infective endocarditis Flashcards
what does dental work have to do with infective endocarditis?
dental treatment has long been implicated as a significant cause of IE. Conventional wisdom has taught that in a patient with a predisposing cardiovascular disorder, IE was most often due to a bacteremia that resulted from a dental procedure, and that through the administration of antibiotics before those procedures, IE could be prevented.
- the effectiveness of the recommendations has never been proved in humans and accumulating evidence suggests that many of the widely held assumptions on which these previous recommendations were made may not be accurate.
what about source and frequency of bacteremia in life?
- it is undisputed that many dental procedures can cause bacteremia, but it’s also clear that bacteremia can result from many normal daily activities such as toothbrushing, flossing, manipulation of toothpicks, use of oral water irrigation devices, and chewing.
how does the bacteremia of daily activities compare with dental work?
the number of microorganisms in blood after a dental procedure or associated with daily activities is similarly low, and cases of IE caused by oral bacteria probably result from frequent exposure to low inocula of bacteria in the bloodstream, resulting from routine daily acitvities and not from a dental procedure.
how does good oral health come into play?
Noteworthy is that most patients with viridians streptococci IE have not undergone a dental rpocedure within the 2 weeks before the onset of symptoms. these findings imply that emphasis on maintaining good oral hygiene and eradicating dental or oral disease is key to decreasing the frequency of bacteremia produced by normal daily activities. One study found that the incidence of bacteremia after toothbrushing was significantly related to poor oral hygiene and gingival bleeding after toothbrushing.
overall what does the efficacy of antibiotic prophylaxis say?
pretty much that it’s not 100% effective and only about 2.6% of cases of IE occurred annually in patients undergoing unprotected dental procedures, and that a “huge numebr of prophylaxis doses would be necessary to rpevent a very low number of IE cases”
what is the risk of bacterial endocarditis due to dental procedures?
An exceedingly small number of these cases are caused by bacteremia-producing dental procedures.
so if antibiotics aren’t really proven to really be effective why do we use it to prevent IE?
The AHA notes: we cannot exclude the possibility that there may be an exceedingly small number of cases of IE that could be prevented by prophylactic antibiotics in patients who undergo an invasive procedure. However, if prophylaxis is effective, such therapy should be restricted to those patients with the highest risk of adverse outcome from IE who would derive the greatest benefit from prevention of IE. In patients with underlying cardiac conditions associated with the highest risk for adverse outcome from IE, IE prophylaxis for dental procedures may be reasonable, even though we acknolwedge that the effectiveness is unknown.
who is recommended to receive endocarditis prophylaxis?
prosthetic cardiac valve
previous infective endocarditis
congentical heart disease (CHD):
- unrepaired cyanotic CHD, including those iwth palliative shunts and conduits
- completely repaired CHD with prosthetic material or device by surgery or catheter intervention during the first 6 months after the procedure
- repaired CHD with residual defects at the site or adjacen to the site of a prosthetic patch or prosthetic device, which inhibits endothelialization
cardiac transplant recipients who develop cardiac valvulopathy
for those who get antibiotic prophylaxis which dental procedures do thye need it for?
all dental procedures that involve the manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa
this includes all dental procedures except the following procedures and events:
- routine anesthetic injections through noninfected tissue
- taking of dental radiographs
- placement of removable prosthodontic or orthodontic appliances
- adjustment of orthodontic appliances
- shedding of deciduous teeth and bleeding from trauma to the lips or oral mucosa
what type of bacteria is the antibiotic prophylaxis directed against? when should it be administered? what should be used?
viridans group streptococci.
- should be administered in single dose 30 to 60 minutes before the procedure.
- If the antibiotic is inadvertently not administered before the procedure, the dosage may be administered up to 2 hours after the procedure.
see p. 32 textbook
what is infective endocarditis?
a microbial infection of the endothelial surfae of the heart or heart valves that most often occurs in proximity to congenital or acquired cardiac defects.
what is the etiology of infective endocarditis?
90% of community-acquired cases of native valve IE are due to streptococci, staphylococci, or enterococci with streptococci being th emost common causative organism. The species that most commonly cause endocarditis are streptococcus sanguis, streptococcus orals (mitis), streptococcus salivarius, streptococcus mutans, and gemella morbillorum.
the proportion of cases of S. aureus - related endocarditis appears to be increasing at community based and university hospitals. This increase appears to be due in large part to increasing health care contact, such as through surgical procedures or the use of indwellign catheters.
pathophysiology of IE?
sequence of events leading to ifnection usually begins with injury or damage to an endothelial surface, most often of a cardiac leaflet. Although IE can occur on normal endothelium, most cases being iwth a damaged surface, usually in proximity to an anatomic defect or prosthesis. Endothelial damage can result from:
- Directed flow from a high-velocity jet onto the endothelium
- Flow from a high- to a low-pressure chamber
- Flow across a narrowed orifice at high velocity
Fibrin and platelets then adhere to the roughened endothelial surface, where they form small clusters or masses resulting in a condition called nonbacterial thrombotic endocarditis (NBTE). Initially these masses are sterile and do not contain microorganisms. With the occurence of a transient bacteremia, however, bacteria can be seeded into and adhere to the mass. Additional platelets and fibrin are then deposited onto the surface of the mass, which serves to sequester and protect the bacteria, which undergo rapid multiplication within the protection of the vegetative mass. Once the vegetative process is established, the metabolic activity and cellular division of the bacteria are diminished, which decreases the effectiveness of antibiotics. Bacteria are slowly and continually released from vegetations and shed into the bloodstream, resulting in a continuous bacteremia; fragments of the friable vegetations break off and embolize. A variety of host immune responses to bacteria may occur. This sequence of events results in the clinical manifestations of IE.
- local destructive effects of intracardiac (valvular) lesions
- embolization of vegetative fragments to distant sites resulting in infarction or infection.
- hematogenous seeding of remote sites during continuous bacteremia
- antibody response to the infecting organism, with subsequent tissue injury caused by deposition of preformed immune complexed or antibody-complement interaction with antigens deposited in tissues.
Most common complications of IE, and leading cause of death, is heart failure, which results from severe valvular dysfunction.
possible stroke, or myocardial infarction as the result of embolism of the coronary arteries
emboli may involved liver, spleen, and kidneys, renal dysfunction is common and may be due to immune complex glomerulonerphritis or infarction.
what is the first choice to give for oral antibiotics prophylaxis?
2g amoxicillin (adults); 50mg/kg (children)
what is the first choice to give for antibiotic prophylaxis if they are unable to take oral medication?
ampicillin 2g IM or IV (adults); 50mg/kg IM or IV (children)
OR cefazolin or ceftriaxone 1g IM or IV (adulst); 50mg/kg IM or IV (children)
