Beware the Wandering Needle: Inadvertent Intramedullary Injection During an Attempted Cervical Medial Branch Block.

A 27-year-old man developed sudden neck pain, severe quadriparesis, and right shoulder allodynia during an outpatient cervical medial branch block procedure. Cervical spine imaging revealed evidence of an interlaminar needle trajectory with abnormal signal in the right hemicord at the level of C4, consistent with intramedullary injection and contusion. Following a 48-hour stay in the intensive care unit, during which hemodynamic vasopressor support was administered to optimize spinal cord perfusion, the patient exhibited almost complete neurologic recovery with resolution of the neuropathic pain. He was eventually discharged home and underwent outpatient physical therapy for a mild residual right hemiparesis.

Evaluation of the B-Smart manometer and the CompuFlo computerized injection pump technology for accurate needle-tip injection pressure measurement during peripheral nerve blockade.

BACKGROUND AND OBJECTIVES: The exact mechanism of peripheral nerve blocks causing/leading to nerve injury remains controversial. Evidence from animal experiments suggests that intrafascicular injection resulting in high injection pressure has the potential to rupture nerve fascicles and may consequently cause permanent nerve injury and neurological deficits. The B-Smart (BS) in-line manometer and the CompuFlo (CF) computerized injection pump technology are two modalities used for monitoring pressure during regional anesthesia. This study sought to explore the accuracy of these two technologies in measuring needle-tip pressures in a simulated environment. METHODS: In seven simulated needle-syringe combinations, the BS and the CF devices were connected in series through a closed system and attached to a digital manometer at the tip of various needles. The pressures were evaluated in three trials per needle-syringe combination. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy (F1 Score) were determined for each needle type and overall. RESULTS: For pressures ≥15 psi and ≥20 psi, respectively, the CF device demonstrated a sensitivity of 100%, 100%; specificity of 96%, 98%; positive predictive value 93%, 93%; and negative predictive value of 100%, 100%. The BS device demonstrated a sensitivity of 60%, 100%; specificity of 99%, 95%; positive predictive value of 96%, 85%; and negative predictive value of 85%, 100%. Accuracy, as measured by the F1 Score, for detecting a pressure of ≥15 psi was 0.96 for the CF and 0.74 for the BS. CONCLUSIONS: Future research is needed to explore in-vivo performance and evaluate whether either of these devices can impact on clinical outcomes.

The Effect of Fixation Technique on Continuous Interscalene Nerve Block Catheter Success: A Randomized, Double-Blind Trial.

BACKGROUND: Continuous peripheral nerve blocks offer advantages over single-injection blocks, including extended analgesia and reduction in opioid consumption. These benefits require that the perineural catheter remain intact for the duration of the planned local anesthetic infusion. Mechanical displacement of catheters, leaking, and consequent failure are known complications. The aim of this study was to evaluate continuous perineural catheter tip-to-nerve apposition in vivo over 48 hours comparing 2 different simple fixation strategies. METHODS: Subjects presenting for a continuous interscalene nerve block were randomized to perineural catheter fixation with 1 of 2 types of adhesive: Dermabond (2-octylcyanoacrylate) or Mastisol (alcohol 23A, gum mastic, storax, and methyl salicylate), covered with a simple transparent dressing. The primary outcome was the evaluation of catheter-to-nerve apposition maintenance over 48 hours via both a blinded ultrasound evaluation of local anesthetic distribution and a blinded clinical assessment. Secondary outcomes included leakage at the catheter site, pain scores, opioid consumption, catheter-to-skin migration at the insertion site, and patient satisfaction. RESULTS: Sixty-six subjects were recruited and randomized to compare adhesive group catheter tip-to-nerve apposition on postoperative day 2 (POD 2). Within the intention-to-treat cohort, a statistically significant decrease of perineural catheter tip-to-nerve apposition in the Mastisol group (64.7%) compared with the Dermabond group (90.6%) on POD 2 (odds ratios [OR] 0.19; 95% confidence interval [CI] 0.05-0.75; P = .012) was observed. Similar results were observed on POD 1 (OR 0.19; 95% CI 0.03-1.38; P = NS) and POD 2 (OR 0.14; 95% CI 0.02-0.97; P = .008) within the as-treated cohort. Catheter leakage (OR 67; 95% CI 7.3-589) and median catheter migration difference at the skin insertion site (2.0 cm; 95% CI 0.5-2.5) were also significantly greater in the Mastisol group than in the Dermabond group from POD 0 to POD 2 (P < .001). Median postoperative opioid consumption difference in morphine equivalents (3.2 mg; 95% CI - 9.0 to 14.2) was not significantly different between the Dermabond and the Mastisol groups through POD 2 (P = .542). CONCLUSIONS: Perineural catheter fixation with Dermabond in continuous interscalene nerve block improves maintenance of catheter-to-nerve apposition when compared with Mastisol.

Ultrasound-guided percutaneous peripheral nerve stimulation for analgesia following total knee arthroplasty: a prospective feasibility study.

BACKGROUND: Peripheral nerve stimulation has been used for decades to treat chronic pain but has not been used for postoperative analgesia due to multiple limitations, beginning with invasive electrode placement. With the development of small-diameter/gauge leads enabling percutaneous insertion, ultrasound guidance for accurate introduction, and stimulators small enough to be adhered to the skin, neurostimulation may now be provided in a similar manner to continuous peripheral nerve blocks. Here, we report on the use of ultrasound-guided percutaneous peripheral nerve stimulation to treat postoperative pain. MATERIALS AND METHODS: Subjects within 60 days of a total knee arthroplasty with pain insufficiently treated with oral analgesics had a 0.2-mm-diameter electrical lead (pre-loaded into a 20 gauge needle) introduced percutaneously using ultrasound guidance with the tip located approximately 0.5-1.0 cm from the femoral nerve (a second lead was inserted approximately 1.0-3.0 cm from the sciatic nerve for posterior knee pain). An external stimulator delivered current. Endpoints were assessed before and after lead insertion and the leads subsequently removed. Due to the small sample size for this pilot/feasibility study, no statistics were applied to the data. RESULTS: Leads were inserted in subjects (n = 5) 8-58 days postoperatively. Percutaneous peripheral nerve stimulation decreased pain an average of 93% at rest (from a mean of 5.0 to 0.2 on a 0-10 numeric rating scale), with 4 of 5 subjects experiencing complete resolution of pain. During passive and active knee motion pain decreased an average of 27 and 30%, respectively. Neither maximum passive nor active knee range-of-motion was consistently affected. CONCLUSIONS: Ultrasound-guided percutaneous peripheral nerve stimulation may be a practical modality for the treatment of postoperative pain following orthopedic surgical procedures, and further investigation appears warranted.

Two-Year Outcomes of Vagal Nerve Blocking (vBloc) for the Treatment of Obesity in the ReCharge Trial.

BACKGROUND: The ReCharge Trial demonstrated that a vagal blocking device (vBloc) is a safe and effective treatment for moderate to severe obesity. This report summarizes 24-month outcomes. METHODS: Participants with body mass index (BMI) 40 to 45 kg/m2, or 35 to 40 kg/m2 with at least one comorbid condition were randomized to either vBloc therapy or sham intervention for 12 months. After 12 months, participants randomized to vBloc continued open-label vBloc therapy and are the focus of this report. Weight loss, adverse events, comorbid risk factors, and quality of life (QOL) will be assessed for 5 years. RESULTS: At 24 months, 123 (76 %) vBloc participants remained in the trial. Participants who presented at 24 months (n = 103) had a mean excess weight loss (EWL) of 21 % (8 % total weight loss [TWL]); 58 % of participants had ≥5 % TWL and 34 % had ≥10 % TWL. Among the subset of participants with abnormal preoperative values, significant improvements were observed in mean LDL (-16 mg/dL) and HDL cholesterol (+4 mg/dL), triglycerides (-46 mg/dL), HbA1c (-0.3 %), and systolic (-11 mmHg) and diastolic blood pressures (-10 mmHg). QOL measures were significantly improved. Heartburn/dyspepsia and implant site pain were the most frequently reported adverse events. The primary related serious adverse event rate was 4.3 %. CONCLUSIONS: vBloc therapy continues to result in medically meaningful weight loss with a favorable safety profile through 2 years. TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT01327976.

Novel technologies and techniques in bariatric surgery.

Obesity has been on the rise globally and more people are now clinically obese than ever before in the US. This issue has a significant impact on both health and cost to healthcare systems. Bariatric surgery is efficacious in treatment of obesity but only in late stages of the disease, and there is a requirement for less invasive techniques/devices to treat obesity at earlier stages. Currently a number of these are either in clinical trials or have recently been approved by the Food and Drug Administration for weight loss. This review aims to give an overview of the newer technologies and techniques being used in bariatric surgery. It will also give a glimpse into future methods and those that have fallen short in recent times.

Novel needle guide reduces time to perform ultrasound-guided femoral nerve catheter placement: A randomised controlled trial.

BACKGROUND: Ultrasound-guided nerve blocks have become the standard when performing regional nerve blocks in anaesthesia. Infiniti Plus (CIVCO Medical Solutions, Kalona, Iowa, USA) is a needle guide that has been recently developed to help clinicians in performing ultrasound-guided nerve blocks. OBJECTIVES: We tested the hypothesis that femoral nerve catheter placement carried out with the Infiniti Plus needle guide will be quicker to perform than without the Infiniti Plus. Secondary aims were to assess whether the Infiniti Plus needle guide decreased the number of block attempts and also whether it improved needle visibility. DESIGN: A randomised, controlled trial. SETTING: Cleveland Clinic, Cleveland, Ohio, USA. PATIENTS: We enrolled adult patients having elective total knee arthroplasty with a femoral nerve block and femoral nerve catheter. Patients, who were pregnant or those who had preexisting neuropathy involving the surgical limb, coagulopathy, infection at the block site or allergy to local anaesthetics were excluded. INTERVENTIONS: Patients were randomised into two groups to receive the ultrasound-guided femoral nerve catheter placement with or without the Infiniti Plus needle guide. MAIN OUTCOME MEASURES: The time taken to place the femoral nerve catheter, the number of attempts, the success rate and needle visibility were recorded. We used an overall α of 0.05 for both the primary and secondary analyses; the secondary analyses were Bonferroni corrected to control for multiple comparisons. RESULT: The median (interquartile range Q1 to Q3) time to perform the femoral nerve catheter placement was 118 (100 to 150) s with Infiniti Plus and 177 (130 to 236) s without Infiniti Plus. Infiniti Plus significantly reduced the time spent performing femoral nerve catheterisation, with estimated ratio of means [(95% confidence interval), P value] of 0.67 [(0.60 to 0.75), P < 0.001] with Infiniti Plus compared with no Infiniti Plus. However, Infiniti Plus had no effect on the odds of a successful femoral nerve catheter placement, number of attempts or percentage of perfect needle visibility. CONCLUSION: We found that the use of Infiniti Plus decreased the median time to successfully place a femoral nerve catheter by 33% compared with not using Infiniti Plus. This difference may be more apparent to clinicians undertaking this procedure less often or by those in training as our team was very experienced, had been trained in the technique and was working in a hospital with a large caseload. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT02080481.

High Opening Injection Pressure Is Associated With Needle-Nerve and Needle-Fascia Contact During Femoral Nerve Block.

BACKGROUND AND OBJECTIVES: High opening injection pressures (OIPs) have been shown to predict sustained needle tip contact with the roots of the brachial plexus. Such roots have a uniquely high ratio of fascicular versus connective tissue. It is unknown if this relationship is preserved during multifascicular nerve blockade. We hypothesized that OIP can predict needle-nerve contact during femoral nerve block, as well as detect needle contact with the fascia iliaca. METHODS: Twenty adults scheduled for femoral block were recruited. Using ultrasound, a 22-gauge needle was sequentially placed in 4 locations: indenting the fascia iliaca, advanced through the fascia iliaca while lateral to the nerve, slightly indenting the femoral nerve, and withdrawn from the nerve 1 mm. At each location, the OIP required to initiate an injection of 1 mL D5W (5% dextrose in water) at 10 mL/min was recorded. Blinded investigators performed evaluations and aborted injections when an OIP of 15 psi was reached. RESULTS: Opening injection pressure was 15 psi or greater for 90% and 100% of cases when the needle indented the femoral nerve and fascia iliaca, respectively. Opening injection pressure was less than 15 psi for all 20 patients when the needle was withdrawn 1 mm from the nerve as well as at the subfascial position (McNemar χ2 P < 0.001). CONCLUSIONS: Opening injection pressure greater than 15 psi was associated with a block needle tip position slightly indenting the epineurium of the femoral nerve (90%) and the fascia iliaca (100%). Needle tip positions not indenting these structures were associated with OIP of less than 15 psi (100%).

A Novel Modified Retrocrural Approach for Celiac Plexus Block: The Single-Needle Retroaortic Technique.

For patients with pain from upper abdominal malignancies, celiac plexus neurolysis can provide an effective means of pain control. However, there are instances when traditionally described percutaneous approaches may not be technically feasible. We describe here the successful use of a novel single-needle retroaortic approach as an alternative approach to celiac plexus neurolysis.We present 4 cases of patients with pain from upper abdominal malignancies in whom we performed celiac plexus neurolysis using a novel single-needle retroaortic approach. All 4 patients had significant pain relief and no significant adverse effects from the retroaortic approach.

Pharmacological treatment and regional anesthesia techniques for pain management after completion of both conservative and surgical treatment of endometriosis and pelvic adhesions in women with chronic pelvic pain as a mandated treatment strategy.

INTRODUCTION: Chronic pelvic pain syndrome occurs in 4-14% of women. Pain pathomechanism in this syndrome is complex, as it is common to observe the features of nociceptive, inflammatory, neuropathic and psychogenic pain. The common findings in women with pelvic pain are endometriosis and pelvic adhesions. OBJECTIVE: Aim of the study was to test the effectiveness of pharmacological treatment and regional anesthesia techniques for pain control as the next step of treatment after the lack of clinical results of surgical and pharmacological methods normally used in the management of endometriosis and pelvic adhesions. MATERIALS AND METHOD: 18 women were treated between January 2010 - October 2013 in the Pain Clinic of the Department of Anaesthesiology and Intensive Care at the Centre for Postgraduate Education in Warsaw due to chronic pelvic pain syndrome related to either endometriosis or pelvic adhesions. During the previous step of management, both conservative and surgical treatments were completed without achieving satisfactory results. Initial constant pain severity was 3-9 points on the Numeric Rating Scale, while the reported paroxysmal pain level was 7-10. The pharmacological treatment implemented was based on oral gabapentinoids and antidepressants, aided by neurolytic block of ganglion of Walther, pudendal nerve blocks and topical treatment (5% lidocaine, 10% amitriptyline, 10% gabapentin). RESULTS: In 17 women, a significant reduction of both constant and paroxysmal pain was achieved, of which complete and permanent cessation of pain occurred in 6 cases. One patient experienced no improvement in the severity of her symptoms. CONCLUSIONS: The combination of pain management with pharmacological treatment, pudendal nerve blocks, neurolysis of ganglion impar (Walther) and topical preparations in cases of chronic pelvic pain syndrome seems to be adequate medical conduct after failed or otherwise ineffective causative therapy.

Established EUS-guided therapeutic interventions.

Over the three last decades, endosonography ultrasound (EUS) has evolved from a diagnostic tool to an interventional modality through cumulative advances in experience, knowledge, equipment, and devices. EUS-guided therapeutic procedures appear feasible and safe when performed in highly-experienced centers. This review covers the technical aspects, indications, and results of the most commonly performed procedures. Celiac plexus neurolysis and collection drainages are now well-established techniques and considered to be first-line treatments. Biliary and pancreatic EUS-guided drainages are, conversely, more challenging, and there is currently insufficient clinical evidence documenting their superiority over established practice. Well-designed prospective trials are thus needed in order to accurately assess this modality's risks and long-term outcomes compared to radiological or surgical techniques.

No correlation between minimal electrical charge at the tip of the stimulating catheter and the efficacy of the peripheral nerve block catheter for brachial plexus block: a prospective blinded cohort study.

BACKGROUND: Stimulating catheters offer the possibility of delivering an electrical charge via the tip of the catheter. This may be advantageous as it allows verifying if the catheter tip is in close proximity to the target nerve, thereby increasing catheter performance. This prospective blinded cohort study was designed to investigate whether there is a correlation between the minimal electrical charge at the tip of the stimulating catheter, and the efficacy of the peripheral nerve block (PNB) catheter as determined by 24 h postoperative morphine consumption. METHODS: Forty adult patients with ASA physical health classification I-III scheduled for upper extremity surgery under combined continuous interscalene block and general anesthesia were studied. Six patients were excluded from analysis.After inserting a stimulating catheter as if it were a non-stimulating catheter for 2-5 cm through the needle, the minimal electrical charge necessary to obtain an appropriate motor response was determined. A loading dose of 20 mL ropivacaine 0.75% ropivacaine was then administered, and postoperative analgesia was provided by a continuous infusion of ropivacaine 0.2% 8 mL.h-1 via the brachial plexus catheter, and an intravenous morphine patient-controlled analgesia (PCA) device.Main outcome measures include the minimal electrical charge (MEC) at the tip of the stimulating catheter necessary to elicit an appropriate motor response, and the efficacy of the PNB catheter as determined by 24 h postoperative PCA morphine consumption. RESULTS: Mean (SD) [range] MEC at the tip of the stimulating catheter was 589 (1414) [30 - 5000] nC. Mean (SD) [range] 24 h morphine consumption was 8.9 (9.9) [0-29] mg. The correlation between the MEC and 24 h postoperative morphine consumption was Spearman's Rho rs = -0.26, 95% CI -0.56 to 0.09. CONCLUSION: We conclude that there is no proportional relation between MEC at the tip of the blindly inserted stimulating catheter and 24 h postoperative morphine consumption. TRIAL REGISTRATION: Trialregister.nl identifier: NTR2328.

[Treatment of a patient with refractory cardiac arrhythmias using stellate ganglion block. Access by the classical and ultrasound-guided approach]. / Tratamiento de las arritmias cardíacas refractarias mediante bloqueo del ganglio estrellado en un paciente. Acceso por técnica clásica y ecodirigida.

Stellate ganglion block is a technique that is often used by anesthesiologists for the treatment of complex regional pain syndromes of the upper extremity. This technique interrupts cardiac sympathetic innervation and has been proposed as treatment for refractory arrhythmias. We present the case of a patient with arrhythmias that were refractory to pharmacological treatment, and were finally treated by continuous stellate ganglion block. Left stellate ganglion is a lynchpin of cardiac arrhythmias due to being a structure where the majority of postganglion sympathetic fibers responsible for preferentially innervating the atriventricular node, bundle of His and ventricular mass are originated, fundamentals in the origin and maintenance of ventricular arrhythmias.

Serum free ropivacaine concentrations among patients receiving continuous peripheral nerve block catheters: is it safe for long-term infusions?

BACKGROUND: Ropivacaine is a long-acting local anesthetic used for continuous peripheral nerve catheter infusions. Catheters may remain in situ for prolonged time periods. In the present study, patients were enrolled to receive continuous peripheral nerve catheters with measurement of free serum ropivacaine concentrations. METHODS: Peripheral nerve catheters were placed for postoperative pain management in trauma patients and infused with ropivacaine 0.2% or bolused with 0.5%. Blood samples were obtained from each subject on days 0 (preinfusion), 3, 5, 7, 10, and every third day until catheter removal. Serum free ropivacaine concentrations were measured via high-performance liquid chromatography and were compared using the Wilcoxon signed rank test. RESULTS: One hundred thirty-three blood samples were analyzed in 35 patients; all serum free ropivacaine concentrations after infusion initiation (99 samples from 35 subjects) were below 0.34 mg/L (previously determined toxic threshold). The highest concentration achieved in a blood sample was 0.19 mg/L; all other values were <0.09 mg/L. The total amount of drug received during the study ranged from 1146 to 22,320 mg (median of 3722 mg). Catheters remained in situ for a median of 7 days (range: 3-23). From day 0 to 3 (preinfusion), 77% of the study participants had an increase in the serum free-fraction ropivacaine concentrations. The median concentration on day 3 was 0.025 mg/L (95% upper confidence limit for mean: 0.05, range: <0.01-0.19); P < 0.001 compared with preinfusion levels). From day 3 to 5, 68% of the participants had a decrease in the serum free ropivacaine concentrations (median level 0.016 mg/L [95% upper confidence limit for mean: 0.021] P = 0.007 for day 5 compared with day 3). CONCLUSIONS: In this study, free serum ropivacaine concentrations remained well below toxic values despite large amounts of drug administration in combat-wounded patients. The administration of continuous ropivacaine infusions over prolonged time periods, coupled with multiple drug boluses, did not produce toxic or near-toxic serum concentrations.

Broken anesthetic needle in the pterygomandibular space. Four case reports.

Needle breakage in the oral cavity during local anesthesia is a rare but possible complication. In the majority of cases this happens in the pterygomandibular space during an inferior alveolar nerve block and the causes are multifactorial. The treatment recommended is localization and removal of the extraneous body, as soon as possible, in a surgical setting so as to prevent possible migration of the metal fragment with consequent possible lesions to the surrounding anatomical structures. We present four case studies that have occurred since 2011.

Lateral injection using a Whitacre needle with patients in the lateral decubitus position maintained for a prolonged time period produces symmetric sensory block.

BACKGROUND: The directional flow of injection through a Whitacre needle can be used to modify the level of sensory blockade. We hypothesized that injection of hyperbaric local anesthetic through a Whitacre needle with the bevel oriented laterally can produce a more symmetric sensory block. METHODS: Patients scheduled for lower limb surgery under spinal anesthesia with the patient in lateral decubitus position were randomized to receive 10 mg, 0.5% hyperbaric bupivacaine with the Whitacre needle orifice in 1 of 2 orientations, cephalad and lateral. The patient's position was maintained for 15 min after the injection, and sensory blocks were recorded. The primary outcome was the sensory levels between the dependent and nondependent side. The Wilcoxon-Mann-Whitney U-test odds was used to compare unpaired nonparametric data. For the paired samples, 95% confidence intervals (CI) of differences between group medians were calculated using the Hodges-Lehman estimator for the median difference in number of blocked segments. RESULTS: There was no significant difference in block level between dependent and nondependent sides in the lateral group. The Hodges-Lehmann point estimator was 0.5% and 95% CI was 0-2.5, suggesting a more symmetric sensory block in patients in the lateral decubitus position maintained for a sufficient period of time. A significantly lower level of blockade was noticed on the nondependent side compared to the dependent side in the cephalad group. The Hodges-Lehmann point estimator was 2.5 segments and 95% CI was 0.5-5. CONCLUSIONS: Injection of 10 mg of 0.5% hyperbaric bupivacaine with the bevel of the Whitacre needle oriented laterally produces more symmetric sensory levels of blockade between the dependent and nondependent sides.

Attempted reversible sympathetic ganglion block by an implantable neurostimulator.

OBJECTIVE: Primary palmar hyperhidrosis is a pathological condition of excessive perspiration of the hands of unknown aetiology. The only effective treatment for permanent cure is the ablation of the sympathetic ganglia supplying the hands. One of the sequelae is compensatory sweating, namely increased perspiration in other parts of the body. Its mechanism is unknown. In a small proportion of patients, it may attend devastating proportions. It has practically no remedy, and the degree of compensatory hyperhidrosis is unpredictable prior to sympathectomy. The purpose of the present study was to obtain a reversible sympathetic block which may disclose subjects prone to develop severe compensatory hyperhidrosis and unfit for permanent ganglionic ablation. METHODS: In three dogs, an experimental electrode was implanted via a left thoracotomy on the stellate ganglion, connected to a stimulator. The stimulation was activated after recovery. The contralateral ganglion served as control. Effect of the stimulation was assessed by observing the development of Horner's syndrome, which includes the appearance of miosis, ptosis and enophthalmus. Reversal of the sympathetic block was expected when the neurostimulation was discontinued and assessed by the disappearance of these signs. RESULTS: Stimulation produced only a partial effect - an incomplete Horner's syndrome (miosis and sometime ptosis), which was not completely reversible after ceasing the stimulation. CONCLUSIONS: Although neurostimulation achieved a partial sympathetic block, the present method failed to obtain a completely reversible effect. However, these results may indicate that different nervous pathways moderate the various components of the Horner's triad. Concerning the creation of a reversible sympathectomy; other approaches must be sought after.

Ultrasound-guided (needle-in-plane) perineural catheter insertion: the effect of catheter-insertion distance on postoperative analgesia.

BACKGROUND: When using ultrasound guidance to place a perineural catheter for a continuous peripheral nerve block, keeping the needle in plane and nerve in short axis results in a perpendicular needle-to-nerve orientation. Many have opined that when placing a perineural catheter via the needle, the acute angle may result in the catheter bypassing the target nerve when advanced beyond the needle tip. Theoretically, greater catheter tip-to-nerve distances result in less local anesthetic-to-nerve contact during the subsequent perineural infusion, leading to inferior analgesia. Although a potential solution may appear obvious-advancing the catheter tip only to the tip of the needle, leaving the catheter tip at the target nerve-this technique has not been prospectively evaluated. We therefore hypothesized that during needle in-plane ultrasound-guided perineural catheter placement, inserting the catheter a minimum distance (0-1 cm) past the needle tip is associated with improved postoperative analgesia compared with inserting the catheter a more traditional 5 to 6 cm past the needle tip. METHODS: Preoperatively, subjects received a popliteal-sciatic perineural catheter for foot or ankle surgery using ultrasound guidance exclusively. Subjects were randomly assigned to have a single-orifice, flexible catheter inserted either 0 to 1 cm (n = 50) or 5 to 6 cm (n = 50) past the needle tip. All subjects received a single-injection mepivacaine (40 mL of 1.5% with epinephrine) nerve block via the needle, followed by catheter insertion and a ropivacaine 0.2% infusion (basal 6 mL/hr, bolus 4 mL, 30-min lockout), through at least the day after surgery. The primary end point was the average surgical pain as measured with a 0- to 10-point numeric rating scale the day after surgery. Secondary end points included time for catheter insertion, incidence of catheter dislodgement, maximum ("worst") pain scores, opioid requirements, fluid leakage at the catheter site, and the subjective degree of an insensate extremity. RESULTS: Average pain scores the day after surgery for subjects of the 0- to 1-cm group were a median of 2.5 (interquartile range, 0.0-5.0), compared with 2.0 (interquartile range, 0.0-4.0) for subjects of the 5- to 6-cm group (P = 0.42). Similarly, among the secondary end points, no statistically significant differences were found between the 2 treatment groups. There was a trend of more catheter dislodgements in the minimum-insertion group (5 vs 1; P = 0.20). CONCLUSIONS: This study did not find evidence to support the hypothesis that, for popliteal-sciatic perineural catheters placed using ultrasound guidance and a needle-in-plane technique, inserting the catheter a minimum distance (0-1 cm) past the needle tip improves (or worsens) postoperative analgesia compared with inserting the catheter a more traditional distance (5-6 cm). Caution is warranted if extrapolating these results to other catheter designs, ultrasound approaches, or anatomic insertion sites.

Needle to nerve proximity: what do the animal studies tell us?

Recent animal studies have provided insight and understanding, as well as promising clinical tools, to help identify needle-to-nerve contact and potentially hazardous intraneural injection. This narrative review describes and summarizes the contemporary animal studies primarily relating to indicators of needle-to-nerve contact and intraneural injection. Resultant nerve injury, whenever sought, is discussed.