Neurological complications after regional anesthesia: contemporary estimates of risk

Prevalence of saphenous nerve injury after adductor-canal-blockade in patients receiving total knee arthroplasty

BACKGROUND

Adductor-canal-blockade is a new technique for pain relief after knee surgery. This block could cause nerve injury and the aim of this follow-up study was to determine the prevalence of saphenous nerve injury in patients receiving adductor-canal-blockade for pain treatment after total knee arthroplasty.

METHODS

All patients included in two former studies of adductor-canal-blockade following total knee arthroplasty were invited to participate in this follow-up study 3-6 months after surgery. We examined the cutaneous area on the medial aspect of the lower leg (medial crural branch of the saphenous nerve), as well as the anterior, posterior, lateral and infrapatellar part of the affected and contralateral lower leg. Sensory function was tested with pinprick (sharp and blunt needle), temperature discrimination (cold disinfectant swabs) and light brush.

RESULTS

We included 97 patients. None of the patients [0-5.3% (99% confidence interval)] had sensory changes related to temperature or light brush corresponding to the medial crural branch of the saphenous nerve, but 10 patients could not discriminate between blunt and sharp stimulation with a needle. In the infrapatellar area of the operated knee, 76 patients could not discriminate between blunt and sharp stimulation with a needle, 81 patients could not discriminate between cold and warmth, and 82 patients displayed an altered sensation to light brush.

CONCLUSION

We found no indications of saphenous nerve injury caused by the adductor-canal-blockade at the mid-thigh level. However, 84% of the patients had signs of injury to the infrapatellar branch of the saphenous nerve in the operated leg. Such findings are well-known complications to the surgical procedure.

Case report: neurological complications associated with epidural analgesia in children: a report of 4 cases of ambiguous etiologies

The safety and utility of pediatric epidural analgesia is well established, but the risk of permanent neurological injury is unknown and largely must be extrapolated from adult literature. In this article we present a series of 4 cases of longterm or permanent neurologic complications associated with epidural analgesia. Possible mechanisms of injury and implications for practice are discussed.

Clinical and electrodiagnostic features of sciatic neuropathies

Sciatic neuropathy is the second most common neuropathy of the lower extremity and a common cause of foot drop. This article reviews the anatomy, clinical features, pathophysiology, and electrodiagnostic assessment of sciatic neuropathies. There are multiple potential sites of pathology, determined in part by the mechanism of insult, including trauma, compression, masses, inflammation, and vascular lesions. Diagnosis is augmented by careful electrodiagnostic studies and imaging to help distinguish sciatic neuropathy from other sources of pathology. Electrodiagnostic studies may also help in assessing for early recovery and in determining prognosis.

Local anaesthetics and regional anaesthesia for preventing chronic pain after surgery

BACKGROUND

Regional anaesthesia may reduce the rate of persistent (chronic) pain after surgery, a frequent and debilitating condition.

OBJECTIVES

To compare local anaesthetics and regional anaesthesia versus conventional analgesia for the prevention of persistent pain six or 12 months after surgery.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 4), PubMed (1966 to April 2012), EMBASE (1966 to May 2012) and CINAHL (1966 to May 2012) without any language restriction. We used a combination of free text search and controlled vocabulary search. The results were limited to randomized controlled clinical trials (RCTs). We conducted a handsearch in reference lists of included trials, review articles and conference abstracts.

SELECTION CRITERIA

We included RCTs comparing local anaesthetics or regional anaesthesia versus conventional analgesia with a pain outcome at six or 12 months after surgery.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data, including information on adverse events. We contacted study authors for additional information. Results are presented as pooled odds ratios (OR) with 95% confidence intervals (CI), based on random-effects models (inverse variance method). We grouped studies according to surgical interventions. We employed the Chi(2) test and calculated the I(2) statistic to investigate study heterogeneity.

MAIN RESULTS

We identified 23 RCTs studying local anaesthetics or regional anaesthesia for the prevention of persistent (chronic) pain after surgery. Data from a total of 1090 patients with outcomes at six months and of 441 patients with outcomes at 12 months were presented. No study included children. We pooled data from 250 participants after thoracotomy, with outcomes at six months. Data favoured regional anaesthesia for the prevention of chronic pain at six months after thoracotomy with an OR of 0.33 (95% CI 0.20 to 0.56). We pooled two studies on paravertebral block for breast cancer surgery; the pooled data of 89 participants with outcomes at five to six months favoured paravertebral block with an OR of 0.37 (95% CI 0.14 to 0.94).The methodological quality of the included studies was intermediate. Adverse effects were not studied systematically and were reported sparsely. Clinical heterogeneity, attrition and sparse outcome data hampered the assessment of effects, especially at 12 months.

AUTHORS' CONCLUSIONS

Epidural anaesthesia may reduce the risk of developing chronic pain after thoracotomy in about one patient out of every four patients treated. Paravertebral block may reduce the risk of chronic pain after breast cancer surgery in about one out of every five women treated. Our conclusions are significantly weakened by performance bias, shortcomings in allocation concealment, considerable attrition and incomplete outcome data. We caution that our evidence synthesis is based on only a few, small studies. More studies with high methodological quality, addressing various types of surgery and different age groups, including children, are needed.

Neurologic complications of anesthesia

Neurologic complications after anesthesia are relatively uncommon but occasionally severe. Intraoperative intracranial hypertension in patients with brain masses, delayed arousal, and postoperative delirium and cognitive dysfunction are among the main complications of general anesthesia. Neuropathy and transient gluteal and leg pain are the most frequent complications of regional blockade. Seizures are infrequent with both anesthesia modalities. Patients with primary neurologic disorders, such as neurodegenerative or neuromuscular conditions, can be at risk for specific complications, and the anesthesia plan must be cautiously adjusted in these patients. In the neurointensive care unit, the complications from large doses of anesthetic agents used for suppression of seizures or control of intracranial pressure are different from those seen perioperatively. Propofol infusion syndrome can be life-threatening when administered for those indications.

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.

Buprenorphine added to levobupivacaine enhances postoperative analgesia of middle interscalene brachial plexus block

PURPOSE

The aim of this study was to assess whether addition of epineural buprenorphine prolonged postoperative analgesia of middle interscalene brachial plexus block (MIB) with levobupivacaine.

METHODS

One hundred and fifty consenting adult patients, scheduled for shoulder arthroscopic surgery for a rotator cuff tear under MIB with 29.5 ml of 0.75 % levobupivacaine, were randomized to receive additionally either saline or intramuscular buprenorphine 0.15 mg or epineural buprenorphine 0.15 mg. Onset of sensory and motor blocks, duration of postoperative analgesia, and consumption of postoperative analgesics were compared among the groups.

RESULTS

There were significant (P < 0.05) differences in the onset and the duration of the sensory block and in the duration of postoperative analgesia. Duration of both sensory block and postoperative analgesia was longer (P < 0.05) in patients who had received epineural buprenorphine (856.1 ± 215.2 and 1,049.7 ± 242.2 min) than in patients who had received intramuscular buprenorphine (693.6 ± 143.4 and 820.3 ± 335.3 min) or saline (488.3 ± 137.6 and 637.5 ± 72.1 min). Requirement of postoperative rescue analgesics was lower in the epineural buprenorphine group than in the other two groups. Few complications occurred from MIB (<1 %) and none from buprenorphine.

CONCLUSIONS

Epineural buprenorphine prolonged postoperative analgesia of MIB more effectively than intramuscular buprenorphine, which suggests that buprenorphine acts at a peripheral nervous system site of action.

Echogenic regional anaesthesia needles: a comparison study in Thiel cadavers

Ultrasound guidance is now the standard procedure for regional nerve block in anesthesiology. However, ultrasonic visualisation of needle manipulation and guidance within tissues remains a problem. Two new echogenic needles (Pajunk and Braun) have been introduced to anesthesiology clinical practice but evaluation has been restricted to preserved animal tissue. In this study, the visibility of both echogenic needles was compared with a standard nonechogenic needle in a Thiel cadaver model. A total of 144 intramuscular injections were made in the upper arm in-plane and out-of-plane to the ultrasound beam at four angles (30°, 45°, 60° and 75°). The visibility of the needle was assessed by two independent, blinded observers using a 5-point Likert ordinal scale. Weighted κ for interobserver agreement was 0.77 (95% confidence interval [CI]: 0.68-0.86). The Pajunk echogenic needle was more visible than the Braun standard needle in-plane (p = 0.04), and the Braun standard and Braun echogenic needles out-of-plane (p = 0.02). Independent predictors of visibility using logistic regression were needle (p < 0.001) and plane of insertion (p = 0.08), receiver operator characteristic (ROC) area under the curve 0.90. In conclusion, the Pajunk echogenic needle offers the best visibility for ultrasound-guided regional anesthesia.

Neuropathic symptoms following continuous popliteal block after foot and ankle surgery

BACKGROUND

Continuous perineural blocks are increasingly popular for postoperative pain control. While the reported incidence of neuropathic symptoms has been low, the experience of the lead author suggested it may be much higher. The objectives of this study were to elucidate the incidence of patient-reported neuropathic symptoms following continuous popliteal block (CPB) for postoperative pain control in patients undergoing foot and ankle surgery, to characterize these symptoms and to identify preoperative risk factors.

METHODS

A prospective cohort study of 147 surgical patients undergoing significant foot and ankle procedures was carried out. Patients were followed for 8 months post-surgery. Preoperative/perioperative questionnaires were completed by anesthesiologists. Patients completed questionnaires at 2, 6, 14, and 34 weeks. Multivariable logistic regression analysis using Generalized Estimating Equations (GEE) was used to examine risk factors for neuropathy.

RESULTS

The prevalence of neuropathic symptoms at 2 weeks was 41% (95% CI, 33% to 49%) decreasing to 24% (95% CI, 15.4% to 32.5%) at 34 weeks. Multivariable analyses revealed that tourniquet placement, tourniquet time, use of prophylactic antibiotics, type of anesthesia, level of training in anesthesiology, patient history of chronic pain and patient age were not significantly associated with neuropathy. Smokers were more likely to report neuropathic symptoms (adjusted OR, 2.25; 95% CI, 0.96 to 5.33).

CONCLUSION

The incidence of neuropathic symptoms may be much higher than previously reported. Smoking may be a risk factor for the development of neuropathic symptoms.

Neurotoxicity of adjuvants used in perineural anesthesia and analgesia in comparison with ropivacaine

BACKGROUND AND OBJECTIVES

Clonidine, buprenorphine, dexamethasone, and midazolam (C, B, D, M) have been used to prolong perineural local anesthesia in the absence of data on the influence of these adjuvants on local anesthetic-induced neurotoxicity. Therefore, the impact of these adjuvants on ropivacaine (R)-induced death of isolated sensory neurons was assessed.

METHODS

The trypan blue exclusion assay was used to assess death of sensory neurons isolated from adult male Sprague-Dawley rats. Drugs were applied, alone or in combination, for 2 or 24 hrs at 37°C.

RESULTS

Neuronal viability was halved by 24-hr exposure to R (2.5 mg/mL), far exceeding the neurotoxicity of C, B, D, or M (at 2-100 times estimated clinical concentrations). Plain M at twice the estimated clinical concentration produced a small but significant increase in neurotoxicity at 24 hrs. After 2-hr exposure, high concentrations of B, C, and M increased the neurotoxicity of R; the combination of R + M killed more than 90% of neurons. Estimated clinical concentrations of C + B (plus 66 μg/mL D) had no influence on (i) R-induced neurotoxicity, (ii) the increased neurotoxicity associated with the combination of R + M, or (iii) the neurotoxicity associated with estimated clinical concentrations of M. There was increased neurotoxicity with 133 μg/mL D combined with R + C + B.

CONCLUSIONS

Results with R reaffirm the need to identify ways to mitigate local anesthetic-induced neurotoxicity. While having no protective effect on R-induced neurotoxicity in vitro, future research with adjuvants should address if the C + B + D combination can enable reducing R concentrations needed to achieve equianalgesia (and/or provide equal or superior duration, in preclinical in vivo models).

Application of sonoelastography to regional anaesthesia: a descriptive study with the Thiel embalmed cadaver model

Introduction

Ultrasound-guided regional anaesthesia (UGRA) is being used increasingly in patients but varying patient characteristics make it difficult to visualize needles and spread of local anaesthetic fluid.

Methods

To evaluate the use of elastography for UGRA by performing ultrasound-guided nerve blocks in Thiel embalmed cadavers. Both upper limb and lower limb blocks were performed on cadavers with ultrasound guidance. B-mode and elastography images obtained on split screen were analysed.

Results

The B-mode images were superior compared with the ultrasound elastography images with respect to the anatomical details; however, dynamic changes such as fluid spread were visualized better with elastography.

Conclusion

The elastography images also had good dose response to the volume of the injectate implying its usefulness in detecting local anaesthetic spread when low volumes are used as test doses.

Is there still a place for the use of nerve stimulation?

The introduction of nerve stimulation as a method of nerve localization sparked a new beginning in regional anesthesia. It was an epochal development akin to the utilization of ultrasound in more recent times. Many experts now consider ultrasound-guided peripheral nerve blockade to be more efficient, less painful, and more successful than landmark and nerve stimulation techniques. However, inadvertent intraneural injection continues to occur despite the widespread use of ultrasound and nerve stimulation. Both of these technologies allow for only limited elucidation of needle position relative to the target nerve and are unable to reliably identify intraneural position of the needle. This article will review the role of nerve stimulation in modern regional anesthesia techniques in light of the introduction of ultrasound technology.

Legal disputes over duties to disclose treatment risks to patients: a review of negligence claims and complaints in Australia

David Studdert and colleagues identified disputes over informed consent among malpractice claims and serious health care complaints in Australia and provide an analysis of disagreements between patients and doctors over whether particular clinical risks should have been disclosed before treatment.

Transient brachial monoparesis following epidural anesthesia for cesarean section

Monoparesis following lumbar epidural block is a rare occurrence, with few cases reported in the literature. We report development of transient brachial monoparesis following epidural anesthesia in a parturient for cesarean section. The patient received a mixture of 15 mL of 2% lignocaine with 50 mcg fentanyl epidurally to achieve a blockade up to T6 level. She remained hemodynamically stable throughout the procedure, with no respiratory distress or desaturation. However, near the end of surgery, she developed weakness in the right upper limb. The weakness lasted for 90 min, followed by complete neurological recovery. Subsequent hospital stay was uneventful.

[Neurologic complications of central neuraxial blocks]

Central neuraxial blocks, which are associated with a low incidence of complications, are safe. When complications do occur, however, the resulting morbidity and mortality is considerable. The reported incidence of complications in all series is under 4 per 10000 patients, but given the absence of formal registries and notification procedures, which have legal implications, the real rate of occurrence of these rare events is uncertain. We searched the literature through PubMed and the Cochrane Plus Library for a 5-year period, using the search terms epidural anesthesia AND safety, spinal anesthesia AND safety, complications AND epidural anesthesia, complications AND spinal anesthesia, neurologic complications AND epidural anesthesia, and neurologic complications AND spinal anesthesia. Neuraxial injury after a central blockade may be the result of anatomical and/or physiological lesions affecting the spinal cord, spinal nerves, nerve roots, or blood supply. The pathophysiology of neuraxial injury may be related to mechanical, ischemic, or neurotoxic damage or any combination. When a complication occurs, factors related to the technique will have interacted with pre-existing patient-related conditions. Various scientific societies have published guidelines for managing the complications of regional anesthesia. Recently published clinical practice guidelines recommend ultrasound imaging as a useful tool in performing a central neuraxial block.

Two continuous femoral nerve block strategies after TKA

PURPOSE

The purposes of this study were to compare the pain score, systemic opioid consumption, and range of motion (ROM) between the group where the use of continuous femoral nerve block (CFNB) was discontinued on postoperative day 3 (POD 3) and the group where it was discontinued on POD 7 within an established clinical pathway for postoperative recovery after total knee arthroplasty (TKA) and to assess the treatment-related side effects and complications, as well as the functional status of these two groups of patients at 2 years after surgery.

METHODS

This prospective, randomized, double-blinded trial compared the analgesic efficacy and the functional outcomes between group A (n = 30) where continuous femoral nerve block was performed until POD 3 (discontinued prior to the initiation of range of motion (ROM) exercises) and group B (n = 33), where the continuous femoral nerve block was performed until POD 7 (discontinued during the ROM exercise) after TKA.

RESULTS

The resting pain scores of group B were lower than those of group A but there was no significant difference between the two groups (n.s., P = 0.387). However, the peak pain scores during ROM exercise, beginning on POD3 through to POD14, were significantly lower in group B than in group A (P = 0.001). The cumulative morphine IV-PCA requirements through the POD 2 were similar in the two groups (n.s., P = 0.811). However, the cumulative oral oxycodone consumption during hospitalization was significantly lower in group B than in group A, P < 0.0001. Group B showed significantly greater satisfaction with their method of analgesia than group A (P = 0.001). Group A scored 2.0 (2.0-3.0), whereas group B scored 1.0 (1.0-2.0). At 2 years, there was no significant difference in the functional outcomes (the knee flexion and extension angle, the Knee Society Score, and WOMAC pain, stiffness, and function scale).

CONCLUSION

The study group who received 7-day continuous femoral nerve block after TKA showed superior analgesia and higher patient satisfaction during the hospital stay than those given 3-day continuous femoral nerve block. Despite the additional time, effort and cost to place and manage continuous femoral nerve catheters, the 7-day continuous femoral nerve block can be recommended as an effective and safe regional component of a multimodal analgesia strategy after TKA.

[Two cases of chronic pain after regional anaesthesia]

We are reporting two cases of chronic neuropathic pain after traumatism during regional anaesthesia (RA). Nerve injury is a rare complication of RA and it is the neurogical deficit, which is the most often quoted in medical literature. However, in both cases the neuropathic pain was the single departure point. The reunion of the clinical element, which incorporates possible traumatism during regional anaesthesia, characteristics of pain and unusual painful localization of surgery, should have allowed a more early diagnostic and treatment. In both cases, persistent neuropathic pain incapacitates the patient several years after the traumatism.

Equipment and monitoring--what is in the future to improve safety?

There have been a number of recent developments in the practice of anesthesia and intensive care aimed at improving outcome in terms of reducing both morbidity and mortality, as well as other less-defined factors, such as quality of service provision. Significant advances have been made in airway devices such as pediatric tracheal tube designs, Microcuff(®) tracheal tubes, and new laryngoscopes. Noninvasive monitoring devices, including continuous hemoglobin analysis and near infrared spectrometry, are being increasingly used in pediatric anesthesia. Other, 'scaled-down' versions from adult anesthesia care, however, have not universally been shown to result in improved safety and outcomes in pediatric anesthesia.

Is anesthesia dangerous?

BACKGROUND

Recent years have seen a rise in overall anesthesia-related mortality.

METHOD

Selective review of the literature.

RESULTS

Anesthesia-related mortality has fallen from 6.4/10 000 in the 1940s to 0.4/100 000 at present, largely because of the introduction of safety standards and improved training. The current figure of 0.4/100 000 applies to patients without major systemic disease; mortality is higher among patients with severe accompanying illnesses, yet in this group, too, perioperative mortality can be reduced by appropriate anesthetic management. Moreover, the use of regional anesthesia can also improve the outcome of major surgery.

CONCLUSION

A recent increase in the percentage of older and multimorbid patients among persons undergoing surgery, along with the advent of newer types of operation that would have been unthinkable in the past, has led to an apparent rise in anesthesia-associated mortality, even though the quality of anesthesiological care is no worse now than in the past. On the contrary, in recent years, better anesthetic management has evidently played an important role in improving surgical outcomes.

[Continuous infusion of local anesthetic at the site of the abdominal surgical wound for postoperative analgesia: a systematic review]

OBJECTIVES

We present a systematic review of clinical trials to evaluate the efficacy of infusing local anesthetic through a catheter placed in the abdominal surgical wound.

METHODS

The Jadad (Oxford) scoring system was used to select trials. The variables considered in relation to each trial selected were as follows: type of intervention and incision; type, dose, and concentration of local anesthetic; site where the catheter was placed; rescue analgesia required; opioid use; and incidence of adverse events.

RESULTS

Fifteen clinical trials with a mean Jadad score of 4.6 were selected. The 1139 patients enrolled in the trials were grouped according to catheter placement: subfascial (6 trials), subcutaneous (8 trials), and both (1 trial). Six additional unpublished trials registered at ClinicalTrials.gov were also located.

CONCLUSIONS

Surgical wound analgesia is a safe technique whose effectiveness has been observed in cesarean sections and hysterectomies performed with Pfannenstiel incisions. Outcomes for other types of surgery are inconsistent. There is a lack of studies of the optimal site for catheter placement as well as of adequate anesthetic concentration and volume.

Multimodal pain management after total joint arthroplasty

Adequate postoperative pain control in patients who have undergone total joint arthroplasty allows faster rehabilitation and reduces the rate of postoperative complications. Multimodal pain management involves the introduction of adjunctive pain control methods in an attempt to control pain with less reliance on opioids and fewer side effects. Current research suggests that traditional nonsteroidal anti-inflammatory drugs (NSAIDs) and the associated cyclooxygenase type-2 (COX-2) inhibitors improve pain control in most cases. Nearly all multimodal pain management modalities have a safe side-effect profile when they are added to existing methods. The exception is the administration of DepoDur (extended-release epidural morphine) to elderly or respiratory-compromised patients because of a potential for hypoxia and cardiopulmonary events.

Histological Consequences of Needle-Nerve Contact following Nerve Stimulation in a Pig Model

Background. Nerve stimulation can facilitate correct needle placement in peripheral regional anesthesia. The aim of this study was to determine whether the high threshold current is associated with reduced nerve injury due to fewer needle-nerve contacts compared with low current. Methods. In anaesthetized pigs, thirty-two nerves of the brachial plexus underwent needle placement at low (0.2 mA) or high current (1.0 mA). The occurrence of needle-nerve contact was recorded. After 48 hours, the nerves were analyzed for occurrence of histological changes. Nerve injury was scored ranging from 0 (no injury) to 4 (severe injury). Results. The frequency of needle-nerve contact was 94% at low compared to 6% at high current. The score was significantly higher at low (median [interquartile range] 2.0 [1.0-2.0]) compared to high current (0.0 [0.0-1.0] P = .001). Conclusions. Inflammatory responses were directly related to needle-nerve contacts. Hence, posttraumatic inflammation may be diminished using higher current for nerve localization.

A prospective analysis of interscalene brachial plexus blocks performed under general anesthesia

BACKGROUND

The purpose of this prospective study was to assess the safety and efficacy of interscalene brachial plexus block anesthesia when performed on patients who were anesthetized with a general anesthetic prior to the performance of the block.

METHODS

Patients were assessed postoperatively through surveys, interviews, and physical examinations to document block success, duration of anesthesia, block side effects, and persistent neurological complications. Nine-hundred fifty-one patients were available for the analysis.

RESULTS

The overall block success rate was 97% and the mean duration of anesthesia provided by the blocks was 23.9 hours. Immediate postoperative block side effects occurred in 16% (142 of 910), persistent neurological complications occurred in 4.4% (40 of 910) of patients, and long-term neurologic complications occurred in 0.8% (8 of 910).

CONCLUSION

Our study results suggest that the rates of success and complications associated with the performance of interscalene block regional anesthesia performed after induction of general anesthesia are similar to the results demonstrated in prior studies in which brachial plexus block was performed on nonanesthetized patients. Although significant complications were not common, this procedure is not without risk and can result in long-term neurologic complications.