Nitric Oxide, Systemic Inflammatory Response Syndrome and Circulatory Shock

Abstract

The medical syndrome of shock can be defined as a “progressive failure of the circulation to provide blood and oxygen to vital organs of the body”. In clinical practice, the key symptom of shock is a severe fall in blood pressure which is often associated with the dysfunction or failure of several important organs including lung, kidney, liver and brain. The most common cause of shock is the contamination of blood with bacteria (bacteremia), viruses, fungi or parasites, resulting in systemic infection and ultimately shock (septic shock). Other causes of shock include severe hemorrhage (hemorrhagic shock), trauma (traumatic shock), failure of the heart to maintain a sufficient cardiac output (cardiogenic shock), interruption of the innervation of blood vessels (neurogenic shock) and severe allergic reactions (anaphylactic shock). Septic shock, regardless of its aetiology, is defined as sepsis (systemic response to infection) with hypotension despite adequate fluid replacement, resulting in impaired tissue perfusion and oxygen extraction (Parrillo, 1990). The definition of septic shock is independent of the presence or absence of a multiple organ dysfunction syndrome (MODS), which is defined as impaired organ function such that homeostasis cannot be maintained without intervention (Baue, 1993). Primary MODS is a direct result of a well-defined insult to a specific organ.