What factors contribute to the elevation of serum free fatty acids (FFA) in newborns in the cardiac surgical setting?

Elevations in serum free fatty acids (FFA) levels during heart surgery have been reported in humans and experimental animals, causing increased arrhythmias, decreased heart function, and contributing to mortality. Factors such as heparin administration, age, cardiopulmonary bypass (CPB) and cyanosis/hypoxia have been implicated but not proven. This study was designed to clarify the contribution of these factors using an experimental pig model as follows: a) adult (n=10) versus 3-day old piglets (n=18) had FFA levels assessed before and after heparin administration; b) 3 day old piglets, the additional effect of CPB (n=8) or just severe hypoxia (PaO2 = 20-25 mmHg; n=6) exposure on FFA levels. This work demonstrated that significant elevations in serum FFA were mainly due to heparin administration, with modest contributions by young age, CPB and hypoxia. Our preliminary clinical investigations also suggest that children undergoing CPB are at risk of being exposed to high FFA levels and that these patients only suffered a decrease in heart function when these elevations were present in conjunction with cyanosis and/or prolonged ischemic time. These initial findings require further confirmation. Given these findings, pharmaco-therapeutics geared towards limiting FFA elevations should be considered, especially in young children undergoing pediatric cardiac surgery.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Comparison of mild and deep hypothermia: do they provide similar protection in all neonatal hearts?

Despite various techniques of hypothermia it is still difficult to provide optimal myocardial preservation in neonatal cardiac surgery. The early effects of moderate and deep hypothermia were examined in neonatal pig hearts by studying metabolism over time and the tolerance of the hearts to global ischemia. The latter was measured by the time to onset of ischemic contracture, an indicator of irreversible ischemic damage. After control right ventricular biopsies were done, 56, 3-day-old neonatal hearts were excised and placed in one of four temperature-regulated baths (37 degrees C, 25 degrees C, 19 degrees C, 12 degrees C). A compliant left ventricular balloon measured onset time to ischemic contracture (TIC) (2 mm Hg increase in pressure). Biopsies were also done at 15 and 30 minutes of ischemia. Progressive hypothermia significantly (p less than 0.001) prolonged TIC but resulted in an increased standard error of the mean (SEM). Lactate accumulation was the least in deep hypothermia (12 degrees C, 19 degrees C) (p less than 0.05) and intermediate with moderate hypothermia (25 degrees C), and all were less (p less than 0.01) than that at normothermia. The decline of adenosine triphosphate was slowed more by hypothermia than normothermia. These observations can be used to improve current methods of myocardial preservation in neonatal hearts