Gram-Negative Sepsis (5)In that investigation, we defined bacteremia as the presence of a positive blood culture obtained within 48 hours of study entry, but we did not require the demonstration of bacteremia for designation of sepsis syndrome.
Fever is the most commonly observed sign of sepsis. Pyrogenic activity is stimulated by at least three endogenous substances: interleukin 1 (IL-1), interferon alpha, and tumor necrosis factor (TNF), also known as cachectin. All of these substances increase hypothalamic prostaglandin E2 synthesis. Whether fever represents a beneficial bactericidal response to infection still remains an open question. Hypothermia occurs less frequently and is observed mainly in very young, elderly, or chronically debilitated patients.
Cardiopulmonary manifestations of sepsis range from tachycardia and tachypnea to ARDS, which is considered a catastrophic complication. Hyperventilation is often noted even before the onset of fever or chills, and respiratory alkalosis is usually found in early metabolic studies. Arterial carbon dioxide pressure is commonly ^30 mm Hg. Hyperventilation tends to mask early hypoxemia, an important development that may signal the development of ARDS. Other early changes include an increase in cardiac output, which generally offsets decreased peripheral resistance.