Prophylaxis Against Infectious Endocarditis
Infectious endocarditis may be caused by bacteria that was ‘introduced into the circulation a~ a result of oral surgery and that attached to sterile vegetation that exists on an abnormal heart valve. This vegetation can arise because of the turbulent flow around an incompetent heart valve. The turbulent flow causes loss of the surface endocardium, which exposes the underlying collagen. Platelets aggregate on the exposed collagen and, together with precipitated fibrin, form a sterile fibrin-platelet thrombus called This vegetation presents no. problems to the patient until it becomes infected with bacteria and produces bacterial endocarditis. When this occurs the patiemust be treated in the hospital with high doses of intravenous (IV) antibiotics for prolonged periods. Although initial recovery from bacterial endocarditis ‘approaches 100%, jecurrent episodes reduce the 5-year survival rate of patients with this disease to approximately 60%. Bacterial endocarditis resulting from introduction of ‘bacteria from an oral source is almost exclusively the result of alpha-hemolytic streptococci with typical antibiotic sensitivity patterns. Prophylaxis regimens against bacterial endocarditis after dental procedures are directed toward effective killing of Streptococcus organisms. The goals of , antibiotic prophylaxis in this case are to reduce the intensity of the bacteremia, assist the reticuloendothelial system in killing the bacteria, and decrease the bacterial adherence to the damaged heart valves and vegetations. The American Heart Association has had formal recommendations for the prevention of bacterial endocarditis after dental treatments sin ce 1960. The latest formal recommendation’s appeared in June 1997. When treating patients surgically, it is important that the dentist specifically inquire about cardiac valvular lesions that may predispose the patient to bacterial endocarditis. (Box 15-11). Antibiotic prophylaxis should be used when a dental procedure is performed- that will produce bleeding of the mucosa. Some procedures, such as tooth extraction and periodontal surgery, obviously cause’ bacteremias; however, vigorous dental prophylaxis’ should also, be included in this category (Box 15-12). ‘ Some procedures, such as supragingival tooth cleaning, placement and adjustment of orthodontic appliances, typical restorative tooth preparation procedures, and conservative nonsurgical endodontic therapy,. do not require antibiotic prophylaxis (Box IS-B). These procedures do not cause bacteremias of sufficient intensity to
predispose the patient to endocarditis. Bacterial endocarditis prophylaxis ~ achieved for most routine conditions ~th the administration of 2 G of
amoxlcillln 1 hour before the procedure (Table 15-4). Amoxicillin is the drug of choice, because it is better absorbed from the’ gastrointestinal tract and provides higher and more ‘sustained plasma levels. Amoxicillin is
an effective killer of alpha-hemolytic streptococcus (i.e., Streptococcus viridansi, which is the organism that most commonly causes endocarditis ‘after dental procedures. The decision to recommend amoxicillin was not made to provide a broader antimicrobial spectrum. For patients who are allergic to penicillin, two alternative drugs have been recommended. The first recommended drug is clindamycin, with a dose of 600 mg orally
1 hour before the surgery. If the patient’s allergy topenicillin is mild and not of an anaphylactic type, first-generation cephalosporin can be prescribed. Either cephalexin ‘or cefadroxil is recommended. Although erythromycin is no longer recommended, the newer macrolide antibiotics’, azithromycin or clarithrornycin, are acceptable alternative drugs. Their chief disadvantage
is that they are more expensive than the other regimens. If the patient is unable to take oral medication, parenteral administration can be used.
For the pediatric patient, the dose of the drugs that are given must be reduced. The recommendations include, clear guidelines for these reductions (see Table 15.-4).