We demonstrated a significant endocrine stress response in infants with well compensated congenital cardiac disease undergoing cardiac surgery, but without adverse postoperative outcome. The use of large-dose fentanyl, with or without midazolam, with the intention of providing "stress free" anesthesia, does not appear to be an important determinant of early postoperative outcome.

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The degradation of atracurium and the formation of laudanosine was examined in vitro in both Sorensen buffer and human plasma using sensitive, specific high pressure liquid chromatographic assays to determine drug concentrations. At normal physiological pH and temperature, the degradation of atracurium was threefold more rapid in plasma than in buffer. Laudanosine is the major end-product of atracurium degradation in buffer or in plasma; its production is more rapid in plasma than in buffer. Dilution of plasma constituents or the use of diisopropylfluorophosphate (a potent esterase inhibitor), slows the degradation of atracurium and the production of laudanosine. We conclude that, although ester hydrolysis is the major metabolic pathway of atracurium degradation, Hofmann elimination provides a "safety net" in its clinical use.