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

Brachial plexus root injection in a human cadaver model: injectate distribution and effects on the neuraxis

BACKGROUND

The potential for injection into the brachial plexus root at cervical levels must be considered during interscalene block or chronic pain interventions in the neck, but this phenomenon has not been well studied. In this investigation, we performed injections into the brachial plexus roots of unembalmed cadavers, with real-time ultrasound guidance, to evaluate the proximal and distal spread of the injected fluids, the potential of the injectate to reach the neuraxis, and whether the injectate could migrate into the actual substance of the spinal cord itself.

METHODS

A solution of particulate dye mixed with local anesthetic was injected into 8 brachial plexus roots at a lower cervical level, in unembalmed cadaver specimens, utilizing an automated pump and pressure monitor. Two injections were made adjacent to nerve roots as controls. The specimens were then dissected, and gross and microscopic analysis utilized to determine the distribution of the dye and the structures affected.

RESULTS

The mean peak pressure achieved during plexus root injections was 48.9 psi. After injections into the plexus root, dye was evident within the neural tissue at the level of injection and spread primarily distally in the plexus. In 1 of 8 injections into the brachial plexus root, the dye in the injectate spread proximally into the spinal canal, but in none of the injections was the spinal cord affected by the dye.

CONCLUSIONS

Injection directly into the neural tissue of a brachial plexus root in a cadaver model produced high pressures suggestive of intrafascicular injection and widespread flow of the injectate through the distal brachial plexus. However, proximal movement of the dye-containing injectate was more restricted, with only 1 of the injections leading to epidural spread and no apparent effects on the spinal cord.

Local anesthetic Schwann cell toxicity is time and concentration dependent

BACKGROUND

Peripheral nerve blocks with local anesthetics (LAs) are commonly performed to provide surgical anesthesia or postoperative analgesia. Nerve injury resulting in persistent numbness or weakness is a potentially serious complication. Local anesthetics have previously been shown to damage neuronal and Schwann cells via several mechanisms. We sought to test the hypothesis that LAs are toxic to Schwann cells and that the degree of toxicity is directly related to the concentration of LA and duration of exposure. Intraneural injection of LAs has been shown to produce nerve injury. We sought to test the hypothesis that a prolonged extraneural infusion of LA can also produce injury.

METHODS

Schwann cells cultured from neonatal rat sciatic nerves were incubated with LAs at different concentrations (10, 100, 500, and 1000 μM), and each concentration was assessed for toxicity after 4, 24, 48 and 72 hours of exposure. Local anesthetics tested were lidocaine, mepivacaine, chloroprocaine, ropivacaine, and bupivacaine. Cell death was assessed by lactate dehydrogenase release measured by optical density.In a separate experiment, a microcatheter was placed along the sciatic nerves of Sprague-Dawley rats. Rats were randomly assigned to receive either 0.9% saline (n = 8) or bupivacaine (0.5%, n = 4; 0.75%, n = 4) via the perineural catheters for 72 hours. The rats were then killed, and their nerves sectioned and stained for analysis. Sections were stained for myelin and with an antimacrophage (CD68) antibody.

RESULTS

None of the LAs tested produced significant Schwann cell death at very low concentrations (10 μM, or 0.0003%) even after prolonged exposure. With prolonged exposure (48 or 72 hrs) to high concentrations (1000 μM, or 0.03%), all of the LAs tested produced significant Schwann cell death (increased lactate dehydrogenase release relative to control as measured by optical density, 0.384-0.974; all P values < 0.001). Only bupivacaine produced significant cell death (0.482, P < 0.001) after prolonged exposure to low concentrations (100 μM, or 0.003%). At intermediate concentrations (500 μM, or 0.015%), cell death was more widespread with bupivacaine (0.768, P < 0.001) and ropivacaine (0.675, P < 0.001) than the other agents (0.204-0.368; all P values < 0.001). Prolonged extraneural exposure of rat sciatic nerves to bupivacaine caused significant demyelination and infiltration of nerves with inflammatory cells.

CONCLUSIONS

Local anesthetics induce Schwann cell death in a time- and concentration-dependent manner. Bupivacaine and ropivacaine have greater toxicity at intermediate concentrations, and prolonged exposure to bupivacaine produces significant toxicity even at low concentrations. Brief exposure to high concentrations of bupivacaine damages Schwann cells. Prolonged extraneural infusion of bupivacaine results in nerve injury.

Regional anesthesia in children: the future

Pediatric regional anesthesia continues to evolve. Education and attention to anatomical detail remain key elements to successful outcomes. New techniques, some adapted from adult practice, provide analgesia for pediatric surgical procedures such cleft palate or congenital hip dysplasia. Despite technological advances a number of controversial issues remain unresolved.

Neuropathic complications after 157 procedures of continuous popliteal nerve block for hallux valgus surgery. A retrospective study

BACKGROUND

Continuous peripheral nerve block (CPNB), in particular at the popliteal fossa, is widely used in orthopedic surgery, allowing good postoperative analgesia. Possible neuropathic complications, however, remain poorly known.

OBJECTIVE

To review the characteristics of peripheral neuropathy (PN) after sciatic CPNB at the popliteal fossa, estimating prevalence, severity, evolution and possible risk factors, especially those relating to the procedure.

METHODS

Retrospective study of PN associated with popliteal fossa CPNB for hallux valgus surgery, between November 1st, 2005 and November 1st, 2009. All procedures were analyzed (type of anesthesia, approach, nerve location technique, number of procedures by operator) with, for each case of PN, analysis of clinical and electromyographic data.

RESULTS

One hundred and fifty seven sciatic CPNBs were performed (92% women; mean age, 55 years). The approach was lateral (n=62), posterior (n=74) or unknown (n=21). Ultrasound guidance was combined to neurostimulation for 69 patients (44%). Three women (prevalence=1.91%), aged 19, 24 and 65 years respectively, developed associated common superficial peroneal and sural nerve injury (2), axonal on electromyography, with motor (n=1) and/or sensory (n=3) residual dysfunction.

DISCUSSION

The higher prevalence found in the present study than in the literature (0 to 0.5%) raises questions of methodological bias or technical problems. The common peroneal and sural nerves seem to be exposed, unlike the tibial. Several mechanisms can be suggested: anesthetic neurotoxicity, direct mechanical lesion, or tourniquet-related ischemia and conduction block. Further studies are necessary to determine the ideal anesthetic procedure.

CONCLUSION

Patients should be informed of the potential risk, however rare, even during mild surgery. The best possible technique should be implemented, with reinforced surveillance.

Incidence and effects of unintentional intraneural injection during ultrasound-guided subgluteal sciatic nerve block

BACKGROUND

The present study was conducted to determine the incidence of unintentional intraneural injection during ultrasound-guided subgluteal sciatic nerve block using a low-frequency transducer. We also observed the effects of intraneural injection using ropivacaine and mepivacaine.

METHODS

Enrolled in the study were 325 patients undergoing arthroscopic knee surgery, who each received a subgluteal sciatic nerve block under ultrasound guidance using 1.5% mepivacaine with 1:400,000 epinephrine or 0.5% ropivacaine. A block needle was inserted in-plane with the ultrasound transducer (5-2 MHz curved array) and advanced slowly under real-time ultrasound guidance until it was positioned immediately adjacent to the nerve. Twenty milliliters of either anesthetic was then injected to produce a circumferential spread. An ultrasound video was recorded and used to examine whether the local anesthetic was injected intraneurally. Sensory and motor blockade was evaluated for 30 mins after completion of the block. Duration of the block and any neurologic complications were also examined.

RESULTS

Intraneural injection was detected in 46 patients (16.3%; 95% confidence interval, 12.3%-20.3%). Onset of sensory and motor blockade was significantly faster in patients with intraneural injection than those without either mepivacaine or ropivacaine. Duration of sensory blockade was similar between patients with and without intraneural injection. No patient developed postoperative neurologic complications.

CONCLUSIONS

Unintentional intraneural injection occurred at an incidence rate of 16.3% for the ultrasound-guided subgluteal approach to the sciatic nerve. Intraneural injection of mepivacaine or ropivacaine hastened the onset of blockade but did not affect block duration, and it did not result in clinical neural injury in our small sample of patients.

Responses to dural puncture during institution of combined spinal-epidural analgesia: a comparison of 27 gauge pencil-point and 27 gauge cutting-edge needles

Pencil-point spinal needles are popular for combined spinal-epidural analgesia because they cause less dural puncture headache than cutting-edge spinal needles. However many parturients move, grimace, vocalise or experience paraesthesia or dysaesthesia during dural puncture when performing 'needle through needle' combined spinal-epidural analgesia. We compared dural puncture responses induced by pencil-point and cutting-edge needles (both 27 gauge). With institutional approval, 115 parturients presenting for elective caesarean section or labour analgesia were audited. After lignocaine infiltration, a Tuohy-type needle was inserted to loss of resistance to saline at a mid-lumbar interspace, and either a 27 gauge cutting-edge or 27 gauge pencil-point needle was inserted 'needle through needle' through the dura. During dural penetration, the occurrence of patient movement, grimacing or vocalisation was noted by a blinded observer, as was the patient's response to the question "Did you feel that?" asked by the anaesthetist. The audit comprised two similar groups of patients (caesarean section, n=30; labour analgesia, n=85). In both groups, grimacing and movement during thecal penetration occurred more frequently with pencil-point needles (P < 0.05 and P < 0.025, respectively). Pooled data analysis revealed that pencil-point and cutting-edge needles induced grimacing and movement in 17 (22%) and 2 (5%), spontaneous vocalisation in 4 (5%) and 1 (3%) and was perceived by 13 (17%) and 3 (8%) parturients (P < 0.025, P=NS, P=NS), respectively. Overall, 34 and 6 objective and subjective patient responses (P < 0.005) occurred when inserting these needles, respectively. Dural puncture by a 27 gauge pencil-point needle inserted 'needle through needle' when instituting combined spinal-epidural analgesia induces more iatrogenic responses than a 27 gauge cutting-edge needle.

Loss of resistance to saline reduces responses accompanying spinal needle insertion during institution of 'needle-through-needle' combined spinal-epidural analgesia

Normal saline or air is used to identify loss of resistance during identification of the epidural space for combined spinal-epidural analgesia. Following epidural needle placement using air for loss of resistance, up to 80% of parturients move, grimace, vocalise or experience paraesthesia or dysaesthesia during subsequent dural puncture by a spinal needle. We compared the effects of saline versus air for loss of resistance on the occurrence of these subjective and objective responses during thecal penetration. With institutional approval, 55 parturients presenting for labour analgesia were studied. After infiltration of lignocaine at an L2-L5 vertebral interspace, a 17 gauge Tuohy epidural needle attached to a 5 ml loss of resistance syringe containing either saline or air was inserted and advanced until loss of resistance was identified by injection of 3 to 5 ml of content. During subsequent 'needle-through-needle' insertion of a 27 gauge pencil-point spinal needle through the meninges, all subjective and objective patient responses were recorded, as well as each patient's reply to the question "Did you feel that?". The two groups (n = 28, n = 27) were comparable. In those given saline and air respectively, 5 (18%) and 12 (44%) parturients responded to and/or acknowledged having perceived dural puncture (P < 0.005). Overall, 7 and 31 (P < 0.0005) subjective and objective responses occurred during dural puncture in those given saline and air, respectively. The study found that use of saline to determine loss of resistance is associated with fewer patient responses at the moment of thecal penetration during 'needle-through-needle' placement of the spinal needle at combined spinal-epidural analgesia.

Complications of peripheral nerve blocks

Complications of peripheral nerve blocks are fortunately rare, but can be devastating for both the patient and the anaesthesiologist. This review will concentrate on current knowledge about peripheral nerve injury secondary to nerve blocks, complications from continuous peripheral nerve catheter techniques, and local anaesthetic systemic toxicity.

Current concepts and future trends in ultrasound-guided regional anesthesia

PURPOSE OF REVIEW

Ultrasound guidance for regional anesthesia has gained enormous popularity during the past several years. This review article highlights the importance of acquiring an understanding and knowledge of human anatomy for well tolerated and effective performance of regional anesthesia; includes description of some of the major principles of ultrasound-guided regional anesthesia techniques (adequate identification of neuronal and adjacent anatomical structures along with the procedure needle); use of adequate volumes of local anesthetic and the proper administration of local anesthetic; and discusses economical along with educational aspects of ultrasound-guided regional blocks.

RECENT FINDINGS

Recent studies by various authors have indicated that ultrasound-guided regional blocks can be performed by using smaller volumes of local anesthetics. Such findings will further contribute to the safety of regional anesthesia in daily clinical practice. Additional positive economical aspects associated with regional anesthesia have also been described in the recent literature.

SUMMARY

With little reservation, it is anticipated that ultrasound-guided regional anesthesia will become the 'GOLD' standard for performance of regional anesthesia. Excellent science and educational concepts will continue to be required with the continued increase in popularity of this exciting specialty of anesthesia.

Neurological adverse events following regional anesthesia administration

Regional anesthesia and analgesia have been associated with improved analgesia, decreased postoperative nausea and vomiting, and increased patient satisfaction for many types of surgical procedures. In obstetric anesthesia care, it has also been associated with improved maternal mortality and major morbidity. The majority of neurological adverse events following regional anesthesia administration result in temporary sensory symptoms; long-term or permanent disabling motor and sensory problems are very rare. Infection and hemorrhagic complications, particularly with neuraxial blocks, can cause neurological adverse events. More commonly, however, there are no associated secondary factors and some combination of needle trauma, intraneural injection, and/or local anesthetic toxicity may be associated, but their individual contributions to any event are difficult to define.

Nerve perforation with pencil point or short bevelled needles: histological outcome

BACKGROUND

In the case of needle nerve contact during peripheral blocks, pencil point needles are considered less traumatic compared with bevelled needles. However, there are not enough data to prove this notion. Therefore, the aim of this study was to challenge the hypothesis that nerve perforation with short bevelled needles is associated with major nerve damage compared with pencil point needles.

METHODS

In five anaesthetised pigs, the brachial plexus was exposed bilaterally. Up to eight nerves underwent needle nerve perforation using a pencil point needles cannula or an short bevelled needle. After 48 h, the nerves were resected. The specimens were processed for visual examination and the detection of inflammatory cells (haematoxylin-eosin, i.e. CD68-immunohistochemistry to detect macrophages), myelin damage (Kluver-Barrera staining) and intraneural haematoma. The grade of nerve injury was characterised by an objective score ranging from 0 (no injury) to 4 (severe injury).

RESULTS

Fifty nerves were examined. According to the injury score applied, there was no significant difference between the pencil point needles [median (inter-quartile range) 2.0 (2.0-2.0)] and the short bevelled-needle group [median 2.0 (2.0-2.0) P=0.23]. No myelin damage was observed. Signs of post-traumatic inflammation were equally distributed among both groups.

CONCLUSIONS

In the present study, the magnitude of nerve injury after needle nerve perforation was not related to one of the applied needle types. Post-traumatic inflammation rather than structural damage of nerve tissue is the only notable sign of nerve injury after needle nerve perforation with either needle type. However, neither the pencil point- nor the short bevelled needle can be designated a less traumatic device.

Functional deficits after intraneural injection during interscalene block

OBJECTIVE

We present an occurrence of a severe but transient neurologic complication after intraneural injection during an ultrasound-guided interscalene block.

CASE REPORT

A 36-year-old man underwent ultrasound-guided interscalene nerve blockade before shoulder incision and drainage. On postoperative day 1, he exhibited new-onset arm weakness with dysesthesias. Intraneural injection was recognized based on a retrospective review of the recorded ultrasound imaging. The symptoms persisted for more than 2 weeks and completely resolved by 6 weeks.

CONCLUSIONS

Our report suggests that intraneural injection during ultrasound-guided interscalene block carries a risk of neurologic complications.

Ultrasound in regional anaesthesia

Ultrasound guidance is rapidly becoming the gold standard for regional anaesthesia. There is an ever growing weight of evidence, matched with improving technology, to show that the use of ultrasound has significant benefits over conventional techniques, such as nerve stimulation and loss of resistance. The improved safety and efficacy that ultrasound brings to regional anaesthesia will help promote its use and realise the benefits that regional anaesthesia has over general anaesthesia, such as decreased morbidity and mortality, superior postoperative analgesia, cost-effectiveness, decreased postoperative complications and an improved postoperative course. In this review we consider the evidence behind the improved safety and efficacy of ultrasound-guided regional anaesthesia, before discussing its use in pain medicine, paediatrics and in the facilitation of neuraxial blockade. The Achilles' heel of ultrasound-guided regional anaesthesia is that anaesthetists are far more familiar with providing general anaesthesia, which in most cases requires skills that are achieved faster and more reliably. To this ends we go on to provide practical advice on ultrasound-guided techniques and the introduction of ultrasound into a department.

Fifteen years of ultrasound guidance in regional anaesthesia: part 1

Ultrasound guidance for regional anaesthesia has gained enormous popularity in the past decade. The use of ultrasound guidance for many regional anaesthetic techniques is common in daily clinical practice, and the number of practitioners using it is increasing. However, alongside the enthusiasm, there should be a degree of informed scepticism. The widespread use of the various techniques of ultrasound-guided regional blocks without adequate training raises the danger of malpractice and subsequent impaired outcome. Adequate education in the use of regional block techniques under ultrasound guidance is essential. This review article addresses ultrasound guidance for regional anaesthesia, and is divided into two parts because of the size of the topic and the number of issues covered. This first part includes a review and preview of ultrasound guidance in regional anaesthesia and discusses all aspects of ultrasound for regional anaesthesia with a focus on recent technical developments, the positive implications in economics, further potential advantages (e.g. detection of anatomical variants, painless performance of blocks) and education. It also attempts to define a 'gold standard' in regional anaesthesia with the most recent findings in adequate volumes of local anaesthetics for peripheral nerve blocks. This standard should include an extraneural needle position, a high success rate, and wide application of ultrasound guidance in regional anaesthesia. The second part describes the impact of ultrasound on the development of nerve block techniques in the past 5 yr.