title: The impact of comorbid [corrected] conditions on critical illness.
abstract: OBJECTIVE
  To review the current knowledge of common comorbidities in the intensive care unit, including diabetes mellitus, chronic obstructive pulmonary disease, cancer, end-stage renal disease, end-stage liver disease, HIV infection, and obesity, with specific attention to epidemiology, contribution to diseases and outcomes, and the impact on treatments in these patients.
  
  
  METHODS
  Review of the relevant medical literature for specific common comorbidities in the critically ill.
  
  
  RESULTS
  Critically ill patients are admitted to the intensive care unit for various reasons, and often the admission diagnosis is accompanied by a chronic comorbidity. Chronic comorbid conditions commonly seen in critically ill patients may influence the decision to provide intensive care unit care, decisions regarding types and intensity of intensive care unit treatment options, and outcomes. The presence of comorbid conditions may predispose patients to specific complications or forms of organ dysfunction. The impact of specific comorbidities varies among critically ill medical, surgical, and other populations, and outcomes associated with certain comorbidities have changed over time. Specifically, outcomes for patients with cancer and HIV have improved, likely related to advances in therapy. Overall, the negative impact of chronic comorbidity on survival in critical illness may be primarily influenced by the degree of organ dysfunction or the cumulative severity of multiple comorbidities.
  
  
  CONCLUSIONS
  Chronic comorbid conditions are common in critically ill patients. Both the acute illness and the chronic conditions influence prognosis and optimal care delivery for these patients, particularly for adverse outcomes and complications influenced by comorbidities. Further work is needed to fully determine the individual and combined impact of chronic comorbidities on intensive care unit outcomes.
authors.affiliation: Division of Pulmonary, Allergy and Critical Care, Emory University School of Medicine, Atlanta, GA, USA. aesper@emory.edu
authors.forename: Annette M
authors.initials: AM
authors.lastname: Esper
authors.forename: Greg S
authors.initials: GS
authors.lastname: Martin
mesh_terms: D015897:Comorbidity; D016638:Critical Illness / Q000453:epidemiology*; D003920:Diabetes Mellitus / Q000453:epidemiology; D058625:End Stage Liver Disease / Q000453:epidemiology; D015658:HIV Infections / Q000453:epidemiology; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data; D007676:Kidney Failure, Chronic / Q000453:epidemiology; D009369:Neoplasms / Q000453:epidemiology; D009765:Obesity / Q000453:epidemiology; D029424:Pulmonary Disease, Chronic Obstructive / Q000453:epidemiology; D014481:United States / Q000453:epidemiology