Intraoperative fluid administration volumes during pediatric liver transplantation and postoperative outcomes: A multicenter analysis.

INTRODUCTION: Fluid administration is an important aspect of the management of children undergoing liver transplantation and may impact postoperative outcomes. Our aim was to evaluate the association between volume of intraoperative fluid administration and our primary outcome, the duration of postoperative mechanical ventilation following pediatric liver transplantation. Secondary outcomes included intensive care unit length of stay and hospital length of stay. METHODS: We conducted a multicenter, retrospective cohort study using electronic data from three major pediatric liver transplant centers. Intraoperative fluid administration was indexed to weight and duration of anesthesia. Univariate and stepwise linear regression analyses were conducted. RESULTS: Among 286 successful pediatric liver transplants, the median duration of postoperative mechanical ventilation was 10.8 h (IQR 0.0, 35.4), the median intensive care unit length of stay was 4.3 days (IQR 2.7, 6.8), and the median hospital length of stay was 13.6 days (9.8, 21.1). Univariate linear regression showed a weak correlation between intraoperative fluids and duration of ventilation (r2 = .037, p = .001). Following stepwise linear regression, intraoperative fluid administration remained weakly correlated (r2 = .161, p = .04) with duration of postoperative ventilation. The following variables were also independently correlated with duration of ventilation: center (Riley Children's Health versus Children's Health Dallas, p = .001), and open abdominal incision after transplant (p = .001). DISCUSSION: The amount of intraoperative fluid administration is correlated with duration of postoperative mechanical ventilation in children undergoing liver transplantation, however, it does not seem to be a strong factor. CONCLUSIONS: Other modifiable factors should be sought which may lead to improved postoperative outcomes in this highly vulnerable patient population.

Direction of arrival filters for improved aberration estimation.

Successful adaptive imaging requires accurate measurements of the aberration profile across the array surface. Two-dimensional spatial filters are used to obtain more accurate estimates of aberrating layers by suppressing wavefronts emanating from off-axis scatterers. Application of these filters to the rf signals of the individual elements rejects wavefronts arriving from angles other than the look direction of the array and results in an increase in element-to-element correlation. Spatial filtering reduced the amount of error in the measured aberration profiles and adaptive spatial filtering further improved the estimates. The improvements in aberration estimation obtained with these methods are verified using simulations and experiments in tissue-mimicking phantoms. The technique is applied to signals obtained from in vivo human thyroid.