The Journal of thoracic and cardiovascular surgery
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J. Thorac. Cardiovasc. Surg. · May 1990
Effects of temperature on myocardial calcium homeostasis and mitochondrial function during ischemia and reperfusion.
An isolated rabbit heart preparation was used to characterize the effects of hypothermia on the deterioration in mitochondrial respiratory function and on the calcium overload that occurs during ischemia and reperfusion. Hearts were perfused aerobically with an asanguineous solution for 120 minutes or made totally ischemic for 90 minutes at 37 degrees, 34 degrees, 28 degrees, 22 degrees C, respectively, and reperfused for 30 minutes at 37 degrees C. Mitochondrial function was assessed by measuring calcium content, yield, oxygen consumption, and adenosine triphosphate-producing capacities. ⋯ These data suggest that a decrease in temperature from 37 degrees to 22 degrees C during ischemia did not significantly prevent depletion of adenosine triphosphate at the end of ischemia but reduced tissue and mitochondrial calcium overload, maintaining mitochondrial function. Thus in our experiments the protective effect of hypothermia might be related to a direct reduction of tissue and mitochondrial calcium accumulation rather than to a slowing in rates of energy utilization. This possibility is supported by the finding that in freshly excised, nonperfused rabbit hearts, hypothermia significantly reduced the initial rate of mitochondrial calcium transport.
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J. Thorac. Cardiovasc. Surg. · May 1990
Intermittent hypothermic asanguineous cerebral perfusion (cerebroplegia) protects the brain during prolonged circulatory arrest. A phosphorus 31 nuclear magnetic resonance study.
A system has been developed for the nuclear magnetic resonance spectroscopic evaluation of cerebral high-energy phosphate levels during hypothermic total circulatory arrest and reperfusion by means of cardiopulmonary bypass in large animals. The use of intermittent hypothermic asanguineous cerebral perfusion, termed cerebroplegia, for the preservation of cerebral high-energy phosphates during a 2-hour period of hypothermic total circulatory arrest and reperfusion has been evaluated. Cardiopulmonary bypass was used to achieve deep hypothermia (12 degrees to 15 degrees C) during 2 hours of circulatory arrest and reperfusion. ⋯ Electroencephalographic activity returned after 36 minutes of reperfusion in group 2, but it did not return until 117 minutes in group 1 (p less than 0.05). In summary, cerebral high-energy phosphates and pH were maintained and the electroencephalographic signal returned more rapidly during circulatory arrest with the institution of cerebroplegia. These studies suggest that cerebroplegia is protective of the brain during circulatory arrest.
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J. Thorac. Cardiovasc. Surg. · Apr 1990
Hemodynamic response to pumpless extracorporeal membrane oxygenation.
Respiratory support by means of arteriovenous extracorporeal membrane oxygenation driven by systemic arterial pressure, in contrast to pump-driven venoarterial extracorporeal membrane oxygenation, is attractive because of its simplicity and lack of trauma to formed blood elements. Although arteriovenous extracorporeal membrane oxygenation has been shown to improve arterial blood gases, useful levels of arteriovenous extracorporeal membrane oxygenation shunt flow may exert detrimental effects on systemic and pulmonary hemodynamics. Therefore the hemodynamic consequences of arteriovenous extracorporeal membrane oxygenation were studied in 11 dogs that were anesthetized, heparinized, and their lungs mechanically ventilated (FIO2 = 0.21) before and after induction of oleic acid pulmonary edema. ⋯ Dopamine infusion (5 micrograms/kg/min) proved to be more effective than volume expansion (15 ml/kg) in maintaining cardiac output, arterial blood pressure, and arterial blood gases. We conclude that pumpless arteriovenous extracorporeal membrane oxygenation, at flow rates adequate for respiratory support, can adversely alter systemic hemodynamics. However, these effects can be beneficially modulated by a moderate dose of inotropic medication.
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J. Thorac. Cardiovasc. Surg. · Apr 1990
Congenital bronchopulmonary malformations. Diagnostic and therapeutic considerations.
Congenital bronchopulmonary malformations are uncommon but potentially life-threatening anomalies of infants and children. Between 1970 and 1988, 45 patients from birth to 13 years of age (23 boys and 22 girls) underwent evaluation and treatment for bronchopulmonary malformations. Thirty-seven had solitary lesions: bronchogenic cyst (n = 13), cystic adenomatoid malformation (n = 9), congenital lobar emphysema (n = 6), pulmonary sequestration (n = 6), arteriovenous malformation (n = 2), and bronchial atresia (n = 1). ⋯ Ancillary studies such as ultrasonography or computed tomography may occasionally be necessary. Combinations of the different types of bronchopulmonary malformations occurred frequently. All lesions, including symptomatic lesions in neonates, can be managed surgically soon after diagnosis.
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J. Thorac. Cardiovasc. Surg. · Mar 1990
Comparative StudyHeparin dosing and monitoring for cardiopulmonary bypass. A comparison of techniques with measurement of subclinical plasma coagulation.
Subclinical plasma coagulation during cardiopulmonary bypass has been associated with marked platelet and clotting factor consumption in monkeys. To better define subclinical coagulation in man, we measured plasma fibrinopeptide A concentrations before, during, and after cardiopulmonary bypass. Patients were assigned to one of three groups of heparin management: group 1 (n = 10)--initial heparin dose 300 IU/kg, with supplemental heparin if the activated coagulation time fell below 400 seconds; group 2 (n = 6)--initial heparin dose 250 IU/kg, with supplemental heparin if activated coagulation time was less than 400 seconds; and group 3 (n = 5)--initial heparin dose 350 to 400 IU/kg, with supplemental heparin if whole blood heparin concentration was less than or equal to 4.1 IU/ml. ⋯ Group 3 patients received the highest heparin doses (p less than 0.05) and had the greatest postoperative blood loss (p less than 0.05). Protamine dose and heparin concentration during cardiopulmonary bypass correlated best with postoperative mediastinal drainage. Our findings support the following conclusions: (1) compensated subclinical plasma coagulation activity occurs during cardiopulmonary bypass despite activated coagulation time greater than 400 seconds or heparin concentration greater than or equal to 4.1 IU/ml; (2) post-cardiopulmonary bypass mediastinal drainage correlates strongly with increased heparin concentration during cardiopulmonary bypass (p less than 0.05) and protamine dose (p less than 0.05); and (3) during cardiopulmonary bypass at both normothermia and hypothermia, activated coagulation times greater than 350 seconds result in acceptable fibrinopeptide A levels and post-cardiopulmonary bypass blood clotting.