PMC:28996 / 3344-9813 JSONTXT

{"project":"2_test","denotations":[{"id":"11056704-8514695-23467979","span":{"begin":2764,"end":2766},"obj":"8514695"}],"text":"Materials and methods\nThe study was performed using five immature female Yorkshire pigs, weighing 28.6 ± 0.6kg. The experimental protocol was reviewed and approved by the Animal Care and Use Committee of the University of Texas Medical Branch at Galveston, with adherence to National Institutes of Health guidelines for the care and use of laboratory animals (DDHS Publication, NIH, 86⌓23).\n\nAnimal preparation\nThe animals were fasted for 12 h before the study, with free access to water. Anesthesia was induced with an intramusclar injection of ketamine hydrochloride (10 mg/kg), atropine sulfate (0.04 mg/kg) and by inhalation of 5% isoflurane. After endotracheal intubation, an intravenous bolus of pancuronium bromide (0.08 mg/kg) and fentanyl (30 μ g/kg) was administered. Anesthesia was then maintained with a continuous infusion of fentanyl (5 μ g/kg/min). The volume and rate of the ventilator (Servo 900C, Siemens-Elema AB, Solna, Sweden) were set to maintain arterial CO2 tension at 35⌓40 mmHg, using the assist control mode an I:E ratio maintained at 1:3. An inspired oxygen fraction of 0.95 was used throughout the experiment, which maintained an arterial oxygen tension of between 400 and 450 mmHg and an arterial oxygen saturation \u003e 97%. Core body temperature was maintained with a heating pad and warming lights.\nPolyethylene cannulas were inserted into the abdominal aorta through the right femoral artery for continuous recording of aortic blood pressure, heart rate and arterial blood sampling for blood gas analysis, and into the inferior vena cava through the right femoral vein for infusion of anesthetic agents, αα Hb and maintenance fluid (lactated Ringer's solution; 5 ml/kg/h). A 7.5-F flow-directed thermodiultion fiberoptic pulmonary artery catheter (Opticath P7110, Abbott Critical Care Systems, Mountain View, CA, USA) was guided by pressure monitoring and wave tracings through the right external jugular vein and the tip placed into the pulmonary artery. This catheter was used for measurement of pulmonary arterial pressure, continuous mixed venous oxyhemoglobin saturation (SvO2), and cardiac output by thermodilution (Oximetric 3 SO2/CO computer, Abbott, Chicago, IL, USA). Each catheter was connected to a pressures transducer (Transpac Disposable Transducer, Abbott) and to a Biopac Data Acquistion System (Model MP100, Biopac Systems, Goleta, CA, USA) for continuous recording of heart rate, systemic and pulmonary arterial pressures, and waveforms. Blood samples and methemoglobin levels were analyzed by a pH/Blood Gas Analyzer 1303 and CO-Oximeter 482 (Instrumentation Laboratory, Lexington, MA, USA).\nThe ααHb used in this study was derived from outdated human blood and prepared according to previously published methods [10,23]. ααHb is crosslinked between the alpha subunits at α-Lys99 and bis-(3,5-dibromosalicyl) fumarate. The ααHb solution had a hemoglobin content of 10 g/dl, an osmolality of 300 mOsm/l, an oncotic pressure of 42 mmHg, a P50 (PaO2 at which 50% of hemoglobin is saturated with oxygen) of 29 mmHg and had ≤ 4% of its hemoglobin in the form of methemoglobin. It was provided through a Cooperative Research \u0026 Development Agreement with the Blood Research Detachment of the Walter Reed Army Institute of Research.\nThe NO (800 ppm in nitrogen) was titrated using a 3500HL blender (Sechrist Industries, Anaheim, CA, USA) with compressed air as the mixing gas. The diluted gas was then connected to the air side of the blender on the Servo 900C. The gas was titrated to achieve concentrations of 5 ppm and 10 ppm with 95% oxygen. The inhaled NO concentration was confirmed using an electrochemical sensor (Pulmonox II NO-NO2 analyzer, Pulmonox Medical Corp, Tofield, Alberta, Canada).\n\nExperimental protocol\nAfter a 30-min period of stabilization following surgical preparation, baseline data were obtained. αα Hb was administered in cumulative doses of 0.1, 0.5, 1.0 and 2.0 ml/kg, in 5-min intervals to a total dose of 2ml/kg (=200 mg/kg ααHb); the data were collected 10 min after the final ααHb infusion. Inhaled NO, in concentration of 5 ppm, was then administered for 10 min and data were recorded. The inhaled NO was discontinued for 10 min, after which data were again recorded. This cycle was repeated with 10 ppm inhaled NO. After the final measurements the animals were killed with an anesthetic overdose and saturated potassium chloride solution.\n\nExperimental measurements\nMean arterial pressure (MAP), mean pulmonary arterial pressure (PAP) central venous pressure (CVP), heart rate and SvO2 were continuously monitored; pulmonary artery occlusion pressure (PAOP) was measured in 5 min intervals. Cardiac output was determined by the thermodilution technique and is presented as cardiac index determined using calculated body surface area. Systemic and pulmonary vascular resistance indices (SVRI and PVRI, respectively) were calculated using standard formulae.\nAll measurements relating to lung volume, pressures, airway resistance and dynamic lung compliance were continuously monitored and recorded with a Ventrak Model 1500 (Novametrix Medical Systems, Wallingford, CT, USA). This system determines dynamic lung compliance by measuring the peak pressure at zero flow [minus any positive end-expiratory pressure (PEEP)] and tidal volume delivered and then calculating the compliance using the following formula:\nLung compliance (ml/cm H2O) = change in volume/(peak pressure-PEEP).\nFor airway resistance, the system measures the pressure at the end of inspiration and the peak expiratory flow, then applies the following formula:\nAirway resistance (cmH2O/I/s) = alveolar pressure/(peak expiratory flow/60).\nEnd expiratory pressure (minus PEEP) is used as the alveolar pressure and is measured at the proximal end of the endotracheal tube.\nFirstly, data were recorded at baseline (BL) and 10 min after 200 mg/kg ααHb infusion (ααHb). Data were then recorded at the end of each of the following 10-min periods: inhaled NO at 5 ppm (NO 5 ppm), NO discontinued (OFF), inhaled NO at 10 ppm (NO 10 ppm), NO discontinued (OFF).\n\nStatistical analysis\nData were analyzed using analysis of variance for a single-factor experiment with repeated measures on time points (baseline, ααHb, NO 5 ppm, OFF, NO 10 ppm, OFF). Fisher's least significant difference procedure was used for multiple comparisons, with Bonferroni adjustment for number of comparisons. For all tests P \u003c 0.05 was considered significant.\n"}

{"project":"Colil","denotations":[{"id":"T20","span":{"begin":2764,"end":2766},"obj":"8514695"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/docs/sourcedb/PubMed/sourceid/"}],"text":"Materials and methods\nThe study was performed using five immature female Yorkshire pigs, weighing 28.6 ± 0.6kg. The experimental protocol was reviewed and approved by the Animal Care and Use Committee of the University of Texas Medical Branch at Galveston, with adherence to National Institutes of Health guidelines for the care and use of laboratory animals (DDHS Publication, NIH, 86⌓23).\n\nAnimal preparation\nThe animals were fasted for 12 h before the study, with free access to water. Anesthesia was induced with an intramusclar injection of ketamine hydrochloride (10 mg/kg), atropine sulfate (0.04 mg/kg) and by inhalation of 5% isoflurane. After endotracheal intubation, an intravenous bolus of pancuronium bromide (0.08 mg/kg) and fentanyl (30 μ g/kg) was administered. Anesthesia was then maintained with a continuous infusion of fentanyl (5 μ g/kg/min). The volume and rate of the ventilator (Servo 900C, Siemens-Elema AB, Solna, Sweden) were set to maintain arterial CO2 tension at 35⌓40 mmHg, using the assist control mode an I:E ratio maintained at 1:3. An inspired oxygen fraction of 0.95 was used throughout the experiment, which maintained an arterial oxygen tension of between 400 and 450 mmHg and an arterial oxygen saturation \u003e 97%. Core body temperature was maintained with a heating pad and warming lights.\nPolyethylene cannulas were inserted into the abdominal aorta through the right femoral artery for continuous recording of aortic blood pressure, heart rate and arterial blood sampling for blood gas analysis, and into the inferior vena cava through the right femoral vein for infusion of anesthetic agents, αα Hb and maintenance fluid (lactated Ringer's solution; 5 ml/kg/h). A 7.5-F flow-directed thermodiultion fiberoptic pulmonary artery catheter (Opticath P7110, Abbott Critical Care Systems, Mountain View, CA, USA) was guided by pressure monitoring and wave tracings through the right external jugular vein and the tip placed into the pulmonary artery. This catheter was used for measurement of pulmonary arterial pressure, continuous mixed venous oxyhemoglobin saturation (SvO2), and cardiac output by thermodilution (Oximetric 3 SO2/CO computer, Abbott, Chicago, IL, USA). Each catheter was connected to a pressures transducer (Transpac Disposable Transducer, Abbott) and to a Biopac Data Acquistion System (Model MP100, Biopac Systems, Goleta, CA, USA) for continuous recording of heart rate, systemic and pulmonary arterial pressures, and waveforms. Blood samples and methemoglobin levels were analyzed by a pH/Blood Gas Analyzer 1303 and CO-Oximeter 482 (Instrumentation Laboratory, Lexington, MA, USA).\nThe ααHb used in this study was derived from outdated human blood and prepared according to previously published methods [10,23]. ααHb is crosslinked between the alpha subunits at α-Lys99 and bis-(3,5-dibromosalicyl) fumarate. The ααHb solution had a hemoglobin content of 10 g/dl, an osmolality of 300 mOsm/l, an oncotic pressure of 42 mmHg, a P50 (PaO2 at which 50% of hemoglobin is saturated with oxygen) of 29 mmHg and had ≤ 4% of its hemoglobin in the form of methemoglobin. It was provided through a Cooperative Research \u0026 Development Agreement with the Blood Research Detachment of the Walter Reed Army Institute of Research.\nThe NO (800 ppm in nitrogen) was titrated using a 3500HL blender (Sechrist Industries, Anaheim, CA, USA) with compressed air as the mixing gas. The diluted gas was then connected to the air side of the blender on the Servo 900C. The gas was titrated to achieve concentrations of 5 ppm and 10 ppm with 95% oxygen. The inhaled NO concentration was confirmed using an electrochemical sensor (Pulmonox II NO-NO2 analyzer, Pulmonox Medical Corp, Tofield, Alberta, Canada).\n\nExperimental protocol\nAfter a 30-min period of stabilization following surgical preparation, baseline data were obtained. αα Hb was administered in cumulative doses of 0.1, 0.5, 1.0 and 2.0 ml/kg, in 5-min intervals to a total dose of 2ml/kg (=200 mg/kg ααHb); the data were collected 10 min after the final ααHb infusion. Inhaled NO, in concentration of 5 ppm, was then administered for 10 min and data were recorded. The inhaled NO was discontinued for 10 min, after which data were again recorded. This cycle was repeated with 10 ppm inhaled NO. After the final measurements the animals were killed with an anesthetic overdose and saturated potassium chloride solution.\n\nExperimental measurements\nMean arterial pressure (MAP), mean pulmonary arterial pressure (PAP) central venous pressure (CVP), heart rate and SvO2 were continuously monitored; pulmonary artery occlusion pressure (PAOP) was measured in 5 min intervals. Cardiac output was determined by the thermodilution technique and is presented as cardiac index determined using calculated body surface area. Systemic and pulmonary vascular resistance indices (SVRI and PVRI, respectively) were calculated using standard formulae.\nAll measurements relating to lung volume, pressures, airway resistance and dynamic lung compliance were continuously monitored and recorded with a Ventrak Model 1500 (Novametrix Medical Systems, Wallingford, CT, USA). This system determines dynamic lung compliance by measuring the peak pressure at zero flow [minus any positive end-expiratory pressure (PEEP)] and tidal volume delivered and then calculating the compliance using the following formula:\nLung compliance (ml/cm H2O) = change in volume/(peak pressure-PEEP).\nFor airway resistance, the system measures the pressure at the end of inspiration and the peak expiratory flow, then applies the following formula:\nAirway resistance (cmH2O/I/s) = alveolar pressure/(peak expiratory flow/60).\nEnd expiratory pressure (minus PEEP) is used as the alveolar pressure and is measured at the proximal end of the endotracheal tube.\nFirstly, data were recorded at baseline (BL) and 10 min after 200 mg/kg ααHb infusion (ααHb). Data were then recorded at the end of each of the following 10-min periods: inhaled NO at 5 ppm (NO 5 ppm), NO discontinued (OFF), inhaled NO at 10 ppm (NO 10 ppm), NO discontinued (OFF).\n\nStatistical analysis\nData were analyzed using analysis of variance for a single-factor experiment with repeated measures on time points (baseline, ααHb, NO 5 ppm, OFF, NO 10 ppm, OFF). Fisher's least significant difference procedure was used for multiple comparisons, with Bonferroni adjustment for number of comparisons. For all tests P \u003c 0.05 was considered significant.\n"}