Confirmation of epidural catheter placement using nerve stimulation

Purpose

To examine the reliability of low current electrical epidural stimulation to confirm epidural catheter placement.

Methods

Forty patients with epidural catheters (19G Arrow Flextip plus) already in place for post-operative pain management were studied. An adapter (Arrow-Johans ECG Adapter) was attached to the connector of the epidural catheter. The epidural catheter and adapter were filled with normal saline. The cathode lead of the nerve stimulator was attached to the metal hub of the adapter. Catheter placement was judged to be correct or incorrect, depending upon the presence or absence of truncal or limb movement to 1 Hz stimulation (1–10 mA). A standard test dose (3 ml lidocaine 1.5% with 1:200,000 epinephrine) was then injected. The efficacy of the epidural morphine was assessed independently.

Results

The sensitivity and specificity of the test was 100% and 91.6% compared with the standard test dose. The positive and negative predictive value was 96% and 100%. In predicting the clinical effect of epidural morphine, the sensitivity and specificity was 96.1% and 76.9%. The positive and negative predictive value was 89% and 90%. The correlation of unilateral or bilateral motor response from the test and sensory response from the lidocaine test with sensitivity and specificity was 91.6% and 53.0%. The predictive value for unilateral response was 61% and for bilateral was 88%.

Conclusion

This study establishes this test as a simple, objective and reliable technique for confirmation of epidural catheter placement.     

Confirmation of direct epidural catheter placement using nerve stimulation in pediatric anesthesia

We evaluated the success rate of using low current electrical stimulation (the Tsui test) to identify and confirm direct epidural catheter placement in a pediatric population. Thirty subjects received a standard anesthetic and administration of the Tsui test on epidural placement. The distribution of myotomal activity was recorded. The intended and actual level of the epidural catheter was compared. Myotomal activity was seen in all patients but one. The median current resulting in myotomal activity was 5.3 mA. The median difference between the intended and actual level as confirmed on radiograph was 1.8 levels. The clinical success rate was 93.9%. The positive predictive value of the Tsui test was 82%; i.e., in 23 of 28 cases, the Tsui test correctly identified the position of the epidural catheter tip within 2 vertebral levels. The test did not offer any added advantage when used in the setting of directly placed epidural catheters in our institution over "blind" methods already used to confirm catheter position when using cutaneous landmarks and test dosing. IMPLICATIONS: A new technique to confirm epidural catheter position uses low current electrical stimulation in pediatric patients. This study evaluated the use of electrical stimulation in 30 pediatric patients for directly placed catheters. Electrical stimulation did not provide any advantage over conventional methods (e.g., cutaneous landmarks) for confirmation of catheter position.     

Ultrasound guidance in caudal epidural needle placement

BACKGROUND: This study was conducted to investigate the feasibility of using ultrasound as an image tool to locate the sacral hiatus accurately for caudal epidural injections. METHODS: Between August 2002 and July 2003, 70 patients (39 male and 31 female patients) with low back pain and sciatica were studied. Soft tissue ultrasonography was performed to locate the sacral hiatus. A 21-gauge caudal epidural needle was inserted and guided by ultrasound to the sacral hiatus and into the caudal epidural space. Proper needle placement was confirmed by fluoroscopy. RESULTS: In all the recruited patients, the sacral hiatus was located accurately by ultrasound, and the caudal epidural needle was guided successfully to the sacral hiatus and into the caudal epidural space. There was 100% accuracy in caudal epidural needle placement into the caudal epidural space under ultrasound guidance as confirmed by contrast dye fluoroscopy. CONCLUSIONS: Ultrasound is radiation free, is easy to use, and can provide real-time images in guiding the caudal epidural needle into the caudal epidural space. Ultrasound may therefore be used as an adjuvant tool in caudal needle placement.     

Inadvertent cervical epidural catheter placement via the caudal route using electrical stimulation

Inadvertent placement of an epidural catheter in the cervical region via the caudal route is described in an infant who underwent revision of a fundoplication. We attempted electrical stimulation (the Tsui test) via the epidural catheter to confirm correct placement and positioning of the catheter tip. In this case, the epidural catheter was inadvertently advanced to the cervical region, resulting in stimulation of the phrenic nerve. These diaphragmatic twitches were misinterpreted as chest wall twitches, and it was incorrectly assumed that the catheter was in the thoracic region. To avoid misinterpretation of the stimulation level, the catheter should be continuously stimulated while it is advanced. We also recommend that the catheter length be estimated before insertion (although doing so did not help in this case) and that the catheter position be radiographically confirmed after surgery.     

Detection of subdural placement of epidural catheter using nerve stimulation

PURPOSE: To report the detection of a subdural catheter placement using nerve stimulation through an epidural catheter. CLINICAL FEATURES: An 85-yr-old gentleman was scheduled for radical cystectomy and creation of an ileal conduit. Combined general anesthesia and regional technqiue was selected. An epidural catheter (19 G Arrow Flextip Plus) was inserted prior to induction of general anesthesia. Intra-operatively, the patient received 5 mg morphine and 10 ml bupivacane 0.5% via the epidural catheter. The patient remained hemodynamically stable throughout the operation and did not require intravenous opioids. The patient was discharged to the ward with an order for epidural morphine for pain control. The next day, the patient remained comfortable. As an ongoing quality assessment to survey the success rate of epidural catheters at our institution, all patients are invited to have their catheter assessed using an electrical epidural stimulation test. Electrical stimulation (1-10 mA) with a segmental motor response (truncal or extremities movement) indicates that the catheter is in the epidural space. No motor response indicates that it is not. In this case, subdural catheter placement was suspected because a diffuse motor response including right anterior chest wall, back muscle, and bilateral lower extremities was observed using only 0.3 mA. Subdural catheter placement was subsequently confirmed by a radiograph showing a very thin film of dye spreading cephalad and caudad over many segments. CONCLUSION: This new electrical test helps to detect subdural placement objectively.     

Determination of epidural catheter placement using nerve stimulation in obstetric patients

Background and Objectives. Peripheral nerve and spinal cord stimulation techniques have been used for many years. However, electrical stimulation methods rarely have been used to confirm epidural catheter placement. This study examines the practicality of this technique to confirm epidural catheter placement in obstetric patients. Methods. Thirty-nine obstetric patients in labor were studied. An electrocardiography (ECG) adapter (Arrow-Johans) was attached to the proximal end of the epidural catheter (19-gauge Arrow Flextip plus). Then, the lowest milliamperage (1–10 mA) necessary to produce a motor response (truncal or limb movement) was applied using this setup. A positive motor response indicated that the catheter was in the epidural space. This test was performed initially after catheter insertion and repeatedly after incremental local anesthetic doses. Results. The sensitivity and specificity of the new test was 100% and 100%, respectively, with 38 true positive tests and 1 true negative test. The threshold current required to produce a positive test increased after incremental doses of local anesthetic. A case of intravascular epidural catheter migration was detected using this new test. In this case, the patient's increased threshold milliamperage returned to the baseline value within 1 hour, despite having received local anesthetic. Intravascular epidural catheter migration was subsequently confirmed by a positive epinephrine test dose. Thus, this test appears to be a potentially useful method to detect intravascular catheter placement. Conclusion. This study demonstrates that this test may have a role in improving the success rate of epidural anesthesia.     

Thoracic epidural analgesia via the caudal approach in pediatric patients undergoing fundoplication using nerve stimulation guidance.

IMPLICATIONS: Epidural catheter placement using electrical stimulation guidance is an alternative approach for positioning the catheter into the thoracic region via the caudal space. This easily performed clinical assessment provides optimization of catheter tip positioning for achieving effective pain control.     

Lumbar plexus posterior approach: a catheter placement description using electrical nerve stimulation

IMPLICATIONS: The authors describe a modified technique of posterior approach to the lumbar plexus in the psoas compartment which allows nerve stimulation for the location of the plexus and catheter placement for extended-duration surgery and postoperative patient-controlled regional analgesia. A frequent incidence of total lumbar plexus block was observed.     

Thoracic epidural analgesia via the caudal approach using nerve stimulation in an infant with CATCH22

PURPOSE: To illustrate insertion of an epidural catheter via caudal route in a small infant under electrical stimulation guidance. CLINICAL FEATURES: A six month old boy, weighting 4.25 kg, with a diagnosis of CATCH22 (Cardiac abnormality/abnormal faces, T cell deficit due to thymic hypoplasia, cleft palate, hypocalcemia due to hypoparathyroidism resulting from 22q11 deletion) was scheduled for fundoplication and gastrostomy tube (G-tube) insertion. A combined light general anesthesia and continuous epidural anesthesia technique was selected. Following induction of general anesthesia and tracheal intubation with 1.5 mg midazolam, 10 microg fentanyl and 10 mg succinylcholine, a 16G intravenous catheter was inserted into the caudal space. A 19G epidural catheter (Arrow Flextip Plus) epidural catheter was then inserted up cranially. A low electrical current (1-10mA) was then applied through the catheter. The level of motor movement was advanced from the lower limb muscles to the upper abdominal muscles as the catheter was threaded cranially. After 19 cm of epidural catheter had been inserted, intercostal muscle movement (T9-10 level) was observed at 4.2mA. The tip of the catheter was later confirmed to be at the T9-10 interspace by radiographical imaging. The patient awakened without distress and the trachea was extubated the same evening. The infant was discharged to the ward next morning with good pain relief from a continuous epidural infusion of bupivacane 0.1% with 1 microg x ml(-1) at 1.6 ml(-1). CONCLUSION: Epidural stimulation may help placement of the epidural catheter at the appropriate dermatome for effective anesthesia and analgesia.     

Usefulness of epidural nerve stimulation to confirm epidural catheter placement

An epidural catheter must be placed in epidural space correctly to give sufficient epidural anesthesia for patients. Recently, as a technique to confirm the catheter placement, electrical stimulation of epidural nerve using an inserted epidural catheter was introduced. This study was conducted to evaluate the reliability of this simple technique in 13 patients. Immediately after an epidural catheter (19 G Arrow Flextip Plus) was placed, an adapter with electrode (Arrow-Johans ECG Adapter) was attached to its connector and nerve stimulation was performed using a peripheral nerve stimulator (1 Hz, 10 mA). Catheter placement was judged to be correct by both presence of muscle contraction in response to stimulation and occurrence of analgesia after the administration of a local anesthetic. In 5 patients, additional roentgen examinations were performed to identify the positions of catheters. In all patients except one, muscle contraction was observed by stimulation, and analgesia was confirmed in all patients after the injection of an anesthetic. X-ray examinations revealed that the tip of catheter placed at the vertebral level corresponded with the spinal segmental level where muscle movement occurred. Our study demonstrates that nerve stimulation can be a reliable method to confirm epidural catheter placement. Our results also suggest that the position of catheter tip can be estimated easily using this technique.     

Subdural placement of an epidural catheter detected by nerve stimulation

PURPOSE: Subdural placement of an epidural catheter is rare and difficult to detect. Electrical stimulation of the epidural space can be useful to detect such an event. The purpose of the present case report is to confirm the efficacy of electrical stimulation to detect a subdural placement of an epidural catheter and to illustrate this unusual positioning by computed tomography (CT) scan images. CLINICAL FEATURES: A 51-yr-old man was scheduled for an aorto-iliac bypass on a combined epidural and general anesthesia technique. Electrical epidural stimulation was used. A very low threshold of 0.3 mA was observed with diffuse response movement at T3 and at T10, without cerebrospinal fluid return on catheter aspiration. An injection of 12 mL of 2% lidocaine with epinephrine 1/200,000 produced signs of iv injection of local anesthetic and an extensive block. Subdural placement of the catheter, suspected by the low current threshold response to epidural catheter stimulation, was confirmed by CT scan imaging. CONCLUSION: The present case report confirms that electrical stimulation of the epidural space is useful to detect misplacement of epidural catheter such as a subdural placement. CT scan imaging of subdural positioning of an epidural catheter is presented.     

Determining the accuracy of caudal needle placement in children: a comparison of the swoosh test and ultrasonography

Background:  The aim of the present study was to compare two confirmatory tests - the 'swoosh' test (auscultation during caudal injection) and real time ultrasound imaging (both transverse 2D imaging and color flow Doppler imaging) in pediatric patients receiving a caudal epidural block.
Methods/Materials:  This was a retrospective observational study of caudal injections administered to 83 pediatric patients (0–11 years) presenting for elective surgery over a 4 month time period. While injecting small aliquots of local anesthetic, a standard stethoscope was placed over the lower lumbar spine to auscultate for the 'swoosh' test. An ultrasound machine (Sonosite Titan, Sonosite Inc., Bothell, WA, USA) was then utilized for real-time visualization of caudal injectate. Each test performed during the caudal injection (swoosh, turbulence on 2D imaging, or color flow on Doppler imaging) was recorded as positive, negative or equivocal.
Results:  Eighty out of 83 patients (96.4%) had a successful caudal block based on minimal or no perioperative narcotic use, minimal or no response to surgical stimulation, the presence of motor blockade and patient comfort in the PACU. Ultrasound was significantly superior to 'swoosh' for sensitivity (96.3% vs 57.5%), negative predictive (40% vs 5.6 value) % and likelihood ratio (2.89 vs 1.73). Specificity and positive predictive value were not different between 'swoosh' and ultrasound. Of the ultrasound tests, turbulence was more sensitive than color flow Doppler (95.0% vs 78.8%).
Conclusion:  Ultrasonography is superior to the 'swoosh' test as an objective confirmatory technique during caudal block placement in children. We found the presence or absence of turbulence during injection within the caudal space to be the best single indicator of caudal success. We think ultrasonography should be used, if available, when teaching this technique.     

Lateral cervical epidural catheter placement using nerve stimulation for continuous unilateral upper extremity analgesia following a failed continuous peripheral nerve block

This case report describes the application of electrical stimulation (Tsui test) to confirm placement of a cervical epidural catheter for postoperative pain management in a patient with a failed brachial plexus block who underwent upper extremity surgery. An epidural catheter was easily advanced under nerve stimulation guidance to the surgical dermatome C4 level without any resistance from the C7-T1 level. Successful analgesia was achieved with a bolus of 2 mg ml(-1) ropivacaine 2 ml and fentanyl 20 microg, followed by a continuous infusion of 2 mg ml(-1) ropivacaine with 2 microg ml(-1) of fentanyl at a rate of 2 ml h(-1). This case reminds the clinician that cervical epidural analgesia may serve as an alternative to a difficult continuous peripheral nerve block. Electrical stimulation may also help to confirm cervical epidural catheter placement at the appropriate dermatome to provide effective analgesia with minimal side-effects.     

A randomised comparison between ultrasound and nerve stimulation for infraclavicular catheter placement

We conducted this study to determine if placement of infraclavicular catheters guided by ultrasound is quicker than placement guided by nerve stimulation. Infraclavicular brachial plexus catheters were inserted in 210 randomly allocated patients who were scheduled for elective hand or elbow surgery. Needle and catheter placement was guided by ultrasound (n = 105) or by nerve stimulation (n = 105). The primary outcome was time to sensory block success. Success rate was similar between the two techniques (83.2% vs 81.4%, p = 0.738). However, placement of ultrasound‐guided catheters took less time (7.2 [2.5] vs 9.6 [3.6] min, p < 0 .001). Pain and satisfaction scores, and incidence of nerve deficit, were also similar with both techniques.