Relationship between cardiopulmonary bypass flow rate and cerebral embolization in dogs

Background: Cerebral embolization is a primary cause of cardiac surgical neurologic morbidity. During cardiopulmonary bypass (CPB), there are well- defined periods of embolic risk. In theory, cerebral embolization might be reduced by an increase in pump flow during these periods. The purpose of this study was to determine the CPB flow-embolization relation in a canine model. Methods: Twenty mongrel dogs underwent CPB at 35°C with α-stat management and a fentanyl-midazolam anesthetic. In each animal, CPB flow was adjusted to achieve a mean arterial pressure of 65-75 mmHg. During CPB, an embolic load of 1.2 x 103 67 μm fluorescent microspheres was injected into the arterial inflow line. Before and after embolization, cerebral blood flow was determined using 15-μm microspheres. Tissue was taken from 12 brain regions and microspheres were recovered. The relation between pump flow and embolization/g of brain was determined. Results: The mean arterial pressure at embolization was 67 ± 4 mmHg, and the range of pump flow was 0.9-3.5 l · min-1 · m-2. Cerebral blood flow was independent of pump flow. At lower pump flow, the percentage of that flow delivered to the brain increased. There was a strong inverse relation between pump flow and cerebral embolization (r = -0.708, P < 0.000 by Spearman rank order correlation). Conclusions: Cerebral embolization is determined by the CPB flow. At an unchanged mean arterial pressure, as pump flow is reduced, a progressively greater proportion of that flow is delivered to the brain

Syndromes of global change

A novel transdisciplinary description of the mega-process called "Global Change" in terms of functional patterns ("Syndromes") is presented. This approach to environmental analysis is inspired by medical sciences, where syndromes are perceived as typical combinations of pertinent co-factors. Sixteen main syndromes are identi ed as the subdynamics generating the world-wide environment and development process with all its negative aspects and impacts. The analysis relies on a specific semi-qualitative methodology, which brings together elements from complex systems theory, fuzzy logic and expert-judgment evaluations. The concept is illustrated by in-depth treatment and comparison of the syndromes Sahel" and "Green Revolution". As a corollary of the syndrome approach, a simple operational de nition o