Some patients may be more prone to sepsis than others, often because of a defect in their host defenses. It is important to recognize this group since management of the sepsis also requires addressing any comorbid conditions that make the patient more vulnerable. This article is part of our ongoing sepsis series and explores sepsis criteria for vulnerable patients, especially those:

  1. With a primary or acquired immunodeficiency
  2. With other comorbid conditions affecting host defenses
  3. With an intravascular catheter
  4. Who are critically ill in the ICU

Because these patients may have more frequent infections they often have a history of recent antibiotic therapy and contact with healthcare facilities. These factors place them at risk for infections with antibiotic resistant bacteria and Clostridium difficile.  Medical calculators that can assist in diagnosis of sepsis for vulnerable patients are suggested for each of the four types of patients mentioned above.


An immunodeficiency places the patient at risk for frequent and recurrent infections, often with different organisms. Some patients are easy to diagnose based on history or medications, but some may go unrecognized for some time if an alternative explanation for the infections is available.

Comorbid Conditions

The host defenses may be affected by disorders affecting normal barriers (such as skin or mucosa) and the inflammatory response. In addition,  the very young and very old may be unable to respond to a physiologic insult because of immature organ development or deteriorating organ function. The presence of severe or multiple comorbid conditions should be a clue warning the clinician to take extra precautions with the patient.

Intravascular Catheter (IVC)

Intravascular catheters increase the risk of infection, especially if they have been present for some time. These devices break the skin barrier, act as a foreign body, and provide ready access of micro-organisms to the blood. For a patient with poor vascular access, there may be reluctance to remove an infected catheter, making the accurate diagnosis of a line infection important.

Admission to the ICU

A patient who has been admitted to the intensive care unit (ICU) may have many risk factors for sepsis, including multiple vascular lines, malnutrition and organ dysfunction. Diagnosis of sepsis may be delayed since the signs and symptoms may be masked or may overlap with the critical illness.

Antibiotic Resistance

The possibility of infection with an antibiotic resistant bacteria needs to be considered in vulnerable patients with a history of antibiotic therapy or therapy at a healthcare facility. Antibiotic resistance organisms may not respond to standard antibiotic regimens, and therapy often must be guided by culture and susceptibility testing. A patient colonized with an antibiotic resistant organism may pose a threat to others.

Predictive Index for Antibiotic Resistance in Gram-Negative Bacteremia


Certain comorbid conditions make a person more susceptible to infections, including sepsis. The sooner that sepsis can be diagnosed the sooner effective therapy can be started. Success in managing sepsis often requires management of the predisposing factors. Medical algorithms can help to alert clinicians to these issues.