Biomedical subjects

Monique Augstburger

Publications and source records attributed to Monique Augstburger.

9 recordsLinked to original sources

PubMed2004

Myocardial and pulmonary effects of aqueous oxygen with acute hypoxia.

BACKGROUND: The purpose of this paper was to evaluate myocardial and pulmonary effects of aqueous oxygen (AO) delivered directly into the pulmonary circulation in acute hypoxia. METHODS: Six calves (2 months old, 68.0 +/- 2.2 kg) after general anesthesia, mechanical ventilation, and median sternotomy underwent total right heart bypass using fixed flow with continuous pressure and blood gas measurements in carotid and femoral arteries, left atrium, the coronary sinus and PA. Measurements of systemic and PA pressures and O2 saturations; myocardial O2 atrioventricular (AV) differences; and O2 extraction were made. After base line measurements, hypoxic ventilation reducing the mean arterial PO2 from 277 +/- 102 mm Hg to 47 +/- 4 mm Hg (p < 0.0005) was maintained for 30 minutes. Without changes in the hypoxic ventilation (mean arterial PO2 = 49 +/- 11 mm Hg) 3 ml/min of hyperbaric aqueous oxygen (AO = oxygen diluted in saline solution) was administered into the PA for 30 minutes. Pulmonary blood flow was maintained during the entire experiment (3.7 +/- 0.3 L/min). RESULTS: Hypoxic ventilation significantly raised (p < 0.05) the systolic (30 +/- 7 vs 21 +/- 4 mm Hg), diastolic (20 +/- 6 vs 12 +/- 3 mm Hg), and mean (23 +/- 7 vs 15 +/- 3 mm Hg) PA pressure; PA/systemic pressure ratio for systolic (0.37 +/- 0.08 vs 0.25 +/- 0.06) and mean (0.56 +/- 0.19 vs 0.29 +/- 0.11) pressures; and pulmonary vascular resistance (PVR) (5.63 +/- 1.06 vs 3.53 +/- 0.75 U). Aqueous oxygen (AO) infusion significantly reduced (p < 0.05) the values obtained with hypoxic ventilation; systolic (23 +/- 5 vs 30 +/- 7 mm Hg), diastolic (11 +/- 4 vs 20 +/- 6 mm Hg), and mean (14 +/- 3 vs 23 +/- 7 mm Hg) PA pressure; PA/systemic pressure ratio for systolic (0.25 +/- 0.05 vs 0.37 +/- 0.08) and mean pressures (0.29 +/- 0.12 vs 0.56 +/- 0.19); and PVR (3.41 +/- 1.01 vs 5.63 +/- 1.06 U). AO infusion in the pulmonary circulation did not influence the myocardial O2 atrioventricular (AV) difference or the O2 extraction. CONCLUSIONS: Infusion of hyperbaric AO solution into the PA can completely reverse the negative effects of acute hypoxia on the pulmonary circulation without affecting the myocardial metabolism.

Animals↗

PubMed2004

Aqueous oxygen: the solution to relief hypoxic pulmonary hypertension.

OBJECTIVE: To evaluate the effects of hyperbaric oxygen solution on hypoxic pulmonary hypertension. METHODS: Eleven calves, 2-month-old, 71+/-6 kg, underwent general anaesthesia, mechanical ventilation and median sternotomy. Catheters for continuous pressure and blood gas measurements were inserted in carotid and femoral arteries, left atrium, right atrium and pulmonary artery (PA), and a flow-probe placed around the PA. After baseline measurements 30 min hypoxic ventilation reduced the mean arterial PO2 from 285+/-115 to 46+/-11 mmHg (P < 0.0001). At this point, without changes in hypoxic ventilation (mean arterial PO2 maintained at 50+/-5 mmHg), 3 ml/min of hyperbaric aqueous oxygen (AO, oxygen diluted in saline solution) was infused directly into the PA for 30 min, with continuous reading of the monitored parameters. RESULTS: Hypoxic ventilation raised significantly (P < 0.005) the values of systolic (36+/-7 vs 22+/-6 mmHg), diastolic (16+/-3 vs 9+/-4 mmHg) and mean (24+/-4 vs 14+/-4 mmHg) PA pressure, PA/systemic pressure ratio for systolic (0.47+/-0.09 vs 0.24+/-0.06) and mean (0.49+/-0.13 vs 0.23+/-0.08) pressures and Pulmonary Vascular Resistance (PVR) (6.89+/-0.87 vs 2.67+/-0.38 U), while the Pulmonary Blood Flow (PBF) decreased (2.7+/-0.4 vs 3.7+/-0.4 l/min). AO infusion reduced significantly (P < 0.005) the values obtained with hypoxic ventilation with systolic (26+/-6 vs 36+/-7 mmHg), diastolic (11+/-4 vs 16+/-3 mmHg) and mean (16+/-4 vs 24+/-4 mmHg) PA pressure, PA/systemic pressure ratio for systolic (0.27+/-0.07 vs 0.47+/-0.09) and mean (0.27+/-0.08 vs 0.49+/-0.13) pressures and PVR (3.42+/-0.31 vs 6.89+/-0.87 U), while the PBF increased (3.6+/-0.4 vs 2.7+/-0.4 l/min). CONCLUSIONS: Acute infusion of hyperbaric AO solution into the PA completely reverses the negative effects of acute hypoxia on pulmonary circulation.

Animals↗

PubMed2004

Ultrasound navigation through the heart for off-pump aortic valved stent implantation: new tools for new goals.

PURPOSE: To validate the use of simultaneous intracardiac and intravascular ultrasound (IVUS) guidance for periprocedural dimension assessment, Residual-Coronary/Sinus-Stent Index (RCSSI) estimation, target site identification, deployment monitoring, and quality control of off-pump aortic Valved Stent implantation. METHODS: Five pigs (56+/-5 kg) underwent off-pump orthotopic aortic valve implantation using a custom-made self-expanding Valved Stent. Intracardiac ultrasound (AcuNav) was introduced via the right femoral vein. After left-sided thoracotomy, pursestring sutures were placed on the left ventricular apex. Following heparinization, a guidewire was inserted through the apex and advanced over the aortic valve under fluoroscopy. A wire-guided IVUS catheter transducer (6-F, 12.5-MHz) was inserted and the aortic target site identified. IVUS probe location was tracked with AcuNav, and measures of the aortic root were taken by both. After removal of the IVUS, the Valved Stent delivery system was introduced over the guidewire under fluoroscopy and AcuNav monitoring; the Valved Stent was deployed over the native valves. In vivo assessment included leaflet motion, planimetric valve orifice and RCSSI (stent to aortic wall distance/coronary diameter) calculations, coronary blood flow characteristics, transvalvular gradient, regurgitation, and paravalvular leaking in combination with continuous cardiac output measures. Macroscopic analysis was performed at necropsy. RESULTS: IVUS dimensions of the aortic root were equal to AcuNav and necropsy dimensions. Both tools showed good valvular function, with full valvular opening and closing in 3 of 5 valves. At necropsy, the 3 aortic Valved Stents were safely anchored. One Valved Stent was placed supra-annularly; 2 dislodged into the left ventricle because of size mismatch. One Valved Stent showed a moderate to severe paravalvular leak. CONCLUSIONS: Simultaneous intracardiac and intravascular ultrasound-guided off-pump orthotopic aortic Valved Stent implantation via left sided thoracotomy is feasible in an animal model. IVUS and intracardiac ultrasound allow adequate aortic dimension assessment and Valved Stent delivery monitoring, as well as postimplantation coronary flow evaluation.

Animals↗

PubMed2002

A new concept of integrated cardiopulmonary bypass circuit.

OBJECTIVE: Standard cardiopulmonary bypass (CPB) circuits with their large surface area and volume contribute to postoperative systemic inflammatory reaction and hemodilution. In order to minimize these problems a new approach has been developed resulting in a single disposable, compact arterio-venous loop, which has integral kinetic-assist pumping, oxygenating, air removal, and gross filtration capabilities (CardioVention Inc., Santa Clara, CA, USA). The impact of this system on gas exchange capacity, blood elements and hemolysis is compared to that of a conventional circuit in a model of prolonged perfusion. METHODS: Twelve calves (mean body weight: 72.2+/-3.7 kg) were placed on cardiopulmonary bypass for 6 h with a flow of 5 l/min, and randomly assigned to the CardioVention system (n=6) or a standard CPB circuit (n=6). A standard battery of blood samples was taken before bypass and throughout bypass. Analysis of variance was used for comparison. RESULTS: The hematocrit remained stable throughout the experiment in the CardioVention group, whereas it dropped in the standard group in the early phase of perfusion. When normalized for prebypass values, both profiles differed significantly (P<0.01). Both O2 and CO2 transfers were significantly improved in the CardioVention group (P=0.04 and P<0.001, respectively). There was a slightly higher pressure drop in the CardioVention group but no single value exceeded 112 mmHg. No hemolysis could be detected in either group with all free plasma Hb values below 15 mg/l. Thrombocyte count, when corrected by hematocrit and normalized by prebypass values, exhibited an increased drop in the standard group (P=0.03). CONCLUSION: The CardioVention system with its concept of limited priming volume and exposed foreign surface area, improves gas exchange probably because of the absence of detectable hemodilution, and appears to limit the decrease in the thrombocyte count which may be ascribed to the reduced surface. Despite the volume and surface constraints, no hemolysis could be detected throughout the 6 h full-flow perfusion period.

Animals↗

PubMed2002

An alternative to left ventricular volume reduction.

BACKGROUND: Left ventricular (LV) remodeling leading to ventricular dilatation is ultimately a maladaptative process according to the law of Laplace. To counteract the wall stress increase, a new concept of reducing the LV cavity radius by changing the LV globular shape to a bilobular one through the insertion of transventricular splints has emerged. This procedure is tested in a model of congestive heart failure. METHODS: A bovine model was used (n = 9). Following splint insertion through a sternotomy, boluses of 2 liters of crystalloid were injected. After every bolus, hemodynamic measurements were performed without and with the splints tightened to a 10% and 20% stress level reduction, respectively. Comparisons between the 3 measurements were performed with analysis of variance test (p < 0.05). RESULTS: Splint tightening significantly reduced right and left heart pressures for central venous pressure (CVP) >10 mm Hg (CVP: 14.7 +/- 5.2, 12.1 +/- 5, 10.6 +/- 4.7 mm Hg, p < 0.001 for baseline, 10% and 20% stress level reduction, respectively; mean pulmonary artery pressure: 33.5 +/- 4.7, 31 +/- 4.4, 29.4 +/- 5.1 mm Hg, p < 0.001; pulmonary capillary wedge pressure: 20.5 +/- 2.8, 18.9 +/- 3.3, 17.5 +/- 3.1 mm Hg, p < 0.001). The same holds true for cardiac output (6.5 +/- 1.6, 6.7 +/- 1.4, 6.8 +/- 1.7 liter/minute, p < 0.001), whereas heart rate and mean arterial pressure were not affected. The systemic and pulmonary resistances did not vary significantly throughout the procedure. Importantly, none of the hemodynamic parameters worsened at any stage with the splints. CONCLUSIONS: In this model, hemodynamic parameters are improved with the splints for higher values of CVP, supporting the concept of reshaping the remodeled LV. This technique has the potential to improve patients with congestive heart failure.

Animals↗

PubMed2002

Small intestine without mucosa as a growing vascular conduit: a porcine experimental study.

OBJECTIVE: This study was conducted to check the feasibility of using small intestine without mucosa as a growing vascular conduit. METHOD: Autologous proximal jejunum without mucosa after treatment with heparin bonding was used as a free inferior vena cava interpositional graft between the renal veins and bifurcation of inferior vena cava in 8 piglets. Intravenous ultrasonography was performed at 1 to 3 months after the operation and at autopsy. RESULTS: One intraoperative death was related to anesthesia. At a mean follow-up of 80 days for the 7 surviving pigs, the weight had increased by 201%, from a mean of 32 kg to a mean of 94 kg. The grafts had increased in length by 128%, from a mean of 2.3 cm at implantation to a mean of 5.1 cm (P <.018) at explantation. In 6 animals the diameter of the graft was equal to that of the adjacent inferior vena cava. At postmortem examination, 6 grafts were patent. The single blocked graft had been patent 1 month after surgery. One graft had extensive septae inside, 2 had minor septae, 2 had microscopic septae, and 2 had no septae at all. Normal appearing adventitia, fibrous tissue, and endothelium (factor VIII-related antigen positive) lined all the grafts. In all 7 grafts, scattered proliferating fibroblasts (MIB1 positive) were observed. CONCLUSIONS: Small intestine without mucosa remodels and acts like a live, growing, layered, endothelialized, nonthrombogenic (after re-endothelialization) vascular conduit in a growing pig. This graft material could have potential as a growing vascular conduit in children.

Animals↗

PubMed2002

Hemocompatibility of a coaxial pump catheter for less invasive heart surgery.

Off-pump coronary artery bypass (OPCAB) requires heart manipulation during exposure of the lateral and posterior walls of the heart, which may cause hemodynamic instability, mainly through right ventricular dysfunction. A coaxial atrial cannula connected to a minicentrifugal pump was developed to bypass the right heart. This study was designed to test the hemocompatibility of this pump ongoing for 6 h. In five calves (bodyweight, 70.3+/-4.2 kg), the pump was inserted and set to its maximal motor speed of 7000 rpm. Blood samples were taken for blood gas analyses, hematology and chemistry on an hourly basis. ANOVA was used for statistical analysis. During the 6-h run, hematocrit and red blood cell count were stable (p=0.77 and 0.87, respectively). Platelet count was not significantly altered (p=0.55). LDH was stable (p=0.61) and plasma free hemoglobin remained below 100 mg/l throughout the experiment. Adequate tissue perfusion was maintained as reflected by the stable mixed venous oxygen saturation (baseline, 72.5+/-2%, and 6 h, 65.6+/-3.4%) and no defect of any pump system was detected during this 6-h testing. This right heart minipump appears to have a minimal impact on red cells and platelets when set at its maximal speed for 6 h, underlining the hematological safety of the system.

Animals↗

PubMedDate not supplied

Antithrombotic properties of trillium coated connectors.

Trillium coating (Medtronic Inc., Minneapolis, MN) offers, in addition to the presence of heparin, endothelium-like properties of its negatively charged surface. Its thromboresistant properties on coated connectors are tested here and compared with uncoated standard connectors, as well as with the Carmeda BioActive surface (CBAS) heparin surface coating. A partial cardiopulmonary bypass bovine model (body weight 68 +/- 5 kg) was selected, and the surfaces were exposed to the blood stream (pump flow 3.5 L/min) for up to 350 minutes without systemic heparinization. Thereafter, another set of samples was exposed to stagnant blood for 20 minutes. Besides hemodynamic, hematologic, and biochemical analyses, the macroscopic appearance of 45 blood exposed surface samples were graded semiquantitatively on a scale of 0 to 10: no macroscopic deposits = grade 0, one spot (1 mm diameter) = grade 1, two spots = grade 2, five or more spots = grade 5, 10% of the surface covered with clots = grade 6, 100% covered = grade 10. When exposed to blood flow, Trillium and CBAS coatings showed a statistically significant (p = 0.03) better thromboresistance (score: 0 +/- 0 for both) than uncoated connectors (score: 0.8 +/- 1.5) in this nonheparinized model. The same holds true when the connectors were exposed to stagnant blood (score: 0 +/- 0 for both coatings vs 4.3 +/- 2.8 for controls; p = 0.03). Therefore, Trillium coating exhibits significant antithrombotic properties that outperform standards for connectors used in clinical perfusion.

Animals↗

PubMedDate not supplied

In vivo testing of a right heart mini-pump during a 24 hour period: is it safe?

A coaxial atrial cannula connected to a mini-centrifugal pump was developed to bypass the right heart during extreme exposures in off-pump coronary artery bypass surgery. This study was designed to test the effect of this pump, running during 24 hours, on blood elements to evaluate its use as a prolonged right heart support. In a calf model (body weight 68+/-5 kg), the pump was inserted and set to its maximal motor speed of 7000 rpm. Blood samples were drawn every 6 hours for blood gas analyses, as well as for hematology and chemistry. The right heart mini-pump performed perfectly at its maximal speed over the 24 hour period. Blood gas parameters and blood lactate levels reflected adequate tissue perfusion (baseline: 2.2+/-0.5 mmol/L vs. 24 h: 2+/-0.3 mmol/L; p = 0.64). Red blood cell count was stable (baseline: 9.8+/-1.4 x 10(12)/L vs. 24 h: 9.6+/-1.1 x 10(12)/L; p = 0.83). Free plasma hemoglobin remained below 100 mg/L throughout the experiment. Platelet count was stable during the first 6 hours and exhibited a tendency to drop thereafter (baseline: 749+/-104 x 10(9)/L vs. 24 h: 486+/-20 x 10(9)/L; p = 0.01). This right heart mini-pump appears to provide sufficient blood flow during a 24 hour period with minimal impact on red cell and moderate platelet damage after 6 hours. These results suggest a potential application of this system for postcardiotomy right heart support.

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