| 1. |
- Kjaergaard, Benedict, et al.
(author)
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A porcine model of massive, totally occlusive, pulmonary embolism
- 2009
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In: Thrombosis Research. - : Elsevier BV. - 0049-3848 .- 1879-2472. ; 124:2, s. 226-9
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Journal article (peer-reviewed)abstract
- BACKGROUND: A reliable, animal model of massive, totally occlusive, pulmonary embolism (PE) is lacking. OBJECTIVES: To design an animal model of totally occlusive PE and to challenge the model by a plasminogen activator. METHODS: In eight anaesthetized pigs (approximately 90 kg) a massive preformed autologous thrombus was injected into the caval vein. One animal was autopsied to assess the extent of injected clot, whereas in the other animals extracorporeal life support (ECLS) was initiated and continued for three hours. These animals received 100 mg rt-PA. Blood gases, coagulation tests, creatine kinase (CK), lactate dehydrogenase (LDH), end-tidal CO2, systemic and pulmonary artery blood pressures and flow were registered. RESULTS: All animals went into circulatory arrest within 2 minutes after injection of the thrombus. In the animal where ECLS was not started, autopsy relieved a totally occlusive embolus of the pulmonary artery. The ECLS maintained a systemic blood flow of 6-8 L/min with adequate oxygenation and CO2-removal. However, lactate increased and base-excess became negative. Ddimer increased, fibrinogen decreased, and CK and LDH increased. All seven animals were weaned from ECLS. Despite the rt-PA treatment, the animals had at that time low end tidal CO2/PaCO2 ratio and increased mean pulmonary arterial pressure, suggesting a significant amount of embolic material remaining in the pulmonary artery. CONCLUSION: This model of massive, totally occlusive, pulmonary embolism mimics well fatal PE seen in the clinic, and has the potential for use in testing of new therapeutic interventions.
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| 2. |
- Kjaergaard, Benedict, et al.
(author)
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Low plasma potassium in deep hypothermic cardiac arrest indicates that cardiac arrest is secondary to hypothermia : a porcine study
- 2010
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In: European journal of emergency medicine. - 0969-9546 .- 1473-5695. ; 17:3, s. 131-135
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Journal article (peer-reviewed)abstract
- OBJECTIVES: In accidental hypothermia, normal signs of death are unreliable. It is generally accepted that a lifeless person is beyond the limits of rescue if plasma potassium (P-potassium) is higher than10 mmol/l. However, the rate of increase in potassium or in other markers after cardiac arrest has not been carefully studied in hypothermic individuals. The aim of this animal study was to assess biochemical changes after anoxic circulatory arrest at hypothermia and at normothermia followed by external cooling. METHODS: Five pigs were treated with heparin and extracorporeal circulation and cooled to 20 degrees C (primary hypothermia group). The animals were weaned from extracorporeal circulation, suffered cardiac arrest, and were cooled externally with ice to mimic victims found in a cold environment. With the use of intermittent external cardiac compressions mixing the blood, arterial P-potassium was followed after cardiac arrest until the level exceeded 10 mmol/l. Another group of five pigs (anoxic cardiac arrest group) were treated with heparin and killed by anoxia at normothermia and were thereafter treated and followed similarly to the primary hypothermia group. RESULTS: In primary hypothermia P-potassium exceeded 10 mmol/l after median 3.5 h, whereas in anoxic cardiac arrest P-potassium exceeded 10 mmol/l after median 1 h. CONCLUSION: This study shows that if cardiac arrest occurs before hypothermia is established, P-potassium increases quickly in contrast to the situation when hypothermia induces cardiac arrest. Thus, a low P-potassium in a hypothermic individual with cardiac arrest indicates that cardiac arrest occurred recently or was secondary to the hypothermic event.
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| 3. |
- Nielsen, Niels D., et al.
(author)
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Alveolar accumulation/concentration of nitrogen during apneic oxygenation with arteriovenous carbon dioxide removal
- 2010
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In: ASAIO journal (1992). - 1058-2916 .- 1538-943X. ; 56:1, s. 30-34
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Journal article (peer-reviewed)abstract
- In a model of acute lung injury (ALI), previously, we have shown that apneic oxygenation, using an inspiratory O2 fraction (FiO2) of 1.0 combined with extracorporeal arteriovenous CO2 removal (AO-AVCR) maintains adequate arterial O2 and CO2 levels for a prolonged period. However, it is important that FiO2 lower than 1.0 can be used to avoid possible pulmonary oxygen toxicity. In preliminary studies, arterial oxygenation decreased to extreme low levels, when FiO2 <1 was used in apneic oxygenation. We assumed that this was caused either by alveolar accumulation/concentration of N2 or by absorption atelectasis. In four anesthetized and mechanically ventilated pigs, mild lung injury was induced. After a lung recruitment maneuver, we initiated two 20-minute periods of AO-AVCR with FiO2 of 1 and 0.5, respectively. By using FiO2 = 1, PaO2 remained above 300 mm Hg. At the end of the period, the alveolar O2 fraction (FAO2) was 0.89 (0.88-0.89; median and ranges). With FiO2 = 0.5, PaO2 decreased 90% compared with baseline values and FAO2 decreased to 0.07 (0.06-0.07). No atelectasis was visible on computed tomography after either period, and we, therefore, conclude that the alveolar hypoxia was caused by the alveolar N2 accumulation/concentration and subsequently by the O2 depletion.
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| 4. |
- Nielsen, Niels D, et al.
(author)
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Apneic oxygenation combined with extracorporeal arteriovenous carbon dioxide removal provides sufficient gas exchange in experimental lung injury
- 2008
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In: ASAIO journal (1992). - 1058-2916 .- 1538-943X. ; 54:4, s. 401-405
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Journal article (peer-reviewed)abstract
- We hypothesized that apneic oxygenation, using an open lung approach, combined with extracorporeal CO2 removal, would provide adequate gas exchange in acute lung injury. We tested this hypothesis in nine anesthetized and mechanically ventilated pigs (85-95 kg), in which surfactant was depleted from the lungs by repeated lung lavage. After a lung recruitment maneuver, the tracheal tube was connected to 20 cm H2O continuous pressure (100% O2) for oxygenation of the blood. A pumpless membrane ventilator (interventional lung assist by Novalung) was connected in an arteriovenous shunt for CO2 removal. PaO2 and PaCO2 were recorded for 3.5 hours. PaO2 was 464 (403, 502) mm Hg (median and interquartile range) throughout the experiment. The O2 uptake through the lungs was 185 (164, 212) ml/min. PaCO2 increased asymptotic towards 60 mm Hg. The CO2 removal through the membrane ventilator was 180 (150, 180) ml/min. Thus, the method provided adequate gas exchange in this experimental model, suggesting that it might have potential as an alternative treatment modality in acute lung injury.
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| 5. |
- Thomassen, Sisse Anette, et al.
(author)
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Cerebral blood flow measured by positron emission tomography during normothermic cardiopulmonary bypass : an experimental porcine study
- 2018
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In: Perfusion. - : SAGE Publications. - 0267-6591 .- 1477-111X. ; 33:5, s. 346-353
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Journal article (peer-reviewed)abstract
- Background: Mean arterial blood pressure (MAP) and/or pump flow during normothermic cardiopulmonary bypass (CPB) are the most important factors of cerebral perfusion. The aim of this study was to explore the influence of CPB blood flow on cerebral blood flow (CBF) measured by dynamic positron emission tomography (PET) using O-15-labelled water with no pharmacological interventions to maintain the MAP.Methods: Eight pigs (69-71 kg) were connected to normothermic CPB. After 60 minutes (min) with a CPB pump flow of 60 mL/kg/min, the pigs were changed to either 35 mL/kg/min or 47.5 mL/kg/min for 60 min and, thereafter, all the pigs returned to 60 mL/kg/min for another 60 min. The MAP was measured continuously and the CBF was measured by positron emission tomography (PET) during spontaneous circulation and at each CPB pump flow after 30 min of steady state.Results: Two pigs were excluded due to complications. CBF increased from spontaneous circulation to a CPB pump flow of 60 mL/kg/min. A reduction in CPB pump flow to 47.5 mL/kg/min (n=3) resulted in only minor changes in CBF while a reduction to 35 mL/kg/min (n=3) caused a pronounced change (correlation coefficient (R-2) 0.56). A return of CPB pump flow to 60 mL/kg/min was followed by an increase in CBF, except in the one pig with the lowest CBF during low flow (R-2=0.44). CBF and MAP were not correlated (R-2=0.20).Conclusion: In this experimental porcine study, a relationship was observed between pump flow and CBF under normothermic low-flow CPB. The effect of low pump flow on MAP showed substantial variations, with no correlation between CBF and MAP.
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| 6. |
- Thomassen, Sisse Anette, et al.
(author)
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Muscle Tissue Saturation Compared With Muscle Tissue Perfusion During Low Blood Flows : An Experimental Study.
- 2017
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In: Journal of Cardiothoracic and Vascular Anesthesia. - : Elsevier BV. - 1053-0770 .- 1532-8422. ; 31:6, s. 2065-2071
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Journal article (peer-reviewed)abstract
- OBJECTIVE: To investigate whether changes in muscle tissue perfusion measured with positron emission tomography would be reflected by parallel changes in muscle tissue oxygen saturation (StO2) measured using near-infrared spectroscopy during high and low blood flow levels achieved using cardiopulmonary bypass (CPB) in an animal model.DESIGN: A prospective, randomized study.SETTING: Research laboratory, single institution.PARTICIPANTS: Eight pigs (69-71 kg).INTERVENTIONS: In anesthetized pigs, normothermic CPB was established with a blood flow of 60 mL/kg/min for 1 hour. Thereafter, a low blood flow of either 47.5 or 35 mL/kg/min was applied for 1 hour followed by a blood flow of 60 mL/kg/min for an additional hour. Regional StO2 was measured continuously by placing a near-infrared spectroscopy electrode on the skin above the gracilis muscle of the noncannulated back leg. Muscle tissue perfusion was measured using positron emission tomography with (15)O-labeled water during spontaneous circulation and the different CPB blood flows. Systemic oxygen consumption was estimated by measurement of venous saturation and lactate levels.MEASUREMENTS AND MAIN RESULTS: The results showed profound systemic ischemia during low CPB blood flow. StO2 remained high until muscle tissue perfusion decreased to about 50%, after which StO2 paralleled the linear decrease in muscle tissue perfusion.CONCLUSION: In an experimental CPB animal model, StO2 was stable until muscle tissue perfusion was reduced by about 50%, and at lower blood flow levels, there was almost a linear relationship between StO2 and muscle tissue perfusion.
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| 7. |
- Thomassen, Sisse Anette, et al.
(author)
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Regional muscle tissue saturation is an indicator of global inadequate circulation during cardiopulmonary bypass : a randomized porcine study using muscle, intestinal and brain tissue metabolomics
- 2017
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In: Perfusion. - : SAGE Publications. - 0267-6591 .- 1477-111X. ; 32:3, s. 192-199
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Journal article (peer-reviewed)abstract
- Background: Muscle tissue saturation (StO(2)) measured with near-infrared spectroscopy has generally been considered a measurement of the tissue microcirculatory condition. However, we hypothesized that StO2 could be more regarded as a fast and reliable measure of global than of regional circulatory adequacy and tested this with muscle, intestinal and brain metabolomics at normal and two levels of low cardiopulmonary bypass blood flow rates in a porcine model. Methods: Twelve 80 kg pigs were connected to normothermic cardiopulmonary bypass with a blood flow of 60 mL/kg/min for one hour, reduced randomly to 47.5 mL/kg/min (Group I) or 35 mL/kg/min (Group II) for one hour followed by one hour of 60 mL/kg/min in both groups. Regional StO(2) was measured continuously above the musculus gracilis (non-cannulated leg). Metabolomics were obtained by brain tissue oxygen monitoring system (Licox) measurements of the brain and microdialysis perfusate from the muscle, intestinal mucosa and brain. A non-parametric statistical method was used. Results: The systemic parameters showed profound systemic ischaemia during low CPB blood flow. StO(2) did not change markedly in Group I, but in Group II, StO(2) decreased immediately when blood flow was reduced and, furthermore, was not restored despite blood flow being normalized. Changes in the metabolomics from the muscle, colon and brain followed the changes in StO(2). Conclusion: We found, in this experimental cardiopulmonary bypass model, that StO(2) reacted rapidly when the systemic circulation became inadequate and, furthermore, reliably indicate insufficient global tissue perfusion even when the systemic circulation was restored after a period of systemic hypoperfusion.
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