Infective endocarditis is an infection of the endothelial surface of the heart. There are an estimated 10,000 to 15,000 new cases of infective endocarditis each year in the United States.1 Despite advances in the diagnosis and treatment of this potentially life-threatening condition, infective endocarditis can be very difficult to treat.2 Antibiotics are routinely given to prevent this condition in many developed countries.2 However, antibiotic prophylaxis is only believed to be useful if it is administered to patients at high risk of developing infective endocarditis. Patients are at increased risk of infective endocarditis if they have specific cardiac lesions and additionally, if they become bacteremic. Specific medical procedures are more strongly associated with bacteremia. Furthermore, only specific procedures increase the risk of bacteremia with organisms that are most likely to cause infective endocarditis.2
Consequently, the American Heart Association (AHA) has issued guidelines that specify which cardiac lesions and which procedures would require patients to receive antibiotic prophylaxis to prevent infective endocarditis.3 The American College of Obstetrics and Gynecology (ACOG) has adopted the AHA recommendations for infective endocarditis prophylaxis.4 Of note, the AHA/ACOG guidelines do not recommend infective endocarditis prophylaxis for either uncomplicated vaginal or cesarean deliveries, because the rates of bacteremia are low with either of these procedures.2 Additionally, the organisms that do rarely cause bacteremia with either of these obstetrical procedures are not frequently associated with infective endocarditis.3 According to AHA/ACOG guidelines, infective endocarditis prophylaxis is optional for patients with high-risk cardiac lesions undergoing uncomplicated vaginal or cesarean deliveries. However, infective endocarditis prophylaxis is recommended for patients with high-risk or moderate-risk cardiac lesions undergoing vaginal or cesarean deliveries and who have suspected bacteremia.4
Excessive antibiotic usage during pregnancy is of concern for several reasons, including the selection of resistant organisms that may cause harmful infections in the mother and her neonate.5 Consequently, we were interested in potential strategies to decrease antibiotic usage. We conducted this study to evaluate infective endocarditis prophylaxis practices during the intrapartum period and to assess obstetric providers’ adherence to the AHA/ACOG guidelines for infective endocarditis prophylaxis.
MATERIALS AND METHODS
We performed a chart review to report this case series of obstetric patients receiving infective endocarditis prophylaxis during the intrapartum period at a single tertiary referral care center. This study was approved by the Columbia University Human Subjects Institutional Review Board.
This case series included patients who were admitted to the Labor and Delivery Unit at Columbia University Medical Center for delivery from August 1, 2004, to July 31, 2005 and who received antibiotics administered specifically for infective endocarditis prophylaxis. We reviewed pharmacy records to identify all patients to whom the pharmacy dispensed any of the antibiotics recommended for infective endocarditis prophylaxis by the AHA/ACOG guidelines while admitted to the Labor and Delivery Unit during the study period. These antibiotics are ampicillin, gentamicin, amoxicillin, and vancomycin. We then reviewed the medication section of each patent’s electronic medical record to confirm that these antibiotics were actually administered to the patients. We further reviewed the physician’s notes section of each patient’s electronic medical record and identified who was administered antibiotics to confirm that a physician ordered the antibiotics specifically for infective endocarditis prophylaxis. The cardiac lesion was noted for every patient who received infective endocarditis prophylaxis. We used the physician notes, nursing notes, and vital signs sections of each patient’s electronic medical record to identify which patients had documented intrapartum infection or intrapartum temperatures of 38.0°C or greater. We used this specific temperature because it is one of the clinical signs used to diagnose chorioamnionitis.6 We used the AHA/ACOG guidelines to classify cardiac lesions into high-, moderate- and negligible-risk categories in Table 1.
Cases were determined to have received infective endocarditis prophylaxis for an appropriate indication if they had high-risk cardiac lesions. They were also determined to have an appropriate indication if they had a moderate-risk cardiac lesion with documentation of intrapartum infection either by physician’s notes or by a maximal intrapartum temperature of 38.0°C or greater. Cases who received infective endocarditis prophylaxis for an appropriate indication were determined to have received an appropriate antibiotic regimen if they received a regimen as specified by the AHA/ACOG guidelines described in Table 2.
We calculated the proportion of cases and binomial exact 95% confidence intervals for those who received infective endocarditis prophylaxis for an appropriate indication according to AHA/ACOG guidelines. We further calculated the proportion of those cases and binomial exact 95% confidence intervals with appropriate indications for infective endocarditis prophylaxis who received an appropriate antibiotic regimen for infective endocarditis prophylaxis. Analyses were performed with SPSS 13.0 (SPSS Inc., Chicago, IL).
During the 12-month study period, 3,743 live births occurred at Columbia University Medical Center. Demographics from hospital databases covering the study period revealed that the insurance status of the mothers with live births at the Medical Center was 42.5% Medicaid insurance and 57.5% private insurance. In 2004, self-reported ethnic and race categories of mothers who delivered at the Medical Center were 42.5% Hispanic or Latino, 36.7% white, 12.8% African American, 6.1% Asian, and 1.9% unknown.
By reviewing pharmacy records, we found 403 patients who received one or more of the antibiotics recommended to prevent infective endocarditis. Of these 403 patients, 28 patients were excluded upon review of the electronic nursing and physician records because the patients neither received, nor were they ordered to receive, any of these antibiotics. A further 32 patients were excluded because they did not undergo a delivery during this admission. Also, 28 other patients were excluded because they only received antibiotics postpartum. Of the remaining 315 patients, nine more were excluded because, although they had antibiotics ordered, they never received them. From this group of 306 patients, another 256 patients were excluded because they received antibiotics for another indication besides infective endocarditis prophylaxis. The most common reasons that patients received antibiotics besides infective endocarditis prophylaxis were Group B Streptococcus prophylaxis, intrapartum infection, and preterm premature rupture of membranes. The remaining 50 patients received antibiotics for infective endocarditis prophylaxis and were included in the study. The demographic characteristics of these 50 patients include the following: 18% Medicaid insurance, 78% private insurance, and 4% self pay; and 12% Hispanic or Latino, 54% white, 14% African American, 2% Asian, and 18% unknown ethnic and race category. Other characteristics of these 50 patients are described in Table 3.
Three of the 50 patients who received infective endocarditis prophylaxis were found to have high-risk cardiac lesions. One of the three patients had a history of cardiac transplant. We could not categorize this cardiac lesion according to Table 1. Patients with heart transplants without evidence of valvular insufficiency are unlikely to be at increased risk of infective endocarditis. However, some transplant centers do elect to use prophylaxis for these lesions.(Bolger A, personal communication) Consequently we decided to categorize history of cardiac transplant as a high-risk cardiac lesion. None of these three patients with high-risk cardiac lesions had evidence of intrapartum infection. However, according to AHA/ACOG guidelines, infective endocarditis prophylaxis is reasonable for patients with these high-risk cardiac lesions.
Sixteen patients had moderate-risk cardiac lesions, of which two had evidence of intrapartum infection. Fifteen patients had low-risk cardiac lesions. A further 16 patients had documented mitral valve prolapse, but valvular regurgitation was not specified in the electronic medical records. Because we could not be sure whether these were moderate- or negligible-risk cardiac lesions, we decided to be conservative and considered these patients as having moderate-risk cardiac lesions. Only one of these patients had evidence of intrapartum infection. Consequently, a total of three patients met AHA/ACOG criteria, because they had moderate lesions and evidence for intrapartum infection.
In summary, of the 50 patients who received antibiotics for infective endocarditis prophylaxis, six (12.0%, 95% confidence interval 4.5–24.3%) met AHA/ACOG criteria for appropriate indication for infective endocarditis prophylaxis. Of the three high-risk patients who received infective endocarditis prophylaxis, none of their antibiotic regimens strictly adhered to AHA/ACOG guidelines. The first patient received ampicillin and gentamicin intrapartum and one dose of ampicillin postpartum, consistent with the guidelines. However, this patient received an additional two doses of ampicillin and gentamicin postpartum that were not indicated. The second high-risk patient received the appropriate regimen of ampicillin and gentamicin intrapartum but did not receive indicated ampicillin or amoxicillin postpartum. The third high-risk patient received vancomycin (despite no penicillin allergy) and gentamicin intrapartum according to guidelines. However, she was given an inappropriate dose of amoxicillin postpartum. The two moderate-risk patients with intrapartum infection received appropriate therapy for both infective endocarditis and for chorioamnionitis. Finally, the patient with mitral valve prolapse for whom regurgitation was not specified and for whom there was evidence of intrapartum infection received appropriate antibiotics for infective endocarditis prophylaxis and for chorioamnionitis. So of these six patients who met AHA/ACOG criteria for appropriate indication for infective endocarditis prophylaxis, three (50.0%, 95% confidence interval 11.8–88.2%) received appropriate antibiotic regimens, one received inadequate antibiotics, and two received excessive doses.
In summary, during a one-year study period at a single tertiary referral care center, we found 50 patients who received infective endocarditis prophylaxis. However, only 12.0% of these patients had an appropriate indication for infective endocarditis prophylaxis according to AHA/ACOG guidelines. Additionally, only one half of those six patients who met AHA/ACOG criteria for appropriate indication for infective endocarditis prophylaxis were actually given an appropriate regimen. Of note, we did not identify patients with cardiac lesions whose practitioners appropriately followed the AHA/ACOG guidelines by not prescribing antibiotics for infective endocarditis prophylaxis. Acquiring those data were beyond the scope of this present study because it would entail reviewing medical records of all deliveries during the study period.
The dangers of inappropriate antibiotic usage are well documented.4 The biggest concern from a public health perspective is that it contributes to the emergence of antibiotic resistance. If the development of new antimicrobials cannot keep pace with the emergence of resistance, then society faces the threat of potentially incurable infections.7 Inappropriate antibiotic usage is also an issue for individuals, because exposure to antibiotics changes their natural flora with an increase in resistant organisms.8 These patients are also at risk of increased infections with organisms not susceptible to the antibiotics, such as fungal infections.9 A concern that is unique to obstetrics is whether the administration of intrapartum antibiotics to the mother increases the frequency of or proportion of neonatal infections by antibiotic-resistant organisms.10 Antibiotics themselves can also be directly harmful to patients. All antibiotics have their own toxicity profiles, which can range from life-threatening hypersensitivity reactions to more routine side effects such as nausea and vomiting.11
We undertook this study because a substantial proportion of patients receive antibiotics while on the Labor and Delivery Unit. A quarter of all delivering patients receive antibiotics for the prevention of Group B Streptococcus disease.5,12 Other patients receive antibiotics for conditions for which antibiotic use is also well supported. Such situations include the use of antibiotics to increase latency for patients with preterm premature rupture of membranes,13 for patients undergoing cesarean deliveries,14 and for patients with chorioamnionitis.15
There are several other instances where antibiotics may be given inappropriately to obstetric patients. Although of no proven benefit, patients are frequently given antibiotics when patients have fourth-degree perineal laceration repairs16 or after manual removal of the placenta.4 Additionally, antibiotics are still given on occasion for the indication of preterm labor despite no proven benefit.13–17 Another instance of inappropriate antibiotic administration is additional postpartum doses to patients who have chorioamnionitis.18–20 If inappropriate antibiotic usage were corrected in all of these instances, that will likely lead to reductions in antibiotic exposure to obstetric patients.
We believe that inappropriate antibiotic usage for infective endocarditis prophylaxis is an area that can be targeted to reduce the overall rates of antibiotic usage. In our case series, 50 (1.3%) of 3,743 live births during the study period received antibiotics in the intrapartum period for infective endocarditis prophylaxis. However, in 88% of the cases, the indication for infective endocarditis prophylaxis was not appropriate according to AHA/ACOG guidelines. If infective endocarditis prophylaxis patterns are similar nationwide, then the mothers of 45,760 live births (1.3% times 4,000,000 live births per year in the United States times 88%) may be exposed to unnecessary antibiotics.21
A limitation of the study is that the sample size of the number of patients who received infective endocarditis prophylaxis is not sufficiently large. Another limitation is that we collected the data by reviewing electronic medical records. Consequently, any error in documenting the patient’s medical history or in the ordering, dispensing, or administration of the antibiotics would have affected our results. However, we used pharmacy records in addition to the patients’ electronic medical records in order in minimize these errors. Also possible is that we may have missed patients who received other antibiotics for infective endocarditis prophylaxis besides those recommended by AHA/ACOG. However, if such patients existed, they would have received antibiotics inappropriately and would only have increased the rate of inappropriate antibiotic use.
Antibiotics are frequently given to obstetric patients during pregnancy. Although many obstetric patients receive antibiotics for recommended indications, some patients, as our study shows, do not. A concerted effort by all practitioners and institutions to reduce the amount of inappropriate antibiotics given to obstetric patients will have positive public health effects in addition to benefiting individual mothers and neonates.
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