Page 863 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

594 PART 5: Infectious Disorders

TABLE 67-1 Etiology of Prosthetic Valve Endocarditis
• Intravascular infection should be considered even in a patient
with negative blood cultures where there is an unexplained Microorganism Early Onset (%) Late Onset (%)
febrile or septic illness. Coagulase-negative staphylococci 38 25
• Intravascular infection should especially be considered when there Staphylococcus aureus 21 11
is S aureus bacteremia.
Methicillin-sensitive S aureus 13 8
Methicillin-resistant S aureus 8 3
Viridans streptococci 4 15
Enterococcus 4 7
PATHOGENESIS OF INTRAVASCULAR INFECTIONS Diphtheroids 4 0

The pathogenesis of intravascular infections depends on the location of Gram-negative bacilli 0 4
the infection, the organism involved, and the integrity of the underlying Candida 0 4
vasculature. Native valve endocarditis (NVE) generally results from a
cascade of events that begins when mechanical lesions promote micro- Peptococcus species 0 1
bial adherence to the injured endothelium during transient bacteremia Miscellaneous 17 11
by certain organisms. This initiates a cycle of monocyte activation along Culture negative 13 19
with cytokine and tissue factor production that causes enlargement of an
infected vegetation, which consists primarily of bacteria, platelets, and
fibrin. Local extension, as well as distant metastasis, may result as the ■
primary infection expands. CLINICAL AND LABORATORY FEATURES
NVE is most often due to streptococci of dental origin. Nosocomial Infective endocarditis (IE) is often suspected in a critically ill patient
NVE in critically ill patients is most often the result of urinary tract only after blood culture results reveal a pathogen typically associated
infection related to urologic catheterization or bacteremia related to with endocarditis. Fever is present in 85% to 95% of patients at presen-
central venous line infection. 1 tation. Prior to finding bacteremia the working diagnosis is typically
Intravascular infection involving veins generally results from exten- urinary tract infection given that 50% of patients have an abnormal
sion of local microbes or infection into local vasculature by certain urinalysis on presentation. Others may be diagnosed with pneumonia,
pathogens prone to intravascular infection. Intravascular infection especially those with right-sided endocarditis and resultant septic pul-
involving arteries usually results from bacteremic seeding of arteries at monary emboli. Drug abusers with right-sided NVE frequently have
8
bifurcation sites in the brain or periphery as well as seeding of preexisting evidence of septic pulmonary emboli on chest x-ray. Encephalitis and
9
aneurysms. 2 diskitis are also in the differential diagnosis as half of the time patients
Infection involving foreign devices is the result of local spread of will have altered mental status and a quarter will present with back pain.
bacteria or bacteremic seeding of a vegetation, which has previously Rarely do patients present with overt systemic embolic stigmata. These
formed on the device. are seen in less than 50% of patients but, when present, are seen most
often on the conjunctiva, soft palate, and distal portions of the extremi-
ties. Most patients with left-sided disease will have a murmur but this is
10
INFECTIVE ENDOCARDITIS a nonspecific finding in a critically ill septic patient. Gouello et al found
■ ETIOLOGY that 41% of patients with nosocomial endocarditis had a new murmur.
11
Viridans streptococci remain the most common cause of NVE, Benito et al found that 55% of patients with nosocomial NVE had a new
or changed murmur. Patients with right-sided endocarditis often do not
4
accounting for 50% of infections. The other causes of NVE are exhibit a heart murmur.
Patients with PVE are at an increased risk of cardiac complica-
• Staphylococcus aureus in 25% tions caused by valve dehiscence and paravalvular abscess formation.
• Enterococci in 7% Abscesses are primarily manifest by persistent fever and conduction
• Coagulase-negative staphylococci in 6% abnormalities. Patients with nosocomial PVE have a new or changing
12
• Gram-negative bacilli in 6% murmur in 31% of cases and peripheral stigmata in 20%. The risk
• Fungi in 1% of embolic phenomena is highest the first week and is more likely in
patients with large vegetations, those with mitral valve involvement, and
• Culture negative in 7% in those infected with S aureus.
• S aureus accounts for 40% to 50% of infections in patients admitted Patients with IE may also present with signs and symptoms due to
to the intensive care unit (ICU). 3 congestive heart failure or renal insufficiency. IE may present with focal
neurologic signs and symptoms due to a stroke caused by septic emboli,
Recently there has been a trend toward an increase in the percent- rupture of a mycotic aneurysm, or rarely from cerebral artery vasculitis.
age of infections caused by both methicillin-sensitive and methicillin- Overall, approximately 30% of patients with IE will have evidence of a
resistant S aureus (MRSA). This is at least partially related to the focal neurologic event during their illness. Mourvillier et al reported
increased usage of central venous catheters among both hospitalized and that 6% and 14% of patients with IE admitted to the ICU presented with
nonhospitalized patients. Enterococci and coagulase-negative staphylo- cerebral hemorrhage or emboli, respectively. The other complications
4
3
cocci are both twice as common a cause of nosocomial NVE compared seen in ICU patients with IE include
to community acquired NVE. 5
The number of infections caused by Streptococcus bovis has also • Congestive heart failure in 28%
increased and has been attributed to the aging population and related • Septic shock in 26%
colonic disease. 6 • Peripheral of pulmonary emboli in 15%
The etiology of prosthetic valve endocarditis (PVE) depends on
the onset of infection in relation to the time of valve replacement • Renal failure in 14%
(Table 67-1). 7 • Death in 45%

section05_c61-73.indd 594 1/23/2015 12:48:00 PM