Orthopaedic metallic artefact reduction algorithm facilitates CT evaluation of the urinary tract after hip prosthesis.

AIM: To examine the improvement in the visualisation of bladder and ureteric pathologies next to a hip prosthesis with metallic artefact reduction for orthopaedic implants (O-MAR). MATERIALS AND METHODS: Thirty-four patients who underwent pelvic computed tomography (CT) for non-prosthesis-related causes were enrolled retrospectively. Portal venous phase scans were reconstructed both with standard iterative reconstruction (ITR) and with O-MAR. The density of the ureters and the bladder was measured at both sides in the plane of the prosthesis. A semi-quantitative score was also used to assess visibility. The R (version 3.4.1) package was used for statistical analysis. RESULTS: The average (µ) density of the 41 prosthesis side ureters was significantly lower on ITR images (µ=-94.76±150.48 [±SD] HU) than on O-MAR images (µ=-13.40±36.37 HU; p<0.0004). The difference between the ITR and O-MAR (µ=-138.62±182.64 versus -35.55±40.21 HU; p<0.0003) was also significant at the prosthesis side of the bladder. The visibility of the prosthesis side ureters was improved: 53.7% was obscured on ITR series compared to 4.9% on O-MAR. The visibility score was also better across all levels (p<0.001) with O-MAR. In four cases (13%), the O-MAR images significantly changed the diagnosis: in two cases ureteric stones, in one case each a bladder stone and a bladder tumour were discovered. CONCLUSIONS: O-MAR reconstruction of CT images significantly improves the visibility of the urinary tract adjacent to metallic hip implants. Thus, O-MAR is essential for detecting ureteric and bladder pathologies in patients with a hip prosthesis.

Effectiveness of intra-arterial steroid administration for the treatment of steroid-refractory acute gastrointestinal graft-versus-host disease.

AIM: To retrospectively assess the clinical effectiveness of intra-arterial steroid administration (IASA) treatment in adult patients who developed steroid-refractory gastrointestinal acute graft-versus-host disease (GI-aGvHD) (≥stage II) following haematopoietic stem cell transplantation. MATERIALS AND METHODS: Clinical data of 10 consecutive adult patients (age range, 19-61 years; mean age, 42 years) of a single centre with GI-aGvHD (≥stage II) who showed no response to intravenous methylprednisolone and received IASA into the superior (SMA) and/or inferior mesenteric arteries (IMA) were analysed. The severity of aGvHD was determined as the volume of diarrhoea (stages 0-IV) and the Glucksberg grading system before and 12±3 SD, 27±4 and 54±6 days after IASA treatment. Median follow-up was 65 days (range, 22-370 days). RESULTS: Six out of 10 patients at 12 days, 8/10 patients at 27 days, 6/10 patients at 54 days after IASA showed gastrointestinal response. Among them, 1/10 patients at 12 days, 4/10 patients at 27 days, and the same 4/10 patients at 54 days showed complete resolution of GI-aGvHD. The 4/10 patients who reached complete resolution of GI-aGvHD at day 12 or 27 showed a sustained symptom-free state. One in 10 patient showed only a temporary response, 5/10 patients died between days 22 and 67. CONCLUSIONS: IASA seems to be a potentially useful second-line therapy for intravenous steroid-refractory GI-aGvHD.

Prognostic value of pre-embolisation MRI features of uterine fibroids in uterine artery embolisation.

AIM: To evaluate the prognostic value of pretreatment pelvic magnetic resonance imaging (MRI) features in uterine artery embolisation (UAE) for symptomatic fibroids. MATERIALS AND METHODS: MRI characteristics of 109 fibroids (≥3 cm) in 70 patients were analysed retrospectively. Imaging was performed 1.8±1.3 (SD) months before and 6.6±1.8 months after UAE. On pretreatment images, signal intensity (SI) of fibroids was compared with that of the myometrium and skeletal muscle on T1- and T2-weighted sequences; the contrast enhancement pattern and localisation of fibroids were also analysed. Fibroid volume reduction (VR) was assessed by control imaging. The numerical analogue quality-of-life score was obtained before and after UAE. Statistical analysis was performed using the Mann-Whitney U-test, Kruskal-Wallis test, and Wilcoxon signed-rank test. RESULTS: The mean fibroid volume decreased by 51.1±30.8% during the 6.6±1.8 months (p<0.001). Mean quality-of-life score improved by 48.2±27.6 points (p<0.001). The mean VR of submucosal fibroids (82.1±18.5%) was greater than that of intramural (49.4±30.7%) and subserosal (43±28.3%) fibroids (p<0.001 for both). Fibroids that were isointense/hyperintense to myometrium on T2-weighted images showed a better response than hypointense fibroids (63.7±25.8% versus 48.6±31.3%, respectively; p=0.041). On contrast-enhanced images, isointense/hyperintense fibroids showed a better VR than hypointense fibroids (61.3±27.4% versus 47.6±31.6%, respectively; p=0.035). Baseline fibroid volume of <50 cm3 was also associated with favourable imaging outcome (p=0.021). T2 SI compared to skeletal muscle and T1 SI compared to myometrium or skeletal muscle did not show association with VR. CONCLUSIONS: Localisation, T2 SI, contrast enhancement, and <50 cm3 fibroid volume were associated with better VR; these may help with treatment decisions.

Safety, clinical outcome, and fracture rate of femoropopliteal stenting using a 4F compatible delivery system.

OBJECTIVE: To determine the safety, clinical outcome, and fracture rate of femoropopliteal interventions using 4F stents. METHODS: Between January 2010 and December 2011, 112 symptomatic patients were treated by stent implantation. Ten patients were lost to follow up; therefore, 102 patients (62 men; mean age 66.4 ± 10.1 years) were retrospectively analyzed. The indication for femoropopliteal revascularization was severe claudication (Rutherford-Becker score = 3) in 63 (62%) patients and chronic critical limb ischemia (Rutherford-Becker score = 4-6) in 39 (38%). Follow up included palpation of peripheral pulses and measurement of ankle brachial index. In patients with suspected in-stent restenosis duplex ultrasonography was performed. In 2013, patients were asked to return for a fluoroscopic examination of the stents. RESULTS: 114 lesions (Trans-Atlantic InterSociety Consensus-C and D, n = 45) were treated with 119 stents (Astron Pulsar, n = 42; Pulsar-18, n = 77). Lesions were long (≥100 mm) in 49 cases and heavily calcified in 35. Stents were long (≥120 mm) in 46 cases. Ten stents were partially overlapped. The technical and clinical success rates were 100%. Two puncture related complications were noted, neither of which required surgical repair. Eleven patients died (myocardial infarction, n = 4; stroke, n = 2; cancer, n = 5) and nine patients underwent major amputation (above knee, n = 4). The primary patency rate was 83% at 6 months and 80% at 12 months. The primary assisted patency rate was 97% at 6 months and 94% at 12 months. The secondary patency rate was 86% at 6 months and 85% at 12 months. The prevalence of fractures was 26% (type III and IV, 10%) after an average follow up of 25 months. CONCLUSION: Femoropopliteal stenting using a 4F compatible delivery system can be accomplished with a low complication rate, acceptable fracture rate, and with similar 12 month patency and revascularization rates as their 6F counterparts.

Different genetic impact in the development of renal length and width: a twin study.

BACKGROUND: Ultrasound measurements of renal dimensions are conventionally limited to renal length, shape and cortical thickness. These are regarded as adequate for normal therapeutic decision-making and volume measurements are reserved for a few clinical trials. However, there is no evidence concerning the degree to which renal length or volume is independently susceptible to heritable and environmental influences. AIM: We aimed to determine whether renal length or width (as a surrogate of volume) was more influenced by heritability. METHODS: A single operator measured renal length and width in 114 adult monozygotic and same-sex dizygotic Hungarian twin pairs (mean age 43.6 ± 16.3 years), using an Esaote MyLab 70X ultrasound machine with curved array transducer (1-8 MHz, CA431). RESULTS: Analysis of within-pair co-twin correlations adjusted for age and gender showed that the age- and sex-adjusted heritability of average renal length was 51% (95% confidence interval, 29-72%). Renal width showed negligible genetic influence. Common environmental effects had no influence, and unshared environments were responsible for 49-80% of the variance, mainly renal width. CONCLUSIONS: This study is the first to demonstrate the moderate heritability and limited environmental influence on renal length, and the contrasting lack of heritability of renal width, which is mainly influenced by unshared environmental components, that is lifestyle habits. Renal width therefore better represents the influence of modifiable environmental factors than renal length. The results suggest that renal width not length should be reported to facilitate early detection and monitoring of renal disease.

Genetic effects on refraction and correlation with hemodynamic variables: a twin study.

Spherical equivalent (SE) has not been linked to increased cardiovascular morbidity. Methods: 132 Hungarian twins(age 43.3±16.9 years) underwent refraction measurements (Huvitz MRK-3100 Premium AutoRefractokeratometer)and oscillometry (TensioMed Arteriograph). Results: Heritability analysis indicated major role for genetic components in the presence of right and left SE (82.7%, 95%CI, 62.9 to 93.7%, and 89.3%, 95%CI, 72.8 to 96.6%),while unshared environmental effects accounted for 17% (95%CI, 6.3% to 37%), and 11% (95%CI, 3.4% to 26.7%)of variations adjusted for age and sex. Bilateral SE showed weak age-dependent correlations with augmentation index (AIx), aortic pulse wave velocity (r ranging between 0.218 and 0.389, all p < 0.01), aortic systolic blood pressure and pulse pressure (r between 0.188 and 0.289, p < 0.05). Conclusions: These findings support heritability of spherical equivalent, which does not coexist with altered hemodynamics (e.g. accelerated arterial aging).Accordingly, SE and the investigated hemodynamic parameters seem neither phenotypically nor genetically associated.

A possible genetic influence in parenchyma and small airway changes in COPD: a pilot study of twins using HRCT.

UNLABELLED: Genetic effects that contribute to the risk of developing chronic obstructive pulmonary disease (COPD) have been reported. Our purpose was to estimate the possible genetic influence on CT features related to COPD in twins. METHODS: Two COPD-discordant and one COPD-concordant monozygotic (MZ) twin pair, in addition to 2 control dizygotic (DZ) twin pairs underwent a low-dose high resolution computer tomography (HRCT) in inspiration and expiration (Philips Brilliance 16). RESULTS: Monozygotic twins were more similar in lung volume expiration and in air trapping score compared to dizygotics (382 cm(3) vs. 2303 cm(3) and 17.6% vs. 26.6%, respectively). In general, MZ twin pairs showed almost identical HRCT features independently of smoking attitude and COPD status. The dizygotic twin pairs showed larger differences in HRCT features compared to MZ twins. CONCLUSIONS: Lung parenchymal and small airway changes (lung density, presence of bronchial wall thickening, bronchiectasis and/or mucus plug formation, air trapping and emphysema score) seem to be genetically associated traits, independently of smoking/COPD history. A future study with a larger sample size should confirm our findings.

Partial absence of superior vena cava in an adult patient. Case report and literature review.

Absence of the superior vena cava (SVC) is a rare variety of vascular anomaly. The purpose of this report is to describe the computed tomography (CT) findings of the partial absence of the SVC without persistent left SVC in a patient with no evidence of congenital cardiovascular disease and no prior history of central venous instrumentation. A 77-year-old woman with a history of colon cancer underwent thoracoabdominal CT imaging because of abdominal pain of uncertain cause. No tumor recurrence was observed. A complicated"investigation" confirmed a thymoid cancer surgery back in 1976, which was accompanied by resection of the SVC and the left brachiocephalic vein because of their invasion. Owing to the absence of the SVC and bilateral brachiocephalic veins, caval hypertension developed in the patient, resulting in the dilation of cavo-caval anastomoses. In addition, new anastomoses were opened. The clinical significance and possible embryogenesis of this anomaly are discussed. The extremely rare condition of the partial absence of the SVC appeared with subcutaneous dilated, tortuous collaterals in an asymptomatic adult patient. This anomaly is becoming clinically more relevant with the increasing use of minimally invasive vascular surgery.

Percutaneous endovascular treatment of innominate artery lesions: a single-centre experience on 77 lesions.

PURPOSE: To assess primary success and safety of percutaneous transluminal angioplasty and/or stenting of innominate artery lesions and to compare its 30-day stroke/mortality level with the literature data. METHODS: A total of 72 patients (77 stenoses, five recurrent, 58 symptomatic and 39 female) with seven innominate vessel occlusions, nine subocclusive lesions and 61 significant (>60%) stenoses of innominate artery treated between 2000 and 2009 were retrospectively reviewed. With the exception of seven, all procedures were performed using a transfemoral approach. A stent was implanted in 49 (63.6%) cases. Follow-up included neurological examination, carotid duplex scan and office/telephone interview. RESULTS: Primary technical success was 93.5% (72/77). There was neither periprocedural (<48 h) death, nor major neurological complication. Minor periprocedural neurological complications consisted of 2/72 (2.6%) ipsilateral TIAs. Access site complications included 4 (5.2%) access site bleedings. Follow-up was achieved in 65/72 (90.3%) of all patients and 68 (88.3%) of all procedures for a mean of 42.3 months and revealed neither major neurological complication, nor additional TIA. The cumulative primary patency rate was 100% at 12 months, 98+/-1.6% at 24 months, and 69.9+/-8.5% at 96 months. The cumulative secondary patency rate was 100% at 12 and at 24 months, and 81.5+/-7.7% at 96 months. Log-rank test showed no significant difference (p=0.79) in primary cumulative patencies between PTA alone (n=28) or PTA/stent (n=49). CONCLUSION: Transfemoral PTA with or without stent appears to be a safe treatment option for innominate artery lesions.

Post-traumatic pseudoaneurysm of the great saphenous vein: a case report.

Venous (pseudo)aneurysms are rare entities. Herewith we report a case of the right lower extremity in a 42-year-old woman in whom a non-pulsatile mass was diagnosed only by physical examination as a hematoma and was treated conservatively. Six months later ultrasound and phlebography identified a pseudoaneurysm of the great saphenous vein. Post-traumatic venous pseudoaneurysm should be considered among the differential diagnostic options of a subcutaneous non-pulsatile mass in patients with a history of physical trauma. Surgery was offered which was rejected by the patient. Further one month follow-up showed no change.

Generalized alterations in the biomechanical properties of large veins in non-thrombotic thrombophilic young patients.

AIM: In young, post-thrombotic patients, venous distensibility is decreased not only in the affected lower limb, but also in the contralateral limb and in the jugular vein when compared to age-matched control subjects. In the present study, we investigated venous wall mechanical properties in young, asymptomatic thrombophilic patients. METHODS: Eleven young (24+/-0.4 years) control subjects and 9 age-matched patients (21.1+/-1.8 years) with proven thrombophilic molecular defects, but without any signs or history of previous deep vein thrombosis, were compared. Anterolateral and mediolateral diameters of the common femoral, axillary and internal jugular veins were measured by ultrasonography in situ. Pressure alterations were induced by altering body positions and by pressure-controlled Valsalva tests. Distensibility was calculated from diameter and pressure changes. RESULTS: In thrombophilic patients, resting diameter of both the common femoral and of internal jugular veins at low transmural pressure was larger than those for the control subjects. Distensibility, however, was significantly less when high pressures were applied. Alterations in diameter of the axillary vein were minimal. CONCLUSION: Our measurements suggest that there are generalized changes in venous mechanical properties in thrombophilic patients even before the appearance of thrombotic processes. These biomechanical alterations of the venous wall and/or surrounding connective tissue are similar to those found in connection with aging and in post-thrombotic patients. The pathological mechanisms behind these processes are unknown.

Long-term retrievability of IVC filters: should we abandon permanent devices?

Thromboembolic disease produces a considerable disease burden, with death from pulmonary embolism in the UK alone estimated at 30,000-40,000 per year. Whilst it is unproven whether filters actually improve longevity, the morbidity and mortality associated with thromboembolic disease in the presence of contraindications to anticoagulation is high. Thus complications associated with filter insertion, and whilst they remain in situ, must be balanced against the alternatives. Permanent filters remain in situ for the remainder of the patient's life and any complications from the filters are of significant concern. Filters that are not permanent are therefore attractive in these circumstances. Retrievable filters, to avoid or decrease long-term filter complications, appear to be a significant advance in the prevention of pulmonary embolism. In this review, we discuss the safety and effectiveness of both permanent and retrievable filters as well as the retrievability of retrievable inferior vena cava (IVC) filters, to explore whether the use of permanent IVC filters can be abandoned in favor of retrievable filters. Currently four types of retrievable filters are available: the Recovery filter (Bard Peripheral Vascular, Tempe, AZ, USA), the Günther Tulip filter (Cook, Bloomington, IN, USA), the OptEase Filter (Cordis, Roden, The Netherlands), and the ALN filter (ALN Implants Chirurgicaux, Ghisonaccia, France). Efficacy and safety data for retrievable filters are as yet based on small series, with a total number of fewer than 1,000 insertions, and follow-up is mostly short term. Current long-term data are poor and insufficient to warrant the long-term implantation of these devices into humans. The case of fractured wire from a Recovery filter that migrated to the heart causing pericardial tamponade requiring open heart surgery is a reminder that any new endovascular device remaining in situ in the long term may produce unexpected problems. We should also bear in mind that the data on permanent filters are much more robust, with reports on over 9,500 cases with follow-up of up to 8 years. The original implantation time of 10-14 days has been extended to more than 100 days as the mean implantation time with some of the filter types. Follow-up (preferably prospective) is necessary for all retrievable filters, whether or not they are retrieved. Until these data become available we should restrict ourselves to the present indications of permanent and retrievable filters. If long-term follow-up data on larger numbers of cases confirm the initial data that retrievable filters are as safe and effective as permanent filters, the use of the retrievable filters is likely to expand.

Safety of arch aortography for assessment of carotid arteries.

PURPOSE: To retrospectively review the safety of arch aortography and compare complication rates with published figures for selective catheter angiography. METHODS: The medical records of patients undergoing arch aortography over the last 3 years (n=311; 180 male, 131 female; mean+/-SD age 71.0+/-9.2 years, range 42-90 years) were retrospectively reviewed. Any peri-procedural (0-48 h) complications were recorded. A certified neurologist (MSR/GSV) classified all questionable neurological events. RESULTS: There were no focal neurological events or deaths (n=0; 0%; CI: 0-0.96%). Non-focal neurological events included mild disorientation (n=2; 0.6%; CI: 0.176-2.31) and unequal pupils (n=1; 0.3%; CI: 0.056-1.79%). Cardiovascular events included symptomatic hypotension (n=4; 1.3%; CI: 0.50-3.25%), angina (n=1; 0.3%; CI: 0.056-1.79%) and arrhythmia (n=4; 1.3%; CI: 0.50-3.25). There were 27 minor access site complications (8.7%; CI: 6.0-12.3). None of these complications extended hospital stay. None of the arch angiograms had to be followed by selective carotid angiography. CONCLUSION: Arch aortography appears to have a lower neurological complication rate than selective carotid angiography.

Placement of Hemobahn stent-grafts in femoropopliteal arteries: early experience and midterm results in 18 patients.

PURPOSE: To determine the outcome of a new polytetrafluoroethylene (PTFE)-covered stent-graft in the treatment of occlusive lesions of the femoropopliteal arteries. MATERIALS AND METHODS: Eighteen patients with intermittent claudication (Fontaine stages IIb-IV; Rutherford classes I/2-III/5) and occlusive lesions of the superficial femoral and/or popliteal artery were treated with use of a new PTFE-covered stent-graft (Hemobahn). Indication for stent-graft insertion was an unsatisfactory result after balloon dilation. RESULTS: Successful stent-graft placement was achieved in 17 patients (94%). In one patient, additional insertion of a Palmaz stent was necessary because of a stent-graft wrinkle. Mean ankle-brachial index increased from 0.72 +/- 0.15 preoperatively to 0.94 +/- 0.17 postoperatively (P =.028). Fifteen patients (83%) experienced an initial improvement of at least one clinical stage. Primary patency was 61% +/- 11% at 3 months and 49% +/- 12% at 6 months. Stent-graft occlusion was observed in 13 patients (72%). In four patients, the stent-graft was reopened percutaneously by balloon angioplasty (n = 2) and/or rotational thrombectomy (n = 2). Therefore, the secondary patency rate was 67% +/- 11% at 3 months and 61% +/- 11% at 6 months. Patency rates proved to be significantly lower for stent-grafts longer than 10 cm (P =.03). Intimal hyperplasia at the proximal or distal end of the stent-graft was observed in seven patients (39%). Complications such as access site hematoma (n = 3), distal thromboembolism (n = 2), and abscess formation around the stent-graft (n = 1) were observed. CONCLUSION: Despite excellent initial angiographic results, the patency rate in lesions treated with the Hemobahn stent-graft in this small study was unsatisfactory. Use of stent-grafts longer than 10 cm and the occurrence of intimal hyperplasia proved to be major factors in the reduction of long-term patency rates.

[Percutaneous angioplasty of the innominate artery in 89 patients: experience of 19 years]. / Az arteria anonyma percutan angioplasztikás kezelése: 19 év tapasztalata 89 betegen.

PURPOSE: To assess retrospectively the success of percutaneous transluminal angioplasty (PTA) in treating innominate artery stenoses and occlusion in a large series of patients with long-term follow-up results. METHODS: In symptomatic patients with high degree (> 60%) stenosis, innominate artery PTA was performed. Long-term follow-up was undertaken by blood pressure measurements on both arms as well as subclavian, right common carotid and right vertebral duplex scan. RESULTS: Between 1981 and 1999, primary success rate of 89 innominate artery PTA (84 stenoses, 5 occlusions) was 96.4%. Complications included 1 left occipital lobe infarction (1.5%), 2 puncture-site thrombosis (2.9%), and 4 TIA (5.8%). Two patients with restenosis were successfully treated with rePTA. Cumulative primary patency was 98 +/- 2% at 6 months, 93 +/- 4% at 16 to 117 months, secondary patency was 100% at 6 months, 98 +/- 2% at 12 to 117 months; 61% of the patients became symptomless, 32% improved, 7% showed no improvement. CONCLUSION: Angioplasty of the innominate artery has been proven to be safe and effective on a large series of patients. For innominate artery stenosis and short occlusion, PTA should be the first treatment of choice.

Venous myogenic tone and its regulation through K+ channels depends on chronic intravascular pressure.

In this study, we compared the level of myogenic tone and its negative-feedback control through specific K+ channels in two types of human veins (saphenous [SV] and cephalic [CV] veins), which experience different ranges of pressure in vivo. We also investigated whether an experimental model of increased venous pressure in rats exposed to head-up tilt for 2 weeks produced changes similar to those observed in the human veins. Cylindrical vein segments were cannulated, their diameters were measured, and the intraluminal pressure was set at different levels (2 to 30 mm Hg) in vitro. Acetylcholine test showed that during the regular harvesting process 76% of the human SVs exposed for coronary bypass grafts had no functional endothelium. We found significant myogenic tone in the human SV, where the in vivo pressure is high, but it was not present in the human CV, where the in vivo pressure is low. The nonspecific K+ channel antagonist, tetraethylammonium (TEA), decreased the diameter of the human SV but not the CV. Iberiotoxin and 4-aminopyridine, blockers of the Ca(2+)-sensitive (KCa) and voltage-gated K+ (KV) channels, also decreased the diameter of the human SV by 10.2 +/- 4.8% and 19.5 +/- 4.7%, respectively. In the rat SV, significant myogenic tone was found, but TEA had no effect, even after 2 weeks of in vivo pressure increase in the hindlimb by head-up tilt. We conclude that (1) an increased venous myogenic tone correlates with higher chronic intraluminal pressure loads, (2) KCa and KV channels counterregulate the myogenic tone in human, but not in rat, saphenous vein, (3) the counterregulatory effect is more effective at high than at low intraluminal in vitro pressure levels, and (4) its development is probably a long-term process.

Differential effects of etomidate, propofol, and midazolam on calcium and potassium channel currents in canine myocardial cells.

BACKGROUND: Intravenous anesthetics etomidate, propofol, and midazolam produce negative inotropic effects of various degrees. The mechanism underlying these differences is largely unknown. METHODS: The effects of intravenous anesthetics on L-type Ca2+, transient outward and inward-rectifier K+ channel currents (ICa, IKto, and IK1) were compared in canine ventricular cells using the whole-cell voltage-clamp technique. ICa and IK were elicited by progressively depolarizing cells from -40 to +40 mV, and from -90 to +60 mV, respectively. The peak amplitude and time-dependent inactivation rate of ICa and IK were measured before, during, and after the administration of equimolar concentrations (5, 30, or 60 microM) of etomidate, propofol, or midazolam. RESULTS: Exposure to etomidate, propofol, and midazolam produced a concentration-dependent inhibition of ICa. Midazolam was the most potent intravenous anesthetic; at 60 microM, etomidate, propofol, and midazolam decreased peak ICa by 16 +/- 4% (mean +/- SEM), 33 +/- 5%, and 47 +/- 5%, respectively. Etomidate, propofol, and midazolam given in a 60-microM concentration decreased IKto by 8 +/- 3%, 9 +/- 2%, and 23 +/- 3%, respectively. IK1 was decreased by 60 microM etomidate and midazolam by 20 +/- 6% and 14% +/- 5%, respectively. Propofol had no effect on IK1. CONCLUSIONS: At equimolar concentrations, intravenous anesthetics decreased the peak ICa, IKto, and IK1 with various degrees of potency. Effects of anesthetics on ICa were significantly greater compared with their effects on K+ currents. These findings suggest that the negative inotropic actions of etomidate, propofol, and midazolam are related, at least in part, to decreased ICa. Some effects, such as IK inhibition, may partially antagonize effects of decreased ICa. Indeed, the final effect of these intravenous anesthetics on myocardium will be the sum of these and other sarcolemmal and intracellular effects.

Local control of veins: biomechanical, metabolic, and humoral aspects.

The incidence of vein diseases (varicosity, thrombophlebitis, phlebosclerosis, orthostatic intolerance) is extremely high. In several countries it may exceed that of the arterial pathology by an order of magnitude. In the last decades, this recognition and the rapid accumulation of experimental data have resulted in a progressive reevaluation of the physiological significance of the venous system, which had been rather neglected earlier by scientists. The major aim of this review is to provide a critical survey of recent selected literature related to different physiological functions of the venous system as well as to biomechanical, metabolic, and humoral (ionic, hormonal) aspects of the local venous control. Local neural control mechanisms, including effects of catecholamines and other transmitters, are regarded to be beyond the scope of this work. At present, the synthesis of information available in the literature meets certain difficulties, because occasionally poorly defined methodological techniques and physiological parameters have been applied. On the other hand, a significant part of works dealing with venous physiology is excellent and inspirational. We have good reason to believe that the fast accumulation of reliable scientific data on this very important field will soon reach a new critical level, then an even more effective integration of knowledge will be possible.

Venous myogenic tone: studies in human and canine vessels.

Active and passive mechanical properties of human saphenous and canine femoral and saphenous vein segments were measured in vitro to assess the degree of pressure-dependent venous myogenic tone (% change in diameter, physiological saline solution vs. Ca(2+)-free solution) in these vessels. Stepwise elevation of intraluminal pressure from 2 to 20 mmHg caused an active myogenic response, which was calcium dependent. Side branches of human saphenous veins (OD at 20 mmHg: 1.92 +/- 0.15 mm control; 2.41 +/- 0.18 mm relaxed) displayed a larger degree of myogenic tone (approximately 25%) compared with dog saphenous (OD: 2.84 +/- 0.16 mm control; 2.89 +/- 0.16 mm relaxed) and femoral (OD: 3.56 +/- 0.32 control; 3.66 +/- 0.31 mm relaxed) veins (2-3%). This alteration in myogenic tone results in over 120% change in lumen capacity for the human saphenous vein, whereas for the dog saphenous and femoral veins, the change in lumen capacity is less than 10%. The vessels showed a constriction to norepinephrine as well as a reversible dilation to Ca(2+)-free perfusion. These results support the hypothesis that an active myogenic response may play an important role in the regulation of vascular capacity in the human saphenous vein, which is subject to substantial pressure variations due to changing orthostatic loads.

Pressure-induced activation of membrane K+ current in rat saphenous artery.

Pressurization of isolated arteries may result in Ca(2+)-dependent contraction and membrane depolarization. Because the open state probability of some vascular muscle K+ channels is augmented by rises in cytosolic Ca2+ and membrane depolarization, we investigated the possibility that increases in intraluminal pressure activate K+ channels in isolated, perfused rat saphenous arteries. Stepwise increases in intraluminal pressure from 5 to 205 mm Hg resulted in increasing, active arterial contraction, measured as smaller diameters in physiological salt solution than in Ca(2+)-free solution. Addition of 10 mM tetraethylammonium to the physiological salt solution to block arterial muscle K+ channels caused progressively greater diameter reductions at pressures above 25 mm Hg. Microelectrode measurements of membrane potential showed that tetraethylammonium depolarized arterial muscle more at 105 mm Hg (16 +/- 1 mV) than at 25 mm Hg (10 +/- 1 mV). The sensitivity of K+ current to tetraethylammonium was also demonstrated in patch-clamped vascular muscle cells from the same arteries. Peak whole-cell K+ current was suppressed 47% and 79% by 1 and 10 mM tetraethylammonium, respectively. This same current was enhanced 3.6-fold by the Ca2+ ionophore A23187 (10 microM), suggesting a Ca2+ dependence. We conclude that increases in intraluminal pressure progressively activate tetraethylammonium-sensitive K+ channels in the arterial muscle membrane. This can serve as a negative feedback mechanism to limit pressure-induced arterial constriction.