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Biomedical subjects

U Stock

Publications and source records attributed to U Stock.

At least 19 recordsLinked to original sources
PubMed2005

[Extravasal position of central venous catheters despite unsuspicious ECG-guidance].

OBJECTIVE: Does the electrocardiographic method for central venous catheter positioning distinguish between a correct intravasal and a malpositioned extravasal position? METHODS: 24 cardiac surgical patients were enrolled in this prospective observational study. In 18 patients the left, in another 6 patients the right internal jugular vein was cannulated. Using a J-wire within a triple-lumen catheter the amplitude of the P-wave was measured at 3 different intravasal sites: Intra-1: (intravasal baseline electrocardiogram), i. e. 10 cm marking of the catheter on skin level; Intra-2: clear rise of the P-wave amplitude upon further insertion of the catheter; Intra-3: maximum P-wave amplitude. At this position the control of the catheter tip was achieved by means of transoesophageal echocardiography (TOE). Intraoperatively, another J-wire within a triple-lumen catheter was placed by the heart surgeon on 3 extravasal sites and the ECG was recorded: Extra-1: extravasal at the left innominate vein above the pericardial reflection; Extra-2: extravasal on the superior vena cava below the pericardial reflection; Extra-A: extravasal on ascending aorta below the pericardial reflection. The catheter was suture fixed with its tip in position Intra-3. Post surgery a chest radiograph was taken. RESULTS: All catheter tips were visualised at the basis of the Crista terminals (border between right atrium and superior vena cava) by TOE control. The rise of the P wave amplitude at Intra-2, Extra-2 and Extra-A was highly significant compared to the base line at Intra-1 (Intra-1/Intra-2, Intra-1/Extra-2, Intra-1/Extra-A: p in each case < 0.001). The P wave amplitudes of the corresponding intra- and extravasal positions of the left innominate vein (Intra-1/Extra-1, n = 18, p = 0.096)) as well as those of the superior vena cava (Intra-2/Extra-2, n = 24, p = 0.859) did not differ. CONCLUSION: The electrocardiographic method can not differentiate between intra- and extravasal position of a central venous catheter, and thus, presumably fails to identify malpositioning as a result of vascular perforation.

Aged↗
PubMed2004

Central venous catheters--the inability of 'intra-atrial ECG' to prove adequate positioning.

BACKGROUND: The classic increase in P wave size, known as 'P-atriale', is a widely accepted criterion for determination of proper positioning of central venous catheter tips. Recent transoesophageal echocardiography (TOE) studies did not confirm intra-atrial position despite advancing the central venous catheter further than indicated by ECG guidance. We postulate that the pericardial reflection rather than the entry into the right atrium corresponds to the ECG changes. In order to test our hypothesis we sought to determine the anatomical substrate for the electrical changes in an animal study. Subsequently, a modified version of the study was undertaken in man and is also reported. METHODS: In six juvenile pigs the left external jugular vein and right carotid artery were cannulated. A triple-lumen central venous catheter was positioned by ECG guidance using a Seldinger wire as an exploring electrode. The venous and arterial catheters were suture fixed 2 cm beyond the onset of an increase in P wave size. The corresponding anatomical catheter tip position was determined by open exploration of the vessels and the heart. Subsequently the catheter tip position (during advancement) of a pulmonary artery catheter and the corresponding electrical ECG changes were examined in 10 patients during open chest cardiac surgery. RESULTS: All catheters-arterial and venous, in animals and humans-revealed an increase in size of the P wave as well as the QRS complex. All venous catheters were positioned in the superior vena cava, beyond the pericardial reflection but outside the right atrium. All arterial catheters were positioned in the ascending aorta thus also beyond the pericardial reflection. CONCLUSIONS: The start of an increase in P wave size does not correspond with the entrance of the right atrium. The anatomic equivalent for the electrophysiological changes of the ECG is the pericardial reflection. ECG guidance is unable to distinguish between venous and arterial catheter position.

Aged↗
PubMed2001

Evaluation of different minimally invasive techniques in pediatric cardiac surgery: is a full sternotomy always a necessity?

STUDY OBJECTIVES: A variety of minimally invasive techniques have been recently introduced in adult cardiac surgery. Experiences with children and newborns are, however, limited. In this report, we present our first experiences with different methods of ministernotomies for closure of atrial septum defect (ASD) and ventricular septum defect (VSD) in pediatric cardiac patients. Also, the current literature for different surgical approaches is reviewed. PATIENTS AND METHODS: Twenty-five pediatric patients (range, 4 months to 12 years old) underwent elective ASD or VSD closure. Surgical access was either without division of the sternum (group A, n = 5), with partial inferior sternotomy (group B, n = 5), total sternotomy with limited skin incision (group C, n = 5), or total sternotomy with full skin incision (group D, n = 10). RESULTS: There were no severe intraoperative complications regarding exposure, cannulation, or bleeding. Conversion to full sternotomy was not necessary in any patient. Bypass time and cross-clamp time in groups A, B, and C were comparable to the standard operation (group D). However, preparation time was significantly increased in one minimally invasive group (group A vs group D, p<0.05). Despite general feasibility, the transxiphoidal access without sternotomy compromises exposure of the ascending aorta, resulting in impaired administration of cross-clamping, cardioplegia, and especially de-airing. CONCLUSIONS: Transatrial pediatric cardiac operations can be performed without or with limited sternotomy. The partial sternotomy allows uncompromised exposure of the great vessels and should be favored over the transxiphoidal approach. The operative access and perioperative risk is comparable to a classical standard surgical approach. Advantages include improved cosmetic results in combination with a high degree of safety.

Cardiac Surgical Procedures↗
PubMed2000

Tissue engineering of pulmonary heart valves on allogenic acellular matrix conduits: in vivo restoration of valve tissue.

BACKGROUND: Tissue engineering using in vitro-cultivated autologous vascular wall cells is a new approach to biological heart valve replacement. In the present study, we analyzed a new concept to process allogenic acellular matrix scaffolds of pulmonary heart valves after in vitro seeding with the use of autologous cells in a sheep model. METHODS AND RESULTS: Allogenic heart valve conduits were acellularized by a 48-hour trypsin/EDTA incubation to extract endothelial cells and myofibroblasts. The acellularization procedure resulted in an almost complete removal of cells. After that procedure, a static reseeding of the upper surface of the valve was performed sequentially with autologous myofibroblasts for 6 days and endothelial cells for 2 days, resulting in a patchy cellular restitution on the valve surface. The in vivo function was tested in a sheep model of orthotopic pulmonary valve conduit transplantation. Three of 4 unseeded control valves and 5 of 6 tissue-engineered valves showed normal function up to 3 months. Unseeded allogenic acellular control valves showed partial degeneration (2 of 4 valves) and no interstitial valve tissue reconstitution. Tissue-engineered valves showed complete histological restitution of valve tissue and confluent endothelial surface coverage in all cases. Immunohistological analysis revealed cellular reconstitution of endothelial cells (von Willebrand factor), myofibroblasts (alpha-actin), and matrix synthesis (procollagen I). There were histological signs of inflammatory reactions to subvalvar muscle leading to calcifications, but these were not found in valve and pulmonary artery tissue. CONCLUSIONS: The in vitro tissue-engineering approach using acellular matrix conduits leads to the in vivo reconstitution of viable heart valve tissue.

Animals↗
PubMed2000

Cardiac performance after deep hypothermic circulatory arrest in chronically cyanotic neonatal lambs.

OBJECTIVES: It is controversial whether immature cyanotic hearts are more susceptible to ischemic injury than normoxemic hearts. Acutely induced alveolar hypoxic stress before cardiopulmonary bypass has been used as a model of cyanosis and is reported to worsen recovery of immature hearts after subsequent ischemic insult by means of a free radical injury mechanism. Because of concerns about the relevance of acute alveolar repair to the chronic cyanosis encountered clinically, we assessed the effects of chronic cyanosis without alveolar hypoxia, acute alveolar hypoxia, and normoxemia on recovery of cardiac function after deep hypothermic circulatory arrest. METHODS: A chronic cyanosis model was created in 8 lambs by an anastomosis between the pulmonary artery and the left atrium (cyanosis group). Eight lambs underwent sham operation (control). One week later, the animals underwent cardiopulmonary bypass with 90 minutes of deep hypothermic circulatory arrest at 18 degrees C. Another 8 lambs underwent 45 minutes of hypoxic ventilation before bypass, with arterial oxygen tension being maintained at 30 mm Hg (acute hypoxia group). Cardiac index, preload recruitable stroke work, and tau were measured. Malondialdehyde and nitrate-nitrite, nitric oxide metabolites, were also measured in the coronary sinus. Myocardial antioxidant reserve capacity at 2 hours of reperfusion was assessed by measuring lipid peroxidation in left ventricular tissue samples incubated with t-butylhydroperoxide at 37 degrees C. RESULTS: Oxygen tension was 35 +/- 3 mm Hg in the acute hypoxia group versus 93 +/- 7 mm Hg in the control group. In the acute hypoxia group the recovery of cardiac index, preload recruitable stroke work, and tau were significantly worse than that found in both the control and cyanosis groups. Preload recruitable stroke work at 2 hours of reperfusion was slightly but significantly lower in the cyanosis group than in the control group. The postischemic level of nitric oxide metabolites was significantly lower in the acute hypoxia group than in the cyanosis and control groups. However, malondialdehyde levels in the coronary sinus and myocardial antioxidant reserve capacity were not significantly different among the groups. CONCLUSION: Recovery of left ventricular function after deep hypothermic circulatory arrest in neonatal lambs with chronic cyanosis was slightly worse than that found in acyanotic animals. Acute hypoxia before bypass was associated with significantly worse recovery of left ventricular function, and the mechanism of injury may be related to an impairment of nitric oxide production. Free radical injury does not appear to explain any differences among cyanotic, acyanotic, and acutely hypoxic animals in recovery of left ventricular function after ischemia.

Analysis of Variance↗
PubMed2000

Fabrication of a trileaflet heart valve scaffold from a polyhydroxyalkanoate biopolyester for use in tissue engineering.

Previously, we reported the implantation of a single tissue engineered leaflet in the posterior position of the pulmonary valve in a lamb model. The major problems with this leaflet replacement were the scaffold's inherent stiffness, thickness, and nonpliability. We have now created a scaffold for a trileaflet heart valve using a thermoplastic polyester. In this experiment, we show the suitability of this material in the production of a biodegradable, biocompatible scaffold for tissue engineered heart valves. A heart valve scaffold was constructed from a thermoplastic elastomer. The elastomer belongs to a class of biodegradable, biocompatible polyesters known as polyhydroxyalkanoates (PHAs) and is produced by fermentation (Metabolix Inc., Cambridge, MA). It was modified by a salt leaching technique to create a porous, three-dimensional structure, suitable for tissue engineering. The trileaflet heart valve scaffold consisted of a cylindrical stent (1 mm X 15 mm X 20 mm I.D.) containing three valve leaflets. The leaflets were formed from a single piece of PHA (0.3 mm thick), and were attached to the outside of the stent by thermal processing techniques, which required no suturing. After fabrication, the heart valve construct was allowed to crystallize (4 degrees C for 24 h), and salt particles were leached into doubly distilled water over a period of 5 days to yield pore sizes ranging from 80 to 200 microns. Ten heart valve scaffolds were fabricated and seeded with vascular cells from an ovine carotid artery. After 4 days of incubation, the constructs were examined by scanning electron microscopy. The heart valve scaffold was tested in a pulsatile flow bioreactor and it was noted that the leaflets opened and closed. Cells attached to the polymer and formed a confluent layer after incubation. One advantage of this material is the ability to mold a complete trileaflet heart valve scaffold without the need for suturing leaflets to the conduit. Second advantage is the use of only one polymer material (PHA) as opposed to hybridized polymer scaffolds. Furthermore, the mechanical properties of PHA, such as elasticity and mechanical strength, exceed those of the previously utilized material. This experiment shows that PHAs can be used to fabricate a three-dimensional, biodegradable heart valve scaffold.

Animals↗
PubMed1999

Effects of cyanosis and hypothermic circulatory arrest on lung function in neonatal lambs.

BACKGROUND: Lung function is often impaired after cardiac surgery and cardiopulmonary bypass (CPB), particularly in chronically cyanotic patients. This study aimed to evaluate lung function in a surgically created chronic cyanotic neonatal lamb model after CPB and deep hypothermic circulatory arrest (DHCA) and to assess the role of nitric oxide (NO) in the pathogenesis of increased pulmonary vascular resistance. METHODS: A chronic cyanosis model was surgically created in 7 lambs (4.7+/-0.8 days old) by anastomosing the pulmonary artery (PA) to the left atrium (LA). Another 7 lambs underwent a sham operation (control). One week later, the animals underwent shunt takedown and CPB with 90 minutes of DHCA at 18 degrees C. Cardiac index (CI), pulmonary vascular resistance index (PVRI), lung dynamic compliance (Cdyn), alveolar-arterial oxygen difference (AaDO2), left atrial plasma nitrate/nitrite (NO metabolites) levels, and pulmonary cGMP production (concentration difference between LA and PA) were measured before CPB and at 1 and 2 hours after reperfusion. RESULTS: The cyanosis model consistently produced significantly lower arterial oxygen tension (34.8+/-2.3 vs 93.1+/-8.8 torr in control, p < 0.001) and Qp/Qs (0.6+/-0.1 vs 1.0+/-0.0 in control, p < 0.001) than controls. Postoperative PVRI was significantly lower in the cyanosis group than in controls, although CPB with DHCA significantly elevated PVR in both cyanotic and control animals. There were no significant differences in AaDO2 and Cdyn after CPB between groups. The level of NO metabolites did not change before or after CPB in either cyanotic or acyanotic animals. NO metabolite levels tended to be higher in the cyanotic animals (p = 0.08). There was no significant difference in pulmonary cGMP production between both groups. CONCLUSIONS: These findings suggest that CPB with DHCA, per se, does not affect NO production in cyanotic or acyanotic neonatal lambs but causes increased PVR in both groups. Chronic cyanosis does not result in reduced pulmonary function after CPB with DHCA, and is associated with lower PVR. The mechanism may involve an increased NO production in cyanotic animals.

Animals↗
PubMed1999

Tissue engineering of autologous aorta using a new biodegradable polymer.

BACKGROUND: Ovine pulmonary valve leaflets and pulmonary arteries have been tissue-engineered (TE) from autologous cells and biodegradable polyglycolic acid (PGA)-polyglactin copolymers. Use of this cell-polymer construct in the systemic circulation resulted in aneurysm formation. This study evaluates a TE vascular graft in the systemic circulation which is based on a new copolymer of PGA and polyhydroxyalkanoate (PHA). METHODS: Ovine carotid arteries were harvested, expanded in vitro, and seeded onto 7-mm diameter PHA-PGA tubular scaffolds. The autologous cell-polymer vascular constructs were used to replace 3-4 cm abdominal aortic segments in lambs (group TE, n = 7). In a control group (n = 4), aortic segments were replaced with acellular polymer tubes. Vascular patency was evaluated with echography. All control animals were sacrificed when the grafts became occluded. Animals in TE group were sacrificed at 10 days (n = 1), 3 (n = 3), and 5 months (n = 3). Explanted TE conduits were evaluated for collagen content, deoxyribonucleic acid (DNA) content, structural and ultrastructural examination, mechanical strength, and matrix metalloproteinase (MMP) activity. RESULTS: The 4 control conduits became occluded at 1, 2, 55, and 101 days. All TE grafts remained patent, and no aneurysms developed by the time of sacrifice. There was one mild stenosis at the anastomotic site after 5 months postoperatively. The percent collagen and DNA contents approached the native aorta over time (% collagen = 25.7%+/-3.4 [3 months] vs 99.6%+/-11.7 [5 months], p < 0.05; and % DNA = 30.8%+/-6.0 [3 months] vs 150.5%+/-16.9 [5 months], p < 0.05). Histology demonstrated elastic fibers in the medial layer and endothelial specific von Willebrand factor on the luminal surface. The mechanical strain-stress curve of the TE aorta approached that of the native vessel. A 66 kDa MMP-2 was found in the TE and native aorta but not in control group. CONCLUSIONS: Autologous aortic grafts with biological characteristics resembling the native aorta can be created using TE approach. This may allow the development of "live" vascular grafts.

Animals↗
PubMed1996

Iatrogenic vertebrojugular arteriovenous fistula.

Arteriovenous fistulae originating from the vertebral artery are rare. We report a patient in whom a vertebral artery-jugular venous fistula developed following insertion of a central venous catheter via the internal jugular vein. The fistula was successfully occluded surgically.

Aged↗
PubMed1995

[CT angiography in the follow-up after carotid endarterectomy].

PURPOSE: To prove the usefulness and clinical value of early CT angiography with maximum intensity projection after carotid endarterectomy: for demonstrating postoperative results. METHODS: In 16 patients with angiographically confirmed 20 high grade stenoses of internal carotid artery CT angiography was performed before and after carotid surgery within 7 days. The evaluation of successful surgery was related to complete plaque removal and patency of internal carotid artery after endarterectomy based on preoperative CT angiography. Classification of stenosis was performed according to the NASCET study. RESULTS: In 2/20 cases severe stenoses remained after surgery, which were demonstrated using CT angiography and confirmed by digital subtraction arteriography. 3/20 cases showed mild stenosis and 15/20 were normal. CONCLUSION: CT angiography is best suited to evaluate results after carotid surgery. The method enables delineation of complete removal of calcified plaque and patency of carotid artery.

Aged↗
PubMed1983

Repression of glycoprotein synthesis and release of surface coat during transformation of Trypanosoma brucei.

The biosynthesis of the variant surface glycoprotein (VSG) and its release from the surface of Trypanosoma brucei 427 variant clone MITat 1.4 (117) during in vitro transformation of bloodstream trypomastigotes to procyclic trypomastigotes was investigated. After transfer to the transformation medium at 27 degrees C, VSG synthesis is repressed with a half-time, t1/2 = 30 min. Concomitantly VSG-specific mRNA is lost suggesting that repression operates at the transcriptional level. The expression-linked extra gene copy, which codes for VSG, is retained during and after completion of transformation. After repression of VSG synthesis, surface VSG is shed from the cells into the culture medium. During release part of VSG (apparent mol. wt. 61 000) is proteolytically cleaved to a product (apparent mol. wt. 51 000) which represents the N-terminal domain of the protein as judged by the absence of the carbohydrate moiety normally linked to the C terminus.

Animals↗
PubMed1976

[The symptomatic treatment of seasonal allergic rhinitis (author's transl)].

The aetiology, pathophysiology and symptomatology of seasonal rhinitis are briefly presented. Symptomatic therapy with antihistamines, nasal decongestants and local and systemic corticosteroids is critically discussed. The results of a trial with Disodium cromoglycate are reported. This is shown to be a valuable drug in the symptomatic management of seasonal rhinitis. It should be tried before resorting to steroid therapy.

Adrenal Cortex Hormones↗
PubMed1975

[Allergies to animal hair in diseases of the upper respiratory tract (author's transl)].

Among 214 patients diagnosed in 1972 as being allergic to animal hair, 79 (48 women) were re-examined later. In almost all cases with a positive personal (33) or family history (26) of allergy there was a particularly rapid sensitization. The largest proportion of pathogenic allergens was from guinea pigs (39), cats (17), golden hamsters (11), rabbits (6), horses, dogs and budgerigars (2 each). 14 patients reacted to the main antigen alone in prick or intracutaneous tests, while in all other cases there were cross-reactions, most frequently to epithelium of sheep, cattle or horse. In interpreting intranasal provocation tests with the chief antigen, the degress of rhinorrhoea was particulary reliable (59 subjects). The most effective treatment was complete withdrawal of allergens: of 65 persons who removed their domestic pet or avoided contact with it, 32 were cured at once and a further 19 within about eight weeks. 14 subjects continued to have symptoms, but in half of these there was also house dust allergy, while others had resumed contact with domestic animals.

Adolescent↗
PubMedDate not supplied

Prospective assessment of carotid bifurcation disease with spiral CT angiography in surface shaded display (SSD)-technique.

PURPOSE: To decide, whether spiral CT-angiography (CTA) in surface display (SSD)-technique is suitable for accurate quantification of carotid artery stenoses. MATERIAL AND METHODS: Forty-four patients (25 male, 19 females) with a total of 80 symptomatic carotid artery were studied prospectively with selective cerebral angiography and spiral CTA in SSD-technique. The degree of stenosis was determined according to the NASCET-study. RESULTS: Assessment of the degree of stenoses with CTA and angiography was the same in 36% of mild stenoses, in 64% of moderate stenoses, in 68% of severe stenoses, and in 95% of the occluded internal carotid arteries. Overall, CTA in SSD-technique showed equivalent results as selective cerebral angiography in 65% of all cases. CONCLUSION: Spiral CTA in SSD-technique is inferior to selective cerebral angiography. Calcified plaques, vessel opacification and thresholding influence the most grading of stenosis.

Adult↗