Sepsis: SIRS due to an infection


The current definition of sepsis is not well known by most physicians. Many think a sepsis diagnosis requires positive blood cultures and is associated with an extremely grim prognosis. This may have been true a few decades ago, but is no longer so.

Sepsis is now defined as SIRS (systemic inflammatory response syndrome) due to an infection. The condition does not represent the infection itself, but rather the body's systemic reaction to it. It can be caused by infectious organisms including bacteria, viruses and fungi, but may just as well be due to toxins. As such, positive cultures—particularly blood cultures—are not required and are not even one of the diagnostic criteria for sepsis.

Photo by Comstock
Photo by Comstock.

The diagnosis of sepsis was determined by the International Sepsis Definition Conference (ISDC) in 2001, an account of which was published in Critical Care Medicine in April 2003. It establishes sepsis as the diagnosis when an adult patient with an infection looks “sick,” “septic” or “toxic” and has any two or more of the following criteria:

  • Fever ≥101°F or hypothermia (<96.8°F)
  • Heart rate >90 beats/minute
  • Respiration rate >20 breaths/minute
  • White blood count >12,000 µL or <4,000 μL or with >10% bands

The Centers for Medicare and Medicaid Services' (CMS) official coding guidelines recognize any two or more of the above criteria as indicative of sepsis, but some experts caution that the diagnosis should not be based on respiration and heart rate only. Other helpful diagnostic criteria according to the 2001 ISDC include altered mental status, hypotension, elevated C-reactive protein (CRP), hyperlactatemia (>1 mmol/L), mottling of the skin, prolonged capillary refill, and non-diabetic hyperglycemia (>120 mg/dL).

Some physicians are reluctant to document the term “sepsis,” even when the evidence-based clinical criteria are clearly met, because of its historically grim prognosis. Such physicians may be more comfortable with the currently equivalent terminology of “SIRS due to [the underlying infection]”.

Once acute organ dysfunction or failure develops, the condition is then classified as “severe sepsis”; if not reversed, septic shock may soon follow. This is the form of sepsis most of us are familiar with. If diagnosis is delayed until this late stage, mortality is extremely high, so it is important to recognize the earliest signs of sepsis described above.

Organ dysfunction associated with severe sepsis includes: hypoxemia/respiratory failure, renal failure or oliguria, encephalopathy, coagulopathy, liver failure (bilirubin >4 mg/dL), hyperlactatemia (>4 mmol/L), ileus and hypotensive shock. Two important coding quirks to remember are:

  • “Urosepsis” must be coded as a simple urinary tract infection unless the physician clearly documents SIRS or sepsis.
  • “Bacteremia” means only a positive blood culture, does not constitute sepsis and would normally not even be coded.

In sum, look for and document sepsis in all patients admitted with any infection who meet two or more of the SIRS criteria. Evaluate for organ dysfunction indicative of severe sepsis, and treat accordingly.