Hemodynamic responses to sepsis: Hypodynamic versus hyperdynamic states

It has never been fully understood why the circulatory responses of some septic patients and experimental septic animal models are hyperdynamic, while others are hypodynamic, the latter often thought to reflect an "overwhelming" sepsis. This study identifies the "focus of infection" as the central factor which governs the host response to sepsis. Similar hosts (piglets) received the same bacteria (Escherichia coli strain U9-41) in comparable doses, by two different routes, one intravenous and the other intramuscular. The intravenous group did not have a focus of infection and developed hypodynamic shock (low cardiac output, hypothermia, leukopenia). The low flow state was not preceded by a high output phase and was not reversed by increasing the preload, indicating myocardial depression. The intramuscular group, with a focus of infection and inflammation, developed a hyperdynamic state (high cardiac output, fever, and leukocytosis). The important pathophysiologic role of a focus of infection should be recognized, particularly in devising experimental models to study septic shock.