Search

The placement of thoracic epidural catheters is complicated by the layering of the vertebral lamina. Therefore, traditional blind palpation techniques require insertion of an epidural needle with likely contact of lamina with redirections into the epidural space. We discuss a safe and consistent technique using true real-time ultrasound visualization of the needle with a paramedian sagittal oblique view to improve the consistency of placing an epidural in the thoracic spine for postoperative analgesia. Successful epidural placement was achieved in every patient. All catheters were found to be effective for use in the postoperative phase.

Background and Objectives: Venous thromboembolism (VTE) is a common cause of preventable harm. Perioperative thoracic epidural analgesia (TEA) presents a challenge to optimal VTE prophylaxis. Our primary aim was to characterize missed doses of VTE prophylaxis associated with epidural catheter placement and removal. Our secondary aim was to measure the effect of an enhanced recovery after surgery (ERAS) pathway on the rate of TEA-associated missed VTE prophylaxis., Methods: We retrospectively reviewed a prospectively collected database of 1264 colorectal surgery patients at a single academic center. Missed preoperative doses between TEA patients and non-TEA patients were compared. Missed postoperative unfractionated heparin (UFH) doses associated with epidural removal were compared before and after implementation of an ERAS program. Other data collected included demographic data, surgical indication, and thrombohemorrhagic complications., Results: Of the 445 TEA patients, 12.6% missed their preoperative heparin doses compared with 8.4% of patients without epidurals (P = 0.017). Of the TEA patients prescribed 3 times daily UFH, 22.5% missed one or more doses associated with epidural removal. The percent of patients missing at least one dose of UFH on epidural removal dropped from 28.1% before ERAS to 17.9% after the ERAS program (P = 0.023). Seven patients developed VTEs. There were zero epidural hematomas., Conclusions: Thoracic epidural analgesia was associated with a 1.5-fold increased risk of missed dose of preoperative VTE prophylaxis, which was not affected by implementation of an ERAS program. The implementation of an ERAS program reduced missed doses associated with epidural removal. This study highlights the challenge posed by providing VTE prophylaxis in the setting of perioperative neuraxial analgesia.

Background: Epidural catheters are routinely used in regional and obstetric anesthesia. The flexible catheter is advanced without imaging control into the epidural space, and coiling or kinking of the catheter may occur, compromising the effectiveness of epidural anesthesia. Potentially near-infrared (NER) light detection may help, tracking advancement of the catheter in the epidural space., Methods: Nonembalmed human cadavers donated to the University of Washington Willed Body program were placed prone. Catheters containing NER-emitting wire were introduced into the lumbar and thoracic epidural space. The progress of the emitting wire was tracked using the LumenVu NER guidance system, and the final location of the catheter was confirmed with fluoroscopy., Results: Total 12 attempts were made to place the catheter. In 7 cases (4 lumbar and 3 thoracic), good progression of the catheter in the epidural space was achieved with excellent visibility at low NER power levels. Maximum light intensity was registered when the catheter tip was found in the midline dorsal interlaminar position, as confirmed by fluoroscopy. The light intensity decreased while the catheter tip was traversing under the lamina. Poor progression of the catheter with negligible visibility of the tip at the highest NER level occurred in obese specimen (n = 2) or when the tip was in extraforaminal (n = 1), paramedian or paravertebral positions (n = 2)., Conclusions: Many variables such as obesity, paravertebral and extraforaminal catheter locations, and intervening bony structures can impede the application of NER technology for epidural catheter placements. Further optimization of the technology for clinical use is necessary.

Background: Although infrequent, subdural block is a complication of epidural anesthesia with obvious implications. Knowledge of the spinal subdural compartment (dura-arachnoid interface) may help elucidate controversies arising from evidence that subdural catheter placement is feasible and may be difficult to identify clinically., Methods: Samples of arachnoid lamina obtained during in vivo lumbosacral surgery (n = 4) and from cadavers (n = 6) were obtained and prepared for transmission electron microscopy and scanning electron microscopy. Subdural spaces were artificially produced in suitable samples, and an epidural catheter was inserted between the arachnoid and dura to compare the dimensions of meninges in relation to epidural catheters., Results: Scanning electron microscopy of the dural sac showed areas of continuity between the arachnoid lamina and dura mater and other parts with both membranes separated by a subdural space. Transmission electron microscopy allowed the study of such border zones, where alternating cellular and collagen layers could be seen. A layer rich in collagen fibers and some fibroblasts separated arachnoid and neurothelial cells (dural border cells). Few specialized membrane junctions were found among cells adjacent to collagen fibers. Dura mater had an average thickness of 260 to 400 μm, with a dural lamina of approximately 4 to 6 μm. In areas where the arachnoid appeared separated from the dural lamina, its thickness measured 35 to 45 μm. Catheters with a diameter of 700 μm were successfully inserted inside the subdural space, between the dura mater and the arachnoid lamina., Conclusions: Dura mater and arachnoid layers act as a single unit but may be pulled apart by traction forces during cadaver processing of the dural sac or in vivo placement of catheters. This generates subdural spaces, either parallel or concentric, because of the minimal resistance offered by the tissue, which may be explained by its few specialized membrane junctions.

Background: Ultrasound (US) imaging of the spine has been shown to be a reliable tool to facilitate lumbar epidural needle placement; however, its feasibility in thoracic epidural placement is still unknown. The objective of this study was to assess the accuracy and reliability of prepuncture US imaging in the paramedian sagittal oblique plane to estimate the depth to the epidural space and optimum insertion point for guiding epidural needle placement at the mid-low thoracic level., Methods: This prospective study included 35 healthy adult patients who requested thoracic epidural analgesia before their upper abdominal surgeries. Ultrasound imaging was done in the paramedian sagittal oblique plane at the desired thoracic level to identify the intervertebral space, the distance from the skin to the epidural space (US depth [UD]) and the needle insertion point. Subsequently, a staff anesthesiologist located the epidural space through the predetermined insertion point and marked the actual distance from the skin to the epidural space (needle depth [ND]) on the needle with a sterile marker. The agreement between the UD and the ND was calculated using the Pearson and concordance correlation coefficients and Bland-Altman analysis with 95% limits of agreement., Results: The average patient age was 56 (SD, 14) years, and body mass index was 28 (SD, 6) kg/m2. The precision of the agreement between UD and ND estimated by Pearson correlation coefficient was 0.75, and the accuracy was 0.80, whereas the concordance correlation coefficient was 0.60 (confidence interval, 0.43-0.78). The mean UD and ND were 4.3 (SD, 0.96) and 5.0 (SD, 1.2) cm, respectively. The Bland-Altman analysis showed a mean difference of -0.71 cm (95% limits of agreement, 0.8 to -2.2 cm). There was a significant direct correlation of the ND with the body mass index (r2 = 0.27, P = 0.008). The mean number of attempts was 1 (p25-p75 = 1-2), and the epidural space was identified with 2 or less redirections in 88% of the cases., Conclusions: We found a good correlation between the US-estimated distance to the epidural space and the actual measured needle distance in our patients. We suggest that our proposed prepuncture US method, using the paramedian sagittal oblique approach, can be a useful guide to facilitate the placement of epidural needles at mid-low thoracic levels. A randomized controlled trial is necessary to confirm the utility of prepuncture US in thoracic epidural placement.

Background and Objectives: Current guidelines from the American Society of Regional Anesthesia state that an international normalized ratio (INR) of 1.4 is the upper limit of warfarin anticoagulation for safe removal of an epidural catheter. However, these guidelines are based primarily on expert consensus, and there is controversy regarding this recommendation as being "too conservative.", Methods: Prospective (3211) and retrospective (1154) patients undergoing total joint replacement followed by daily warfarin thromboprophylaxis were enrolled in this observational study. All nonsteroidal anti-inflammatory drugs and anticoagulants were held before surgery, and all patients had normal coagulation test results before surgery. Patients were followed twice a day by the acute pain service, no other anticoagulants except nonsteroidal anti-inflammatory drugs were administered, and epidural analgesia was discontinued per institutional protocol. Only patients with INR greater than 1.4 at the time of removal of epidural catheter were included. Neurologic checks were performed for 24 hrs after removal., Results: A total of 4365 patients were included, and 79% underwent knee replacement and 18% hip replacement. Mean age was 68 yrs, and mean weight was 81 kg. Mean (SD) duration of epidural analgesia was 2.1 (0.6) days. Mean (SD) INR at the time of epidural removal was 1.9 (0.4), ranging from 1.5 to 7.1. No spinal hematomas were observed (0% incidence with 95% confidence interval, 0%-0.069%)., Conclusions: Our series of 4365 patients had uncomplicated removal of epidural catheters despite INRs ranging from 1.5 to 5.9. Removal was only during initiation of warfarin therapy (up to approximately 50 hrs after warfarin intake) when several vitamin K factors are likely to still be adequate for hemostasis.

Background and Objectives: While epidural anesthesia (EA) is frequently used, success rate varies and complications associated with incorrect needle placement can occur. Different methods of objective identification of the epidural space (ES) have been suggested, without receiving widespread popularity. This prospective pilot study evaluated continuous pressure measurement during low speed injection with a computerized injection pump to objectively identify the ES., Methods: While EA was performed using a conventional loss of resistance technique in 20 consecutive patients, the injection pump technology was used to obtain pressure readings from the supraspinous ligament, the ligamentum flavum, and the ES. In the next 20 patients, the epidural space was solely identified with the computerized injection pump., Results: Pressure reading obtained during the first part of the study revealed significant differences between the ES vs. the supraspinous ligament, and the ES vs. the ligamentum flavum (8 mm Hg, 95% confidence interval [CI] 6-11 vs 79 mm Hg, 95% CI 74-83 and 92 mm Hg, 95% CI 83-102, respectively) (P < .001). In the second part of the study, the injection pump allowed for successful identification of the ES and performance of EA in all 20 patients., Conclusions: This investigation demonstrates that a computerized injection pump can be used to identify the epidural space and can serve as a base for further comparative research to determine whether this technology can increase the success rate of EA or lower the incidence of side effects.

Background and Objectives: Epidural cannulation is technically difficult in children who have small anatomic structures. Ultrasound information regarding the distance of skin-to-ligament flavum may be useful, leading to an increase in success rate without dural puncture. This study was performed to assess whether ultrasound-measured, skin-to-ligament flavum distance would reflect the needle depth during epidural puncture in infants and children., Methods: The study compromised 180 children, aged 2 to 84 months, undergoing urologic surgery. After induction of anesthesia, ultrasound images of the longitudinal median and transverse views were acquired from L4-L5 in lateral decubitus position. Measured distance of skin-to-ligament flavum in each view was compared with the perpendicular skin-to-epidural depth, which was obtained from needle depth and angle by use of a trigonometric ratio equation. Additionally, we evaluated the ultrasound visibility of the ligament flavum and dura mater, number of puncture attempts, and complications., Results: The correlation coefficient between measured distance and perpendicular epidural depth was slightly higher in longitudinal median view (R2 = 0.848) than in transverse view (R2 = 0.788). The visibility of ligament flavum and dura mater was "good" in 91 and 170 of 180 patients, respectively, and "sufficient" in the remaining subjects. The epidural space was located on first puncture attempt in 179 of 180 cases (99.4%). No incidents of dural puncture or bloody tap occurred., Conclusions: Ultrasound, particularly in the longitudinal median view, provides accurate information on the distance of skin-to-ligament flavum in infants and children. With reference to the measured distance, epidural puncture can be performed with minimal risk of dural puncture (upper limit of 95% CI = 1.67%).

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.

Background and Objectives: Epidural space infection is a potential complication of epidural catheter placement. In this study, we investigated the incidence of epidural needle and catheter contamination after skin surface disinfection with 10% povidone-iodine (PI)., Methods: Sixty seven patients having surgery under epidural anesthesia were enrolled in this prospective study. After preparation with 10% PI, skin swab cultures were taken from the site of catheter insertion. Epidural needles were cultured immediately after epidural catheters were placed. Catheters were removed at 48 hours and 2 to 3 cm of the distal tips were cultured as well., Results: Fifty-six skin swabs, 52 epidural needles, and 48 catheters were cultured. Although only 3.5% (2) colonization was observed on skin surface cultures, 34.6% (18) of the epidural needles and 45.8% (22) of the catheters were colonized. No systemic or local infection was observed., Conclusions: Our results suggest that despite skin surface disinfection with PI, there is still significant risk for contamination of needles and catheters during epidural catheterization.

Objective: Knotting and looping of catheters in the epidural space occur rarely. Visualization of a catheter by radiograph or fluoroscopy is not always possible and often inaccurate in locating the knot and/or the loop with precision. We report the case of an entrapped lumbar epidural catheter. Computed tomography (CT) clearly showed a knotted and looped catheter., Case Report: A 27-year-old woman underwent epidural analgesia during labor. The epidural catheter was inserted 7 cm into the epidural space. After unsuccessful attempts at removing the catheter, a CT scan was performed, and it showed a catheter knot in the epidural space as well as a loop within the interlaminar ligamentum flavum between L3 and L4. This explained why attempts to remove the catheter by manual traction failed. Surgical removal of the catheter was subsequently performed., Conclusions: CT is useful in showing an entrapped epidural catheter and the mechanisms of entrapment. Surgery should be considered when gentle traction fails to retrieve the catheter. CT allows the clinician to localize the catheter with accuracy, thus facilitating surgical follow-up.

Objective: Epidural pressure has remained a relatively unused test of physiological monitoring for the past 3 decades. It is our hypothesis that epidural pressure waveforms (EPWFs) obtained by transducing an epidural catheter (EC) can be used as a surrogate for the accurate location of the EC. The goal of this study was to validate this new method by comparing it with a more objective radiographic technique such as computed tomography cathetergram (CTC)., Methods: The EPWF and CTC were studied in 13 patients receiving continuous epidural analgesia (12 patients who had postoperative pain and 1 patient who had chronic pain). Of these 13 patients, 8 patients had reported inadequate analgesia, and 5 had reported satisfactory analgesia. First, the end of the EC was connected to a disposable pressure transducer, this was followed by a 5-mL normal saline bolus injection to ensure the patency of the EC, and the EPWF was recorded. Next, the patient was taken to an imaging suite and, after injecting contrast through the EC, the course of the catheter was imaged with computed tomography (CT). The CT images were studied by the neuroradiologist and correlated with the EPWF., Results: The EPWF of 5 patients with clinically adequate analgesia revealed a pulsatile waveform on transducing the EC and a crescentic spread of contrast in the epidural space on CTC. In 8 patients with inadequate epidural analgesia, the EPWF measurement failed to show oscillations, and contrast collections were observed in the paraspinous muscles. The results of EPWF and CTC were compared using Fisher's exact test., Conclusions: The strong relationship between EPWF and CTC suggests that EPWF can be used reliably to confirm the correct placement of the EC in a selected group of patients.

Background and Objectives: The combined spinal and epidural (CSE) technique can reduce or eliminate some of the disadvantages of spinal and epidural anesthesia, while still preserving their advantages. CSE anesthesia is now commonly performed with a single-segment needle-through-needle technique; however, this technique involves some controversies about needle handling and the risk of catheter migration. To avoid some of these potential problems, special CSE sets have been produced. In the present study, 2 of these sets were compared with the traditional double-segment technique., Methods: Ninety patients undergoing orthopedic surgery of the lower extremity were randomly allocated into 3 groups of equal size: Group 1, CSE set with an interlocking device between the spinal and epidural needle; group 2, CSE set with a "backeye" at the epidural needle curve for the passage of the spinal needle; group 3, double-segment technique. All epidural needles were 18-gauge, and spinal needles were 27-gauge with a pencil-point tip. In groups 1 and 2, the puncture was performed at the L3-4 interspace, and in group 3 the epidural catheter was first inserted at the L2-3 interspace followed by spinal puncture one interspace lower. Hyperbaric 0.5% bupivacaine, 2 mL, was used for the spinal block, and 4 mL of 2% lidocaine with epinephrine through the epidural catheter was used as a test dose. The block performance characteristics were recorded, and the level of analgesia was studied in a blinded fashion. Postoperatively, a bolus of epidural morphine 2 to 4 mg was used for the control of postoperative pain. All patients were interviewed on the 1st and the 7th postoperative days. Afterwards, the needles and catheters were examined by microscopy., Results: The frequency of the successful CSE block was higher in groups 3 (100%) and 2 (90%) than in group 1 (63%) (P <.05). The mean duration of successful block performance, as well as the median level of analgesia, were similar in all the groups. One case of epidural catheter migration intrathecally was observed (group 1). Postoperative nausea and vomiting occurred in 23% of patients, and the incidence of postdural puncture headache was 2.2%. The incidence of backache at the puncture site was similar in the groups. Microscopy showed 6 distorted spinal needle tips (all in group 1), but no material damage to the epidural catheters., Conclusions: The use of the CSE sets does not seem to save time compared with the double-segment technique. Technical problems, unsuccessful CSE block, and damaged spinal needle tip were noted relatively often with the interlocking CSE set. Anesthetic characteristics in the successful blocks were similar with the different techniques.

Background and Objectives: The use of epidural stimulation to confirm epidural catheter placement has been shown. This case report describes the benefits and problems of using the epidural stimulation test to confirm epidural catheter placement and provides supporting evidence for these observations using radiological imaging., Methods: A nerve stimulator was connected to the proximal end of an epidural catheter via an adapter. The cathode lead was connected to the adapter. The anode lead was connected to an electrode placed on the upper extremity as a grounding site. Using 1 to 10 mA current, a segmental motor response indicated that the catheter was in the epidural space. The absence of a motor response indicated that it was not., Cases: In the first patient, the new test predicted subcutaneous epidural catheter placement, which was subsequently confirmed radiologically. In the second patient, the catheter tip was found to be lying near a nerve root, which was again confirmed radiologically. In the third case, a negative test was initially observed with only local muscle movement over the biceps area (T2). After relocation of the grounding electrode to the lower extremity, segmental intercostal muscle movement (T4-5 level) was observed. The catheter placement was radiologically shown to be in the T4-5 region., Conclusion: This report illustrates some of the potential benefits and problems of using the nerve stimulation test to confirm epidural catheter placement, with radiological verification.