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