Page 853 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

584 PART 5: Infectious Disorders

unique chest x-ray pattern of rounded cavitary infiltrates along the HCAP patient is more frequent in large academic medical centers with
bronchovascular bundle (Fig. 65-2). However, extensive workup for active oncology and transplant programs. The availability of home
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endocarditis is overwhelmingly negative. wound care and antibiotic infusion services also varies tremendously by
locale. In these settings, HCAP may be more common than traditional
Acute Cardiac Events: Patients with CAP in severe sepsis or septic shock CAP. In smaller hospitals, the relative frequency is dramatically lower
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are prone to multiorgan system failure, including septic cardiomyopa- and the number of patients with MDR pathogens is extremely small. 97
thy, similar to other serious infections. However, acute cardiovascular Missing from the original description, the recent use of antibiotics is
complications appear to be more common in CAP patients than in other also a major predictor of the risk of MDR pathogens. As broader spectrum
types of sepsis. Up to 20% of patients with pneumococcal pneumonia oral antibiotics have become available, the selective pressure for MDR
can develop acute myocardial infarction, new onset congestive heart pathogens has increased. This is best illustrated by a study of NHAP, which
failure, or new onset arrhythmia when hospitalized for pneumonia. 77,78 demonstrated that the risk of MDR pathogens was primarily determined
This increased risk of cardiovascular complications extends past the by recent antibiotic use and secondarily by dependence in activities of daily
duration of hospitalization and may be related to persistent procoagu- living. Therefore, nursing home patients who have not been recently hos-
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lant cytokine elevation even at the time of discharge. 92 pitalized or given broad-spectrum antibiotics and who are independently
■ PREVENTION functioning can be treated safely with traditional CAP drugs.
Surprisingly, the most common risk factor for HCAP is consistently
Secondary prevention of CAP in patients who have been admitted to recent hospitalization, with nursing home residence constituting a
the ICU with one episode of SCAP has not been specifically studied. smaller proportion of patients in all studies. 96,97,99-101 Many patients have
However, patients with one episode of bacteremic pneumococcal multiple risk factors, with the most common overlap again being recent
pneumonia are 50 times more likely to develop recurrent disease than hospitalization. The risk of MDR pathogens in stable nursing home
is the general population to develop a first episode. This is likely due patients, chronic hemodialysis patients, or even patients receiving che-
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to genetic risk factors for severe infection, especially in patients who motherapy is unclear if they have not been recently hospitalized.
do not have hematologic malignancies or HIV disease. Therefore, both Because many of the early studies were based on retrospective analysis
pneumococcal vaccination and yearly influenza vaccination are prob- of large administrative databases, the analysis was limited to culture-
ably indicated even if the patient is not otherwise in a high-risk group. positive cases. Prospective studies demonstrate both a lower incidence
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Efficacy of vaccination at the end of the original hospitalization or even of HCAP and a lower frequency of MDR pathogens. A recent com-
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subsequent to recovery is unclear in this population if indeed they have parison demonstrated that culture-negative HCAP patients can be safely
a form of immunocompromise. treated with CAP antibiotic regimens with good success. However,
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risk factors for culture positive HCAP include ICU admission. 103,104
HEALTH CARE–ASSOCIATED PNEUMONIA Therefore, patients with HCAP risk factors admitted to the ICU are at
increased risk for MDR pathogens.
HCAP is technically a subgroup of CAP. This category of pneumonia
was developed in response to the fairly consistent finding of patients Mortality: One justification for separating HCAP from CAP was that
who develop pneumonia while outside the hospital yet have patho- the associated mortality in HCAP was much greater than in CAP and
gens traditionally associated with HAP, such as MRSA, Pseudomonas, closer to that of HAP. This finding is not surprising given that the
and drug-resistant Enterobacteriaceae. 55,94 Initially, this appeared to be most frequent risk factor is recent hospitalization. Subsequent studies
predominantly patients admitted from nursing homes and an exten- suggest that this excess mortality is primarily due to the underlying
sive literature on nursing home–acquired pneumonia (NHAP) exists. disease rather than the presence of MDR pathogens. 101
However, subsequently it became obvious that this criterion alone did ■ ETIOLOGIC SPECTRUM AND RECOMMENDED ANTIBIOTIC THERAPY
not describe the spectrum of patients who presented with CAP due to
MDR pathogens. This entity is extremely controversial, in part because The implication of separating HCAP from CAP is that the pathogens
the frequency truly differs between hospitals and health care systems. are more similar to those of HAP and VAP (Table 65-8). However, the
■ DEFINITION patients receiving broad-spectrum antibiotics without a positive culture
criteria for HCAP are consistently oversensitive and result in many
One cause of the HCAP controversy is that the risk factors were initially for MDR pathogens. In addition, the risk for all MDR pathogens is
not the same. While a case can be made that home infusion therapy or
adapted from a study of bacteremia. The initial criteria for HCAP were wound care and chronic hemodialysis may be risk factors for MRSA
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proposed in the ATS/IDSA guidelines for hospital-acquired pneumonia, pneumonia, no evidence exists that they increase the risk of MDR gram-
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and are listed in Table 65-6. Subsequent studies have used variations on negative pathogens such as Pseudomonas and Acinetobacter. In these
the criteria that affect both frequency and etiology. Probably the most situations, anti-MRSA coverage can simply be added to the traditional
significant is the inclusion of immunocompromised patients in the CAP antibiotic regimen.
HCAP category. The immunocompromised patient was technically An accurate diagnosis is critical to management and is often avail-
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a separate category and not included in HCAP in the original guide- able in ventilated HCAP patients via tracheal aspirates or BAL. Initial
lines. However, with the expansion of both the indications for immu- empirical antibiotic therapy for patients truly at risk for MDR patho-
nosuppressive therapy and the types of immunosuppression, defining gens is the same as described for HAP in Table 65-8. If HCAP patients
immunocompromise is no longer easy. In addition, the criterion for are culture negative, they can be safely de-escalated to traditional CAP
prior hospitalization has been increased from 3 months to as much as coverage, such as a fluoroquinolone. No RCT is available for HCAP
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a year in some studies. Hospitalization within the previous month has patients admitted to the ICU and retrospective studies often exclude
traditionally been considered hospital-acquired pneumonia. However, ICU patients and have often been contradictory regarding the clinical
this has also been challenged and many of these patients are included benefit of HAP-like versus traditional CAP treatment. 96,97,100,102
in the HCAP group. Surprisingly, given the frequent concern regarding aspiration, patients
Clearly HCAP is a diagnosis in transition. Further refinements of the with NHAP who developed respiratory failure do not have evidence
definition are expected in the future. that anaerobes play a significant role. Therefore, specific anaerobic
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■ EPIDEMIOLOGY coverage is not necessarily required. Conversely, poor infection control
practices in nursing home patients, particularly those with skin break-
Several patterns have emerged as the database of HCAP has increased. down, surgical wounds, tracheostomy, or who are incontinent, increase
The first is that HCAP is clearly a disease of medical progress. The the risk of MDR gram-negative pathogens.

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