Development of an ultrasound-guided technique for pudendal nerve block in cat cadavers.

The objective of this prospective experimental cadaveric study was to develop an ultrasound-guided technique to perform an anaesthetic pudendal nerve block in male cats. Fifteen fresh cadavers were used for this trial. A detailed anatomical dissection was performed on one cat in order to scrutinise the pudendal nerve and its ramifications. In a second step, the cadavers of six cats were used to test three different ultrasonographic approaches to the pudendal nerve: the deep dorso-lateral, the superficial dorso-lateral and the median transperineal. Although none of the approaches allowed direct ultrasonographical identification of the pudendal nerve branches, the deep dorso-lateral was found to be the most advantageous one in terms of practicability and ability to identify useful and reliable landmarks. Based on these findings, the deep dorso-lateral approach was selected as technique of choice for tracer injections (0.1 ml 1% methylene blue injected bilaterally) in six cat cadavers distinct from those used for the ultrasonographical study. Anatomical dissection revealed a homogeneous spread of the tracer around the pudendal nerve sensory branches in all six cadavers. Finally, computed tomography was performed in two additional cadavers after injection of 0.3 ml/kg (0.15 ml/kg per each injection sites, left and right) contrast medium through the deep dorso-lateral approach in order to obtain a model of volume distribution applicable to local anaesthetics. Our findings in cat cadavers indicate that ultrasound-guided pudendal nerve block is feasible and could be proposed to provide peri-operative analgesia in clinical patients undergoing perineal urethrostomy.

Intraoperative fabrication of patient-specific moulded implants for skull reconstruction: single-centre experience of 28 cases

BACKGROUND Intraoperatively fabricated polymethylmethacrylate (PMMA) implants based on computer-designed moulds were used to improve cosmetic results after hard tissue replacement. To assess the implant's cosmetic and functional results we performed both subjective and objective assessments. METHODS This retrospective analysis was performed using a cohort of 28 patients who received PMMA implants between February 2009 and March 2012. The cosmetic and functional results were assessed using a patient questionnaire. Furthermore an objective volumetric subtraction score (0-100) was applied and implant thickness, as well as gaps and tiers, were measured. RESULTS Patients mainly judged their cosmetic result as "good". Two of the 28 patients found their cosmetic result unfavourable. The functional result and stability was mainly judged to be good. Measurements of implant thickness showed a very high correlation with the thickness of the contralateral bone. Volumetric subtraction led to a median quality of 80 on a scale from 0 to 100. Median gaps around the margins of the implant were 1.5 mm parietally, 1.7 mm frontally and 3.5 mm fronto-orbitally, and median tiers were 1.2 mm, 0 mm and 0 mm respectively. The overall rate of surgical revisions was 10.7 % (three patients). Two patients suffered from wound healing disturbances (7.1 %). The overall complication rate was comparable to other reports in the literature. CONCLUSIONS Implantation of intraoperatively fabricated patient-specific moulded implants is a cost-effective and safe technique leading to good clinical results with a low complication rate.

Ultrasound-assessed non-culprit and culprit coronary vessels differ by age and gender

AIM To investigate age- and gender-related differences in non-culprit versus culprit coronary vessels assessed with virtual histology intravascular ultrasound (VH-IVUS). METHODS In 390 patients referred for coronary angiography to a single center (Luzerner Kantonsspital, Switzerland) between May 2007 and January 2011, 691 proximal vessel segments in left anterior descending, circumflex and/or right coronary arteries were imaged by VH-IVUS. Plaque burden and plaque composition (fibrous, fibro-fatty, necrotic core and dense calcium volumes) were analyzed in 3 age tertiles, according to gender and separated for vessels containing non-culprit or culprit lesions. To classify as vessel containing a culprit lesion, the patient had to present with an acute coronary syndrome, and the VH-IVUS had to be performed in a vessel segment containing the culprit lesion according to conventional coronary angiography. RESULTS In non-culprit vessels the plaque burden increased significantly with aging (in men from 37% ± 12% in the lowest to 46% ± 10% in the highest age tertile, P < 0.001; in women from 30% ± 9% to 40% ± 11%, P < 0.001); men had higher plaque burden than women at any age (P < 0.001 for each of the 3 age tertiles). In culprit vessels of the lowest age tertile, plaque burden was significantly higher than that in non-culprit vessels (in men 48% ± 6%, P < 0.001 as compared to non-culprit vessels; in women 44% ± 18%, P = 0.004 as compared to non-culprit vessels). Plaque burden of culprit vessels did not significantly change during aging (plaque burden in men of the highest age tertile 51% ± 9%, P = 0.523 as compared to lowest age tertile; in women of the highest age tertile 49% ± 8%, P = 0.449 as compared to lowest age tertile). In men, plaque morphology of culprit vessels became increasingly rupture-prone during aging (increasing percentages of necrotic core and dense calcium), whereas plaque morphology in non-culprit vessels was less rupture-prone and remained constant during aging. In women, necrotic core in non-culprit vessels was very low at young age, but increased during aging resulting in a plaque morphology that was very similar to men. Plaque morphology in culprit vessels of young women and men was similar. CONCLUSION This study provides evidence that age- and gender-related differences in plaque burden and plaque composition significantly depend on whether the vessel contained a non-culprit or culprit lesion.

Ultrasound-guided block of sciatic and femoral nerves: an anatomical study

The sheep is a popular animal model for human biomechanical research involving invasive surgery on the hind limb. These painful procedures can only be ethically justified with the application of adequate analgesia protocols. Regional anaesthesia as an adjunct to general anaesthesia may markedly improve well-being of these experimental animals during the postoperative period due to a higher analgesic efficacy when compared with systemic drugs, and may therefore reduce stress and consequently the severity of such studies. As a first step 14 sheep cadavers were used to establish a new technique for the peripheral blockade of the sciatic and the femoral nerves under sonographic guidance and to evaluate the success rate by determination of the colorization of both nerves after an injection of 0.5 mL of a 0.1% methylene blue solution. First, both nerves were visualized sonographically. Then, methylene blue solution was injected and subsequently the length of colorization was measured by gross anatomical dissection of the target nerves. Twenty-four sciatic nerves were identified sonographically in 12 out of 13 cadavers. In one animal, the nerve could not be ascertained unequivocally and, consequently, nerve colorization failed. Twenty femoral nerves were located by ultrasound in 10 out of 13 cadavers. In three cadavers, signs of autolysis impeded the scan. This study provides a detailed anatomical description of the localization of the sciatic and the femoral nerves and presents an effective and safe yet simple and rapid technique for performing peripheral nerve blocks with a high success rate.

Laparoscopic computer-navigated ablation of liver metastases

Objective In order to benefit from the obvious advantages of minimally invasive liver surgery there is a need to develop high precision tools for intraoperative anatomical orientation, navigation and safety control. In a pilot study we adapted a newly developed system for computer-assisted liver surgery (CALS) in terms of accuracy and technical feasibility to the specific requirements of laparoscopy. Here, we present practical aspects related to laparoscopic computer assisted liver surgery (LCALS). Methods Our video relates to a patient presenting with 3 colorectal liver metastases in Seg. II, III and IVa who was selected in an appropriate oncological setting for LCALS using the CAScination system combined with 3D MEVIS reconstruction. After minimal laparoscopic mobilization of the liver, a 4- landmark registration method was applied to enable navigation. Placement of microwave needles was performed using the targeting module of the navigation system and correct needle positioning was confirmed by intraoperative sonography. Ablation of each lesion was carried out by application of microwave energy at 100 Watts for 1 minute. Results To acquire an accurate (less 0.5 cm) registration, 4 registration cycles were necessary. In total, seven minutes were required to accomplish precise registration. Successful ablation with complete response in all treated areas was assessed by intraoperative sonography and confirmed by postoperative CT scan. Conclusions This teaching video demonstrates the theoretical and practical key points of LCALS with a special emphasis on preoperative planning, intraoperative registration and accuracy testing by laparoscopic methodology. In contrast to mere ultrasound-guided ablation of liver lesions, LCALS offers a more dimensional targeting and higher safety control. This is currently also in routine use to treat vanishing lesions and other difficult to target focal lesions within the liver.

Fixed low-dose ultrasound-assisted catheter-directed thrombolysis for intermediate- and high-risk pulmonary embolism

AIMS No standardized local thrombolysis regimen exists for the treatment of pulmonary embolism (PE). We retrospectively investigated efficacy and safety of fixed low-dose ultrasound-assisted catheter-directed thrombolysis (USAT) for intermediate- and high-risk PE. METHODS AND RESULTS Fifty-two patients (65 ± 14 years) of whom 14 had high-risk PE (troponin positive in all) and 38 intermediate-risk PE (troponin positive in 91%) were treated with intravenous unfractionated heparin and USAT using 10 mg of recombinant tissue plasminogen activator per device over the course of 15 h. Bilateral USAT was performed in 83% of patients. During 3-month follow-up, two [3.8%; 95% confidence interval (CI) 0.5-13%] patients died (one from cardiogenic shock and one from recurrent PE). Major non-fatal bleeding occurred in two (3.8%; 95% CI, 0.5-13%) patients: one intrathoracic bleeding after cardiopulmonary resuscitation requiring transfusion, one intrapulmonary bleeding requiring lobectomy. Mean pulmonary artery pressure decreased from 37 ± 9 mmHg at baseline to 25 ± 8 mmHg at 15 h (P < 0.001) and cardiac index increased from 2.0 ± 0.7 to 2.7 ± 0.9 L/min/m(2) (P < 0.001). Echocardiographic right-to-left ventricular end-diastolic dimension ratio decreased from 1.42 ± 0.21 at baseline to 1.06 ± 0.23 at 24 h (n = 21; P < 0.001). The greatest haemodynamic benefit from USAT was found in patients with high-risk PE and in those with symptom duration < 14 days. CONCLUSION A standardized catheter intervention approach using fixed low-dose USAT for the treatment of intermediate- and high-risk PE was associated with rapid improvement in haemodynamic parameters and low rates of bleeding complications and mortality.

Increased intraoperative epidural pressure in lumbar spinal stenosis patients with a positive nerve root sedimentation sign

Purpose The sedimentation sign (SedSign) has been shown to discriminate well between selected patients with and without lumbar spinal stenosis (LSS). The purpose of this study was to compare the pressure values associated with LSS versus non-LSS and discuss whether a positive SedSign may be related to increased epidural pressure at the level of the stenosis. Methods We measured the intraoperative epidural pressure in five patients without LSS and a negative SedSign, and in five patients with LSS and a positive SedSign using a Codman TM catheter in prone position under radioscopy. Results Patients with a negative SedSign had a median epidural pressure of 9 mmHg independent of the measurement location. Breath and pulse-synchronous waves accounted for 1–3 mmHg. In patients with monosegmental LSS and a positive SedSign, the epidural pressure above and below the stenosis was similar (median 8–9 mmHg). At the level of the stenosis the median epidural pressure was 22 mmHg. A breath and pulse-synchronous wave was present cranial to the stenosis, but absent below. These findings were independent of the cross-sectional area of the spinal canal at the level of the stenosis. Conclusions Patients with LSS have an increased epidural pressure at the level of the stenosis and altered pressure wave characteristics below. We argue that the absence of sedimentation of lumbar nerve roots to the dorsal part of the dural sac in supine position may be due to tethering of affected nerve roots at the level of the stenosis.

Minimally Invasive Intraoperative Stiffness Measurement of Lumbar Spinal Motion Segments

OBJECTIVE: To test a new tiny-tipped intraoperative diagnostic tool that was designed to provide the surgeon with reliable stiffness data on the motion segment during microdiscectomy. A decrease in stiffness after nuclectomy and a measurable influence of muscle tension were assumed. If the influence of muscle tension on the motion segment could at least be ruled out, there should be no difference with regard to stiffness between women and men. If these criteria are met, this new intraoperative diagnostic tool could be used in further studies for objective decision-making regarding additional stabilization systems after microdiscectomy. METHODS: After evaluation of the influence of muscle relaxation during in vivo measurements with a spinal spreader between the spinous processes, 21 motion segments were investigated in 21 patients. Using a standardized protocol, including quantified muscle relaxation, spinal stiffness was measured before laminotomy and after nuclectomy. RESULTS: The decrease in stiffness after microdiscectomy was highly significant. There were no statistically significant differences between men and women. The average stiffness value before discectomy was 33.7 N/mm, and it decreased to 25.6 N/mm after discectomy. The average decrease in stiffness was 8.1 N/mm (24%). CONCLUSION: In the moderately degenerated spine, stiffness decreases significantly after microdiscectomy. Control for muscle relaxation is essential when measuring in vivo spinal stiffness. The new spinal spreader was found to provide reliable data. This spreader could be used in further studies for objective decision-making about additional stabilization systems after microdiscectomy.

Randomized, controlled trial of ultrasound-assisted catheter-directed thrombolysis for acute intermediate-risk pulmonary embolism.

BACKGROUND In patients with acute pulmonary embolism, systemic thrombolysis improves right ventricular (RV) dilatation, is associated with major bleeding, and is withheld in many patients at risk. This multicenter randomized, controlled trial investigated whether ultrasound-assisted catheter-directed thrombolysis (USAT) is superior to anticoagulation alone in the reversal of RV dilatation in intermediate-risk patients. METHODS AND RESULTS Fifty-nine patients (63±14 years) with acute main or lower lobe pulmonary embolism and echocardiographic RV to left ventricular dimension (RV/LV) ratio ≥1.0 were randomized to receive unfractionated heparin and an USAT regimen of 10 to 20 mg recombinant tissue plasminogen activator over 15 hours (n=30; USAT group) or unfractionated heparin alone (n=29; heparin group). Primary outcome was the difference in the RV/LV ratio from baseline to 24 hours. Safety outcomes included death, major and minor bleeding, and recurrent venous thromboembolism at 90 days. In the USAT group, the mean RV/LV ratio was reduced from 1.28±0.19 at baseline to 0.99±0.17 at 24 hours (P<0.001); in the heparin group, mean RV/LV ratios were 1.20±0.14 and 1.17±0.20, respectively (P=0.31). The mean decrease in RV/LV ratio from baseline to 24 hours was 0.30±0.20 versus 0.03±0.16 (P<0.001), respectively. At 90 days, there was 1 death (in the heparin group), no major bleeding, 4 minor bleeding episodes (3 in the USAT group and 1 in the heparin group; P=0.61), and no recurrent venous thromboembolism. CONCLUSIONS In patients with pulmonary embolism at intermediate risk, a standardized USAT regimen was superior to anticoagulation with heparin alone in reversing RV dilatation at 24 hours, without an increase in bleeding complications. CLINICAL TRIAL REGISTRATION URL http://www.clinicaltrials.gov. Unique identifier: NCT01166997.

Fixed low-dose ultrasound-assisted catheter-directed thrombolysis followed by routine stenting of residual stenosis for acute ilio-femoral deep-vein thrombosis.

Patients with ilio-femoral deep-vein thrombosis (DVT) are at high risk of developing the post-thrombotic syndrome (PTS). In comparison to anticoagulation therapy alone, extended venography-guided catheter-directed thrombolysis without routine stenting of venous stenosis in patients with ilio-femoral DVT is associated with an increased risk of bleeding and a moderate reduction of PTS. We performed a prospective single-centre study to investigate safety, patency and incidence of PTS in patients with acute ilio-femoral DVT treated with fixed-dose ultrasound-assisted catheter-directed thrombolysis (USAT; 20 mg rt-PA during 15 hours) followed by routing stenting of venous stenosis, defined as residual luminal narrowing >50%, absent antegrade flow, or presence of collateral flow at the site of suspected stenosis. A total of 87 patients (age 46 ± 21 years, 60% women) were included. At 15 hours, thrombolysis success ≥50% was achieved in 67 (77%) patients. Venous stenting (mean 1.9 ± 1.3 stents) was performed in 70 (80%) patients, with the common iliac vein as the most frequent stenting site (83%). One major (1%; 95% CI, 0-6%) and 6 minor bleedings (7%; 95%CI, 3-14%) occurred. Primary and secondary patency rates at 1 year were 87% (95% CI, 74-94%) and 96% (95% CI, 88-99%), respectively. At three months, 88% (95% CI, 78-94%) of patients were free from PTS according to the Villalta scale, with a similar rate at one year (94%, 95% CI, 81-99%). In conclusion, a fixed-dose USAT regimen followed by routine stenting of underlying venous stenosis in patients with ilio-femoral DVT was associated with a low bleeding rate, high patency rates, and a low incidence of PTS.