Prediction by computerised tomography of distance from skin to epidural space during thoracic epidural insertion

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 < 0.0001). The mean (95% CI) difference between CT-derived and actual depths was 0.26 (0.03-0.49) cm. Thus, the CT-derived depth tends to be greater than the actual depth by between 0.03 and 0.49 cm. There were no associations between either the CT-derived or the actual depth of the epidural space and age, weight, height or body mass index.     

A formula for determining the distance from the skin to the lumbar epidural space in infants and children

In paediatric epidural anaesthesia, the distance from the skin to the epidural space is of special importance because of the great differences in size of the patients. We measured the distance from the skin to the lumbar epidural space (L3/4) in 355 paediatric patients. The epidural space was punctured using a midline approach under general anaesthesia, and was identified by the micro-drip infusion technique. There was a good correlation between the distance to the epidural space and body weight. A clinically useful formula for estimating the distance from the skin to the lumbar epidural space was derived as follows: D = (W+10) × 0.8 where D = distance from the skin to the lumbar epidural space (L3/4) (mm) and W = body weight (kg).     

The distance from the skin to the epidural space

To determine whether there is any systemic relationship between the distance from the skin to the epidural space and physical constitution, the distance from the skin to the epidural space was measured in 1007 epidural punctures. The distance from the skin to the epidural space in male was greater than that in female (P 0.001). However, the analysis of the distance from the skin to the epidural space of the selected patients who had both a weight of 50–60kg and a height of 1.5–1.7m indicated no statistical difference between male and female. The best correlation was found between the distance from the skin to the epidural space and body weight. The correlation between the distance from the skin to the epidural space and height was less striking. Ninety-five percent of the patients who received epidural puncture at the thoraco-cervical area (C7-T2) had a distance to the epidural space of 4.0–6.9cm; 87% at the lower-thoracic area (T8–T10), 4.0–6.9cm; 93% at the thoraco-lumbar area (T12-L2), 3.0–4.9cm; 85% at the mid-lumbar area (L2–L4), 3.0–4.9cm. These results may be useful for young anesthesiologists to master epidural block safely and efficiently.(Hirabayashi Y, Matsuda I, Inoue S et al.: The distance from the skin to the epidural space. J Anesth 2: 198–201, 1988)     

Subcutaneous effusion resulting from an epidural catheter fragment

The breakage of an epidural catheter within a patient is uncommon,but troublesome, complication of epidural block, and its causeis rarely discovered. In this case report, our aim was to presentan effusion between s.c. tissue and fascia in the lumbar regionbecause of a broken fragment of epidural catheter which wasunnoticed during its removal.     

Intrapartum epidural catheter migration: a comparative study of three dressing applications

We compared three types of catheter fixation application fortheir ability to minimize the incidence and magnitude of epiduralcatheter movement during labour. Patients were randomized tohave their epidural catheter secured by a Tegaderm dressing(group T; n=35), a Tegaderm dressing plus filter-shoulder fixation(group F; n=39), or a Niko Epi-Fix dressing (group N; n=37).The length of catheter visible at the patient’s skin surfacewas recorded (to the nearest 0.5 cm) after insertion and beforeremoval; the difference was defined as ‘catheter movement’.Outward movement of the catheter was greatest when a Niko Epi-Fixwas used (P<0.01). Concerning minimization of displacementof the epidural catheter per se, only a Tegaderm dressing withadditional filter-shoulder fixation proved more effective thanusing a Niko Epi-Fix dressing (P<0.05). Br J Anaesth 2001; 86: 565–7     

Posture and epidural catheter insertion. The relationship between skill, experience and maternal posture on the outcome of epidural catheter insertion

This study was undertaken to investigate the outcome of epidural catheter insertion in the sitting or lateral position in mothers during labour. An initial prospective randomised study period (144 patients) suggested that the sitting position offered some superiority over the lateral in terms of technical ease of insertion. It was concluded, by minimising the subjective aspects in a follow-up, prospective nonrandomised study period (152 patients), that the determining factor lies in the skill and experience of the anaesthetist. There was no significant difference in complication rates or maternal discomfort between the two positions in either study period.     

The depth of the lumbar epidural space from the skin

The depth of the epidural space at different intervertebral interspaces was measured in 1000 parturients. Overall the median distance from the skin to the epidural space was 4.7 cm, but this varied with the lumbar interspace at which it was measured, being greatest at the third (L3-4) interspace (4.93 cm) and least at the first (L1-2) interspace (4.23 cm). The clinical significance of these findings is discussed.     

Bacterial contamination of epidural needles after multiple skin passes

Background. Infection and epidural abscess are important complicationsof epidural analgesia. Difficult insertion may be associatedwith an increased risk of bacterial contamination of the epiduralneedle or catheter. Methods. Bacterial contamination of epidural needles and trocarsafter difficult epidural insertion, defined as two or more skinpasses, was assessed in 38 obstetric and ten gynaecologicalpatients. Results. There was no bacterial growth on any of the 48 epiduralneedles or trocars despite the mean (range) insertion time being20 (10–30) min and the number of insertion attempts being3 (2–4). Conclusions. Difficult epidural insertion is not associatedwith an increased risk of needle contamination and is thereforean unlikely source of epidural infection. Br J Anaesth 2002; 89: 922–4     

Advantages of the paramedian approach for lumbar epidural analgesia with catheter technique

Forty-nine patients, scheduled for transurethral resection of the prostate or a bladder neoplasm on 50 occasions, were studied. The patients were randomly allocated to one of the two methods of puncture, midline or paramedian. Technical difficulties and the occurrence of complications were recorded. The extent of sensory and motor blockade was also compared. The paramedian approach was associated with a lower frequency of technical problems compared to the midline approach. Statistically significant differences were demonstrated between the two techniques for the following factors: repeated attempts at needle insertion; difficulty in identification of the epidural space; resistance to introduction of the catheter; resistance to injection through the epidural catheter; and the production of paraesthesiae (nine patients in the midline group compared to only one patient in the paramedian group, p less than 0.01). The catheter entered a vessel at first in two patients in each group. No significant differences were demonstrated between the groups in the extent of sensory and motor blockade. The study supports the view that the paramedian approach has technical advantages over the midline approach for lumbar epidural analgesia with catheter technique.     

Efficacy of spray disinfection with a 2-propanol and benzalkonium chloride containing solution before epidural catheter insertion--a prospective, randomized, clinical trial

Background. Skin disinfection before neuroaxial blockade proceduresis usually obtained with sterile swabs impregnated in disinfectant.Spray disinfection is also an option which is frequently usedin minor invasive procedures. The purpose of our study was tocompare the efficacy of conventional swab disinfection withspray disinfection prior to epidural catheterization. Methods. Seventy patients who requested epidural analgesia wererandomly selected. The first group (n=35) received disinfectionwith swabs (SW) containing 2-propanol and benzalkonium chloride.The other 35 patients received spray (SP) disinfection withthe same solution. Three microbiological cultures were obtained:one culture prior to skin disinfection, a second immediatelyafter disinfection and a third from the tip of the epiduralcatheter upon removal. Results. One patient in the SW group had a positive skin cultureimmediately after the disinfection with a very low number ofcolony forming units. The other skin culture specimens wereall sterile in both groups. The colonization rate of catheterswas not statistically different between the groups at removal. Conclusion. In this study, spray disinfection was equally efficaciouscompared with the conventional skin disinfectant technique.Our results support the routine use of this simple and cheapalternative method of skin disinfection before epidural anaesthesia.     

Spinal epidural abscess--a rare complication after epidural analgesia for labour and delivery

We report a case of spinal epidural abscess formation aftershort-term epidural catheter placement for analgesia duringlabour and delivery. The patient was previously healthy anddid not have any predisposing factors. Increasing back painwas the only complaint. A contrast-enhanced CT study on day5 was inconclusive. Magnetic resonance imaging was performedand showed a large triangular-shaped abscess with adjacent inflammationof the paravertebral muscles. One day later, the patient developeda sensory deficit in the left lower limb. The neurological deficitcompletely resolved after surgical decompression and debridement,which was followed by antibiotic treatment. Br J Anaesth 2004; 92: 896–8     

Block of the sacral segments in lumbar epidural anaesthesia

Background. Block of the first sacral segment is often delayedin lumbar epidural anaesthesia. The addition of either epinephrineor sodium bicarbonate to the local anaesthetic enhances theefficacy of epidural block. We assessed the block of lumbo-sacralsegments in lumbar epidural anaesthesia adding epinephrine and/orbicarbonate to lidocaine. Methods. Twenty-seven patients undergoing lumbar epidural anaesthesiawith lidocaine 2%, 17 ml at L4-5 or L5-S1 were randomly dividedinto three groups. Plain lidocaine, lidocaine with 1:200 000epinephrine or lidocaine–epinephrine–bicarbonatewas administrated via an epidural catheter. The pain thresholdafter repeated electrical stimulation was used to assess thesensory block at the L2, S1, and S3 segments. Motor block wasevaluated using the Bromage scale. Results. Patient characteristics were comparable between thegroups. The pH of lidocaine in the lidocaine–epinephrine–bicarbonategroup was significantly higher than that in other groups. Painthresholds at the S1 and S3 segments in the lidocaine–epinephrine–bicarbonategroup were significantly higher than those in the lidocaine–epinephrinegroup. However, differences in the pain threshold at the L2segment between groups were insignificant. The time to onsetof sensory block at the S1 and S3 in the lidocaine–epinephrine–bicarbonategroup was significantly shorter than that in the lidocaine group.Pain threshold by pinprick test was approximately within the30–50 mA range. Conclusion. A combination of lidocaine, bicarbonate, and epinephrineincreases the pain threshold over the sacral segments. Br J Anaesth 2003; 90: 173–8     

Urinary catheterization in labour with high-dose vs mobile epidural analgesia: a randomized controlled trial

Background: Dense perineal block from epidural analgesia increases the riskof urinary catheterization in labour. Mobile epidurals usinglow-dose local anaesthetic in combination with opioid preservematernal mobility and may reduce the risk of bladder dysfunction.We conducted a three-arm randomized controlled trial to comparehigh-dose epidural pain relief with two mobile epidural techniques. Methods: A total of 1054 primparous women were randomized to receivehigh-dose bupivacaine, epidural analgesia (Control), combinedspinal epidural (CSE), or low-dose infusion (LDI). The requirementfor urinary catheterization during labour and postpartum wasrecorded. Both end points were pre-specified secondary trialoutcomes. Women were evaluated by postnatal interview, whentheir bladder function had returned to normal. Results: Relative to Control, more women who received mobile epiduraltechniques maintained the ability to void urine spontaneouslyat any time (Control 11%, CSE 31% and LDI 32%) and throughoutlabour (Control 3.7%, CSE 13% and LDI 14%), for both mobiletechniques P<0.01. There was no difference in the requirementfor catheterization after delivery. Women in the CSE group reporteda more rapid return of normal voiding sensation, relative tohigh-dose Control (P=0.02). Conclusions: Relative to conventional high-dose block, mobile epidural techniquesencourage the retention of normal bladder function and reducethe risk of urinary catheterization in labour.     

Cannulation of the epidural space

A group of 685 obstetric patients were randomly allocated to have their epidural block performed using either a 16-gauge or an 18-gauge Tuohy needle. Bleeding was noted from needle or catheter trauma in 18% of patients and it proved impossible to insert the catheter in 3%. The majority of mothers experienced little discomfort during the procedure but 2% found insertion to be very uncomfortable. There was no significant difference in the complication rate, ease of use, or patient discomfort between the 18- or 16-gauge needles. Epidural analgesia, although safe, is not without hazard. It may be difficult to perform and may, rarely, cause considerable discomfort.     

Accidental pleural puncture by a thoracic epidural catheter

We report the occurrence of an accidental pleural puncture by an epidural catheter that happened during the attempted induction of thoracic epidural anaesthesia using a paramedian approach in an awake patient. The incorrect placement of the catheter was recognised while the patient was undergoing thoracoscopic surgery. The possibility of accidental pleural puncture during attempted thoracic epidural catheter placement by either the paramedian or the midline approach should be borne in mind. A misplaced catheter may injure lung tissue and result in a potentially dangerous intra-operative tension pneumothorax.     

Measuring the quality of continuous epidural block for abdominal surgery

Background. In view of the wide variation in pain experiencebetween patients, a clinical standard—the time from theend of surgery to the first experience of pain—was appliedto 1359 consecutive patients in order to investigate whetherthe initial quality of epidural block has an effect on the overallquality of postoperative pain relief. Methods. Clinical data were recorded in 58 118 out of 72 412h in 1359 patients, and transferred to a database. Data collectedincluded pain scores on a four-point verbal rating scale; nauseaand vomiting; motor block; sedation scores; systolic blood pressure<100 and <90 mm Hg; ventilatory frequency <10 and <8bpm; and hourly epidural infusion rate. Results. As the time to first experience of pain increased fromnil to >24 hours, the time from the first to last experienceof pain shortened from 34 (19–50) h to 3 (1–12)h (p<0.001) and the proportion of patients receiving an epiduralbolus decreased from 53 to 8% (p<0.001). Increases in theinitial pain free time increased the proportion of patientswith systolic BP<100 mmHg from 59 to 77%, (p<0.001) andincreased the proportion of patients with respiratory rate <10bpm from 13 to 26%, (p<0.001). Conclusion. Extending pain relief for more than 12 h beyondthe end of abdominal surgery significantly improves the overallquality of postoperative pain relief, but is associated withan increase in side-effects. ¹Present address: John Radcliffe Hospital, Oxford, UK. ²Present address: Royal Hospital for Sick Children, Edinburgh,UK     

Location of the paravertebral space in children and adolescents in relation to surface anatomy assessed by computed tomography

A series of 52 thoracic and/or upper abdominal computer tomography scans were reviewed in order to determine the optimal puncture site and depth for performing paravertebral blocks in the mid-thoracic region in children and adolescents. Both the lateral distance from the spinous process to the paravertebral space (SP-PVS distance) and the depth from the skin to the paravertebral space (S-PVS depth) correlated well (r values 0.86–0.95) to all patient related parameters (age, height, weight and body surface area). Since patient weight is usually readily obtainable and correlates well with both SP-PVS distances (r= 0.89; SP-PVS distance (mm) = 0.12 x body weight (kg) + 10.2) and S-PVS depth (r= 0.95; S-PVS depth (mm) = 0.48 x body weight (kg) + 18.7) this parameter might provide the best and easiest prediction of the location of the paravertebral space when performing paravertebral blocks in children and adolescents.     

硬膜外预充生理盐水对置管诱发剖宫产术患者硬膜外血管损伤的影响

目的 评价硬膜外预充生理盐水对置管诱发剖宫产术患者硬膜外血管损伤的影响.方法 单胎足月妊娠拟在硬膜外麻醉下行子宫下段剖宫产术的患者150例,ASA分级Ⅰ或Ⅱ级,年龄27～33岁,体重66～75 kg.随机分为3组(n=50),Ⅰ组直接置入硬膜外导管,Ⅱ组和Ⅲ组在硬膜外置管前通过硬膜外针注射0.9%生理盐水或含肾上腺素(1:200 000)的生理盐水5 ml,注射完后保持注射器压缩针栓20 s,使液体充分扩散.记录置入硬膜外导管时硬膜外穿刺针针尾见淡红色血水、硬膜外导管回抽见淡红色血水、硬膜外导管置入血管(从导管回抽出新鲜血液)的发生情况.结果 与Ⅰ组比较,Ⅱ组和Ⅲ组硬膜外穿刺针针尾见淡红色血水的发生率、硬膜外导管回抽见淡红色血水的发生率和硬膜外导管置入血管的发生率均明显降低(P＜0.01);Ⅱ组和Ⅲ组间上述指标差异无统计学意义(P＞0.05).结论硬膜外预充生理盐水5 ml可有效预防置管诱发剖宫产术患者硬膜外血管的损伤.1∶200 000肾上腺素并不能进一步预防置管诱发的硬膜外血管损伤.     

The coiling length of thoracic epidural catheters: the influence of epidural approach angle

BACKGROUND: Thoracic epidural catheters are used for anaesthesia and postoperativeanalgesia. Usually, epidural catheters are placed without confirmationof their position despite frequent reports of complicationsas a result of malposition. In this study, we evaluated thethreading length of thoracic epidural catheters without coilingand assessed the influence of two different epidural approachangles on the threading length without coiling. METHODS: Eighty-three patients scheduled for thoracotomy were enrolledand randomly allocated into the acute angle group and the obtuseangle group. In both groups, skin insertion was performed atthe T8–9 intervertebra level. Epidural access was performedunder fluoroscopy using a paramedian approach at the T7–8level in the acute angle group and at the T6–7 level inthe obtuse angle group, and an end-hole 19-gauge epidural catheterwas inserted. Coiling length, defined as the length of the catheterwithin the epidural space when any part of the catheter justbegins to head caudally, was measured in both groups. RESULTS: The coiling length was 7.4(4.4) cm (95% CI 6.0–8.7 cm)in the obtuse angle group compared with 4.9(3.3) cm (95%CI 3.8–6.0 cm) in the acute angle group (P = 0.005). CONCLUSIONS: Approaching the thoracic epidural space with an obtuse approachangle provides longer coiling length. We recommend that an obtuseapproach angle should be used to maximize the chance of thecatheter reaching the intended level with minimum risk of coiling.     

Technical advantages of the paramedian approach for lumbar epidural puncture and catheter introduction

The lumbar epidural space of 14 autopsy subjects was examined by epiduroscopy. The aim was to compare the midline and paramedian approaches of locating the space, the estimated risk of accidental dural puncture, the course taken by the epidural catheter after introduction and with special attention to the influence of the dorsomedian connective tissue band. The paramedian needle passed a greater distance within the epidural space before contact with the dura mater and demonstrated a low risk of accidental dural puncture. The catheter passed by the paramedian approach did not cause any tenting of the dura and took a straight cephalad direction in all 14 cases. The midline catheter caused tenting of the dura in all 14 cases and the direction of travel was variable. Differences were statistically significant. Influence of the dorsomedian connective tissue band was greatest on the behaviour of the midline needle and catheter.