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Pressure waveform analysis provides a reliable confirmatory adjunct to the loss-of-resistance technique to identify the epidural space during thoracic epidural anaesthesia, but its role remains controversial in lumbar epidural analgesia during labour. We performed an observational study in 100 labouring women of the sensitivity and specificity of waveform analysis to determine the correct location of the epidural needle. After obtaining loss-of-resistance, the anaesthetist injected 5 ml saline through the epidural needle (accounting for the volume already used in the loss-of-resistance). Sterile extension tubing, connected to a pressure transducer, was attached to the needle. An investigator determined the presence or absence of a pulsatile waveform, synchronised with the heart rate, on a monitor screen that was not in the view of the anaesthetist or the parturient. A bolus of 4 ml lidocaine 2% with adrenaline 5 μg.ml-1 was administered, and the epidural block was assessed after 15 min. Three women displayed no sensory block at 15 min. The results showed: epidural block present, epidural waveform present 93; epidural block absent, epidural waveform absent 2; epidural block present, epidural waveform absent 4; epidural block absent, epidural waveform present 1. Compared with the use of a local anaesthetic bolus to ascertain the epidural space, the sensitivity, specificity, positive and negative predictive values of waveform analysis were 95.9%, 66.7%, 98.9% and 33.3%, respectively. Epidural waveform analysis provides a simple adjunct to loss-of-resistance for confirming needle placement during performance of obstetric epidurals, however, further studies are required before its routine implementation in clinical practice.

Epidural volume extension, a modification of combined spinal-epidural anaesthesia, involves the epidural injection of saline in order to increase the spread of drugs given intrathecally. Results from individual studies have so far been contradictory and we aimed to gather the available evidence for this technique. We performed a systematic literature search for randomised, controlled trials comparing epidural volume extension after spinal injection with a control group without epidural injection in patients undergoing surgery. Conventional meta-analyses, trial sequential analyses and meta-regression were performed, with the Grading of Recommendations on Assessment, Development and Evaluation (GRADE) approach used to express reliability of outcome estimates. We included 15 studies with 1177 participants. Meta-analyses for the primary outcomes, such as maximum sensory height (6 studies, 274 participants, mean difference (MD) (95%CI) -0.59 (-1.24 to 0.07) dermatomes, low-quality evidence) and hypotension (10 studies, 683 participants, risk ratio (95%CI) 0.84 (0.66-1.07), low-quality evidence), did not differ significantly between the two treatment arms, but trial sequential analysis suggested insufficient evidence to be certain of these findings. Meta-regression suggested a volume-dependent effect, with higher volumes causing a higher spread of intrathecal drugs and a higher incidence of hypotension. A sub-group analysis indicated a pronounced effect on motor block recovery time when a lower anaesthetic dose plus epidural volume extension was compared with a higher anaesthetic dose without epidural volume extension, the MD (95%CI) being -66.75 (-76.0 to -57.5) min, with trial sequential analysis suggesting the evidence was sufficient to draw this conclusion. In trials using the same anaesthetic mixture in the epidural volume extension and the control groups, motor block recovery time did not differ between groups, with a MD (95%CI) of -1.06 (-5.48 to 3.36) min, although trial sequential analysis suggested insufficient evidence. In summary, there is not enough evidence to draw definite conclusions on the effect of epidural volume extension. The quality of the current evidence is low for both efficacy (maximum sensory height) and safety (hypotension). However, there may be a significantly shorter motor block recovery time when different anaesthetic mixtures are used in epidural volume extension and control groups; this warrants further investigation.

Ultrasound assistance for neuraxial techniques may improve technical performance; however, it is unclear which populations benefit most. Our study aimed to investigate the efficacy of neuraxial ultrasound in women having caesarean section with combined spinal-epidural anaesthesia, and to identify factors associated with improved technical performance. Two-hundred and eighteen women were randomly allocated to ultrasound-assisted or control groups. All the women had a pre-procedure ultrasound, but only women in the ultrasound group had this information conveyed to the anaesthetist. Primary outcomes were first-pass success (a single needle insertion with no redirections) and procedure difficulty. Secondary outcomes were block quality, patient experience and complications. Exploratory sub-group analysis and regression analysis were used to identify factors associated with success. Data from 215 women were analysed. First-pass success was achieved in 67 (63.8%) and 42 (38.2%) women in the ultrasound and control groups, respectively (adjusted p = 0.001). Combined spinal-epidural anaesthesia was 'difficult' in 19 (18.1%) and 33 (30.0%) women in the ultrasound and control groups, respectively (adjusted p = 0.09). Secondary outcomes did not differ significantly. Anaesthetists misidentified the intervertebral level by two or more spaces in 23 (10.7%) women. Sub-group analysis demonstrated a benefit for ultrasound in women with easily palpable spinous processes (adjusted p = 0.027). Regression analysis identified use of ultrasound and easily palpable spinous processes to be associated with first-pass success.

Summary The aim of this randomised study was to compare the incidence of intravascular injections during S1 transforaminal epidural steroid injection performed in the anteroposterior and oblique views. We also compared epidural spread patterns of contrast media, which included 201 injections at the S1 level. The overall incidence of intravascular injection during S1 transforaminal epidural steroid injection in the anteroposterior view was 29% (29/99), significantly higher than in the oblique view (11%, 11/102, p = 0.001). There were no significant differences between the two groups for epidural spread of contrast media in cases where intravascular injections did not occur (p = 0.77). Performing S1 transforaminal epidural steroid injection in the oblique view rather than the anteroposterior view reduces the risk of intravascular injections.

Summary We have developed an ultrasound probe through the centre of which an epidural needle can pass, intended to reduce the rate of contact between bone and needle during epidural insertion. We tested the ability of this probe to identify the lumbar interspace, using A-mode ultrasound, in a submerged plastic model, a porcine phantom and five human volunteers. In the plastic model, the minimum echo representing the interspace was only 8.8% of the maximum echo from the ‘bone’. In the porcine model, the echo variations between the interspace and L3 were up to 48% and the needle was safely inserted into the interspace without bone contact under guidance. The human study also showed that the maximum bone echo was at least three times stronger than the interspace echo. Axial ultrasound guidance, with the needle passing through the probe, offers a method for reducing bone contact during epidural insertion.

The aim of this prospective clinical study was to evaluate the location of paravertebral catheters that were placed using the classical landmark puncture technique and to correlate the distribution of contrast dye injected through the catheters with the extent of somatic block. Paravertebral catheter placement was attempted in 31 patients after video-assisted thoracic surgery. In one patient, an ultrasound-guided approach was chosen after failed catheter placement using the landmark method. A fluoroscopic examination in two planes using contrast dye was followed by injection of local anaesthetic and subsequent clinical testing of the extent of the anaesthetised area. In nine patients (29%), spread of contrast dye was not seen within the paravertebral space as intended. Misplaced catheters were in the epidural space (three patients), in the erector spinae musculature (five patients), and in the pleural space (one patient). There was also a discrepancy between the radiological findings and the observed distribution of loss of sensation. We have demonstrated an unacceptably high misplacement rate of paravertebral catheters using the landmark method. Additional research is required to compare the efficacy and safety of continuous paravertebral block using ultrasound-guided techniques or surgical inserted catheters.

This randomised controlled trial investigated the efficacy of Epi-Fix(™) , LockIt Plus(®) and Tegaderm(™) as fixation devices for intrapartum epidural catheters. One hundred and sixty-five women requesting intrapartum epidural analgesia were randomised to receive different fixation devices to secure their epidural catheter. The amount of epidural catheter migration (measured to the nearest 0.5 cm) was analysed for three devices: Epi-Fix (n = 55); LockIt Plus (n = 54); and Tegaderm dressing (n = 51). Median (IQR [range]) catheter migration for Epi-Fix was 1.0 cm (0.0-2.0 [-2.0 to 9.5]), vs 0.0 cm (0.0-0.5 [-1.0 to 5.5]) for LockIt Plus and 0.5 cm (0.0-1.8 [-1.5 to 8.0]) for Tegaderm (p = 0.003). Thirty-eight (69.1%) epidural catheters secured with Epi-Fix migrated < 2.0 cm, compared with 49 (90.7%) with LockIt Plus and 40 (78.4%) with Tegaderm. Sixteen epidural catheters required resiting due to failure of analgesia of which 12 (75.0%) occurred in patients with epidural catheters that had migrated ≥ 2.0 cm. This study shows that intrapartum epidural catheters secured with the LockIt Plus device exhibit less catheter migration compared with fixation with Epi-Fix and Tegaderm.

With the current prevalence of obesity and trends in ethnic diversity amongst parturients in UK maternity units, we performed a prospective, observational study to establish the effect of ethnicity and body mass index on the distance from skin to epidural space in parturients. A total of 1210 parturients participated in this study. The mean (SD) distance from skin to lumbar epidural space was 5.4 (1.1) cm. When tested in a multiple regression model, both body mass index and ethnicity significantly influenced the distance from skin to lumbar epidural space in parturients. The distance from skin to lumbar epidural space amongst ethnic groups differed at any given body mass index. It was significantly greater in Black/British Black and White parturients compared with their Asian and Chinese counterparts. You can respond to this article at http://www.anaesthesiacorrespondence.com.

In current practice, the length of epidural catheter that should be left in the epidural space is not standardised for effective postoperative analgesia. This prospective, randomised, double-blinded study aimed to determine the most appropriate length of epidural catheter that should be inserted into the epidural space for postoperative analgesia. We recruited 102 women and assigned them into three study groups (3, 5 and 7 cm insertion). An epidural catheter was inserted and epidurography was performed. Postoperatively, mean pain scores, motor and sensory levels, and any complications associated with the epidural catheter were recorded. No statistically significant difference for mean postoperative pain score was found at all study timings. Motor and sensory blockade was also statistically insignificant. Unilateral sensory analgesia developed in one patient in the 7 cm group and epidural catheter dislodgement was observed in four patients in the 3 cm group. In order to minimise catheter-related complications for postoperative analgesia, the most appropriate length that an epidural catheter should be left in the epidural space is 5 cm. You can respond to this article at http://www.anaesthesiacorrespondence.com.

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.

Summary This study was performed to evaluate the histopathological effects of epidural drug injection given either by intermittent bolus or continuous infusion through a catheter on epidural tissue. Fourteen ewes received intermittent bolus injections of morphine with bupivacaine, or a bolus of the same drugs followed by continuous infusion for 5 days. After 5 days, histopathological examination of the epidural space revealed mild to moderate inflammatory changes, and focal fibrosis surrounding the catheter in all ewes. The similarity of the inflammatory reaction in the control and drug treated groups seems to indicate that neither intermittent bolus or continuous infusion after a bolus dose caused histopathological changes in the epidural space beyond that caused by the catheter itself.

We conducted a prospective study to determine the epidural tip culture pattern and its clinical implication in postoperative cancer patients. All patients scheduled to undergo various cancer surgeries requiring epidural analgesia were included. Epidural catheter tips were sent for culture on removal. Of the 466 epidural catheter tips sent for culture, 27 showed a positive culture (5.7%). The commonest organism identified was Staphylococcus aureus. There were no signs of local or epidural space infection in any of the patients. The rates of epidural catheter tip cultures in cancer patients are comparable to those in the general patients and the presence of a positive tip culture is not a predictor of epidural space infection. Hence, we recommend that even in cancer patients, routine culture of epidural catheters is not advisable, provided strict asepsis is maintained at the time of insertion, and patients are constantly monitored for early signs of epidural infection.

A postal survey of all UK members of the Obstetric Anaesthetists' Association was carried out to ascertain their preferred method for identifying the epidural space in obstetric and non-obstetric patients. Over 1200 questionnaires were returned (79.3% response rate). In obstetric patients, the single most common technique (used by 58% of anaesthetists) was continuous advancement of the epidural needle and loss of resistance with saline, followed by intermittent needle advancement with air (21%). A minority of respondents used other variants, including intermittent advancement with saline (16%) and continuous advancement with air (4%). Consultant anaesthetists showed greater variety in techniques used than did trainees (p < 0.001). Less than 5% of respondents used a paramedian approach, and these were almost exclusively senior staff. Only 48% of anaesthetists said they would try an alternative if they experienced difficulty with their preferred technique. A similar pattern was seen for lumbar epidurals in non-obstetric surgical patients (89% used the same technique as in obstetrics), although for thoracic epidurals, 23% used a different technique to that which they would use for obstetrics, and the paramedian approach was more popular (21%). When inserting lumbar epidurals to supplement general anaesthesia in surgical patients, 18% of anaesthetists said they usually performed the block with the patient asleep, whereas for thoracic epidurals, this figure fell to 14%.

Epidural abscess is a rare but life threatening condition that requires early diagnosis and prompt management. We report a case of cervical epidural abscess following an intravenous cannula site infection. The organism responsible was Methicillin Resistant Staphylococcus Aureus (MRSA). Management involved surgery, prolonged antibiotics and ventilation. Despite this, there was no return of neurological function and the patient died. We review the literature on epidural abscesses unrelated to catheterisation or instrumentation of the epidural space and discuss the aetiology and clinical features of this acute medical emergency.

Fifty patients scheduled for surgery under lumbar epidural anaesthesia were included in a study to evaluate the possibility of localising the epidural space solely by means of an acoustic signal. With an experimental set-up, the pressure generated during the epidural puncture procedure was translated into a corresponding acoustic signal. One anaesthetist held the epidural needle with both hands and detected the epidural space by means of this acoustic signal. At the same time, a second anaesthetist applied the loss of resistance technique and functioned as control. In all patients the epidural space was located with the acoustic signal. This was confirmed by conventional loss of resistance in 49 (98%) of the patients; in one patient (2%) it was not. We conclude that it is possible to locate the epidural space using an acoustic signal alone.

Summary In this single group observational study on 29 patients, we describe a technique that predicts the depth of the epidural space, calculated from the routine pre-operative chest computerised tomography (CT) scan using Pythagorean triangle trigonometry. We also compared the CT-derived depth of the epidural space with the actual depth of needle insertion. The CT-derived and the actual depths of the epidural space were highly correlated (r = 0.88, R2 = 0.78, p

During central neuraxial blockade, identifying the midline in parturients can be difficult, particularly if they are obese. We assessed the ability of women in late pregnancy, both obese and non-obese, to identify the midline of their own back by pointing and by pinprick discrimination with reference to the true midline identified by ultrasound. Thirteen out of 25 (52%) obese women were accurate to within 5 mm in identifying the midline of their back by pointing with their fingertip, compared with 21/25 (84%) non-obese women (p = 0.03). The median (IQR [range]) fingertip-midline distance was greater in obese women (5 (5-10 [0-10]) mm compared with non-obese women (2 (0-5 [0-12]) mm; p = 0.007). Identification of the midline using pinprick was poorer by obese women (median (IQR [range]) 33 (25-45 [3-85]) mm) than by non-obese women (18 (13-25 [8-40]) mm; p0.0001). However, women in both groups were correct99% of the time in identifying that a stimulus was either to the left or to the right side.

Amide local anaesthetics impair blood clotting in a concentration-dependent manner by inhibition of platelet function and enhanced fibrinolysis. We hypothesised that the presence of ropivacaine in the epidural space could decrease the efficacy of an epidural blood patch, as this technique requires that the injected blood can clot in order to be effective. Ropivacaine is an aminoamide local anaesthetic used increasingly for epidural analgesia during labour. The concentration of local anaesthetic in blood achieved in the epidural space during the performance of an epidural blood patch is likely to be the greatest which occurs (intentionally) in any clinical setting. This study was undertaken to investigate whether concentrations of ropivacaine in blood, which could occur: (i) clinically in the epidural space and (ii) in plasma during an epidural infusion of ropivacaine, alter platelet function. A platelet function analyser (Dade PFA-100, Miami) was employed to assess the effects of ropivacaine-treated blood on platelet function. The greater concentrations of ropivacaine studied (3.75 and 1.88 mg x ml(-1)), which correspond to those which could occur in the epidural space, produced significant inhibition of platelet aggregation. We conclude that the presence of ropivacaine in the epidural space may decrease the efficacy of an early or prophylactic epidural blood patch.

Epidural anaesthesia using the loss of resistance to saline technique, without air, was successfully performed in a 65-year-old man scheduled for elective vascular surgery of the right leg. Epidural catheterisation was uneventful. Fifteen minutes after the initial dose of plain 0.5% bupivacaine, the patient experienced severe pain in his lower abdomen and legs which coincided with a supplementary injection of 2 ml bupivacaine and 50 μg fentanyl, and a change from the lateral to the supine position. General anaesthesia was induced and CT and MRI scans were performed showing trapped air in the epidural space at the L4 level causing compression of the thecal sac. After excluding other causes, the spontaneous entry of air through the Tuohy needle was thought to be the most likely explanation for this complication. The patient recovered uneventfully.

We investigated whether the increase in epidural pressure produced by jugular compression could be used as a test for correct placement of epidural catheters in 20 postpartum women who had good epidural analgesia during labour. We measured the epidural pressure by using the epidural catheter as a manometer, and measured the rise in the meniscus in response to jugular vein compression whilst the epidural catheter was still in the epidural space. The catheter was then withdrawn until the tip lay just outside the epidural space and the response to jugular vein compression reassessed. In all subjects, jugular vein compression produced a rise in the meniscus only whilst the catheter tip lay in the epidural space. Jugular compression is a useful test for confirming the correct placement of the epidural catheter.

The pressures in the intercostal and interpleural spaces were measured in 20 patients using an 18 gauge epidural catheter to confirm accurate catheter positioning for continuous intercostal and interpleural local anaesthetic blockade. In the intercostal space the mean (SD) pressure was negative (-1.8 (0.3)) mmHg and positive (+2.1 (0.3)) mmHg at the end of inspiration and expiration respectively. In contrast, in the interpleural space although the pressure varied with the respiratory cycle it remained negative both at the end of inspiration (-8.3 (1.0)) mmHg and expiration (-2.1 (0.8)) mmHg. We conclude that measurement of intercostal and interpleural pressures with an epidural catheter is a straightforward procedure which may be helpful in confirming accurate catheter placement for continuous intercostal or interpleural local anaesthetic blockade.

We randomly allocated 93 women in early active labour and requesting epidural analgesia to receive either epidural (n = 48) or combined spinal–epidural analgesia (n = 45). For epidural analgesia 15 ml of bupivacaine 0.1% with 75 μg of fentanyl were injected into the epidural space. For combined spinal–epidural analgesia 1 ml of bupivacaine 0.25% with 25 μg of fentanyl were injected into the subarachnoid space. For both groups subsequent top-ups of 10 ml of bupivacaine 0.1% with fentanyl 20 μg were given using a lightweight patient-controlled epidural analgesia (PCEA) pump with a lockout time of 30 min. We assessed analgesia and the degree of motor blockade and found no significant differences in pain or maternal satisfaction scores between the two groups. The time to first top-up was significantly longer in the epidural group than in the CSE group (p = 0.01). The combined spinal–epidural group had significantly greater motor blockade at 30 min than the epidural group (p = 0.01), but there was no difference after this. The PCEA machine failed completely twice and temporarily many times. We conclude that the combined spinal–epidural technique confers no advantages in early active labour. Also, a lightweight PCEA pump needs to be more reliable before we can recommend its use.

Five hundred members of the Obstetric Anaesthetists Association were surveyed regarding their technique for identification of the epidural space. Eighty-one per cent of the questionnaires were returned completed. Fifty-nine per cent of respondents first learned a loss of resistance to air technique, 33.4% to saline and 7.4% another technique. Presently, 37.1% and 52.7% use only a loss of resistance to air or saline, respectively. Six per cent use both techniques and 3.2% use other techniques. Twenty-eight per cent taught a loss of resistance to air, 57.2% taught a loss of resistance to saline and 12.9% taught both techniques. Twenty-three per cent changed from a loss of resistance to air, to a saline technique, and 4.2% vice versa. Forty-seven per cent of those using air felt that loss of resistance to air was not associated with a clinically significant difference in the incidence of accidental dural puncture compared with saline.

Summary A postal survey of all maternity units in the UK was conducted to gain information regarding the management of inadvertent dural taps occurring during the siting of epidurals for pain relief in labour. Of the units surveyed only 58.5% had a written protocol for the management of dural taps. Following their occurrence, 99% of the units resiled the epidural and in 22%, the midwives continued to give the top-ups. In only one-third of this latter group was the dose of the top-up reduced. In 46% of the units, patients who had a dural tap were allowed to push in the second stage of labour. As prophylaxis against the development of headache, 70% of the units infused crystalloids into the epidural space, whereas only 8.6% were in favour of an early prophylactic blood patch.

Twenty patients undergoing elective abdominal aortic aneurysm repair were randomly allocated to two groups and studied for 24 h following surgery. Postoperative analgesia was provided by epidural bupivacaine infusion and intravenous patient-controlled 0.05 mg boluses of alfentanil. One treatment group received 7 ml.h-1 of a 0.25% solution of bupivacaine, the other 25 ml.h-1 of a 0.07% solution. The rate of infusion was thus 17.5 mg.h-1 in both groups. Patients receiving 7 ml.h-1 of epidural infusate required more doses of alfentanil (median 26.5, range 0-50) than the group receiving 25 ml.h-1 of the dilute infusion (median 3.0, range 0-16). It is concluded that 17.5 mg.h-1 of bupivacaine infused into the epidural space produces better analgesia when infused in a volume of 25 ml.h-1 (0.07%) than when given in a volume of 7 ml.h-1 of solution (0.25%).

With the current prevalence of obesity and trends in ethnic diversity amongst parturients in UK maternity units, we performed a prospective, observational study to establish the effect of ethnicity and body mass index on the distance from skin to epidural space in parturients. A total of 1210 parturients participated in this study. The mean (SD) distance from skin to lumbar epidural space was 5.4 (1.1) cm. When tested in a multiple regression model, both body mass index and ethnicity significantly influenced the distance from skin to lumbar epidural space in parturients. The distance from skin to lumbar epidural space amongst ethnic groups differed at any given body mass index. It was significantly greater in Black/British Black and White parturients compared with their Asian and Chinese counterparts. You can respond to this article at http://www.anaesthesiacorrespondence.com.

In current practice, the length of epidural catheter that should be left in the epidural space is not standardised for effective postoperative analgesia. This prospective, randomised, double-blinded study aimed to determine the most appropriate length of epidural catheter that should be inserted into the epidural space for postoperative analgesia. We recruited 102 women and assigned them into three study groups (3, 5 and 7 cm insertion). An epidural catheter was inserted and epidurography was performed. Postoperatively, mean pain scores, motor and sensory levels, and any complications associated with the epidural catheter were recorded. No statistically significant difference for mean postoperative pain score was found at all study timings. Motor and sensory blockade was also statistically insignificant. Unilateral sensory analgesia developed in one patient in the 7 cm group and epidural catheter dislodgement was observed in four patients in the 3 cm group. In order to minimise catheter-related complications for postoperative analgesia, the most appropriate length that an epidural catheter should be left in the epidural space is 5 cm. You can respond to this article at http://www.anaesthesiacorrespondence.com.

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.

The records from 34,819 obstetric epidurals performed at Birmingham Maternity Hospital over the period 1969-1988 were examined. During that time there were 460 dural taps (overall incidence 1.3%). Of the methods used to detect the epidural space, loss of resistance to injection of saline was associated with the lowest incidence of dural tap (0.6%). The incidence of typical postdural puncture headache when managed conservatively was 86%. Provision of an epidural drip after delivery reduced the incidence of headache to 70%. Elective forceps delivery conferred no additional benefit, and tended to delay the onset of headache. Blood patches were performed on 135 patients and provided complete relief of headache in 93 (68%). A further 23 patients (16%) obtained partial relief.

This study was performed to evaluate the histopathological effects of epidural drug injection given either by intermittent bolus or continuous infusion through a catheter on epidural tissue. Fourteen ewes received intermittent bolus injections of morphine with bupivacaine, or a bolus of the same drugs followed by continuous infusion for 5 days. After 5 days, histopathological examination of the epidural space revealed mild to moderate inflammatory changes, and focal fibrosis surrounding the catheter in all ewes. The similarity of the inflammatory reaction in the control and drug treated groups seems to indicate that neither intermittent bolus or continuous infusion after a bolus dose caused histopathological changes in the epidural space beyond that caused by the catheter itself.

We retrospectively reviewed 60 normal magnetic resonance imaging scans to assess the anatomical shape of the thecal sac at the L3/4 and L4/5 vertebral interspaces. In all cases the thecal sac was oval at L3/4 but in 26 (43%; 95% CI 31-55%) the thecal sac changed from oval at the L3/4 interspace to triangular at L4/5 (with the apex of the triangle presenting to the posterior epidural space). We propose that this anatomical variant would make it more difficult to obtain cerebrospinal fluid at the lower level, as a slightly lateral approach could lead to identification of the epidural space but failure to puncture the thecal sac. This may offer an explanation for a 'dry tap' when a lower interspace is chosen.

In a quality improvement audit on epidural analgesia in 300 patients after major abdominal surgery, we identified postoperative lower leg weakness and premature catheter dislodgement as the most frequent causes of premature discontinuation of postoperative epidural infusion. Lower limb motor weakness occurred in more than half of the patients with lumbar epidural analgesia. In a second period monitoring 177 patients, lumbar catheter insertion was abandoned in favour of exclusive thoracic placement for epidural catheters. Additionally, to prevent outward movement, the catheters were inserted deeper into the epidural space (mean (SD) 5.2 (1.5) cm in Period Two vs 4.6 (1.3) cm in Period One). Lower leg motor weakness declined from 14.7% to 5.1% (odds ratio 0.35; 95% confidence interval 0.16-0.74) between the two periods. Similarly, the frequency of premature catheter dislodgement was reduced from 14.5% to 5.7% (odds ratio 0.35; 95% confidence interval 0.17-0.72). With a stepwise logistic regression model we demonstrated that the odds of premature catheter dislodgement was reduced by 43% for each centimetre of additional catheter advancement in Period Two. We conclude that careful audit of specific complications can usefully guide changes in practice that improve success of epidural analgesia regimens.

A caudal epidural catheter was inserted in 20 premature, high risk infants for abdominal or thoracic surgery under combined caudal epidural and general anaesthesia. Epidurography was used to confirm the position of the catheter which was found to be misplaced in three patients. The catheter penetrated the dura in one case, in another the tip was located in an epidural vessel and in the third the catheter was seen to be curled up within the epidural space. It was concluded that epidurographic control is essential with this method of anaesthesia in very small infants, in whom it was found to provide considerable advantages despite serious risks.

We investigated whether the increase in epidural pressure produced by jugular compression could be used as a test for correct placement of epidural catheters in 20 postpartum women who had good epidural analgesia during labour. We measured the epidural pressure by using the epidural catheter as a manometer, and measured the rise in the meniscus in response to jugular vein compression whilst the epidural catheter was still in the epidural space. The catheter was then withdrawn until the tip lay just outside the epidural space and the response to jugular vein compression reassessed. In all subjects, jugular vein compression produced a rise in the meniscus only whilst the catheter tip lay in the epidural space. Jugular compression is a useful test for confirming the correct placement of the epidural catheter.