Infections in elderly intensive care unit patients
The elderly population is increasing in the developed world, therefore elderlies account for a considerable proportion of intensive care unit (ICU) admissions. A precise threshold for “elderly” is a matter of debate. The process of ageing is associated with physiological and functional alterations of the human body and organs that render elderly people vulnerable to infections. As a result of dysfunction of specific parts of immune response called immunosenescence, elderly patients may be threatened by severe infections. Chronic low-grade inflammation, termed inflammaging, is another contributor. In addition to these, comorbidities associated with increasing age, such as diabetes mellitus and immunosuppressive conditions pose an additive risk for infections and in some studies they were associated with increased mortality. Epidemiology of ICU infections may differ in elderlies, compared to other adults. Infections tend to be less microbiologically confirmed and site of infection may be obscure on presentation. The identified pathogens are frequently Gram-negative and particularly Enterobacteriaceae exhibiting a multidrug-resistant (MDR) phenotype. Multiple antibiotic prescriptions in this age-group, specific comorbidities (such as bronchiectasis or chronic obstructive pulmonary disease), residence in long term care facilities and frequent hospitalisations, are among others recognized risk factors for MDR infections. Data from two large European databases show that intra-abdominal infections are predominant among ICU infections in the elderly and Candida spp infections rank second, after Enterobacteriaceae. Age may pose important implications in treatment decisions. Organ derangements, physiological changes caused by increasing age and multiple concomitant medications call clinicians for vigilance about adverse events and toxicity. Despite all the above, elderlies in the ICU did not exhibit worse outcomes compared to younger counterparts in a straightforward manner. Studies however are heterogenous and most of them are single centers. As age is a continuous process, only analysis performed in subgroups of 65–74 (young-old elderlies), 75–84 (old elderlies) and >85 (old-old or oldest old elderlies) provides a better depiction of ICU outcomes. Most studies have shown a worse ICU outcome for the group of oldest-old elderlies, compared with young adults and elderlies in the range of 65 to 84 years of age. These data indicate that age per se may not represent a barrier in decisions concerning ICU admission and triage has to be done on an individual basis. However, epidemiological particularities of this age group should be taken into account in the selection of early and appropriate antimicrobial treatment, which will optimize patients’ outcomes.