Ultrasound imaging of the thoracic epidural space.

BACKGROUND AND OBJECTIVES: In thoracic epidural anesthesia, the "loss of resistance" technique is the standard technique for the identification of the epidural space (EDS), the feedback to the operator is often solely tactile. Our aim was to establish ultrasonography for the prepuncture demonstration of the anatomic structures surrounding the thoracic EDS and to evaluate its precision and imaging quality. METHODS: We examined 20 volunteers. In each participant, the extradural space and the neighboring anatomic landmarks in the intervertebral space Th 5-6 were identified using 2 imaging techniques: magnetic resonance imaging (MRI) and ultrasonography. We compared corresponding images regarding distance measurements and the visibility of anatomic landmarks. RESULTS: The capacity of ultrasound imaging (US) to depict the thoracic EDS was limited. Due to the better overview, MR images were easier to interpret. However, US proved to be of better value than MRI in the depiction of the dura mater. All important landmarks for the puncture of the thoracic EDS could be identified with both techniques. The overall correlation was satisfactory. US depicted the different structures of the thoracic EDS with an acceptable precision (confidence interval, 4.6 to 8.7 mm). CONCLUSIONS: US showed good correlation with MRI, which is a standard imaging technique for the depiction of the spine. We anticipate that prepuncture ultrasonography may facilitate thoracic epidural anesthesia by needle placement.

Paramedian access to the epidural space: the optimum window for ultrasound imaging.

STUDY OBJECTIVE: To establish a useful ultrasonic approach to the epidural space so as to optimize pre-puncture diagnostics. DESIGN: Prospective study. SETTING: University clinic. PATIENTS: 60 participants (19 to 34 years of age), 40 healthy volunteers (20 male, 20 female) and 20 parturients. INTERVENTIONS: Ultrasound scanning of the lumbar spine was performed at the L(3)-L(4) vertebral interspace. Three ultrasound planes were employed: the transverse, median, and paramedian longitudinal approaches. MEASUREMENTS: We compared the width of the ultrasound-permeable area in the median and paramedian planes and assessed the visibility of the epidural space and its surrounding structures. MAIN RESULTS: In the paramedian plane, the permeable window was larger (p < 0.001) than in the median approach. The visibility of the ligamentum flavum (p < 0.0001), dura mater (p < 0.0001), and cauda equina (p < 0.0001) was significantly higher. Pulsation of epidural vessels could be observed more frequently (p < 0.0001) in the paramedian plane. CONCLUSIONS: The longitudinal paramedian plane provided information about the epidural space depth in excellent imaging quality. The additional information might be beneficial in epidural anesthesia and in other clinical specialties (e.g., neurosurgery, trauma care).

Ultrasound control for presumed difficult epidural puncture.

BACKGROUND: The efficacy of epidural anaesthesia depends on the accurate identification of the epidural space (ES). Abnormal anatomical conditions may make the procedure difficult or impossible. The aim of this study was to investigate whether pre-puncture ultrasound examination of the spinal anatomy might be beneficial in expected cases of difficult epidural anaesthesia. METHODS: We used digital ultrasound equipment with a 5-MHz transducer to assess the anatomy of the ES and the posterior parts of the spinal column. We examined 72 parturients with abnormal anatomical conditions who were scheduled for epidural anaesthesia. The women were randomised into two equal groups. In all patients, the standard loss of resistance technique was used. In the ultrasound group, an ultrasound examination of the appropriate spinal region was conducted prior to epidural puncture. ES depth seen on the ultrasound images was compared to the ES depth measured by the needle. We compared the number of puncture attempts with the standard method (control group) to the number of attempts under ultrasound guidance. RESULTS: Ultrasonography significantly improved operating conditions for epidural anaesthesia. The maximum VAS scores and patient acceptance were significantly better. CONCLUSIONS: With ultrasound measurement of the ES depth, the quality of epidural anaesthesia was enhanced.

Real-time ultrasonic observation of combined spinal-epidural anaesthesia.

BACKGROUND AND OBJECTIVE: The quality of combined spinal-epidural anaesthesia mainly depends on accurate identification of the epidural space. The real-time ultrasound control of the procedure for puncture was therefore evaluated. METHODS: Thirty parturients scheduled for Caesarean section were randomized to three equal groups. Ten control patients received conventional combined spinal-epidural anaesthesia. Ten of the remaining patients received ultrasonic scans by an offline scan technique, and 10 received online imaging of the lumbar region during epidural puncture. The epidural space was identified and needle advancement was surveyed through the interspinal and flaval ligaments. The number of attempts to advance the needle to achieve a successful puncture was measured and compared, as well as the number of vertebral interspaces punctured before successful entry into the epidural space. RESULTS: There was no difference between patient characteristics in the three groups. The visualization of the epidural structures and of the needle manipulations was very effective. In the ultrasound group, the reduction in the number of attempts at puncture was significant (P < 0.036). The number of interspaces necessary for puncture was reduced (P < 0.036) in the ultrasound online group compared with controls. The number of spinal needle manipulations was significantly reduced (P < 0.036). CONCLUSIONS: Real-time ultrasonic scanning of the lumbar spine is an easy procedure. It provides an accurate reading of the location of the needle tip and facilitates the performance of combined spinal-epidural anaesthesia.

Colour Doppler imaging of the interspinous and epidural space.

BACKGROUND AND OBJECTIVE: In recent studies, ultrasonic diagnostic imaging has proved useful in the screening of the trajectory of the epidural needle. With regard to possible side-effects of spinal and epidural anaesthesia caused by vessel injury, we aimed to evaluate the usability of Colour Doppler imaging for the depiction of interspinous vessels in prepuncture examination. METHODS: Ultrasonic examination of the L3/4 interspace area was performed in 20 volunteers. Using a 4-MHz and a 7-MHz probe with B-mode and Colour Doppler imaging, respectively, we compared four settings for the quality of vessel depiction in the puncture area. Overall resolution was evaluated according to the distinction of landmarks. Vascular structures were identified by pulsation (B-mode) or blood flow (Doppler). RESULTS: Colour Doppler imaging of the L3/4 interspace was unachievable using the 7-MHz transducer. Vessel detection was possible in 50% of the B-mode images and in all of the 4-MHz Doppler images. Vessels were perceptible from a diameter of 0.5 mm. Veins were the predominantly visible structures. Overall vessel visibility was best using 4-MHz Colour Doppler. CONCLUSIONS: Prepuncture Doppler imaging can provide the epiduralist with information regarding the position of vessels in the needle trajectory. This might help to reduce complications in regional anaesthesia.

[The visualisation of dura perforation and blood patches with ultrasound]. / Die Darstellung von Duraperforationen und Bloodpatches mit Ultraschall.

The postdural puncture headache (PDPH) is a possible complication after spinal or epidural puncture. The therapeutic concept is usually organised step by step, but the epidural blood patch is the most reliable and effective therapy. In earlier studies myelographie, epidurographie and MRT were used, to visualise the localisation of the dural defect and to describe the effects of patching the epidural space. Our working group focused on the utilisation of ultrasound and we decided to use this technique for the visualisation of bloodpatches. With agreement of the local ethics committee we monitored the performance of 4 epidural bloodpatches in pregnant women, who suffered from PDPH. We used a General Electric LQ 400 ultrasonograph with a 7-MHz-probe. To ensure sterile conditions we used sterile ultrasound sleeves and sterile ultrasound gel. In 3 of 4 cases a continuity loss could be represented in the doppel layer signal of the dura. It had the size of the diameter of a Tuohy needle. In one case the defect of the dura was larger than in the preliminary investigations (2,5 - 3 mm). The ultrasonography of the epidural space was performed in the paramedian scan. All patches were placed by using the conventional loss of resistance technique with using online ultrasound support. The epidural puncture and the application of the blood patches were visualised simultaneously in all cases. With the injection of blood a brief expansion of the epidural space was seen. The patients recieved a mean injection volume of 17 ml sterile blood. 10 to 40 seconds after the injection of blood the disconituity of the dura doppel layer signal was no longer provable. Within a short time we could detect the increase of cerebrospinal fluid and the patients headache was treated sucessfully. The clinical use of this diagnostic technique can be found in the simultaneous presentation of the dura leakage and the intervention while performing an epidural bloodpatch. Since these informations are relevant for further clinical practice further investigations are warranted.

The lumbar epidural space in pregnancy: visualization by ultrasonography.

Epidural anaesthesia is an important analgesia technique for obstetric delivery. During pregnancy, however, obesity and oedema frequently obscure anatomical landmarks. Using ultrasonography, we investigated the influence of these changes on spinal and epidural anatomy. We examined 53 pregnant women who were to receive epidural block for vaginal delivery or Caesarean section. The first ultrasound imaging was performed immediately before epidural puncture; the follow-up scan was done 9 months later. The ultrasound scan of the spinal column was performed at the L3/4 interspace in transverse and longitudinal planes, using a Sonoace 6000 ultrasonograph (Kretz, Marl, Germany) equipped with a 5.0-MHz curved array probe. We measured two distances from the skin to the epidural space: the minimum (perpendicular) and the maximum (oblique) needle trajectory. The quality of ultrasonic depiction was analysed by a numerical scoring system. An average weight reduction of 12.5 kg had occurred by the follow-up examination. During pregnancy, the optimum puncture site available on the skin for epidural space cannulation was smaller, the soft-tissue channel between the spinal processes was narrower, and the skin-epidural space distance was greater. The epidural space was narrower and deformed by the tissue changes. The visibility of the ligamentum flavum, of the dura mater and of the epidural space decreased significantly during pregnancy. Nevertheless, ultrasonography offered useful pre-puncture information. Thus far, palpation has been the only available technique to facilitate epidural puncture. Ultrasound imaging enabled us to assess the structures to be perforated. We anticipate that this technique will become valuable clinically.