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The Infectious Diseases Society of America and American Thoracic Society recently updated the guidelines for managing adults with hospital-acquired and ventilator-associated pneumonia (HAP/VAP). These guidelines were initially published 11 years ago, and the revision reflects the use of Grading of Recommendations Assessment, Development and Evaluation methodology and recent evidence in the face of emerging bacterial resistance (1).
The most striking change in the new guidelines is the elimination of the term healthcare-associated pneumonia (HCAP). The previous rationale that many of these patients were high risk for multidrug-resistant (MDR) pathogens by virtue of their contact with the healthcare system has not been borne out in subsequent studies (2, 3). Although the term HCAP is gone, patients still do present from the community setting with risks for MDR pathogens (4). As a result, the new HAP/VAP guidelines refer to the upcoming community-acquired pneumonia guidelines as the future location of recommendations pertaining to this population. Hence, the new HAP/VAP guidelines are more narrowly focused and pertain to a more limited range of patient profiles.
The 2016 HAP/VAP guidelines focus on the need to monitor local bacterial resistance via antibiograms, preferably ones specific to certain areas of the hospital, such as the intensive care unit. This is to accomplish two goals: to ensure appropriate empiric therapy while culture results are pending and to decrease the amount of inappropriately broad coverage for HAP or VAP. The guidelines are intended to decrease patient-level drug toxicity and antibiotic resistance, two ostensible untoward consequences of the 2005 iteration (5).
The current guidelines make specific antibiotic recommendations that take into account local resistance patterns. For methicillin-resistant Staphylococcal aureus (MRSA), empiric treatment is recommended only when patients have risk factors for MDR pathogens, when at least 10 to 20% of local isolates are resistant, or if local patterns are not known. A similar recommendation is made regarding Pseudomonas and the decision to double cover, with at least 10% resistance to monotherapeutic agents as the threshold to start dual therapy. Although these resistance thresholds are arbitrary, they are estimates based on a desire to ensure that approximately 95% of patients receive empiric therapy active against their likely pathogen. In addition, MRSA coverage and combination therapy for patients with suspected Pseudomonas who are considered to be at high risk of mortality is recommended regardless of local susceptibility patterns. The recommendations for MDR pathogen coverage are summarized in Table 1.
Given that the new guidelines pertain only to hospitalized patients, there is a shift in defining risk factors for MDR pathogens toward prior intravenous antibiotic exposure. Invasive diagnostic measures such as bronchoscopy are not routinely recommended. Among biomarkers, procalcitonin alone is recommended as complementary to clinical criteria, but only for antibiotic discontinuation. Biomarkers are not recommended as adjuncts to clinical decision making for the initiation of antibiotics in HAP or VAP.
Appropriate empiric therapy for HAP/VAP is important, given the consequences of both HAP and VAP. The attributable mortality of VAP is an estimated 13% (6), with both conditions having associated increases in resource use and hospital length of stay (7). Timely administration of appropriate antibiotics is associated with better outcomes, including survival (8). Yet antibiotic resistance has occurred over time resultant from an increased selection pressure due to inappropriate antibiotic use (9, 10). In addition, escalating rates of Clostridium difficile infection have occurred due to antibiotic overuse (11, 12). The empiric treatment of HCAP in many individuals who were not necessarily at risk for MDR pathogens may have inadvertently contributed to these trends.
The new HAP/VAP guidelines attempt to reconcile these two opposing concerns. Ostensibly, the implementation of the new guidelines will result in a decrease in selection pressure for antibiotic resistance. Ideally, patients will continue to receive appropriate empiric antibiotics, but patients with suspected HAP or VAP who fail to meet the criteria outlined above will not be treated for MRSA or with double coverage for Pseudomonas. This attempted “selection correction” from earlier practices, if implemented appropriately, could potentially decrease local antibiotic resistance patterns over time.
Importantly, broad-spectrum coverage for MRSA and double coverage of Pseudomonas continue to be recommended in institutions with a significant resistance problem as demonstrated by their site-based antibiogram. Given that significant antibiotic resistance problems are already prevalent in many large hospitals (i.e., >10–20% for MRSA and >10% for Pseudomonas), it is unlikely that empiric antibiotic selection practices will be significantly altered as a result of the new guidelines in these institutions. In addition, the impact of the new guidelines will also be less in high-intensity intensive care units, where many patients meet high risk of mortality criteria.
Having used Grading of Recommendations Assessment, Development and Evaluation criteria, essentially only six recommendations were listed as strong recommendations with at least moderate-quality evidence. These are (1) use clinical criteria alone rather than procalcitonin plus clinical criteria to decide when to empirically treat HAP/VAP; (2) use clinical criteria alone rather than bronchoalveolar fluid soluble triggering receptor expressed on myeloid cells plus clinical criteria to decide when to empirically treat HAP/VAP; (3) treat suspected HAP/VAP in patients with MRSA risk factors with either vancomycin or linezolid; (4) treat confirmed HAP/VAP due to MRSA with either vancomycin or linezolid; (5) use intravenous polymyxins in patients with HAP/VAP with a carbapenem-resistant pathogen, which is sensitive only to polymyxins; and (6) treat VAP with antibiotics for 7 days. Seemingly none of these are particularly feasible for performance measure development with regard to either data availability or the presence of an explicitly specified numerator and denominator. For example, the recommendation to treat VAP for 7 days, in acknowledging exemptions that are either difficult to define or fairly subjective (“rate improvement of clinical, radiologic, and laboratory parameters”), prohibits the establishment of a valid denominator in a potential performance measure of this sort. As a result, these recommendations should not be championed for development as performance measures (13).
In sum, the new HAP/VAP guidelines are appropriate for hospitalized, immunocompetent patients. Local antibiograms and previous intravenous antibiotic exposure are important determinants of initial empiric antibiotic selection. If implemented as intended, institutions having lower-acuity patients without a high rate of antibiotic resistance may be aided by these guidelines in not seeing their rates of drug resistance rise. Others, such as tertiary care institutions, with already significant rates of antibiotic resistance, will not likely see much change in their empiric antibiotic prescribing patterns.