Temporal patterns of blood volume, hemodynamics, and oxygen transport in pathogenesis and therapy of postoperative adult respiratory distress syndrome.

Time relationships of physiologic patterns that are relevant to the pathogenesis of adult respiratory distress syndrome (ARDS) have not been well studied. The purpose of this review is to summarize the temporal relationship of blood volume, hemodynamics, and oxygen transport patterns occurring in postoperative patients before and after ARDS in order to develop a more complete mechanistic evaluation of its pathophysiology and to propose more rational therapeutic strategies. The data indicate that hypovolemia, reduced or uneven blood flow, inadequate delivery of oxygen, and insufficient consumption of oxygen precede the appearance of ARDS and are the primary precipitating physiologic events. This is contrary to conventional thinking which emphasizes capillary leak and fluid overload as the primary problems. The conventional approach also ignores events antecedent to ARDS that produce hypoxia of the lung tissue, result in pulmonary vasoconstriction, and increased pulmonary venous admixture (shunt). Therapy to prevent or rapidly treat these antecedent events has been shown to prevent or attenuate postoperative and posttraumatic ARDS. Various mediators such as interleukin (IL)-1, IL-6, and IL-8 and tumor necrosis factor as measured by plasma concentrations do not precede diagnostic criteria of ARDS, but may accelerate and augment the disorder as it is occurring.