Relationship between the bevel of the Tuohy needle and catheter direction in thoracic epidural anesthesia

BACKGROUND AND OBJECTIVES: Directing an epidural catheter cephalad or caudad is usually attempted by orienting the beveled edge of the epidural needle. However, there have been few studies about the relationship between the direction of the bevel of epidural needle and the resulting position of the catheter. We studied this relationship in thoracic epidural catheter placement. Catheter position was confirmed by using picture archiving communication systems (PACS). PACS is a workstation that stores radiologic images, which can be manipulated to visualize the catheters. METHODS: One hundred six patients receiving thoracic epidural anesthesia were enrolled. The cephalad and caudad groups (each with 53 patients) received epidural anesthesia at the T6-7 interspace with either a cephalad- or caudal-directed Tuohy needle. The final position of all of the catheters was confirmed by PACS. RESULTS: In the cephalad group, 63.5% of the catheters were confirmed to travel in a cephalad direction. In the caudad group, 22.0% of the catheters advanced in a caudad direction. Curling of the catheters occurred in 17.6%. PACS showed the catheter positions with satisfactory quality. CONCLUSIONS: The correlation between bevel direction and location of the thoracic epidural catheter was relatively low. Practices such as threading an epidural catheter by manipulation of the Tuohy needle for the control of pain at a distant site may not yield good results.     

The epidural structure changes during deep breathing

PURPOSE: Previous experience has suggested that the insertion of an epidural catheter becomes easier when the patient takes a deep breath. The purpose of this study is to investigate the effects of respiration on the epidural space. METHODS: We examined the epidural space using a flexible epiduroscope in 20 patients undergoing thoracic epidural anesthesia. A 17-gauge Tuohy needle was inserted using the paramedian technique and the loss-of-resistance method with 5 ml air. The epiduroscope was introduced into the epidural space via the Tuohy needle. Each patient was requested to take a deep breath when the epiduroscope was positioned at the needle tip and at approximately 10 cm cephalad from the needle tip within the epidural space. The changes in the epidural structure during deep breathing at each site were then measured. RESULTS: In 80% of the patients, fatty tissue occupied the needle tip. Through the patients' maximal inspiration, the fatty tissue moved and a visible cavity expanded at the needle tip. Cross section area of the visible cavity at the needle tip was greater at the maximal inspiratory level than at the resting expiratory level: 12.1 +/- 6.7% vs 2.8 +/- 2.1% (mean +/- SD, P < 0.0001). In all patients, the visible cavity within the epidural space, which had already been expanded by injected air, became more expanded after maximal inspiration. Cross section area of the visible cavity at the 10 cm cephalad position was greater at the maximal inspiratory level than at the resting expiratory level: 20.6 +/- 10.0% vs 7.0 +/- 5.3% (P < 0.0001). CONCLUSION: Epiduroscopy showed that deep breathing expanded the potential cavity of the epidural space. We suggest that the changes in the epidural structure during deep breathing may assist in the insertion of an epidural catheter.     

Lumbar epidural catheterization: estimation of the length of the inserted catheter

A catheter in the epidural space can be the cause of various iatrogenic complications. In order to avoid leaving too great a length in the lumbar epidural space during epidural anaesthesia, graduated Tuohy needles can be used (Perifix), together with graduated epidural catheters. On the latter, a special marking shows that, when it reaches the needle hub, the catheter tip is at the needle bevel. Approximately 5 to 7 cm of catheter length are introduced into the epidural space. The needle is removed and placed upside down next to the catheter, with the hub in contact with the patient's skin. In this position, the distance between the special marking on the catheter and the graduation on the needle which marked the skin level is equivalent to the length of catheter in the epidural space. This distance, and therefore catheter length, can then be reduced to about 4 cm by carefully withdrawing the catheter. Some possible improvements of catheters and needles are discussed. Knowing exactly how much catheter is within the epidural space could be of particular importance whenever that space is uncommonly far from the patient's skin: obesity, oedema, use of the paramedian route or a very oblique angle of the needle in the sagittal plane.     

Thoracic Epidural Anesthesia Via the Lumbar Approach in Infants and Children

Background: In upper abdominal or chest surgery, the segmental approach to thoracic epidural space has the advantage of reducing the total dose of local anesthetic needed. This approach, however, is associated with greater risk of neurologic damage or dural puncture. The aim of this study was to assess the success and the degree of difficulty in advancing a 19-G catheter from the lumbar epidural space to the thoracic level in patients aged 0-96 months.

Methods: In 39 patients undergoing abdominal surgery, the cutaneous distance between the L4-L5 and T10-T11 interspaces was measured, and an appropriate length of 19-G catheter was inserted into the epidural space through an 18-G Tuohy needle with bevel directed cephalad. The intent was to advance the full length of catheter measured to reach the objective. The tips were observed radiologically, and all those positioned cephalad to the T12 level were considered well placed. The degree of difficulty in advancing the catheter was classified as easy, difficult, or impossible. Complications reported were vascular and/or spinal puncture and difficulty removing the catheter.

Results: The catheter tip reached T10-T12 in 7 patients, L2 in 1, L3 in 8, and L4-L5 in 23. Forty-eight percent of the catheters described as easily advanced remained at the L4-L5 level, and only 22% reached the desired level. Difficult insertions occurred in eight patients, in whom the objective was never reached. One case of intravascular insertion was reported. All catheters were removed without difficulty.     

AN ANALYSIS OF THE RADIOLOGICAL VISUALIZATION OF THE CATHETERS PLACED IN THE EPIDURAL SPACE

Radiographs of the position of the epidural catheter were takenin each of 90 patients in whom this form of analgesia was employedfor surgery. Radiopaque dye was injected through the catheter.In 33 patients the average length of catheter threaded intothe epidural space was 20 cm; the desired cephalad directionwas followed in 16. When the average length of catheter insertedwas 12.5 cm the tip followed the cephalad direction in 27 of57 patients. Straight, curled up, and winding patterns wereobserved, and in 6 of 90 patients the catheter passed out ofthe epidural space.     

Lumbar Epidural Anaesthesia With Bupivacaine in Old Patients: Effect of Speed and Direction of Injection

The spread of lumbar epidural analgesia was studied in 48 old urological patients (56–81 years). Bupivacaine 0.5% 20 ml was injected at either 1 ml/s with a Tuohy needle with the bevel directed cephalad (Group I) or caudad (II) and at 0.22 ml/s directed cephalad (III) or caudad (IV). Immediately after injection, the patients moved from a sitting to a horizontal position and analgesia was tested every 2 min by skin pin-prick. At 10 min, there were differences in the mean caudad spread; the greatest spread in Group II was 4.5 segments and the smallest in Group III 2.4 segments, not significant (n.s.). The differences became smaller with time and the maximal spread after 30 min was similar in all groups. In six patients, who all belonged to either Group I or Group III (bevel cephalad), skin analgesia did not reach the S 5 segment. One of the Group I patients developed a transient motor paralysis of the lower extremities immediately upon injection. All patients recovered completely from the block and no toxic reactions were observed. The duration of the block and the accompanying fall of blood pressure were similar in the different groups. The mean venous blood levels of bupivacaine were highest in Group III and lowest in Group I (n.s.). The highest individual bupivacaine blood level was 1.25 μg/ml 30 min after injection, while generally the highest concentrations appeared at 20 min after injection. The study indicated a lack of significant difference on varying the speed of injection or turning the Tuohy needle, but it has to be emphasized that this may apply only to bupivacaine, which has distinct physicochemical properties, and also to old patients with an age-dependently modified epidural space.     

Bevel direction of epidural needles reliably predicts direction of catheter placement and contrast spread in human cadavers: results of a pilot study

Study ObjectiveTo confirm the relationship between bevel orientation, catheter direction, and radiopaque contrast spread in the lumbar region.DesignPilot cadaver study.SettingAnatomy laboratory of a university hospital.MeasurementsCadavers were randomized to two groups of 4 cadavers each. In Group 1, needle bevel direction at epidural entry was cephalad; in Group 2, it was caudad. After placement of each epidural catheter in L₄-L₅ interspace, 2 mL of radiopaque contrast was injected and a lumbar posterior-anterior radiograph was obtained. Catheter direction and direction of radiopaque contrast spread were collected.Main ResultsDue to the inability to access the epidural space secondary to surgical changes in the lumbar spine, one cadaver in the cephalad group was excluded. In 7 of 7 (100%) cadavers, the catheter tip direction according to the radiograph corresponded directly with bevel direction.ConclusionsA strong relationship exists between bevel orientation and catheter direction; however, catheter position does not reliably predict the direction in which the injected fluid spreads in all cadavers.     

Thoracic epidural analgesia via the lumbar approach using nerve stimulation in a pediatric patient with Down syndrome

This case illustrates the threading of an epidural catheter with electrical stimulation guidance from the lumbar epidural space to the thoracic space in a pediatric patient. A 17-year-old boy with Down syndrome, weighing 48 kg, was scheduled to undergo a laparotomy for duodenal obstruction and gastrostomy tube insertion. Combined general and continuous epidural anesthesia was selected for his anesthetic. Following the induction of general anesthesia and tracheal intubation, a 17G Tuohy needle (Arrow International, Inc., Reading, PA) was inserted into the lumbar space (L3-4) using loss of resistance with air. A 20G styletted epidural catheter was then inserted and threaded cranially. As the catheter was advanced, a low electrical current (1-10mA) was applied to the catheter. Motor response was observed from the lower limb muscles to the upper abdominal muscles as the catheter advanced cranially. After 22 cm of the epidural catheter had been inserted, intercostal muscle movement (T9 - 10) was observed at 3.0 mA. Radiographical imaging later confirmed the catheter tip at T10. The patient awoke without distress and was discharged to the ward with subsequent good pain control from a continuous epidural infusion of bupivacaine 0.1% with 1 microg ml(-1) fentanyl at 4-6 ml(-1).     

Inadvertent knotting of a thoracic epidural catheter

We report a case of corrosive injury of upper gastrointestinal and respiratory tracts scheduled for feeding jejunostomy under thoracic epidural anesthesia. An epidural catheter was inserted at the T8-T9 intervertebral space and threaded 7 cm beyond the tip of the Tuohy needle in a rostral direction. Resistance was noticed during attempts to inject the local anesthetic. As resistance could not be relieved by changing the position of the patient, kinking of the epidural catheter was suspected. Following informing the patient of the associated risks, the catheter was retrieved successfully by gentle and steady pulling. A tight double-knot of catheter was found. No neurological sequelae to the procedure were noticed.     

The lumbar subdural extraarachnoid space of humans: an anatomical study using spinaloscopy in autopsy cases

The lumbar subdural extraarachnoid space was examined by spinaloscopy in 15 autopsy subjects. Special attention was paid to the ease with which the space opened up and also to the extent of view achieved. In ten cases the space opened up with ease, in four cases with difficulty, and in one case it was not possible to establish the subdural space at all. The bevel of an 18-gauge Tuohy needle introduced into the subdural space could be visualized in eight of 13 cases. An epidural catheter was then passed through the Tuohy needle into the subdural space in eight cases and was visualized in six of them. Although care must be exercised in drawing conclusions for clinical epidural anesthesia from autopsy cases, this study confirms the possibility of placing both the bevel of a Tuohy needle and an epidural catheter in the subdural space. The results reemphasize the need for caution suggested by other reports regarding the possibility of subdural puncture in epidural anesthesia and subsequent injection of anesthetic solution into the subdural space.     

A prospective, randomized evaluation of the effects of epidural needle rotation on the distribution of epidural block

We evaluated the effects of turning the tip of the Tuohy needle 45 degrees toward the operative side before threading the epidural catheter (45 degrees -rotation group, n = 24) as compared to a conventional insertion technique with the tip of the Tuohy needle oriented at 90 degrees cephalad (control group, n = 24) on the distribution of 10 mL of 0.75% ropivacaine with 10 microg sufentanil in 48 patients undergoing total hip replacement. The catheter was introduced 3 to 4 cm beyond the tip of the Tuohy needle. A blinded observer recorded sensory and motor blocks on both sides, quality of analgesia, and volumes of local anesthetic used during the first 48 h of patient-controlled epidural analgesia. Readiness to surgery required 21 +/- 6 min in the control group and 17 +/- 7 min in the 45 degree-rotation group (P > 0.50). The maximum sensory level reached on the operative side was T10 (T10-7) in the control group and T9 (T10-6) in the 45 degree-rotation group (P > 0.50); whereas the maximum sensory level reached on the nonoperative side was T10 (T12-9) in the control group and L3 (L5-T12) in the 45 degree-rotation group (P = 0.0005). Complete motor blockade of the operative limb was achieved earlier in the 45 degree-rotation than in the control group, and motor block of the nonoperative side was more intense in patients in the control group. Two-segment regression of sensory level on the surgical side was similar in the two groups, but occurred earlier on the nonoperative side in the 45 degree-rotation group (94 +/- 70 min) than in the control group (178 +/- 40 min) (P = 0.0005). Postoperative analgesia was similar in the 2 groups, but the 45 degree-rotation group consumed less local anesthetic (242 +/- 35 mL) than the control group (297 +/- 60 mL) (P = 0.0005). We conclude that the rotation of the Tuohy introducer needle 45 degrees toward the operative side before threading the epidural catheter provides a preferential distribution of sensory and motor block toward the operative side, reducing the volume of local anesthetic solution required to maintain postoperative analgesia. IMPLICATIONS: Turning the Tuohy introducer needle 45 degrees toward the operative side before threading the epidural catheter is a simple maneuver that produces a preferential distribution of epidural anesthesia and analgesia toward the operative side, minimizing the volume of local anesthetic required to provide adequate pain relief after total hip arthroplasty.     

The placement of the epidural catheter at the predicted site by electrical stimulation test

More accurate segmental and sagittal positioning of the epidural catheter tip is required for the success of continuous epidural analgesia, spinal cord monitoring, and percutaneous epidural spinal cord stimulation. We examined the usefulness of an electrical stimulation test for verifying the proper placement of the epidural catheter tip at the predicted site in the posterior epidural space by using a locally developed epidural catheter with electrodes at its tip. The test included the observation of segmental bilateral muscle twitches and the patient's report of feeling in the region stimulated by moving the epidural catheter electrode back and forth and changing the direction of the bevel of the Tuohy needle. The success rate of midline placement at the required spinal segment was significantly more frequent (99%; P < 0.001) in the group (n = 289) receiving the electrical stimulation test compared with the group (n = 277) not receiving the test (success rate 57%). The results indicate the usefulness of this method. We concluded that the electrical stimulation test is effective for verifying the proper placement of the catheter electrode tip. IMPLICATIONS: Ideally the epidural catheter tip should be positioned in the posterior epidural space near the midline. We concluded that the electrical stimulation test is effective for verifying the proper placement of the catheter electrode tip.     

Injecting saline through the epidural needle decreases theiv epidural catheter placement rate during combined spinal-epidural labour analgesia

PURPOSE: To determine if injecting 10 mL saline before epidural catheter threading (pre-cannulation epidural fluid injection) can decrease the incidence of iv epidural catheter placement during combined spinal-epidural (CSE) labour analgesia. METHODS: One hundred healthy women requesting CSE labour analgesia with either fentanyl 20 microg or sufentanil 10 microg were prospectively randomized to receive either no epidural injection (dry group, n = 50) or epidural 10 mL saline injection (saline group, n = 50) before epidural catheter placement. A nylon multiport catheter was then threaded 3-5 cm into the epidural space and the needle was removed. We diagnosed iv catheter placement if blood was freely aspirated, if the mother became tachycardic after injection of epinephrine 15 microg, or if intracardiac air was heard (using ultrasound) after injection of air 1.5 mL. RESULTS: Intravenous epidural catheter placement occurred in one saline and ten dry group patients (P < 0.01). No complications of excessive cephalad intrathecal opioid spread (i.e., difficulty swallowing, hypoxemia, or respiratory arrest) occurred. CONCLUSIONS: Injecting 10 mL or saline through the epidural needle after intrathecal opioid injection and before threading the catheter significantly decreased accidental venous catheter placement without any apparent increase in complications from excessive cephalad intrathecal opioid spread.     

The Fiberscopic Findings of the Epidural Space in Pregnant Women

Background: The spread of epidural analgesia is facilitated by pregnancy. Changes in the epidural structure during pregnancy may affect the spread of analgesia in pregnant women. To investigate the changes in the epidural space produced by pregnancy, the authors performed epiduroscopy in pregnant women.

Methods: Using a flexible fiberscope, the authors evaluated the epidural space in 73 women undergoing lumbar epidural anesthesia. Patients were classified into three groups: a nonpregnant group (n = 21), a first trimester pregnant group (8-13 weeks, n = 23), and a third-trimester pregnant group (27-39 weeks, n = 29). A 17-gauge Tuohy needle was inserted using the paramedian technique and the loss-of-resistance method with 5 ml air. The epiduroscope was introduced into the lumbar epidural space via the Tuohy needle and was advanced approximately 10 cm in a cephalad direction from the needle tip within the epidural space. The differences in the epidural space among the three groups then was evaluated.

Results: The epiduroscopy showed that the epidural pneumatic space, after injection of a given amount of air, was narrower and the density of the vascular network greater in the third-trimester group than in the other two groups. The amount of engorged blood vessels was greater in the third and first trimester groups than in the nonpregnant group. The amount of bleeding at the needle tip and the amount of fatty and fibrous connective tissue did not differ among the three groups.     

Dural tissue trauma and cerebrospinal fluid leak after epidural needle puncture: effect of needle design, angle, and bevel orientation

BACKGROUND: The effects of epidural needle design, angle, and bevel orientation on cerebrospinal fluid leak after puncture have not been reported. The impact of these factors on leak rate was examined using a dural sac model. Dural trauma was examined using scanning electron microscopy. METHODS: Human cadaveric dura, mounted on a cylindrical model, was punctured with epidural needles using a micromanipulator. Tissue was punctured at 15 cm H2O (left lateral decubitus) system pressure, and leak was measured at 25 cm H2O (semisitting) pressure. Leak rates and trauma were compared for the following: (1) six different epidural needles at 90 degrees, bevel parallel to the dural long axis; (2) 18-gauge Tuohy and 18-gauge Special Sprotte epidural needles, 30 degrees versus 90 degrees; (3) 18-gauge Tuohy, bevel perpendicular versus parallel to the dural long axis. RESULTS: With the 90 degrees puncture, bevel parallel, the greatest leak occurred with a 17-gauge Hustead (516 +/- 319 ml/15 min), and the smallest leak occurred with a 20-gauge Tuohy (100 +/- 112 ml/15 min; P = 0.0018). A 20-gauge Tuohy puncture led to statistically significant reductions in leak (P value range, 0.0001-0.0024) compared with all needles except the Special Sprotte. With the 30 degrees versus 90 degrees angle, 30 degrees punctures with an 18-gauge Tuohy produced nonstatistically significant leak reductions compared with the 18-gauge Tuohy at 90 degrees. The puncture angle made no difference for the Special Sprotte. Nonsignificant reductions were found for the Special Sprotte compared with the Tuohy. With the 18-gauge Tuohy bevel orientation, perpendicular orientation produced nonstatistically significant reductions in leak compared with parallel orientation. CONCLUSIONS: Cerebrospinal fluid leak after puncture was influenced most by epidural needle gauge. Leak rate was significantly less for the 20-gauge Tuohy needle.     

No additional metal particle formation using the needle-through-needle combined epidural/spinal technique

Background. Combined epidural/spinal analgesia utilizing a needle-through-needle technique has become very popular in anesthesia. However, findings of concave deformities at the orifice of Tuohy needles after spinal needle passage have raised concerns that metal fragments might be deposited within the epidural space. This study was proposed to investigate whether the needle-through-needle technique does produce metallic flecks.
Methods. Ten unused Tuohy and Hustead epidural needles were inspected microscopically and photomicrographed prior to flushing saline through each into a single tissue culture well. After drying, a single pass was made with a 120 mm 24-gauge Sprotte needle through each epidural needle to maximal extension while the orifice was within another tissue culture well. Each needle was again flushed into a third well before reexamination and photomicroscopy. Each of the wells was inspected for metallic particles by microscopy. Additional freshly unpackaged Tuohy needles were microscopically examined after exposure to a magnetic field.
Results. Comparison of micrographs before and after needle experiments revealed concave deformities at the orifice of all the Tuohy and Hustead needles. No particles were observed in either of the two saline-flushed wells or within the well in which the needle-through-needle passes were made. Inspection of unused Tuohy needles exposed to a magnetic field revealed metal filings "standing up" along the bevel of every needle examined.
Conclusions. Metallic particles are not produced by the needle-through-needle technique. However, metal particles are an apparent contaminant of all epidural needles and are probably routinely introduced into patients when the needle is placed.     

An epidural catheter introducer in children

Usefulness of an epidural catheter introducer was tested in paediatric epidural anaesthesia. We tried to place an epidural catheter in 100 infants and children. When catheter insertion was difficult, an epidural catheter introducer, which was made of a piece of 6-Fr suction tubing, was utilized. The introducer is threaded over the epidural catheter down to the hub orifice of the epidural needle. The catheter can then be advanced into the epidural space through this introducer. In this way, we were able to place the catheter in 94 percent of patients. Even a simple introducer is effective in passing the epidural catheter into the epidural space in infants and children. Perhaps manufacturers should provide threading devices with catheters or epidural needles.     

The fiberscopic findings of the epidural space in pregnant women

BACKGROUND: The spread of epidural analgesia is facilitated by pregnancy. Changes in the epidural structure during pregnancy may affect the spread of analgesia in pregnant women. To investigate the changes in the epidural space produced by pregnancy, the authors performed epiduroscopy in pregnant women. METHODS: Using a flexible fiberscope, the authors evaluated the epidural space in 73 women undergoing lumbar epidural anesthesia. Patients were classified into three groups: a nonpregnant group (n = 21), a first trimester pregnant group (8-13 weeks, n = 23), and a third-trimester pregnant group (27-39 weeks, n = 29). A 17-gauge Tuohy needle was inserted using the paramedian technique and the loss-of-resistance method with 5 ml air. The epiduroscope was introduced into the lumbar epidural space via the Tuohy needle and was advanced approximately 10 cm in a cephalad direction from the needle tip within the epidural space. The differences in the epidural space among the three groups then was evaluated. RESULTS: The epiduroscopy showed that the epidural pneumatic space, after injection of a given amount of air, was narrower and the density of the vascular network greater in the third-trimester group than in the other two groups. The amount of engorged blood vessels was greater in the third and first trimester groups than in the nonpregnant group. The amount of bleeding at the needle tip and the amount of fatty and fibrous connective tissue did not differ among the three groups. CONCLUSIONS: Epidural blood vessels become engorged in the first trimester; the density of the vascular networks increase in the third trimester. These changes in the epidural space during pregnancy may affect the spread of epidural analgesia in pregnant women.     

Epidural analgesia in labor for a woman with an intrathecal baclofen pump

A 28-year-old woman in active labor at 38 weeks of gestation requested epidural analgesia. She had previously received an intrathecal baclofen infusion pump to relieve the spasticity of cerebral palsy. She had right hemiparesis and cerebral palsy but was otherwise healthy. The patient had been seen one month before her expected delivery date by a staff anesthesiologist. A lumbar X-ray demonstrated the intrathecal catheter entering the L3-4 interspace and extending to the mid-thoracic region. For labor analgesia the epidural space was identified at L4-5 with the patient sitting, using a standard 17-gauge Tuohy needle. An epidural catheter was threaded to 5 cm and provided effective analgesia until delivery four hours later. There were no postnatal complications.     

Epidural injection of lidocaine reduces the response to dural puncture accompanying spinal needle insertion when performing combined spinal-epidural anesthesia

During placement of needles for combined spinal-epidural anesthesia (CSEA), patients may experience pain, pressure, paresthesia, or discomfort during skin and deeper injection of local anesthetic, needle impingement on periosteum, dural puncture by the spinal needle, and insertion of the epidural catheter. We investigated the incidence of perception of and spontaneous verbal and motor responses to insertion of a spinal needle through the dura mater and pia mater and the effect of injecting lidocaine into the epidural space through the epidural needle before inserting the spinal needle through the meninges. Forty-three patients presenting for elective cesarean delivery under CSEA were studied. After localization of the epidural space using loss of resistance to air using a 17-gauge Tuohy needle, either 3 mL preservative free normal saline or 3 mL lidocaine 2% plus epinephrine 1:200,000 was injected through the Tuohy needle. "Needle through needle" dural puncture was performed 1 min later using a 27-gauge Whitacre pencil-point needle. At the moment of dural puncture, 2 (9%) parturients given lidocaine and 17 (81%) parturients given saline (P < 0.005) responded to dural puncture by spontaneously moving (33%), spontaneously vocalizing (62%), or, in response to direct questioning, by acknowledging (76%) having perceived sensation during thecal penetration. This study reveals that dural puncture by a Whitacre 27-gauge pencil-point needle inserted through a Tuohy epidural needle sited using loss of resistance to air causes involuntary movement, spontaneous vocalization, or is perceived by the majority of patients presenting for cesarean delivery under CSEA and that lidocaine injected into the epidural space before dural puncture largely eliminates these responses and sensations.