Anesthesiology
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Cutaneous infiltration of dilute solutions of epinephrine for hemostasis during halothane anesthesia can result in ventricular dysrhythmias. Our clinical experience, published reports, and a study comparing piglets with adult swine suggest that children may be less susceptible than adults to dysrhythmias under these conditions. We therefore undertook a prospective survey of heart rate and rhythm in halothane-anesthesized children who received subcutaneous epinephrine for hemostasis. ⋯ The authors conclude that children tolerate higher doses of subcutaneous epinephrine than adults during halothane anesthesia. The arrhythmogenic dose of epinephrine in children receiving halothane has yet to be determined, but at least 10 micrograms/kg of epinephrine infiltration may be used safely in normocarbic and hypocarbic pediatric patients without congenital heart disease. The presence of PAC and tachycardia emphasize the need for continuous ECG monitoring and caution during halothane anesthesia with epinephrine injection.
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The authors investigated whether the increases in venous admixture and intrapulmonary shunt which occur with increases in cardiac output (Qt) results from an effect mediated by mixed venous PO2 (PVO2) or an effect mediated by the increase in pulmonary blood flow. Using a veno-venous bypass system thay were able to alter PVO2 independent of variations in Qt and vice versa. During room air ventilation of dogs with normal lungs at constant Qt, an increase in PVO2 from 33 +/- 7 (mean +/- SD) to 54 +/- 9 mmHg (P less than 0.05) resulted in a decrease in venous admixture from 22 +/- 11 to 13 +/- 4% (P less than 0.05). ⋯ The authors conclude that during oxygen ventilation, normal dogs have shunts which are unaffected by changes in blood flow or PVO2. Increases in pulmonary blood flow increase venous admixture during room air ventilation, while increases in PVO2 decrease venous admixture during air ventilation. In edematous lungs, increases in either PVO2 or pulmonary blood flow increase shunt.