Needle Reinsertions Research Articles

In Vivo Feasibility Study: Evaluating Autonomous Data-Driven Robotic Needle Trajectory Correction in MRI-Guided Transperineal Procedures.

This study addresses the targeting challenges in MRI-guided transperineal needle placement for prostate cancer (PCa) diagnosis and treatment, a procedure where accuracy is crucial for effective outcomes. We introduce a parameter-agnostic trajectory correction approach incorporating a data-driven closed-loop strategy by radial displacement and an FBG-based shape sensing to enable autonomous needle steering. In an animal study designed to emulate clinical complexity and assess MRI compatibility through a PCa mock biopsy procedure, our approach demonstrated a significant improvement in targeting accuracy (p<0.05), with mean target error of only 2.2 ± 1.9 mm on first insertion attempts, without needle reinsertions. To the best of our knowledge, this work represents the first in vivo evaluation of robotic needle steering with FBG-sensor feedback, marking a significant step towards its clinical translation.

A Modified Suture Technique to Improve Scar Appearance in Wounds Under High Tension.

The purpose of this study was to introduce a modified suture technique and to compare its effects on skin scar formation with 2 traditional suture methods: simple interrupted suture (SIS) and vertical mattress suture (VMS). Three groups of healthy adult female Sprague-Dawley rats were selected (6 replicates in each group), and the full-thickness skin of 5 cm × 0.2 cm was cut off on the back of the rats after anesthesia. The wounds were then sutured using 1 of the 3 methods for each group: SIS, VMS, and a newly introduced modified vertical mattress suture (M-VMS) technique with the needle reinsertion at the exit point. A traction device was installed on the back of the rats to achieve high tension wounds. The tensile distance was increased by 1 mm every day for 20 days. After 20 days of healing, the hematoxylin-eosin staining method was used for observation of scar morphology. The collagen production rate was measured by Masson staining, and the type I collagen and type III collagen were detected by the immunofluorescence method. Immunohistochemical staining was used to detect the expression of myofibroblast marker α-smooth muscle actin, and real-time quantitative polymerase chain reaction and Western blot techniques were used to detect the expressions of transforming growth factors TGFβ1, TGFβ2, and TGFβ3 to understand the mechanisms of scar formation. Results showed that the quantity and density of collagen fibers were both lower in the M-VMS group than in the other 2 groups. Immunofluorescence results showed that type I collagen was significantly lower, whereas type III collagen was significantly higher in the M-VMS group than in the other 2 groups. The expressions of α-smooth muscle actin and TGFβ1 both were lower in the M-VMS group than in the other 2 groups. The expression of TGFβ2 and TGFβ3 had no obvious difference among the 3 groups. For wounds under high tension, compared with SIS and VMS methods, the M-VMS technique we proposed can reduce scar formation due to the reduction of collagen formation, myofibroblast expression, and TGFβ1 expression.

Intrathecal Catheter Use After Accidental Dural Puncture in Obstetric Patients: Literature Review and Clinical Management Recommendations

(Anaesthesia. 2021;76:1111–1121) In the event of an accidental dural puncture (ADP) the epidural can be either resited or a catheter can be inserted intrathecally for use as a continuous spinal (intrathecal, IT) catheter, thus eliminating the need for needle reinsertion. An IT catheter may also permit swift labor analgesia and facilitate cesarean delivery anesthesia. However, clinical management of IT catheters for labor analgesia is not without risk of adverse effects. Accordingly, this review evaluates recent studies on IT catheters for parturients, including the management and quality of analgesia and anesthesia, the effect on postdural puncture headache (PDPH) risk, obstacles to use, and deficiencies in our current understanding.

A comparison of first-attempt cannulation success of peripheral venous catheter systems with and without wings and injection ports in surgical patients\u2014a randomized trial

BackgroundA peripheral venous catheter (PVC) is the most widely used device for obtaining vascular access, allowing the administration of fluids and medication. Up to 25% of adult patients, and 50% of pediatric patients experience a first-attempt cannulation failure. In addition to patient and clinician characteristics, device features might affect the handling and success rates. The objective of the study was to compare the first-attempt cannulation success rate between PVCs with wings and a port access (Vasofix® Safety, B. Braun, abbreviated hereon in as VS) with those without (Introcan® Safety, B. Braun, abbreviated hereon in as IS) in an anesthesiological cohort.MethodsAn open label, multi-center, randomized trial was performed. First-attempt cannulation success rates were examined, along with relevant patient, clinician, and device characteristics with univariate and multivariate analyses. Information on handling and adherence to use instructions was gathered, and available catheters were assessed for damage.ResultsTwo thousand three hundred four patients were included in the intention to treat analysis. First-attempt success rate was significantly higher with winged and ported catheters (VS) than with the non-winged, non-ported design (IS) (87.5% with VS vs. 78.2% with IS; PChi < .001). Operators rated the handling of VS as superior (rating of “good” or “very good: 86.1% VS vs. 20.8% IS, PChi < .001). Reinsertion of the needle into the catheter after partial withdrawal—prior or during the catheterization attempt—was associated with an increased risk of cannulation failure (7.909, CI 5.989–10.443, P < .001 and 23.023, CI 10.372–51.105, P < .001, respectively) and a twofold risk of catheter damage (OR 1.999, CI 1.347–2.967, P = .001).ConclusionsFirst-attempt cannulation success of peripheral, ported, winged catheters was higher compared to non-ported, non-winged devices. The handling of the winged and ported design was better rated by the clinicians. Needle reinsertions are related to an increase in rates of catheter damage and cannulation failure.Trial registrationClinicalTrials.gov, Identifier: NCT02213965, Date: 12/08/2014.

Optically Tracked Needle for Ultrasound-Guided Percutaneous Nephrolithotomy Puncture: A Preliminary Report.

Background and Aim: Precise needle puncture of the renal collecting system is an essential step for effective percutaneous nephrolithotomy (PCNL). The use of ultrasound for puncture is receiving increased attention. Ultrasound has recognized limitations related to poor observation of the needle tip. We aimed to assess whether an affordable open-source computerized needle navigation training system, using optically tracked ultrasonography, could improve performance of simulated PCNL puncture by urologic trainees, compared with conventional free hand manual sonographic puncture. Materials and Methods: This study describes a PCNL navigation system that can be recreated with any standard ultrasound machine using relatively inexpensive components. The system allows the needle tip to be precisely appreciated in the ultrasound image, its trajectory planned, and the appreciation of needle tip to target calix proximity sound effect. Eight participants (six trainees and two qualified urologists) assessed the PCNL training model. Alternating starting with freehand (control) and tracked needle (experimental) punctures were performed on a phantom kidney. Total procedure and the number of reinsertions required were recorded. Results: The mean time for freehand puncture was 89 seconds (range 13-173), whereas that of the optically tracked needle was 36 seconds (range 12-72). Thus, puncture time was significantly reduced by an average of 53 seconds (p = 0.045) in the experimental arm. The mean number of needle reinsertions was 3.3 with freehand compared with 1.3 in the optically tracked puncture (p = 0.005). The mean square root error of the optical tracking system was 1.8 mm (four calibrations averaged). Conclusion: This study demonstrates that affordable hardware and open-source software can be used to construct an optically tracked ultrasound navigation system for PCNL training. Statistically significant reduced puncture time and number of passes required for effective puncture are demonstrated. We feel that computerized needle tracking during PCNL puncture deserves further evaluation in a training and, potentially, in a clinical setting.

Computed Tomography–Guided Optimization of Needle Insertion for Combined Intracavitary/Interstitial Brachytherapy With Utrecht Applicator in Locally Advanced Cervical Cancer

PurposeThere are no international guidelines for optimal needle insertion during interstitial intracavitary brachytherapy (IS-ICBT) for cervical cancer. We aimed to investigate the clinical feasibility and added value of computed tomography (CT) guidance to optimize needle insertion in IS-ICBT using the Utrecht applicator and to evaluate needle shifts. Methods and MaterialsWe enrolled 24 patients who were treated with interstitial-brachytherapy. Two CT scans each were performed for every patient: (1) after applicator insertion without needles (CTpreneedle) and (2) after needle insertion (CTpostneedle). In addition to magnetic resonance imaging after external-beam radiation therapy, CTpreneedle was used to determine optimal needle locations and insertion lengths based on applicator and organs at risk positioning on the day of treatment; CTpostneedle was used for IS-ICBT planning. The needle-channel axis was used as a reference to determine needle-shift evolution. ResultsA total of 266 interstitial needles were inserted in 76 of 93 BT fractions with high intra- and interpatient variations in the number of inserted needles. Based on CTpreneedle findings, needle insertion was avoided in 9, 4, 2, and 2 patients at the first, second, third, and fourth fractions, respectively. The unloaded needle frequency was 4%. Average needle contribution to total dwell time was 37.2% ± 19.2%. Shifting was observed in 68% of the needles (mean shift 2.0 ± 2.3 mm), mostly in the posterior direction, and in needles with a larger insertion length. Needle reinsertion was not needed in any patient. No complication due to needle insertion was observed, except for minor vaginal bleeding in 1 patient after needle removal. ConclusionsThe adaptive CT-guided IS-ICBT application was feasible and resulted in fewer unloaded needle insertions or complications and more efficient use with higher needle contribution to the treatment. Needle shift was frequent but did not require needle reinsertion with the proposed method.

Comparison of Ultrasound-Guided Direct versus Ultrasound-Guided Dart Technique of Radial Artery Cannulation: A Randomized Control Study.

Background:Three different types of cannulation method for radial artery are Direct technique, Seldinger technique, and modified Seldinger technique (Dart). Their comparative efficacy has been studied using palpatory method but not with ultrasound guidance.Aims:We compared the efficacy of ultrasound-guided Direct and ultrasound-guided Dart technique of arterial cannulation.Settings and Design:One hundred and sixty patients posted for elective surgeries were included in prospective randomized control, single-blind study in a tertiary care center.Materials and Methods:The study comprised of two groups: Direct method (n = 80) and Dart method (n = 80), which were compared for the rate of successful cannulation within 5 min. The secondary objectives were time for successful cannulation, number of attempts, and rate of complications (hematoma, posterior wall puncture, and needle reinsertion) between two groups.Statistical Analysis:The group comparison for continuously distributed data was compared using the independent sample t-test. The Chi-square test was used for the group comparison of categorical data. Binary logistic regression was conducted to ascertain significant predictors for successful cannulation in 5 min.Results:Cannulation success rate was similar in both Direct (57.5%) and Dart (55%) groups. There was no significant difference in time for successful cannulation, number of attempts, number of needle redirection, and posterior wall puncture. However, the incidence of hematoma (Direct 22.5% [18]; Dart 8% [10]) was significant. There was better success rate of cannulation (n = 90) in patients with normal pulse and bigger radial artery lumen.Conclusion:There was no significant difference between Dart and Direct technique with the use of ultrasound guidance.

An out-of-plane approach for pericapsular nerve group block: A case series

Pericapsular nerve group (PENG) block is a new ultrasound (US)-guided nerve block, which has been used successfully to manage fractured hip pain. As an alternative approach to give PENG block, we have investigated the out-of-plane (OOP) approach instead of the in-plane approach, which is conventionally used. Ten patients aged between 55 and 72 years scheduled for hip surgery under spinal anesthesia were given US-guided PENG block by the OOP approach. The success of block was assessed by reduction in rest pain and pain during 15° straight leg raising (SLR) (passive SLR test) on a numeric rating Score (NRS) after 30 min of block. Ease of positioning score was also assessed during spinal anesthesia. The procedural difficulty was assessed by the number of attempts (needle re-insertion at the skin). All patients had successful blocks and showed a significant pain relief in resting pain (6.5 ± 1.3 vs. 3.8 ± 0.78) as well as pain during 15° SLR (8.5 ± 1.1 vs. 5.1 ± 0.73). All blocks required single needle entry; however, in three patients, medial redirection of the needle was required before final positioning. No complication was observed in any case. PENG block provides effective analgesia during positioning for spinal anesthesia in patients with hip fracture. OOP approach can easily be used as an alternative to conventional in-plane technique.

Quality Improvement of Blood Drawing Through Targeted Training Using an Operation Support System.

In order to reduce the rate of needle re-insertion (hereafter, retaking) during a blood drawing operation, we proposed a method for training blood drawing staff, based on data analysis. The method is composed of three steps: (1) analysis of collected data for selecting staff to be trained intensively, (2) training, and (3) assessment of training results. We obtained the result that the retaking rate was reduced for the trained staff.

Differentiating False Loss of Resistance from True Loss of Resistance While Performing the Epidural Block with the CompuFlo® Epidural Instrument.

Background The occurrence of false losses of resistance may be one of the reasons for inadequate or failed epidural block. A CompuFlo® epidural instrument has been introduced to measure the pressure of human tissues in real time at the orifice of a needle and has been used as a tool to identify the epidural space. The aim of this study was to investigate the sensitivity and the specificity of the ability of CompuFlo® to differentiate the false loss of resistance from the true loss of resistance encountered during the epidural space identification procedure. Method We performed epidural block with the CompuFlo® epidural instrument in 120 healthy women who requested labor epidural analgesia. The epidural needle was considered to have reached the epidural space when an increase in pressure (accompanied by an increase in the pitch of the audible tone) was followed by a sudden and sustained drop in pressure for more than 5 seconds accompanied by a sudden decrease in the pitch of the audible tone, resulting in the formation of a low and stable pressure plateau. We evaluate the sensitivity, specificity, and positive and negative predictive values of the ability of CompuFlo® recordings to correctly identify the true LOR from the false LOR. Results The drop in pressure associated with the epidural space identification was significantly greater than that recorded after the false loss of resistance (73% vs 33%) (P=0.000001). The sensitivity was 0.83, and the AUC was 0.82. Discussion We have confirmed the ability of CompuFlo® to differentiate the false loss of resistance from the true loss of resistance and established its specificity and sensitivity. Conclusion An easier identification of dubious losses of resistance during the epidural procedure is essential to reduce the number of epidural attempts and/or needle reinsertions with the potential of a reduced risk of accidental dural puncture especially in difficult cases or when the procedure is performed by trainees.

Experimental validation of the CompuFlo® epidural controlled system to identify the epidural space and its clinical use in difficult obstetric cases

BackgroundThis prospective study was designed to validate the CompuFlo® device and to assess its use in difficult epidural placement. MethodsIn the first part of the study, 30 parturients requesting labor epidural analgesia were recruited. The block was performed by an expert anesthesiologist, with the Tuohy needle connected to the CompuFlo® device to evaluate the agreement between the anesthesiologist’s reported sensation and the variation of pressure recorded by the CompuFlo®. In the second part of the study, 56 consecutive parturients, for whom at least two complete needle reinsertions were made by trainees during epidural placement for labor analgesia, were enrolled. CompuFlo® was used as a rescue tool for the subsequent attempt. ResultsIn all cases epidural analgesia was successful and no complications were noted. There was a good correlation between the operator’s feelings and the delta of pressure recorded by the CompuFlo®, for both identification of the ligamentum flavum and of the epidural space (Rho = 0.79; tau = 0.67). In the second part of the study, all the difficult blocks performed with the CompuFlo® were successful after a single attempt. The pressure curves of false loss-of-resistance were significantly different from the true loss-of-resistance (P <0.0001) DiscussionCompuFlo® was validated as a tool to identify the epidural space. It may also assist trainees in successful epidural placement in difficult cases.

Ultrasound-Guided Spine Anesthesia: Feasibility Study of a Guidance System

Spinal needle injections are guided by fluoroscopy or palpation, resulting in radiation exposure and/or multiple needle re-insertions. Consequently, guiding these procedures with live ultrasound has become more popular, but images are still challenging to interpret. We introduce a guidance system based on augmentation of ultrasound images with a patient-specific 3-D surface model of the lumbar spine. We assessed the feasibility of the system in a study on 12 patients. The system could accurately provide augmentations of the epidural space and the facet joint for all subjects. Following conventional, fluoroscopy-guided needle placement, augmentation accuracy was determined according to the electromagnetically tracked final position of the needle. In 9 of 12 cases, the accuracy was considered sufficient for successfully delivering anesthesia. The unsuccessful cases can be attributed to errors in the electromagnetic tracking reference, which can be avoided by a setup reducing the influence of the metal C-arm.

Joint registration of ultrasound, CT and a shape+pose statistical model of the lumbar spine for guiding anesthesia.

Facet joint injections and epidural needle insertions are widely used for spine anesthesia. Accurate needle placement is important for effective therapy delivery and avoiding complications arising from damage of soft tissue and nerves. Needle guidance is usually performed by fluoroscopy or palpation, resulting in radiation exposure and multiple needle re-insertions. Several ultrasound (US)-based approaches have been proposed but have not found wide acceptance in clinical routine. This is mainly due to difficulties in interpretation of the complex spinal anatomy in US, which leads to clinicians' lack of confidence in relying only on information derived from US for needle guidance. We introduce a multimodal joint registration technique that takes advantage of easy-to-interpret preprocedure computed topography (CT) scans of the lumbar spine to concurrently register a shape+pose model to the intraprocedure 3D US. Common shape coefficients are assumed between two modalities, while pose coefficients are specific to each modality. The joint method was evaluated on patient data consisting of ten pairs of US and CT scans of the lumbar spine. It was successfully applied in all cases and yielded an RMS shape error of 2.1mm compared to the CT ground truth. The joint registration technique was compared to a previously proposed method of statistical model to US registrationRasoulian etal. (Information processing in computer-assisted interventions. Springer, Berlin, pp 51-60, 2013). The joint framework improved registration accuracy to US in 7 out of 17 visible vertebrae, belonging to four patients. In the remaining cases, the two methods were equally accurate. The joint registration allows visualization and augmentation of important anatomy in both the US and CT domain and improves the registration accuracy in both modalities. Observing the patient-specific model in the CT domain allows the clinicians to assess the local registration accuracy qualitatively, which is likely to increase their confidence in using the US model for deriving needle guidance decisions.

Prospective evaluation of point-of-care ultrasound for pre-procedure identification of landmarks versus traditional palpation for lumbar puncture.

The objective of this study is to determine if point-of-care ultrasound (POCUS) pre-procedure identification of landmarks can decrease failure rate, reduce procedural time, and decrease the number of needle redirections and reinsertions when performing a lumbar puncture (LP). This was a prospective, randomized controlled trial comparing POCUS pre-procedure identification of landmarks versus traditional palpation for LP in a cohort of patients in the emergency department and intensive care unit. A total of 158 patients were enrolled. No significant difference was found in time to completion, needle re-direction, or needle re-insertion when using POCUS when compared to the traditional method of palpation. Consistent with findings of previous studies, our data indicate that there was no observed benefit of using POCUS to identify pre-procedure landmarks when performing an LP.

Just another acute myocardial infarction?

Introduction: Acute Myocardial Infarction in young people can be challenging to manage, as the underlying pathology can be different to the conventional atherosclerosis with plaque rupture. Case Description: A 36-year old man presented with sudden onset central chest pain and diaphoresis. Apart from smoking he did not have other risk factors for coronary disease. One week prior he underwent elective hip replacement and had been treated with prophylactic clexane to prevent venous thromboembolism. He was on no other regular prescribed or recreational medication. The EKG showed changes consistent with an inferoposterior STEMI. Emergency angiography revealed an occluded left circumflex with heavy thrombus burden. Following prolific thrombus aspiration TIMI 3 flow was restored, the patient became pain-free and the EKG started to normalize. The circumflex artery appeared smooth with no evidence of plaque rupture. An embolic cause was suspected and given that the patient was pain-free he was managed medically with aspirin, clopidogrel, beta-blockers and ace inhibitors and planned to re-study him in 48 hours. Bilateral lower limb ultrasound and CT pulmonary angiography did not reveal deep vein thrombosis or pulmonary embolus. Transthoracic bubble echocardiography revealed right to left shunting on valsava manoevre consistent with a PFO, also visualized on 3D transesophageal echocardiography. At coronary angiography 48 hours later, the circumflex coronary remained smooth with no evidence of further obstruction thus no stent insertion was needed. Histology of the thrombus confirmed a platelet thrombus forming on a foreign plastic material that was likely part of an intravenous cannula. It is likely that the plastic entered the circumflex at the time of orthopedic surgery and acted as nidus for thrombus formation. He has since underwent successful percutaneous closure of his PFO. Discussion: Paradoxical coronary embolism is a rare but recognized clinical entity. It requires a high index of suspicion for diagnosis and should always be considered in young patients presenting with acute myocardial infarction and no obvious coronary lesion as its correct identification can guide appropriate management and preclude inappropriate stent implantation. Implications to clinical practice: 1. Always beware of paradoxical embolism in young patients presenting with a STEMI, particularly if coronary arteries appear smooth. 2. Always be meticulous when inserting intravenous cannulae. Avoid needle re-insertion as this increases the risk of the cannula breaking off and embolizing with adverse outcomes as exemplified in our case.

Advanced Needle Coatings for Improved Lumbar Drain Procedure

Advanced Needle Coatings for Improved Lumbar Drain Procedure

Une nouvelle technique de ponction de l’articulation radio-carpienne

Objective Previous techniques for radiocarpal joint injection introduce the needle directly between the navicular and the radius. We propose here a new technique using the same puncture site for midcarpal and radiocarpal arthrograms without need for needle reinsertion. Materials and methods A prospective study of 85 radiocarpal injections for arthrography was performed. For each case, the needle tip was positioned at the medial part of the proximal scaphoid, under the mid carpal joint, and directed obliquely with a 45̊ angle to the joint space to reach the radiocarpal joint. In case of midcarpal and radiocarpal arthrograms, a single puncture site was always used. Results Injection of the radiocarpal joint was successful in 82 of the 82 cases. Conclusion The method proposed here is simple, efficient and uses a single site of puncture in cases requiring bi-compartmental injections.

Development of multi-channel radiofrequency (RF) interstitial hyperthermia system compatible with high-dose rate iridium-192 brachytherapy

9694 Background: We have developed a multi-channel RF interstitial hyperthermia system compatible with the high-dose rate Iridium-192 remote after loading system (Ir-192 RALS). The purpose of this presentation is to evaluate the heating characteristics of the system. Methods: The system is composed of eight channel RF signal generators, which can be controlled individually. Each RF generator consists of two types of electrodes: 1) an internal electrode made of stainless steel, which is originally an Ir-192 RALS applicator; and 2) a shared rectangular external electrode made of copper plate. For the computer simulation, we used simulation software (e-m CAD system, MAFIA ver. 3.20, CST, Germany) to calculate RF field distribution, magnetic field distribution and the specific absorption rate (SAR) distribution, in an arrangement using 4 needles inserted in a square-like formation, 2cm in distance from one another. For the experiments using the agar phantom, we generated a 5W 13.56 MHz RF signal for 5 minutes for 4 electrodes in the same square fashion. Results: The results from the computer simulation showed that SAR distribution outside each electrode was elevated, but the area inside the 4 electrodes did not show temperature elevation. The results from the experiments using the agar phantom showed a temperature increase in the center of the area surrounded by the 4 electrodes. Conclusions: Using an independently controlled RF signal, the results from the experiments with the agar phantom showed satisfactory temperature rise. The RF interstitial system we developed can provide greater heating volume compared to using a single internal electrode or multiple electrodes with a single generator. In addition, our system is compatible with the Ir-192 RALS, allowing for less-invasive interstitial hyperthermoradiotherapy by eliminating the trauma of needle re-insertion. No significant financial relationships to disclose.

Development of multi-channel radiofrequency (RF) interstitial hyperthermia system compatible with high-dose rate iridium-192 brachytherapy

9694 Background: We have developed a multi-channel RF interstitial hyperthermia system compatible with the high-dose rate Iridium-192 remote after loading system (Ir-192 RALS). The purpose of this presentation is to evaluate the heating characteristics of the system. Methods: The system is composed of eight channel RF signal generators, which can be controlled individually. Each RF generator consists of two types of electrodes: 1) an internal electrode made of stainless steel, which is originally an Ir-192 RALS applicator; and 2) a shared rectangular external electrode made of copper plate. For the computer simulation, we used simulation software (e-m CAD system, MAFIA ver. 3.20, CST, Germany) to calculate RF field distribution, magnetic field distribution and the specific absorption rate (SAR) distribution, in an arrangement using 4 needles inserted in a square-like formation, 2cm in distance from one another. For the experiments using the agar phantom, we generated a 5W 13.56 MHz RF signal for 5 minutes for 4 electrodes in the same square fashion. Results: The results from the computer simulation showed that SAR distribution outside each electrode was elevated, but the area inside the 4 electrodes did not show temperature elevation. The results from the experiments using the agar phantom showed a temperature increase in the center of the area surrounded by the 4 electrodes. Conclusions: Using an independently controlled RF signal, the results from the experiments with the agar phantom showed satisfactory temperature rise. The RF interstitial system we developed can provide greater heating volume compared to using a single internal electrode or multiple electrodes with a single generator. In addition, our system is compatible with the Ir-192 RALS, allowing for less-invasive interstitial hyperthermoradiotherapy by eliminating the trauma of needle re-insertion. No significant financial relationships to disclose.

Confirmation of caudal needle placement using nerve stimulation.

The study was designed to examine a new method of confirming proper caudal needle placement using nerve stimulation. Thirty-two pediatric patients were studied. A 22-gauge insulated needle was inserted into the caudal canal via the sacral notch until a "pop" was felt. The needle placement was classified as correct or incorrect depending upon the presence or absence of anal sphincter contraction (S2-S4) to electrical simulation (1 to 10 mA). Three patients were excluded, two because they inadvertently received neuromuscular blockers and one because the patient's anatomy precluded any attempt at a caudal block. The sensitivity and specificity of the test were both 100% in predicting clinical outcomes of the caudal block. Six patients had a negative stimulation test after the first attempt to place the needle. Four of these went on to receive a second attempt of needle insertion after a subcutaneous bulge or resistance to local anesthetic injection were observed. Following needle reinsertion, positive stimulation tests were elicited. These patients received the local anesthetic injection with ease and had good analgesia postoperatively. No attempt was made to reinsert the needle in the remaining two patients with a negative stimulation test, as they did not show subcutaneous bulge or resistance upon injection. These patients had poor analgesia postoperatively. The positive predictive value of the test was greater than the presence of a "pop" alone (P < 0.05) but not significantly different (P = 0.492) over the presence of "pop" and easy injection. This test may be used as a teaching and adjuvant tool in performing caudal block.