In vivo responses of mitochondrial redox levels to Eschericia coli bacteremia in primates

Near-infrared spectroscopy. Clinical applications

NIRS is an attractive monitoring technology because it is a noninvasive, real-time, repeatable method that allows for regional assessment of the adequacy of tissue oxygenation. It is able to evaluate the oxygenation state of hemoglobin in tissue and redox state of cyt a1,a3, which reflects the overall activity of oxidative metabolism in the cells. The primary technical limitation of current technology is the inability to measure accurately the optical pathlength online, limiting the ability to quantify precisely concentrations of oxygen-dependent chromophores. Even with this limitation, NIRS can provide unique and valuable in vivo metabolic information without invasive intervention.

VA/Q abnormalities during gram negative sepsis

Hypoxemia in bacterial sepsis develops by mechanisms which are incompletely understood. In this study, we measured pulmonary gas exchange in eight baboons to determine the causes of hypoxemia after infusion of live Escherichia coli (1 x 10(10) CFU/kg) followed by resuscitation with intravenous fluid. VA/Q distributions were measured periodically using the multiple inert gas elimination technique until death or for a maximum of 42 h. After E. coli infusion, dispersion of perfusion (logSDq) increased rapidly and a transient rise in dead space was observed at 6 h coinciding with systemic hypotension and acidosis. The intrapulmonary shunt developed later and reached 27 +/- 6% at 24 h. PaO2 began to decrease at 12 h and correlated with increases in intrapulmonary shunt and logSDq. There was no evidence of diffusion limitation. Lung edema was mild despite aggressive fluid resuscitation. Morphometric analysis of postmortem lungs revealed dramatic intravascular accumulation of granulocytes. There were increases in arithmetic mean thicknesses of epithelium and interstitium. These data indicate that gram negative sepsis with fluid resuscitation causes progressive hypoxemia, primarily due to the development of intrapulmonary shunt and very low VA/Q regions in the lung. The VA/Q abnormalities occur early and likely reflect ongoing cellular responses in pulmonary vasculature and smaller airways in sepsis.

Oxidative metabolism in sepsis and sepsis syndrome

The high mortality associated with sepsis syndrome and multiple organ dysfunction syndrome has persisted despite extraordinary research efforts in the laboratory and the intensive care unit. These syndromes produce systemic tissue damage that is likely to result from widespread inflammation and subsequent endothelial injury. This article reviews the oxidative metabolic effects and responses to sepsis syndrome at several levels: the oxygen transport system, the cell, and the mitochondrion. Specifically, aerobic metabolism of carbon substrates and oxygen is altered in sepsis. As a result of systemic inflammation and nonmetabolic oxygen use, oxidative stress may occur both outside and inside the cell. The consequences of these oxidative processes during sepsis may be ongoing cell damage mediated by reactive oxygen and nitrogen oxide species that culminates in multisystem organ failure.