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.     

Coiling of lumbar epidural catheters

BACKGROUND: The difficulties in threading an epidural catheter to vertebral levels remote to the puncture level have been well documented. This study was undertaken to determine the length that a single orifice epidural catheter can be threaded into the lumbar space without coiling (coiling length), and whether this is affected by the direction of the epidural needle bevel. METHODS: Forty-five young male patients scheduled for surgery under epidural analgesia were enrolled. The epidural space was identified using a midline approach at the L(2-3) or L(3-4) interspace with the loss of resistance to air technique. A 19-G single-orifice epidural catheter (Flextip Plus, Arrow International, Inc, Reading, PA, USA) was inserted through a Tuohy needle oriented either cephalad (n=20) or caudad (n=25). During insertion, the path and the position of the catheter tip was determined by fluoroscopy using iohexol dye. RESULTS: The median coiling length was 2.8 cm, ranging from 1.0 to 8.0 cm. Only 13% of epidural catheters could be threaded 4 cm beyond the tip of the needle without coiling. No significant difference was found in coiling length between the cephalad group (2.9 cm) and the caudad group (2.5 cm). CONCLUSION: This study demonstrates that coiling length is independent of whether the bevel of the Tuohy needle is directed cephalad or caudad. We recommend that an optimal insertion depth of an end-hole single orifice catheter is 3 cm.     

The use of a sound-enabled device to measure pressure during insertion of an epidural catheter in women in labour

The insertion of an epidural catheter for labour analgesia may be challenging. This observational study compared pressures during insertion of an epidural catheter in pregnant (n = 35) and non-pregnant (n = 10) women, using an acoustic device for locating the epidural space that also records and stores pressure data during the procedure. In both groups, we compared the maximum pressure just before loss of resistance, the pressure in the epidural space and the pressure in the inserted epidural catheter. Maximum pressure just before loss of resistance in the pregnant women was significantly lower compared with the non-pregnant women. Pressures in the epidural space and with the disposable tubing connected to the inserted epidural catheter were greater in pregnant women than in non-pregnant women. The results support the hypothesis that physiological changes in the third trimester of pregnancy are the reason why epidural catheters are more difficult to insert in women in labour.     

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.     

Epidural analgesia for painless delivery. Our experience

BACKGROUND: We know that a stress condition causes hormonal responses (cortisol, prolactin, TSH, ACTH, catecholamines, beta-endorphines). This hormonal "storm" causes metabolic and haemodynamic changes that can get worse postoperative outcome as well as birth. Analgesia for labour is an anesthesiological procedure which spreading in Italy resulted very difficult, for instance, especially in southern Italy, "old popular believes" (such as paralysis risk after lumbar puncture, Post-Dural Puncture Headache (PDPH) and the confusion between epidural and subdural anesthesia). METHODS: In front of these problems we report our experience in this field. Experimental plan: in our retrospective study we examined painless labour cases and we compared them with natural labour cases without analgesia. Environment: women of this study were pregnant admitted in obstetrics department of our hospital at the end of pregnancy. Patients: pregnant women who wanted epidural analgesia were 50 (group A); data group A were compared with data of 50 pregnant women who refused analgesia (group B). Technique: beginning labour, when cervical dilatation was 3 cm and foetal head was going down we performed epidural puncture and positioned, catheter in epidural space giving opiate and local anesthetic drugs using "top-up" method. Data: we compared APGAR-score after birth and the judgement expressed by women of the two groups. RESULTS AND CONCLUSIONS: APGAR-score in new-borns with epidural analgesia in higher than new-born without epidural analgesia; furthermore, patients who choose painless labour expressed a better judgement than women who refused epidural analgesia.     

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.     

Postural stability following ambulatory regional analgesia for labor

BACKGROUND: The safety of mobilization following low-dose regional analgesia in parturients remains controversial. Previous studies have demonstrated preserved balance function despite clinically elicited sensory deficits. The aim of this study was to use the Balance Master 6.1, a device capable of real-time analysis of ambulation, to score the performance of basic maneuvers following initiation of low-dose combined spinal-epidural analgesia in laboring women compared with pregnant and nonpregnant controls. METHODS: Using the Balance Master, balance function during the performance of several simple tasks, including walking and standing up from a sitting position, was evaluated in a prospective, controlled, observational study with 50 laboring women after combined spinal-epidural analgesia compared with 50 pregnant and 50 nonpregnant controls. RESULTS: Nonpregnant women scored significantly better results in 6 of the 13 measured balance function parameters compared with both the combined spinal-epidural and pregnant control groups. Compared with the nonpregnant subjects, the pregnant groups generated less force standing up from the sitting position (P < 0.0001), walked more slowly (P = 0.0067), and took shorter steps (P < 0.0001). They also took longer to step up onto and over a 20-cm-high obstacle (P < 0.0001), and they generated less force while stepping up. Initial spinal analgesia in laboring women did not significantly affect performance in comparison to the pregnant controls. Thirty-four percent of women in the combined spinal-epidural group required supplemental epidural analgesia following the initial spinal injection (n = 17) before testing; they had significantly impaired balance function in four tests compared with those receiving a spinal injection only (n = 33). CONCLUSIONS: Being pregnant at term significantly affects balance function, although initial low-dose spinal-epidural analgesia does not impair function further. Subsequent supplemental epidural analgesia may have a detrimental effect on balance, but properly designed studies are awaited to confirm this. This study supports the practice of allowing laboring women with initial low-dose spinal-epidural analgesia to ambulate, but indicates that further studies need to be conducted on the effects of subsequent epidural supplementation.     

Comparison of double-segment technique with single-space technique for cesarean section using combined spinal epidural anesthesia

In patients scheduled for cesarean section (c-section) using combined spinal epidural anesthesia (CSEA), we compared the cephalad spreading speed during double-segment technique (DST) with that of single-space technique (SST) of CSEA. In the patients of SST group (n = 169), a 17-G Tuohy needle was introduced at the L 3-4, and then a long spinal needle was inserted through the Tuohy needle. In the patients of DST group (n = 16), a Tuohy needle was introduced at the T 11-12, and a spinal needle was inserted at the L 3-4. After 0.3% hyperbaric dibucaine 1.0 ml was injected through the spinal needle, 1.5% mepivacaine 10 ml was injected through the epidural catheter in both the groups. The analgesic level was measured at 5-min intervals, and blood pressure and complaints of patients were also recorded. The cephalad spread of analgesia was significantly higher in DST group than in SST group at 5 and 10 min after the administration of local anesthetics. Two patients in SST group, epidural catheterization was not possible. There were no difference in the incidences of hypotension, nausea and dyspnea between the groups. We conclude from these results that DST for CSEA is preferable to SST for c-section.     

Transient second-degree A-V block during an epidural procedure]

A 26 year old pregnant female had a left ovarian tumor and was scheduled to have an operation. No specific complication was noted preoperatively except pregnancy of 16 weeks and one day. Spinal anesthesia for the operation and continuous epidural catheter placement for postoperative pain relief were planned. During the epidural procedure on L2-3 under left lateral recumbent position, patient developed a bradycardia when the tip of Tuohy needle touched the 3rd lumbar bone (lamina arcus vertebrae). This bradycardia occurred three times and the last episode was recorded on the ECG (Fig 2). Blood pressure at this period was 82/44 mmHg, but patient did not complain any discomfort. The recorded ECG showed II degree A-V block (Wenkebach type). We considered this A-V block is probably due to sharp pain from touching of Tuohy needle on the lamina arcus vertebrae. This kind of periosteal pain is sometime associated with vagal stimulation and it could produce II degree A-V block. During a spinal or epidural procedure, ECG should be monitored and we have to pay attention to these kinds of arrhythmia to prevent more profound hemodynamic changes.     

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.     

The effect of epidural needle type on postdural puncture headache: a randomized trial

PURPOSE: A prospective, randomized trial in labouring parturients was undertaken to assess whether the 18G Special Sprotte epidural needle is associated with a lower incidence of accidental dural puncture (ADP) in comparison with the 17G Tuohy needle. A secondary purpose was to determine if the incidence of postdural puncture headache (PDPH ) differed between groups when ADP occurred. METHODS: Following Institutional Review Board approval 1,077 parturients requesting epidural analgesia at three tertiary obstetrical units were randomized to epidural catheter insertion with a 17G Tuohy or 18G Special Sprotte needle. Patients were followed for seven days by a blinded assessor to determine the occurrence of PDPH using standardized criteria. If postural headache or neck ache presented, an ADP was diagnosed even if cerebrospinal fluid (CSF) was not observed at insertion. This subgroup was followed daily to assess headache characteristics and response to blood patch. RESULTS: Six Tuohy group patients, and two patients in the Sprotte group were excluded. One of the six excluded in the Tuohy group had an ADP. Twenty-eight ADPs occurred, nine unrecognized by CSF visualization (1.8% Tuohy, 3.4% Sprotte, P = 0.12). The incidence of unrecognized ADPs was higher in the Sprotte group (40% Sprotte vs 20% Tuohy, P < 0.05). If ADP occurred, the incidence of PDPH was lower in the Sprotte group (100% Tuohy vs 55% Sprotte, P = 0.025). The ease of use, and user satisfaction were higher in the Tuohy group (84 +/- 17.3% Tuohy vs 68.2 +/- 25.3% Sprotte, P < 0.001). CONCLUSION: The incidence of ADP was not reduced with the Special Sprotte epidural needle in comparison with the Tuohy needle, but PDPH after ADP occurred less frequently in the Sprotte group.     

Postural Stability following Ambulatory Regional Analgesia for Labor

Background: The safety of mobilization following low-dose regional analgesia in parturients remains controversial. Previous studies have demonstrated preserved balance function despite clinically elicited sensory deficits. The aim of this study was to use the Balance Master 6.1, a device capable of real-time analysis of ambulation, to score the performance of basic maneuvers following initiation of low-dose combined spinal-epidural analgesia in laboring women compared with pregnant and nonpregnant controls.

Methods: Using the Balance Master, balance function during the performance of several simple tasks, including walking and standing up from a sitting position, was evaluated in a prospective, controlled, observational study with 50 laboring women after combined spinal-epidural analgesia compared with 50 pregnant and 50 nonpregnant controls.

Results: Nonpregnant women scored significantly better results in 6 of the 13 measured balance function parameters compared with both the combined spinal-epidural and pregnant control groups. Compared with the nonpregnant subjects, the pregnant groups generated less force standing up from the sitting position (P < 0.0001), walked more slowly (P = 0.0067), and took shorter steps (P < 0.0001). They also took longer to step up onto and over a 20-cm-high obstacle (P < 0.0001), and they generated less force while stepping up. Initial spinal analgesia in laboring women did not significantly affect performance in comparison to the pregnant controls. Thirty-four percent of women in the combined spinal-epidural group required supplemental epidural analgesia following the initial spinal injection (n = 17) before testing; they had significantly impaired balance function in four tests compared with those receiving a spinal injection only (n = 33).     

Epidrum<Superscript>®</Superscript>: a new device to identify the epidural space with an epidural Tuohy needle

Epidrum^® is an optimal pressure, loss of resistance device for identifying the epidural space. We investigated the usefulness of Epidrum versus the loss of resistance or hanging drop techniques while performing epidural anesthesia. Eighty adult patients who were scheduled for elective surgery under lumbar epidural anesthesia were randomized into two groups. The first group (Epidrum group) consisted of 40 adult patients who were scheduled for epidural anesthesia using Epidrum. The second group (control group) consisted of 40 adult patients who were scheduled for epidural anesthesia using the loss of resistance or hanging drop technique. We recorded the time required to identify the epidural space and outcomes of epidural catheterization. The attending anesthesiologists were also questioned regarding the ease of control of the Tuohy needle and of epidural space identification with each method. The time required to perform epidural anesthesia was significantly shorter in the Epidrum group than in the control group [28 s (10–76) vs. 90 s (34–185); median (interquartile range)] (p < 0.05). Tuohy needle control was significantly easier in the Epidrum group than in the control group (p < 0.05). Epidrum is useful for performing epidural anesthesia quickly while obtaining good Tuohy needle control.     

A comparison of Espocan and Tuohy needles for the combined spinal-epidural technique for labor analgesia

When using the needle-through-needle combined spinal-epidural (CSE) technique for labor analgesia, failure to obtain cerebrospinal fluid (CSF), paresthesias, and intrathecal or intravascular migration of the catheter are of concern. Epidural needles with spinal needle apertures, such as the back-hole Espocan (ES) needles, are available and may reduce these risks. We describe the efficacy and adverse events associated with a modified epidural needle (ES) versus a conventional Tuohy needle for CSE. One-hundred parturients requesting labor analgesia (CSE) were randomized into 2 groups: 50-ES 18-gauge modified epidural needle with 27-gauge Pencan atraumatic spinal needle, 50-conventional 18-gauge Tuohy needle with 27-gauge Gertie Marx atraumatic spinal needle. Information on intrathecal or intravascular catheter placement, paresthesia on introduction of spinal needle, failure to obtain CSF through the spinal needle after placement of epidural needle, unintentional dural puncture, and epidural catheter function was obtained. No intrathecal catheter placement occurred in either group. Rates of intravascular catheter placement and unintentional dural puncture were similar between the groups. Significant differences were noted regarding spinal needle-induced paresthesia (14% ES versus 42% Tuohy needles, P = 0.009) and failure to obtain CSF on first attempt (8% ES versus 28% Tuohy needles, P < 0.02). Use of ES needles for CSE significantly reduces paresthesia associated with the insertion of the spinal needle and is associated with more frequent successful spinal needle placement on the first attempt. IMPLICATIONS: The use of modified epidural needles with a back hole for combined spinal-epidural technique significantly reduces paresthesia associated with the insertion of the spinal needle and is associated with more frequent successful spinal needle placement on the first attempt.     

Continuous epidural anaesthesia for major abdominal surgery in young children

The benefits of epidural anaesthesia combined with general anaesthesia were studied in young children scheduled for major abdominal surgical procedure (pull-through for Hirschsprung's disease). Two groups of nine children were studied receiving, respectively, general anaesthesia or general anaesthesia plus epidural anaesthesia. In the group receiving both general and regional anaesthesia, a polyurethane 24 G catheter was inserted via a Tuohy needle 19 G into the lumbar epidural space after induction of anaesthesia and intubation and bupivacaine, 0.25%, was injected epidurally (mean initial volume 0.71 +/- 0.04 ml kg-1). No opiates were needed during operation on the children in this group. After epidural anaesthesia, heart rate decreased significantly but systolic blood pressure remained unchanged. During surgery mean values of both heart rate and systolic blood pressure were significantly lower in the regional analgesia group compared to the general anaesthesia group. The need for blood replacement was also significantly lower, whereas pre- and post-operative haematocrit values were not significantly different. Administration of fluid and electrolytes during operation was also similar in both groups. A combination of epidural and general anaesthesia avoids the use of opiates during surgery, provides excellent per- and post-operative analgesia, allows a rapid and safe recovery, and facilitates the nursing of young children.     

Comparison of continuous spinal and epidural analgesia for pain relief in labour

We have compared continuous spinal analgesia with continuous epidural analgesia for pain relief in labour. Twenty-six women were randomly allocated to receive either epidural 0.25% bupivacaine 5-10 ml via a 20 gauge catheter inserted through a 16 gauge Tuohy needle or intrathecal 0.25% bupivacaine 0.5-1.0 ml via a 32 gauge catheter inserted through a 24 gauge Sprotte needle. This was supplemented with fentanyl 5-10 mcg (spinal) or 1 mcg per kg (epidural) if analgesia was unsatisfactory. Outcome was measured by the success and timing of the procedure, time to analgesia, amount of drug given, visual analogue scoring of pain relief by the patient and an observer and degree of motor block. Onset time and dosage were significantly reduced in the continuous spinal group. Two catheters failed to feed in the spinal group. One catheter became displaced in each group. Pain relief was satisfactory in all patients and none had post-dural puncture headache. Continuous spinal analgesia may offer significant advantages over epidural analgesia but technical difficulties remain with the present equipment. The reasons for the withdrawal of the spinal catheters in the United States of America are discussed.     

Observations on deliberate dural puncture with a Tuohy needle: depth measurements

Observations were made during the use of a Tuohy needle to perform deliberate dural puncture for the insertion of lumbar drains to improve operating conditions for intracranial aneurysm surgery. The most striking finding was the distance from identification of the epidural space to penetration of the dura. We postulate that this was because of tenting of the dura by the blunt Tuohy needle. This was facilitated by the absence of a negative epidural space pressure because an open system was used, which allowed time for pressure equilibration. This minimised the reactive forces across the dura. Aspiration and rotation of the Tuohy needle revealed dural puncture in some cases.     

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.     

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.     

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.