[Hemodynamics during septic shock]

Septic shock usually induces a hyperdynamic state characterized by normal or high cardiac output, associated with a fall in peripheral resistances which is responsible for arterial hypotension; when the evolution is prolonged it usually leads to a low output syndrome with elevated peripheral resistances, suggesting the hemodynamic pattern of hypovolemic shock. All intermediate situations can be observed within these extremes. The hyperdynamic state corresponds to a decrease in aortic impedance, which is indirectly related to the effects of endotoxin on vascular bed. The low output syndrome is more usual at the advanced stage and corresponds to the intervention of associated factors such as progressive hypovolemia and/or myocardial dysfunction. In certain cases--e.g. peritonitis--septic shock is immediately associated with hypovolemia. Many hypotheses have been advanced to explain the circulatory, cardiac and metabolic effects of septic shock. The effect of kinines on the circulation appears to predominate but there are still many unanswered questions concerning the real sequence of events. Hemodynamic monitoring is of great advantage in identifying the type of circulatory distortion, determining its severity, guiding therapy and evaluating its effects.