Antimicrobial prophylaxis for bacterial endocarditis has become standard and routine in most developed countries. The antimicrobial prophylaxis guidelines of the American College of Cardiology (ACC) and the American Heart Association (AHA) were revised in 1997 and updated by the Medical Letter in 2005; (40,41) the recommendations were unchanged in the 2006 ACC/AHA guidelines on the management of valvular heart disease (33).
The cardiac conditions in which antimicrobial prophylaxis is indicated are situations where the risk of endocarditis is considered by most authorities to be high and in which antimicrobial prophylaxis is generally indicated. These include patients with prosthetic heart, a prior history of endocarditis, complex cyanotic congenital heart diseases, and those with surgically constructed systemic or pulmonary conduits. Prophylaxis is also recommended in those with conditions in which the risk of endocarditis is moderate. These include most other congenital cardiac malformations, acquired valvular dysfunction and patients who have undergone valve repair, those with hypertrophic cardiomyopathy with obstruction, mitral valve prolapse with valvular regurgitation on auscultation and/or thickened leaflets on echocardiography, and intracardiac defects that have been repaired within the preceding six months or that are associated with significant hemodynamic instability.
The AHA has listed those dental and nondental procedures in which prophylaxis is generally indicated for patients with high or intermediate risk of endocarditis (40,41).
These include tonsillectomy and/or adenoidectomy, surgical operations that involve the respiratory mucosa, bronchoscopy with a rigid bronchoscope, sclerotherapy for esophageal varices, esophageal stricture dilation, biliary tract endoscopy or surgery, surgery involving the intestinal mucosa, prostatic surgery, cystoscopy, and urethral dilatation.
The prophylactic antimicrobial regimen for dental, oral, or upper respiratory tract procedures is a single dose of amoxicillin, 2 g orally one hour before the procedure (41). Those allergic to penicillins can be treated one hour before the procedure with clindamycin (600 mg), cephalexin or cefadroxil (2 g), or azithromycin (500 mg). To those unable to take oral medications, 2 g of intravenous or intramuscular ampicillin is given 30 minutes before the procedure. Patients allergic to penicillin can be given clindamycin (600 mg IV) or cefazolin (1 g IV) 30 minutes before the procedure.
For genitourinary or gastrointestinal procedures, the antimicrobials given are ampicillin (2 g intravenously or intramuscularly) plus gentamicin (1.5 mg/kg up to a maximum dose of 120 mg) 30 minutes before the procedure followed by ampicillin (1 g IV or IM) or amoxicillin (1 g orally) six hours later. Those allergic to penicillin receive the same dose of gentamicin plus vancomycin (1 g IV) one to two hours prior to the procedure.
A patient with a moderate risk for endocarditis is treated with amoxicillin (2 g orally) or ampicillin (2 g IVor IM) within 30 minutes of starting the procedure. Those allergic to penicillin can be treated with vancomycin (1 gm IV).
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