Circulation
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Comparative Study
Use of equilibrium (gated) radionuclide ventriculography to quantitate left ventricular output in patients with and without left-sided valvular regurgitation.
We examined the accuracy with which left ventricular output can be estimated by equilibrium radionuclide ventriculography. After red blood cells were labeled in vivo, we measured left ventricular end-diastolic and end-systolic count rates and the count rate in 5 ml of the patient's blood. ⋯ Regurgitant fraction, calculated as the difference between the radionuclide and Fick outputs divided by the radionuclide output, correlated with the severity of of regurgitation as assessed angiographically. The equilibrium radionuclide ventriculogram is an excellent means for noninvasive estimation of left ventricular output.
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Twenty-two consecutive infants and children underwent aortopulmonary shunt operations with polytetrafluoroethylene grafts. Thirteen infants younger than 6 months of age (group I) received 14 grafts (4--5 mm in diameter, 0.5--2.5 cm long). Two shunts became obstructed, including kinking in the single 2.5-cm graft. ⋯ On late follow-up, blood hemoglobins were less than 20 g% as late as 30 months of age; acceptable palliation may be expected until at least 2 years of age and 12 kg in weight are reached. We conclude that short, 4-mm-diameter polytetrafluoroethylene grafts provide good palliation in infants with cyanotic congenital heart disease, with minimal risks from pulmonary hypertension or pulmonary artery distortion. Such grafts are less successful in older children, and should only be considered when other forms of surgical relief are not feasible.
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Comparative Study
Hemodynamic and metabolic effects of morphine in the critically ill.
To assess the effects of i.v. injection of morphine, 0.5 mg/kg, hemodynamic studies were performed on 24 critically ill patients under controlled ventilation. An esophageal balloon was used to estimate intrapleural pressure and transmural cardiac filling pressures were calculated. After injection of morphine, there were significant decreases in heart rate (13%), cardiac index (18%), stroke index (17%) and arterial pressure (15%) and there was a nonsignificant increase in esophageal pressure (15%). ⋯ Oxygen consumption decreased significantly, by 21%, in 10 patients with initially elevated oxygen consumption and by 9% in 14 patients with initially normal oxygen consumption. The oxygen extraction ratio was unchanged, suggesting that the decrease in oxygen consumption was caused by decreased oxygen demand rather than by inadequate oxygen delivery. These results indicate that the hemodynamic effects of morphine (0.5 mg/kg) administered to critically ill patients were associated with a significant decrease in oxygen consumption, which probably reflected sedation and analgesia.
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Changes in the capacitance vasculature influence venous return and cardiac performance, so an understanding of the effects of pathophysiologic states on the human capacitance vasculature is necessary to understand integrated cardiovascular function in man. Techniques available to assess the capacitance vasculature in man, however, have limitations. We performed radionuclide imaging of the calf or forearm in 51 patients whose erythrocytes had been labeled in vivo with technetium-99m, basing our approach on the principle that counts from the radiolabeled intravascular space are proportional to blood volume. ⋯ Volume displacements, recorded simultaneously with a fluid-filled plethysmograph about the contralateral forearm, correlated linearly in all nine patients. Thus, gamma camera imaging of the radiolabeled peripheral intravascular space provides a quantitative and reliable assessment of peripheral vascular capacity in man. The technique could be used in conjunction with gated cardiac imaging in order to assess the interactions of peripheral vascular capacity and ventricular performance.