultrasound-guided brachial plexus block and explain the basic principles of ultrasound imaging.