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PROPHYLACTICANTIBIOTICENDOCARDITISMEDICALBACTERIALINFECTION EXAMINING THE NEED FOR CLINICAL PROPHYLACTIC ANTIBIOTIC COVERAGE Examining the need for clinical prophylactic antibiotic coverage ---------------------------------------------------------------- The use of antibiotics for the prevention of infective endocarditis has been a problem for the practitioner. This is due to the wide range of clinical entities requiring antibiotic coverage along with the multitude of prophylaxis regimens which have been recommended. Advancements in medical treatment (i.e., organ transplantation) have necessitated the development of new clinical management protocols. The medicolegal implications of prophylactic antibiotic use (or misuse) makes the subject a confusing one indeed. This article will outline and categorize the medical conditions requiring antibiotic coverage, and state the most appropriate antibiotic regimen for each. Infective endocarditis defined Infective endocarditis is an infection on the endocardial lining of the heart. The term Subacute Bacterial Endocarditis (SBE) implies that the infection is of bacterial origin. Since endocardial fungal, viral, and rickettsial infections are not unknown, the term infective endocarditis is a more complete description of the disorder. Such infections arise after the implantation and subsequent vegetative proliferation of blood- borne microorganisms and platelet-fibrin deposits. Generally, three conditions must be present for infective endocarditis to develop (see figure 1). -Firstly, an area of damaged endocardium provides a focus at which the infection process may begin; this could be a diseaesd valve, a structural defect, or a prosthetic valve or implant. -Secondly, hemodynamic turbulence favours the deposition of sterile thrombi. -Thirdly, a bacteremia is necessary to initiate the process. Since transient bacteremias have been found to be elicited during invasive dental procedures, infective endocarditis can occur. The most reasonable method of interrupting this triad of events leading to infective endocarditis is to decrease or eliminate the effects of the bacteremia by administering a regimen of prophylactic antibiotic coverage. The chance of developing infective endocarditis subsequent to a dental procedure is related to two factors: the nature of the dental procedure precipitating the bacteremia and the type of heart lesion involved. Dental procedures that produce gingival or mucosal hemorrhage are most likely to cause bacteremia. Thus, a procedure which is unlikely to produce intraoral hemorrhage doea not require antibiotic coverage. The risk of infective endocarditis increases as the nature of the dental procedure becomes more invasive. For example, an extraction will cause a greater bacteremia than will a prophylaxis. Cardiac conditions vary in their susceptibility to infective endocarditis. These conditions may be divided into high, intermediate, and very low or negligible risk categories for simplicity. High risk conditions are those which requir special attention to endocarditis prophyaxis because of the high incidence of infective endocarditis in unprotected patients (see table 1). Included in this category are patients with prosthetic heart valves. They usually require parenteral antibiotic coverage because of their extremely high risk. All other conditions in this category require the standard regimen, unless otherwise directed by the patient's physician (see table 6). Intermediate risk conditions also require antibiotic covergae (see table 2). Here, the standard regimen is recommended. The use of prophylactic antibiotics for very low risk conditions is controversial. On the one hand, this condition does represent a risk, albeit a small one. On the other hand, some investigators have calculated that the risk of a severe adverse reaction to the antibiotic in the covered patient is much greater than the risk of infectve andocarditis in the patient without coverage. For this category of conditions, antibiotic coverage should be optional; therefore, some element of clinical judgement should be exercised (see table 3). For instance, a patient in this category who requires one or two simple Class II amalgams would probably not need coverage, even though some degree of gingival bleeding would be expected during the procedure. However, a patient with very poor oral hygiene who requires flap curettage perhaps should be covered. Diagnosing cardiac conditions A frequently asked question is "How can these patients at risk be identified?" We cannot overstress the importance of a good medical history. Specific questions should be asked concerning past and present heart conditions, such as rheumatic fever, congenital heart defects, heart murmurs, artifical heart valves, or any serious illnesses or hospitilization. Also, it should be noted that the uneducated patient might not appreciate the significance of such information and may provide only a brief medical history. If a medical problem is suspected, the patient's physician should be contacted. In some instances it may be wise to suggest to the physician that the patient should consult with a cardiologist. The patient may not like the inconvenience, but the genuine concern for his/her health will be appreciated. Congenital syndromes frequently exhibit cardiac lesions (see Table 4). All patients with congenital syndromes should be investigated for cardiac or other medical conditions. Patients with severe or multiple cardiac defects may be treated more safely in a hospital dental department. Two major types of heart murmurs have been identified (see Figure 2). Functional (or innocent) heart murmurs are considered benign lesions with no significant hemodynamic abnormalities. Such murmurs do not require antibiotic prophylaxis. Conversely, organic heart murmurs are pathologic and, therefore, antibiotic coverage is recommended. Using auscultation, a physician can differentiate between a functional murmur and an organic murmur. Occasionally, further investigation by a cardiologist may be necessary. MVP relatively common Mitral valve prolapse (MVP) is a cardiac condition where one or both leaflets of the mitral valve billow into the left atrium at the end of systole. It is a relatively common phenomenon, occuring in about four to eight per cent of the population. Contrary to popular belief, MVP is a very low risk lesion and antibiotic coverage is generally not required for invasive dental procedures (i.e., prophylaxis is optional). There is, however, a realted cardiac condition referred to as mitral valve prolapse syndrome (MVPS). This occurs when MVP is accompanied by regurgitation of blood back through the mitral valve. MVPS is a condition which has an intermediate risk of infective endocarditis and, therefore, antibiotic coverage is necessary. It is important to note that only a very small percentage of MVP patients have MVPS. Proper diagnosis usually requires such advanced diagnostic procedures as echocardiography or angiocardiography performed by a cardiologist. A thorough medical history, in addition to consultation with the family physician and/or cardiologist, will remove any doubt regarding the cardiac status of a patient. Rheumatic fever a factor Patients who have suffered a previous attack of rheumatic fever with cardiac involvement may be on a continuous chemoprophylactic regimen to prevent recurrent attacks. Such a patient is more susceptible to rheumatic fever recurrence, especially if the initial episode occurred at an early age. These patients are at considerable risk of developing infective endocarditis. The long-term prophylactic regimen frequently given to these patients is a monthly injection of Benzathine Penicillin G. This regimen is insufficient to prevent infective endocarditis. Thus, these patients should be given the standard regimen for endocarditis prophylaxis in addition to their regular long-term antibiotic therapy. Since a patient on long-term Penicillin will have developed resistant strains of intraoral bacteria, an alternate antibiotic should be used for endocarditis prophylaxis. In the standard regimen, the alternate antibiotic of choice is Erythromycin. Relationship with infection unclear Total joint replacement has been used in the treatment of degenerative joint diseases, such as rheumatoid arthritis, autoimmune disorders, non-union of fracture, acute traume, avascular necrosis of the femoral head, and even hemophilia. Researchers have been unable to establish a definite causative relationship between dentally-induced bacteremia and secondary prosthetic joint infection. In some cases of joint infection, a chronological relationship has been found to exist and this has caused some to recommend routine prophylactic coverage for dental procedures. A review of the literature suggests that routine coverage is probably not required. There are, however, patients for whom antibiotic coverage would be desirable. In order to determine the need for antibiotic coverage, and the specific regimen to be used, the patient's physician and/or orthopaedic surgeon should be contacted. Shunts can become infected Hydrocephalus is a pathologic condition characterized by dilatation of the cerebral ventricles by cerebrospinal fluid (CSF). It can be caused by an increase in the volume of CSF, but more commonly by obstruction of the normal CSF circulation. Hydrocephalus cannot be prevented but it can be controlled by shunting the accumulated CSF to the peripheral venous circulation or to other body cavities. This is accomplished using a variety of surgically placed shunts. Six to 23 per cent of these shunts subsequently become infected, although, none have been directly related to dental procedures. This does not mean, however, that dentally-induced bacteremia cannotcause infection of hydrocephalic shunts. Although some researchers maintain that antibiotic coverage is not required, the high rate of late shunt infection indicates that these patients must be treated with caution. Antibiotic regimens have been established and may be indicated for some patients. It is best to contact the patient's physician and/or neurosurgeon to determine the need for antibiotic coverage and the specific regimen to be used. Renal problems create risk Two types of dialysis are utilized in the treatment of endstage renal disease: peritoneal dialysis and hemodialysis. Patients who undergo peritoneal dialysis do not require antibiotic coverage for dental procedures. Patients undergoing hemodialysis are considered a moderate risk and must be covered by the standard regimen. Hemodialysis patients have an atriovenous shunt which is created subcutaneously to allow frequent and readily accessible venipuncture. A dental bacteremia may cause infection of the shunt leading to endocarditis or endarteritis. Recommended doses of Penicillin and Erythromycin are acceptable for mild to meoderate renal failure. The use of Streptomycin and Gentamicin are contraindicated as they are metabolized by the kidney. Kidney transplants have become a relatively common surgical procedure for many endstage renal patients. Postoperatively, however, these patients live with the threat of immediate and long-term host-graft rejection. Thus, they are placed on a life- long immunosuppresive drug regimen (i.e. Cyclosporin and corticosteroids) to suppress rejection of the new tissue. As a result of decreased immune response, they experience delayed wound healing and are prone to infection. Such patients may develop post-operative infections subsequent to dental procedures causing bacteremia. The pateint's physician should be consulted about antibiotic coverage prior to invasive dental procedures. Be wary of SLE lesions Systematic Lupus Erythematosus (SLE) is a disease of unknown etiology in which patients develop an autoimmune response to their own connective tissue cells. The condition is characterized by the presence of chronic inflammatory lesions. Dentists are particularly concerned with lesions affecting the cardiovascular system. An atypical endocarditis involving the heart valves may occur as well as fibrinoid degeneration of the epicardium and myocardium. Approximately 50 per cent of SLE patients experience valvular abnormalities. In addition to the cardiac abnormalities, kidney and brain lesions resulting in progressive degeneration may occur. Medical treatment for SLE includes the use of corticosteroids to suppress the autoimmune response. Therefore, these patients have an increased incidence of infective endocarditis and other infections. Consultation with the patient's physician is recommended to determine the extent of the disease and potential associated blood dyscrasias (i.e. thrombocytopenia, Von Willebrand's disease, platelet dysfunction,etc.). It is recommended that these patients be covered with the standard regimen for invasive dental procedures. Blood count often required The effectiveness of antineoplastic therapy is based primarily on interfering with the reproduction of rapidly proliferating cells. Therefore, not only is there an ablation of cancer cells, but also a depressant action on such tissues as bone marrow and oral mucosa epithelium which have high rates of replication. Firstly, neutropenia renders the patient incapable of mounting an effective inflammatory response. The risk of infection rises when the granulocyte count drops below 1,000/ul and peaks when the count is less than 100/ul. Secondly, lymphocytopenia results in humoral and cell mediated immune deficiencies. The cumulative effect of granulocytopenia and lymphocytopenia creates an immunosuppressive state in which the patient becomes susceptible to a myriad of bacterial (especially gram negative bacilli, i.e. Pseudomonas), fungal (i.e., Candida), and viral (i.e., Herpes simplex and Varicella zoster) infections. The potential for infection is further enhanced because the oral epithelium which normally acts as a natural barrier is damaged. Therefore, the damaged area presents a portal of entry for microorganisms into the bloodstream and subsequent hematogenous dissemination. Lastly, a thrombocytopenia can occur, resulting in soft tissue ecchymosis and hemorrhage with even the slightest amount of trauma. Spontaneous gingival hemorrhage occurs with platelet counts below 20,000/mm. For dental treatment, the platelet count should ideally exceed 100,000/mm. With the cancer patient's increased susceptibility to infection and hemorrhage, consultation with the patient's physician is advised, as no recommended protocol for antibiotic coverage exists. Usually, a complete blood count is required prior to extensive dental work. The literature mentions favorable results with the use of Carbenicillin and Gentamicin, or Ticarcillin alone, for treatment of infections. .................................................................. With thanks to the Ontario Dental Association ..................................................................