A 65-year-old man undergoes a low anterior resection for rectal cancer. On the fifth day in hospital, his physical examination shows a temperature of 39degC (102degF), blood pressure of 150/90 mm Hg, pulse of 110 beats per minute and regular, and respiratory rate of 28 breaths per minute. A computed tomography (CT) scan of the abdomen reveals an abscess in the pelvis. Which of the following most accurately describes his present condition?

The correct diagnosis is sepsis. Systemic inflammatory response syndrome (SIRS) involves 2 or more of the following: temperature >38degC (100degF) or 90 beats per minute, respiratory rate >20 or PaCO2 12,000 or 10% immature neutrophils. Sepsis = SIRS + documented infection. Severe sepsis = sepsis + organ dysfunction or hypoperfusion (lactic acidosis, oliguria, or altered mental status). Septic shock = sepsis + organ dysfunction + hypotension (systolic blood pressure 90 mm Hg with vasopressors).