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

Nerve block, nerve damage, and fluid injection pressure: overturning the myth

Histological and micro-ultrasound evidence rebuffs deep-rooted views on the nature of nerve block, nerve damage, and injection pressure monitoring. We propose that the ideal position of the needle tip for nerve block is between the innermost circumneural fascial layer and outer epineurium, with local anaesthetic passing circumferentially through adipose tissue. Thin, circumferential, subepineural expansion that is invisible to the naked eye was identified using micro-ultrasound, and could account for variability of outcomes in clinical practice. Pressure monitoring cannot differentiate between intrafascicular and extrafascicular injection. High injection pressure only indicates intraneural extrafascicular spread, not intrafascicular spread, because it is not possible to inject into the stiff endoneurium in most human nerves.

Neurological injury following peripheral nerve blocks: a narrative review of estimates of risks and the influence of ultrasound guidance

BACKGROUND

Peripheral nerve injury or post-block neurological dysfunction (PBND) are uncommon but a recognized complications of peripheral nerve blocks (PNB). A broad range of its incidence is noted in the literature and hence a critical appraisal of its occurrence is needed.

OBJECTIVE

In this review, we wanted to know the pooled estimates of PBND and further, determine its pooled estimates following various PNB over time. Additionally, we also sought to estimate the incidence of PBND with or without US guidance.

EVIDENCE REVIEW

A literature search was conducted in six databases. For the purposes of the review, we defined PBND as any new-onset sensorimotor disturbances in the distribution of the performed PNB either attributable to the PNB (when reported) or reported in the context of the PNB (when association with a PNB was not mentioned). Both prospective and retrospective studies which provided incidence of PBND at timepoints of interest (>48 hours to <2 weeks; >2 weeks to 6 weeks, 7 weeks to 5 months, 6 months to 1 year and >1 year durations) were included for review. Incidence data were used to provide pooled estimates (with 95% CI) of PBND at these time periods. Similar estimates were obtained to know the incidence of PBND with or without the use of US guidance. Additionally, PBND associated with individual PNB were obtained in a similar fashion with upper and lower limb PNB classified based on the anatomical location of needle insertion.

FINDINGS

The overall incidence of PBND decreased with time, with the incidence being approximately 1% at <2 weeks' time (Incidence per thousand (95% CI)= 9 (8; to 11)) to approximately 3/10 000 at 1 year (Incidence per thousand (95% CI)= 0. 3 (0.1; to 0.5)). Incidence of PBND differed for individual PNB with the highest incidence noted for interscalene block.

CONCLUSIONS

Our review adds information to existing literature that the neurological complications are rarer but seem to display a higher incidence for some blocks more than others. Use of US guidance may be associated with a lower incidence of PBND especially in those PNBs reporting a higher pooled estimates. Future studies need to standardize the reporting of PBND at various timepoints and its association to PNB.

Sonographic peripheral nerve cross-sectional area in adults, excluding median and ulnar nerves: A systematic review and meta-analysis

INTRODUCTION/AIMS

Although electromyography remains the "gold standard" for assessing and diagnosing peripheral nerve disorders, ultrasound has emerged as a useful adjunct, providing valuable anatomic information. The objective of this study was to conduct a systematic review and meta-analysis evaluating the normative sonographic values for adult peripheral nerve cross-sectional area (CSA).

METHODS

Medline and Cochrane Library databases were systematically searched for healthy adult peripheral nerve CSA, excluding the median and ulnar nerves. Data were meta-analyzed, using a random-effects model, to calculate the mean nerve CSA and its 95% confidence interval (CI) for each nerve at a specific anatomical location (= group).

RESULTS

Thirty groups were identified and meta-analyzed, which comprised 16 from the upper extremity and 15 from the lower extremity. The tibial nerve (n = 2916 nerves) was reported most commonly, followed by the common fibular nerve (n = 2580 nerves) and the radial nerve (n = 2326 nerves). Means and 95% confidence interval (CIs) of nerve CSA for the largest number of combined nerves were: radial nerve assessed at the spiral groove (n = 1810; mean, 5.14 mm2 ; 95% CI, 4.33 to 5.96); common fibular nerve assessed at the fibular head (n = 1460; mean, 10.18 mm2 ; 95% CI, 8.91 to 11.45); and common fibular nerve assessed at the popliteal fossa (n = 1120; mean, 12.90 mm2 ; 95% CI, 9.12 to 16.68). Publication bias was suspected, but its influence on the results was minimal.

DISCUSSION

Two hundred thirty mean CSAs from 15 857 adult nerves are included in the meta-analysis. These are further categorized into 30 groups, based on anatomical location, providing a comprehensive reference for the clinician and researcher investigating adult peripheral nerve anatomy.

"Knowing It Before Blocking It," the ABCD of the Peripheral Nerves: Part D (Approach to the Patient With Nerve Injuries)

"Prevention is always better than cure." However, despite all precautions or preventive measures, sometimes patients develop neurodeficits due to suspected nerve injury in the perioperative period. Assessment and evaluation of the patient's symptoms can provide clues to the causative factors. Such causative factors can be corrected immediately to avoid further deterioration, or some may require further workup. The management plan for such a diagnosed nerve injury depends on the symptoms, the finding of the medical history, and the diagnostic imaging and tests. Simultaneous symptomatic relief in the form of pain medications, steroids, anti-inflammatory drugs, psychological counseling, and reassurance is essential to expedite treatment goals. Diagnosing and treating nerve injuries cannot be laid down as a straightforward part. It is a zigzag puzzle in its own right, playing with time and injury progression. Careful assessment to diagnose the extent of nerve damage plays an important role in treatment plans. It helps decide when to proceed and when to postpone, whether conservative strategies would suffice, or surgical repair would be required. Although most nerve injuries are self-limiting, some cases require surgical intervention that needs to be diagnosed early. The revolution was started by Sunderland in 1945 when he described neurosurgical techniques that drastically changed the entire scenario of nerve repairs. The ultimate effective treatment and full recovery may not be guaranteed, but attempts must be made to achieve the best results. With the patient's interests in mind, it is important to formulate a plan ensuring a good quality of life with minimal impact on their daily activities. Multifactorial nerve injury requires a multidisciplinary approach that primarily includes reassuring, psychological counseling, multimodal analgesia, and neurological and occupational consultations. This article describes the step-by-step approach known as the symptoms categorization-history taking-examination-diagnostic evaluations (SHED) approach to managing patients with peripheral nerve injuries. It also details the various modalities for diagnosing nerve injuries, sequential electrodiagnostic studies, and treatment plans depending on the type and extent of nerve injuries. It will help readers to design a treatment plan based on the patient's symptoms and evaluation results.

Traumatic needle damage to nerves during regional anesthesia: presentation of a novel mechanotransduction hypothesis

Despite advances in needle positioning techniques, nerve damage still occurs after regional anesthesia. Recognized causes include local anesthetic toxicity, subperineural injection, high subepineural fluid injection pressures and subepineural hematoma after forceful needle--nerve contact.We hypothesize that subperineural injection is still possible, but less likely to be the cause of nerve damage because needle penetration of fascicles and mechanical damage is difficult to achieve. High-resolution (75 µm) 40 MHz micro-ultrasound images of pig axillae show short-bevelled 22 g, 0.7 mm wide block needles that are three times larger than the average fascicle. Fascicular bundles are extremely difficult to puncture because they spin away on needle contact. Histology from fresh cadavers after supposed intrafascicular injection shows fluid spread within perineurium and intrafascicular perineural septae, but no breach of endoneurium or axons.We propose that mechanotransduction, the cellular changes that occur in response to force, contributes to nerve damage. Piezo ion channel proteins transduce force into electrical activity by rapid entry of cations into cells. Excessive Ca2+ influx into cells has the potential to inhibit nerve regeneration. Cellular changes include regulation of gene expression. The forces associated with purposeful needle insertion are generally unknown. Our experiments in the soft embalmed Thiel cadaver showed a lognormal range of forces between 0.6 N and 16.8 N on epineural penetration.We hypothesize that forceful needle injury may cause nerve damage by activation of Piezo receptors and release of intracellular Ca2.

Real-time visualisation of peripheral nerve trauma during subepineural injection in pig brachial plexus using micro-ultrasound

BACKGROUND

Nerve damage is consistently demonstrated after subepineural injection in animal studies, but not after purposeful injection in patients participating in clinical studies. There is a need to better visualise nerves in order to understand the structural changes that occur during subepineural injection.

METHODS

We scanned the brachial plexuses of three anaesthetised pigs using micro-ultrasound imaging (55-22 MHz probe), inserted 21 gauge block needles into the radial, median, and axillary nerves, and injected two 0.5 ml boluses of saline into nerves at a rate of 12 ml min^-1. Our objectives were to measure the area and diameter of nerves and fascicles, and to describe changes in nerve anatomy, comparing our findings with histology.

RESULTS

Images were acquired at 42 sites across 18 nerves in three pigs and compared dimensions (geometric ratio; 95% confidence interval; P value). As expected, the nerve cross-sectional area was greater in the proximal brachial plexus compared with the mid-plexus (2.10; 1.07-4.11; P<0.001) and the distal plexus (2.64; 1.42-4.87; P<0.001). Nerve area expanded after 0.5 ml injection (2.13; 1.48-3.08; P<0.001). Using microultrasound, subepineural injection was characterised by nerve and fascicle rotation, uniform, or localised swelling and epineural rupture. Micro-ultrasound revealed a unique pattern suggestive of subperineural injection after a median nerve injection, and good face validity with histology. Histology showed epineural trauma and inflammation to the perineurium.

CONCLUSION

We accurately identified fascicles and real-time structural changes to peripheral nerves using micro-ultrasound. This is the first study to visualise in vivo and in real-time the motion of nerves and fascicles in response to anaesthetic needle insertion and fluid injection.

Ultrasound-guided subparaneural popliteal sciatic nerve block: there is more to it than meets the eyes

The popliteal sciatic nerve block is routinely used for anesthesia and analgesia during foot and ankle surgery. This article reviews our current understanding of the anatomy of the sciatic nerve and discusses how fascial tissue layers associated with the nerve may affect block outcomes . The anatomy of the sciatic nerve is more complex than previously described. The tibial and common peroneal nerves within the sciatic nerve trunk appear to be centrally separated by the Compton-Cruveilhier septum and encompassed by their own paraneural sheaths. This unique internal architecture of the sciatic nerve appears to promote proximal spread of local anesthetic to the internal aspect of the sciatic nerve trunk after a subparaneural injection at or below the divergence of the tibial and common peroneal nerves.

Short-Term Effects of Deliberate Subparaneural or Subepineural Injections With Saline Solution or Bupivacaine 0.75% in the Sciatic Nerve of Rabbits

Background: Ultrasound (US)-guided techniques for peripheral nerve blockade have revealed that intraneural injections are relatively frequent and not necessarily associated with neurological deficits. Objectives: To evaluate the short-term effects of deliberate injections performed under direct vision in two different sites of the sciatic nerve (ScN). Material and Methods: Seventy-two New Zealand white rabbits randomly assigned to one of four experimental groups (n = 18) were employed. All procedures were conducted at a proximal femoral level where the ScN incorporates the common peroneal nerve and the tibial nerve (TN). Fixed volumes of 0.5 ml of saline solution (ES group) or bupivacaine 0.75% (EB group) were administered extrafascicularly inside the paraneurium of the ScN or intrafascicularly (IS and IB groups) under the epineurium of the TN. Cross-sectional area (CSA) and relative echogenicity (RE) of the entire ScN were determined by US before injections, after injections, and at 3 and 7 days. ScN samples were obtained for structural and ultrastructural histopathological studies. Proprioceptive, sensorial, and motor function were clinically evaluated on a daily basis. Results: The CSA of the ScN increased significantly immediately after injections when compared with pre-injection values in all groups (p < 0.05). The RE of the ScN decreased in relation to pre-injection values in all groups (p < 0.05). The CSA and RE of the ScN returned to normal values 7 days after injections in almost all groups. Injected nerves showed histological signs of mild perineural inflammation. Histopathological scores were not significantly different between groups (p > 0.05). The architecture of the ScN was preserved in all rabbits at 3 days and in 31/32 rabbits at 7 days. A focal area of damaged nerve fibers with degeneration of the axons and myelin sheath affecting the TN was observed in one rabbit of the IB group. Nerve function was not clinically impaired in any case. Conclusion: Despite the lack of severe nerve disruption observed in most rabbits, the evidence of a focal area of damaged nerve fibers in one rabbit injected intrafascicularly with bupivacaine confirms that intrafascicular injections should be avoided as they may increase the risk of nerve damage.

Comparison of the effectiveness of circumferential versus non-circumferential spread in median and ulnar nerve blocks. A double-blind randomized clinical trial

BACKGROUND AND OBJECTIVES

Circumferential (C) spread of local anesthetic around the nerve is recommended for a successful nerve block. We tested the hypothesis that C spread produces a more complete block than non-circumferential (NC) spread.

METHODS

We randomized 124 patients undergoing open carpal tunnel syndrome surgery to receive C or NC spread ultrasound-guided median and ulnar nerve blocks. The primary outcome was the proportion of patients who developed complete sensory block measured at 5, 15 and 30 min. The loss of cold sensation was graded as: 0 (complete block), 1 (incomplete block), or 2 (no block). Secondary outcomes included motor block, nerve swelling and adverse events.

RESULTS

In group C, complete sensory block at 5 min was 2.4 (95% CI 1.0 to 5.7; p=0.04) times more frequent in the median nerve and 3.0 (95% CI 1.2 to 7.2; p=0.01) times more frequent in the ulnar nerve compared with group C. However, at 15 and 30 min, it was similar between groups. Complete motor block was more frequent in group C than in group NC for both the median nerve: 1.5 (95% CI 1.1 to 2.2; p<0.01) at 15 min, 1.1 (95% CI 1.0 to 1.2; p=0.02) at 30 min, and the ulnar nerve: 1.7 (95% CI 1.2 to 2.6; p<0.01) at 15 min, 1.2 (95% CI 1.0 to 1.4; p<0.01) at 30 min. The incidence of nerve swelling and adverse effects was similar between groups.

CONCLUSIONS

C spread around the median and ulnar nerves at the level of the antecubital fossa generates more complete sensory and motor blocks compared with NC spread.

TRIAL REGISTRATION NUMBER

EudraCT 2011-002608-34 and NCT01603680.

Mini-invasive methods of treatment of diabetic foot pain

Neuropathic pain occurs with diabetic polyneuropathy more often than with all polyneuropathies of another etiology. Because the cause of pain can rarely be cured, treatment is usually symptomatic. Neuropathic pain is usually poorly controlled by analgesics. Management of neuropathic pain is started with conservative pharmacotherapy before invasive pain management is applied. Although there are many drugs that can be used in patients with diabetic pain syndrome, pain syndrome can not be surely stoped with monotherapy. In addition, the patient may not tolerate the full therapeutic dose of the drug. All this dictates the need for combination therapy. It is believed that regional anesthesia as an independent type of analgesia or a component of combined anesthesia is the method of choice for the elderly and senile patients. The main reasons for this choice, when comparing regional anesthesia with narcosis, are less stressful response of the organism, absence of depression of the central nervous system, stable reliable analgesia with complete blockade of nociceptive reflexes with the provision of adequate muscle relaxation, prevention of neurovegetative reactions, which ultimately helps to reduce the incidence of postoperative complications and mortality. Clinicians have accumulated considerable experience demonstrating the need for regional analgesia in the management of diabetic foot pain.

[Blockade of the distal sciatic nerve in the supine position with a newly developed ultrasound probe holder]

Sonographically controlled blockade of the distal sciatic nerve is usually performed by placing the ultrasound probe on the dorsal side of the thigh. This requires positioning maneuvers (prone or side positioning) of the patient as well as additional assistance. In order to avoid these positioning maneuvers, a positioning aid with integrated ultrasound probe holder has been developed and its practicability was examined on patients with lower limb surgery. The sonographically controlled block of the sciatic nerve was performed with the patient under general anesthesia and in a supine position with the help of the new positioning aid with an integrated ultrasound probe holder. A total of >100 patients were treated, who underwent elective lower leg, ankle or foot surgery with a continuous blockade of the distal sciatic nerve using catheters for postoperative analgesia. The advantages are easy performance, hands-free needle movement and catheter placement. The disadvantages might be the need for in-plane catheter placement and a fixed ultrasound angle.

Subparaneural Injection in Popliteal Sciatic Nerve Blocks Evaluated by MRI

Intraneural injection of a local anesthetic can damage the nerve, yet it occurs frequently during distal sciatic block with no neurological sequelae. This has led to a controversy about the optimal needle tip placement that results from the particular anatomy of the sciatic nerve with its paraneural sheath.

The study population included patients undergoing lower extremity surgery under popliteal sciatic nerve block. Ultrasound-guidance was used to position the needle tip subparaneurally and to monitor the injection of the local anesthetic. Sonography and magnetic resonance imaging were used to assess the extent of the subparaneural injection.

Twenty-two patients participated. The median sciatic cross-sectional area increased from 57.8 mm2 pre-block to 110.8 mm² immediately post-block. An intraneural injection according to the current definition was seen in 21 patients. Two patients had sonographic evidence of an intrafascicular injection, which was confirmed by MRI in one patient (the other patient refused further examinations). No patient reported any neurological symptoms.

A subparaneural injection in the popliteal segment of the distal sciatic nerve is actually rarely intraneural, i.e. intrafascicular. This may explain the discrepancy between the conventional sonographic evidence of an intraneural injection and the lack of neurological sequelae.

Cross-sectional area of the median nerve after intraneural vs perineural low volume administration

INTRODUCTION

To recognise the relationship between the needle tip and the median nerve during peripheral nerve block is of interest to avoid neural damage. However, signs of intraneural injection are not clearly established. The aim of this study was to define the changes observed in the peripheral nerve after the intraneural or perineural administration of 1ml of solution.

MATERIAL AND METHODS

Ultrasound guided median nerve blocks were performed in the forearm of 10 fresh cadavers on 60 occasions (3 per forearm). They were randomised into the intraneural (n=30) or perineural (n=30) location of the needle tip, after the consensus of location by 7 specialists. After 1ml of solution was injected an evaluation was made of the changes in the cross-sectional area of the nerve, as well as the displacement along the nerve.

RESULTS

The cross-sectional area of the median nerve was increased in both groups, however, the increase was significantly higher in the intraneural group (perineural 0.007±0.013cm2 vs. intraneural 0.032±0.021cm2, P<.0001). An increase of more than 27% of the area ensures an intraneural injection in the median nerve according to the ROC curve analysis. Both proximal and distal diffusion were observed more frequently in the intraneural group (proximal: 86% vs 14%, P<.0001, Distal: 43% vs 4%, P<.0001).

CONCLUSIONS

Based on this experimental study, it is concluded that the injection of a small volume (1ml) allows to discriminate the disposition of the intraneural vs perineural needle in a high percentage of cases. Therefore, it is suggested that this "dose test" should be considered in the safety algorithms if it is required to reduce the incidence of intraneural injection.

Effects of Stellate Ganglion Block on Analgesia Produced by Cervical Paravertebral Block as Established by Quantitative Sensory Testing: A Randomized Controlled Trial

Objective

To use quantitative sensory testing (QST) to assess whether a stellate ganglion block (SGB) modulates the analgesia induced by cervical paravertebral block (CPVB).

Design

A prospective double-blind randomized controlled trial.

Setting

Department of Anesthesia, Antwerp University Hospital, October 2011 to December 2015.

Subjects

Twenty-eight adults scheduled for arthroscopy of a nonfractured shoulder were enrolled.

Methods

Participants were randomly assigned to receive either single CPVB (5 mL of levobupivacaine 0.5%) or combined CPVB + SGB (5 mL and 3 mL of levobubivacaine 0.5%, respectively). The detection thresholds for cold/warm sensations and cold/heat pain were established using thermal QST on the C4-C7 dermatomes before local anesthetic infiltration and at 0.5, 6, 10, and 24 hours thereafter. Our primary outcome was the time course of QST thresholds for the different neurosensitive/nociceptive modalities. As secondary and tertiary outcomes, we evaluated the degree of motor block and the time to first administration of rescue analgesics.

Results

We randomized 20 patients. There were no significant differences in the detection thresholds for the neurosensitive/nociceptive modalities, motor block, or timing for rescue analgesics between the groups (P = 0.15-0.94). All patients with CPVB + SGB exhibited Horner's signs, whereas patients in the CPVB group did not exhibit these signs; however, this does not exclude sympathetic block.

Conclusions

We were unable to demonstrate any analgesic benefit of CPVB + SGB in arthroscopic shoulder surgery. It is therefore not unreasonable to suppose that pain from soft tissue injuries without bony lesions is transmitted mainly by somatic nerves with no or only minimal involvement of the sympathetic nervous system.

Regional anesthetic techniques for the pelvic limb and abdominal wall in small animals: A review of the literature and technique description

Increasing interest in using peripheral nerve blocks in small animals is evident, given the numerous studies published recently on this topic in important veterinary journals. Initially, research was focused on intraoperative analgesia to the pelvic limb, and several descriptions of lumbosacral plexus, femoral and sciatic nerve blocks have been described in studies. There is recent interest in developing techniques for somatosensory blockade of the abdominal wall. This article is the second part of a two-part review of regional anesthesia (RA) in small animals, and its aim is to discuss the most relevant studies in the veterinary literature, where objective methods of nerve location have been used, and to illustrate in pictures the currently used techniques for providing RA to the abdominal wall and the pelvic limb in small animals.

Low-concentration distal nerve blocks with 0.125% levobupivacaine versus systemic analgesia for ambulatory trapeziectomy performed under axillary block: a randomized controlled trial

BACKGROUND

Trapeziectomy is one of the most painful procedures in ambulatory surgery. This prospective randomized trial aimed to compare postoperative pain control using distal peripheral nerve blocks (dPNB) with a low concentration of a long-acting local anesthetic versus conventional systemic analgesia.

METHODS

Fifty-two patients undergoing trapeziectomy were randomized to receive levobupivacaine 0.125% 5 mL on radial and median nerves at the elbow (dNB group), or not to receive these blocks (control group). In both groups, surgery was performed under axillary block (mepivacaine 1% 20 mL) and the same analgesic regimen was prescribed at discharge. The primary outcome was postoperative pain at 24 and 48 hours after surgery and maximum pain score on the first and second postoperative day. Secondary outcomes were duration of dPNB, rescue analgesia requirements, opioid-related side effects, consumption and effectiveness of antiemetic therapy, and upper limb motor block.

RESULTS

Fifty patients were analyzed. Maximum pain intensity was moderate to severe (dPNB vs. control) in 33.3% vs. 92.3% (P=0.002) on the first day after surgery and 20.8% vs. 80.8% (P<0.001) on the second day. The average duration of analgesia after dPNB was 10 hours and no patient reported motor block. dPNB reduced rescue analgesia requirements and the incidence of postoperative nausea and vomiting (PONV).

CONCLUSIONS

dPNB on target nerves provided better analgesia than systemic analgesia after trapeziectomy performed under axillary block. Opioid consumption and the incidence of PONV were lower in the dPNB group.

Diabetic neuropathy increases stimulation threshold during popliteal sciatic nerve block

BACKGROUND

Peripheral nerve stimulation is commonly used for nerve localization in regional anaesthesia, but recommended stimulation currents of 0.3-0.5 mA do not reliably produce motor activity in the absence of intraneural needle placement. As this may be particularly true in patients with diabetic neuropathy, we examined the stimulation threshold in patients with and without diabetes.

METHODS

Preoperative evaluation included a neurological exam and electroneurography. During ultrasound-guided popliteal sciatic nerve block, we measured the current required to produce motor activity for the tibial and common peroneal nerve in diabetic and non-diabetic patients. Proximity to the nerve was evaluated post-hoc using ultrasound imaging.

RESULTS

Average stimulation currents did not differ between diabetic (n=55) and non-diabetic patients (n=52). Although the planned number of patients was not reached, the power goal for the mean stimulation current was met. Subjects with diminished pressure perception showed increased thresholds for the common peroneal nerve (median 1.30 vs. 0.57 mA in subjects with normal perception, P=0.042), as did subjects with decreased pain sensation (1.60 vs. 0.50 mA in subjects with normal sensation, P=0.038). Slowed ulnar nerve conduction velocity predicted elevated mean stimulation current (r=-0.35, P=0.002). Finally, 15 diabetic patients required more than 0.5 mA to evoke a motor response, despite intraneural needle placement (n=4), or required currents ≥2 mA despite needle-nerve contact, vs three such patients (1 intraneural, 2 with ≥2 mA) among non-diabetic patients (P=0.003).

CONCLUSIONS

These findings suggest that stimulation thresholds of 0.3-0.5 mA may not reliably determine close needle-nerve contact during popliteal sciatic nerve block, particularly in patients with diabetic neuropathy.

CLINICAL TRIAL REGISTRATION

NCT01488474.

Pathophysiology and Etiology of Nerve Injury Following Peripheral Nerve Blockade

This review synthesizes anatomical, anesthetic, surgical, and patient factors that may contribute to neurologic complications associated with peripheral nerve blockade. Peripheral nerves have anatomical features unique to a given location that may influence risk of injury. Peripheral nerve blockade-related peripheral nerve injury (PNI) is most severe with intrafascicular injection. Surgery and its associated requirements such as positioning and tourniquet have specific risks. Patients with preexisting neuropathy may be at an increased risk of postoperative neurologic dysfunction. Distinguishing potential causes of PNI require clinical assessment and investigation; a definitive diagnosis, however, is not always possible. Fortunately, most postoperative neurologic dysfunction appears to resolve with time, and the incidence of serious long-term nerve injury directly attributable to peripheral nerve blockade is relatively uncommon. Nonetheless, despite the use of ultrasound guidance, the risk of block-related PNI remains unchanged.

WHAT'S NEW

Since the 2008 Practice Advisory, new information has been published, furthering our understanding of the microanatomy of peripheral nerves, mechanisms of peripheral nerve injection injury, toxicity of local anesthetics, the etiology of and monitoring methods, and technologies that may decrease the risk of nerve block-related peripheral nerve injury.

The effect of needle dimensions and infusion rates on injection pressures in regional anaesthesia needles: a bench-top study

Animal studies have shown that injection pressures > 75 kPa indicate probable intrafascicular needle tip position. This study describes the flow/pressure characteristics of seven common needle systems. A syringe pump delivered flow rates of 5, 6.67, 10, 13.3, 15 and 20 ml.min(-1) through these needle systems, while keeping the needle tips open to atmosphere. A pressure transducer connected between the syringe and needle provided a real-time graphical display for analysis. Mean plateau pressures increased linearly with flow and with decreasing needle diameter (2.7-92 kPa). Flow rates > 17 ml.min(-1) and needle sizes 22 G and smaller produced mean plateau pressures > 75 kPa. Pressure monitors upstream from the needle may produce false-positive alarms at high flow rates due to needle resistance, and unreliable readings due to non-laminar flow. We recommend injection rates ≤ 15 ml.min(-1) (0.25 ml.s(-1) ) to reduce the effect of factors upstream from the needle tip as a cause of high pressure readings.

Intraneural or extraneural: diagnostic accuracy of ultrasound assessment for localizing low-volume injection

BACKGROUND AND OBJECTIVES

When one is performing ultrasound-guided peripheral nerve blocks, it is common to inject a small amount of fluid to confirm correct placement of the needle tip. If an intraneural needle tip position is detected, the needle can then be repositioned to prevent injection of a large amount of local anesthetic into the nerve. However, it is unknown if anesthesiologists can accurately discriminate intraneural and extraneural injection of small volumes. Therefore, this study was conducted to determine the diagnostic accuracy of ultrasound assessment using a criterion standard and to compare experts and novices in ultrasound-guided regional anesthesia.

METHODS

A total of 32 ultrasound-guided infragluteal sciatic nerve blocks were performed on 21 cadaver legs. The injections were targeted to be intraneural (n = 18) or extraneural (n = 14), and 0.5 mL of methylene blue 1% was injected. Cryosections of the nerve and surrounding tissue were assessed by a blinded investigator as "extraneural" or "intraneural." Ultrasound video clips of the injections were reviewed by 10 blinded observers (5 experts, 5 novices) independently who scored each injection as either "intraneural," "extraneural," or "undetermined."

RESULTS

The mean sensitivity of experts and novices was measured to be 0.84 (0.80-0.88) and 0.65 (0.60-0.71), respectively (P = 0.006), whereas mean specificity was 0.97 (0.94-0.98) and 0.98 (0.96-0.99) (P = 0.53).

CONCLUSIONS

Discrimination of intraneural or extraneural needle tip position based on an injection of 0.5mL is possible, but even experts missed 1 of 6 intraneural injections. In novices, the sensitivity of assessment was significantly lower, highlighting the need for focused education.

Femoral nerve injury following a lumbar plexus blockade

BACKGROUND

Lumbar plexus blockade (LPB) combined with sciatic nerve block (SNB) is frequently used for lower extremity surgery. Perioperative nerve injury is a rarely encountered complication of peripheral nerve blocks (PNB).

CASE REPORT

Here we report a 44-year-old male patient who developed a partial femoral nerve injury (FNI) following a LPB which was performed before the surgery of a patellar fracture. The clinical and electroneuromyographic findings of the patient were recovered almost completely within the following six months.

CONCLUSION

The presented case demonstrated a FNI despite the absence of any pain or paresthesia sensation, with the disappearance of motor response under 0.3 mA of neurostimulation in the experienced hands.

Ultrasound guided injection inside the common sheath of the sciatic nerve at division level has a higher success rate than an injection outside the sheath

BACKGROUND AND OBJECTIVE

The recommendations for the level of injection and ideal placement of the needle tip required for successful ultrasound-guided sciatic popliteal block vary among authors. A hypothesis was made that, when the local anesthetic is injected at the division of the sciatic nerve within the common connective tissue sheath, the block has a higher success rate than an injection outside the sheath.

METHODS

Thirty-four patients scheduled for hallux valgus repair surgery were randomized to receive either a sub-sheath block (n=16) or a peri-sheath block (n=18) at the level of the division of the sciatic nerve at the popliteal fossa. For the sub-sheath block, the needle was advanced out of plane until the tip was positioned between the tibial and peroneal nerves, and local anesthetic was then injected without moving the needle. For the peri-sheath block, the needle was advanced out of plane both sides of the sciatic nerve, to surround the sheath. Mepivacaine 1.5% and levobupivacaine 0.5% 30mL were used in both groups. The progression of motor and sensory block was assessed at 5min intervals. Duration of block was recorded.

RESULTS

Adequate surgical block was achieved in all patients in the subsheath group (100%) compared to 12 patients (67%) in the peri-sheath group at 30min. Sensory block was achieved faster in the subsheath than peri-sheath (9.1±7.4min vs. 19.0±4.0; p<.001).

CONCLUSIONS

Our study suggests that for successful sciatic popliteal block in less than 30min, local anesthetic should be injected within the sheath.

[Localization of peripheral nerves. Success and safety with electrical nerve stimulation]

Peripheral electrical nerve stimulation is one of the standard applications in peripheral regional anesthesia in addition to the ultrasound technique. Among other findings, the visualization of needle and nerve during ultrasound-guided blockade caused a change in clinical practice of peripheral nerve stimulation in the last decade. In the present article old and new aspects of principles and clinical practice of the nerve stimulation technique are presented and summarized in a total clinical concept in order to achieve safe and successful peripheral regional anesthesia using electrical peripheral nerve stimulation.

Procedure-oriented sectional anatomy of the knee

This is the fifth in a series of articles related to procedure-oriented joint anatomy. This article reviews the anatomy of the knee and its relationship to procedures in the clinical setting with or without ultrasound/electromyographic guidance. Anatomically correct axial schematics allow injections to be envisioned relative to clinically important anatomy for common knee procedures. Cross-sectional schematics for the knee were drawn as they appear in imaging projections. The levels and planes of cross section were selected to highlight important anatomic landmarks for injection. It is hoped that these schematics allow for safer and more accurate needle procedures in the knee area.

Incidence of intraneural needle insertion in ultrasound-guided femoral nerve block: a comparison between the out-of-plane versus the in-plane approaches

BACKGROUND

The optimal method of ultrasound-guided femoral nerve block (in-plane vs. out-of-plane) has not been established. We tested the hypothesis that the incidence of needle-nerve contact may be higher with out-of-plane than with in-plane needle insertion.

METHODS

Forty-four patients with hip fracture (American Society of Anaesthesiologists physical status I-III) were randomized to receive the femoral block with an out-of-plane approach (needle inserted at a 45-60° angle 1cm caudal to the midpoint of the ultrasound probe just above the femoral nerve) or with an in-plane technique (needle inserted 0.2-0.4 cm from the side of the probe lateral to the femoral nerve). Data collected included depth of needle insertion, response to nerve electric stimulation, and distribution of the injected volume in relation to the nerve (anterior vs. posterior, the latter assuming needle-nerve contact). The sensory block onset was tested at 20 min and block recovery and any neurologic symptoms were evaluated at 24h.

RESULTS

The incidence of needle-nerve contact was significantly higher with the out-of-plane approach (14/22 patients [64%]) than with the in-plane approach (2/22 patients [9%]) (p<0.001) (OR=17.5, 95% CI: 4-79). The rate of paraesthesia on crossing the fascia iliaca was similar in the two groups. All blocks uneventfully regressed; and no patient developed neurologic symptoms.

CONCLUSIONS

Under the conditions of our study, needle-nerve contact during femoral nerve block occurs frequently with the out-of-plane approach. An in-plane approach results in an equally effective femoral block and less incidence of needle-nerve contact.

Electron microscopy of human peripheral nerves of clinical relevance to the practice of nerve blocks. A structural and ultrastructural review based on original experimental and laboratory data

AIM

The goal is to describe the ultrastructure of normal human peripheral nerves, and to highlight key aspects that are relevant to the practice of peripheral nerve block anaesthesia.

METHOD

Using samples of sciatic nerve obtained from patients, and dural sac, nerve root cuff and brachial plexus dissected from fresh human cadavers, an analysis of the structure of peripheral nerve axons and distribution of fascicles and topographic composition of the layers that cover the nerve is presented. Myelinated and unmyelinated axons, fascicles, epineurium, perineurium and endoneurium obtained from patients and fresh cadavers were studied by light microscopy using immunohistochemical techniques, and transmission and scanning electron microscopy. Structure of perineurium and intrafascicular capillaries, and its implications in blood-nerve barrier were revised.

RESULTS

Each of the anatomical elements is analyzed individually with regard to its relevance to clinical practice to regional anaesthesia.

CONCLUSIONS

Routine practice of regional anaesthetic techniques and ultrasound identification of nerve structures has led to conceptions, which repercussions may be relevant in future applications of these techniques. In this regard, the ultrastructural and histological perspective accomplished through findings of this study aims at enlightening arising questions within the field of regional anaesthesia.

Standard approaches for upper extremity nerve blocks with an emphasis on outpatient surgery

PURPOSE OF REVIEW

Currently, no standards exist with regard to the techniques and administration of ultrasound-guided peripheral nerve blocks. Consequently, the techniques and teaching substantially vary among practitioners and institutions. The purpose of this review is to propose a set of standard US-guided techniques for upper extremity nerve blocks.

RECENT FINDINGS

On the basis of the synthesis of information in available literature and the consensus of an internationally recognized collaborative panel of regional anaesthesia experts, the review recommends a standardized approach to common upper extremity nerve blocks using ultrasound guidance.

SUMMARY

A set of structured recommendations and approaches are suggested to help standardize clinical practice and teaching of ultrasound-guided upper extremity nerve blocks. Additional emphasis is placed on the discussion of nerve blocks in outpatient surgery.

[Ultrasound-guided block at the antecubital fossa for carpal tunnel syndrome surgery]

INTRODUCTION

There are various anaesthetic techniques for ambulatory surgery of carpal tunnel release. The ultrasound-guided nerve blocks offer advantages compared to other techniques. The purpose of this study was to evaluate the efficacy using ultrasound-guided block at the antecubital fossa, as well as to evaluate complications, patient satisfaction and surgeon satisfaction with the block.

MATERIALS AND METHODS

Prospective observational study with 32 elective patients for carpal tunnel release in a one-day case unit. An ultrasound-guided block with mepivacaine 1% was performed at the antecubital fossa, aiming for the median, ulnar and the lateral and medial cutaneous nerves of the forearm. The measurements of the anteroposterior and laterolateral diameters of the median and ulnar nerves were recorded, before and after injection. Motor and sensory levels were evaluated for the median and ulnar nerves at 5 and 30 min post injection, and compared with the contralateral hand. Pain from the surgical incision time and recovery were recorded, together with complications, and patient and surgeon satisfaction with the block.

RESULTS

The antecubital fossa ultrasound-guided block was successful in 93.7% of the patients. No patients needed rescue analgesia in recovery and no complications were recorded. Patient satisfaction was 93.7% and surgeon satisfaction was 97%.

CONCLUSIONS

A selective block of the medial, ulnar and medial and lateral cutaneous nerves of the forearm are effective and satisfactory anaesthetic techniques for carpal tunnel release in a one-day case unit. It allows early mobilization, minimises risks and amount of local anaesthetic used.