Blood Stream Infections Flashcards
what is the mortality rate of severe sepsis?
28-50%
why is the incidence of severe sepsis anticipated to increase?
due to the disproportionate growth of elderly americans and the high incidence of sepsis in these patients
how do infection and colonization differ?
infection is microorganisms in a normally sterile site while colonization is on an epithelial surface
what is the difference between bacteremia and sepsis?
bacteremia only implies that there is bacteria in the blood stream. it may be of no consequence
what is the classification for systemic inflammatory response syndrome?
must have two or more of the following:
temperature over 38 or under 36C, tachycardia, tachypnea (over 20 or CO2 less than 32 mmHg), and WBC over 12k or under 4k (may also have >10% bands)
what is sepsis?
SIRS associated with proven or clinically suspected infection
define hypotension
systolic bp of 40 mmHg from baseline
what is severe sepsis?
sepsis associated with dysfunction of organs distant from the site of infection, hypoperfusion or hypotension. Hypotension is reversible by administering fluids
what abnormalities are typically included in severe sepsis?
lactic acidosis, oliguria, altered mental status, thrombocytopenia and acute lung injury.
define septic shock.
sepsis with hypotension that does not respond to fluid resuscitation and requires vasopressor therapy. There are perfusion abnormalities also seen in severe sepsis
what does refractory septic shock describe?
septic shock that lasts for greater than one hour and does not respond to vasopressor admin
what causes SIRS?
the body’s response to an inciting event (not the direct effect of the event)- cytokines and dysregulation of inflammation
what is the cause of mortality with sepsis?
multiple organ dysfunction syndrome
how is septic shock initiated?
LPS of gram negative bacteria is recognized by TLR4. This activates the cell and promotes the production of inflammatory mediators
other than the immune system, what else is dysregulated in SIRS and sepsis?
the coagulation system
what molecule can be tracked to identify and watch the progression of sepsis?
procalcitonin level is elevated in sepsis. it is stimulated by endotoxin
what is transient bacteremia? what causes it, typically?
it lasts for minutes or a few hours, often when manipulating a nonsterile body part or at the onset of acute bacterial infections
what is intermittent bacteremia?
bacteremia of the same microorganism that goes through cycles of clearance and recurrence
what is the cause of intermittent bacteremia?
associated with undrained, closed space infections (abscesses) or focal infections
how is persistent bacteremia categorized?
bacteremia that is detectable over a long period of time
what are some infections that cause persistent bacteremia?
infective endocarditis and other intravascular infections. Also occurs during early stages of systemic bacterial infections
what is a primary blood stream infection?
a BSI without a documented primary source of infection (the source is intravascular)
what organisms are associated with endocarditis?
staph aureus, streptococci and coagulase negative staph. among several others
who is at risk for developing infective endocarditis?
IV drug abusers and individuals who have heart valve damage
what is a mycotic aneurysm?
damage to endothelial cells by inflammatory reaction to infection. results from an infection by staph, strep or salmonella, of the aortic wall
what is suppurative thrombophlebitis? where does it occur most frequently?
venous thrombosis associated with bacteremia and inflammation. occurs most frequently with IV catheter or PICC lines
what do catheter associated bloodstream infections colonize?
colonize dwelling catheters that provide more accessible long term venous access for blood testing and treatment.
what is a secondary blood stream infection?
a BSI that has a documented portal of bacterial entry or a known associated site of infection
what two infections of the elderly may lead to a bsi?
UTIS and bacterial pneumonias
how is bacteremia detected?
by culturing blood (most sensitive method) prior to initiation of antimicrobials
when are circumstances in which blood cultures are especially important?
sepsis, meningitis, osteomyelitis, arthritis and endocarditis
how many blood cultures are necessary to detect bacteremia?
must have at least two sets of blood cultures with large volumes of blood from seperate sites at the same time. a total of 3 over 24 hours is usually adequate
what is the typical concentration of bacteria in the blood of a patient with bacteremia?
generally less than 1 bacterial cell/ mL of blood
what does a blood culture set consist of?
an aerobic bottle and an anaerobic bottle, each inoculated with 10 mL of blood
what percentage of bacteremias are detected with one set of blood cultures? two? three?
1- 80%
2- 90%
3- 99%
why is it important to avoid contamination of blood culture samples?
because normal skin flora may cause systemic diseases and it would be impossible to distinguish the two if the sample was contaminated.
what is one method that would avoid contamination of blood samples?
by avoiding use of existing IV lines for culture collection
how long does a lab hold the blood culture? when are bacteremia cases generally detected? why are they held longer?
held for 5 days but most cases detected in the first 48 hours. Some organisms take a longer time so they are held for a longer times
