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Ann Thorac Surg 2007;84:1316-1319
© 2007 The Society of Thoracic Surgeons
a Sibley Heart Center Cardiology, Children’s Healthcare of Atlanta, Atlanta, Georgia
b Department of Surgery, Emory University School of Medicine, Atlanta, Georgia
Accepted for publication April 27, 2007.
* Address correspondence to Dr Mahle, 1405 Clifton Rd NE, Atlanta, GA 30322 (Email: mahlew{at}kidsheart.com).
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Abstract |
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Methods: The present study examined the relationship of routine immunizations with adverse events, which were defined as sudden death or hospital readmission. The diphtheria–tetanus–acellular pertussis (DTaP) vaccine was considered in the analysis. The patient population consisted of infants younger than 9 months old who resided locally and had not yet undergone bidirectional cavopulmonary anastomosis (BCPA). Immunization data were obtained from a mandatory statewide database.
Results: During a 35-month period, 137 patients with single-ventricle physiology were discharged home after neonatal surgery or directly from the newborn nursery. Hypoplastic left heart syndrome (HLHS) was the diagnosis in 58 patients (42%) and was the most common. In the entire cohort, there were four sudden deaths (3%), and 53 patients (38%) had at least one interval hospital admission. Immunization within 48 hours was not associated with adverse events (odds ratio, 1.48; 95% confidence interval, 0.73 to 2.90; p = 0.31). No sudden death events occurred within 48 hours of immunization.
Conclusions: No association could be identified between routine immunizations and adverse events in infants with single-ventricle physiology. As such, the proposal to alter the immunization regimen in this population does not appear justified.
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Introduction |
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It is believed that fever, irritability, and dehydration may predispose infants with single-ventricle heart defects to hemodynamic compromise. As such, concerns have been raised about the potential deleterious effects of routine immunization in this population. Accordingly, some have suggested that immunizations should be deferred until after the BCPA, when the risk of sudden death is less. In the present study, we sought to analyze the relationship of routine infant immunizations with adverse events, defined as sudden death or interim hospital admission in a cohort of infants with functional single-ventricle physiology.
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Patients and Methods |
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Data Collection
Data on interstage mortality and interim hospital admission were obtained by reviewing the clinical database of Children’s Healthcare of Atlanta. Children’s Healthcare of Atlanta is a health care facility that provides inpatient care to more than 90% of the children in metropolitan Atlanta, which itself accounts for more than 60% of the state’s population. The families of infants with single-ventricle physiology residing outside the metropolitan Atlanta region were also instructed to seek follow-up at Children’s Healthcare of Atlanta. To determine if infants had been hospitalized at other facilities, we reviewed the hospital admission notes at the time of the BCPA. Reason for hospital admission, length of stay, and other patient and procedure-related variables were examined.
Of importance is that our institution has used a home surveillance strategy similar to that described by Ghanayem and colleagues [5]. Caregivers are instructed to seek immediate attention at a hospital or emergency department if the child (1) has a fever of more than 100.4°F, (2) has significant emesis or diarrhea, (3) has a marked decrease in fluid intake, (4) fails to gain weight of 20 grams within a 3-day period, or (5) has a change in oxygen saturation of greater than 5% from baseline (families are provided with home oximetry). In addition, a nurse performs weekly home visits. The home surveillance program is instituted for all infants with a functional single ventricle, whereas previous investigators have applied this strategy only to those with hypoplastic left heart syndrome (HLHS).
Immunization records were obtained from the Georgia Registry of Immunization Transactions and Services (GRITS), a state database of immunization records. GRITS was developed in accordance with Georgia Immunization Registry Law, which mandates that all providers who administer vaccines to children ages 18 and younger must report these immunization encounters to a statewide registry. Patients for whom search of the GRITS database yielded no documentation of immunization were assumed to have not been immunized. To reduce the risk of a fever or irritability developing, administration of acetaminophen is recommended just before diphtheria–tetanus–acellular pertussis (DtaP) administration and 4 hours later.
The Institutional Review Boards of Emory University School of Medicine and Children’s Healthcare of Atlanta approved the study. Individual consent for the study was waived.
Statistical Analysis
The goal of the study was to determine whether an association existed between routine immunization with DTaP and adverse events; therefore, in our analysis we determined the risk of an adverse event within 48 hours of immunization. This risk of an adverse event was compared with the relative risk of adverse events for all other days that the infant was at home, excluding those 48 hours immediately after immunization. Immunization with palivizumab was not considered in the risk factor analysis because adverse effects from this agent are thought to be quite low. The risk factor analysis was performed using the logistic regression model. Analysis was performed with Stata 7.0 software (StataCorp, College Station, TX). A value of p < 0.05 was considered significant.
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Results |
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Hospital readmission occurred in 53 (39%) of the 137 patients, of whom 16 patients had two hospital readmissions and 8 had three or more readmissions. The median length of stay for interval admission was 3 days (range, 1 day to 45 days). The indications for hospital readmission are summarized in Table 2. The most common reason for readmission was cyanosis. The cumulative number of days of hospitalization for all readmissions was 598; therefore, the total number of days that the patients were at home between hospital discharge and bidirectional Glenn was 13,340 days, or a mean of 97 days per subject.
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Analysis of all patient-related and procedure-related variables for an adverse event (death or hospital admission) demonstrated no significant association between routine immunization and the adverse event (odds ratio, 1.48; 95% confidence interval, 0.73 to 2.9; p = 0.31). The diagnosis of HLHS was associated with a higher risk of an adverse event (odds ratio, 2.22; 95% confidence interval, 1.09 to 4.50; p = 0.026).
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Comment |
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Sudden unexpected death has been reported in children with congenital heart disease who have undergone reparative or palliative surgery. Infants with functional single ventricle are thought to be at particular risk of sudden death and acute hemodynamic compromise for a number of reasons. Most of these infants require a systemic–to–pulmonary artery shunt, such as a modified Blalock-Taussig shunt, to provide all or most of the pulmonary blood flow. Thrombosis of the shunt can occur and may result in sudden death [4]. After examining autopsy data, Fenton and colleagues [4] suggested that acute shunt thrombosis accounted for one third of sudden death events in infants with systemic–to–pulmonary artery shunts.
Infants with single-ventricle physiology also appear to be susceptible to acute changes in systemic or pulmonary vascular resistance. Wright and colleagues [6] suggested that increases in systemic vascular resistance predispose infants with palliated HLHS to acute decompensation. One could therefore imagine that the pain, irritability, and fever that some have attributed to routine immunizations might result in cardiac decompensation in this patient population.
To date, however, data that link routine immunizations to sudden death are lacking. Mahle and colleagues [3] described the occurrence of sudden, unexpected death in a cohort of 536 infants with HLHS who were discharged to home after the Norwood procedure. In this series, there were 22 sudden death events (4.1%) but no reports of immunization immediately before cardiovascular collapse. Ghanayem and colleagues [5] attributed three cases of a sudden at-home death to respiratory illnesses in infants with HLHS who had been discharged to home after the Norwood procedure. Given that infant immunizations might also result in tachypnea and fever, this group began to defer routine immunizations in their patients with HLHS. Other publications examining sudden death in infants with single-ventricle physiology make no mention of the potential association between immunization and acute decompensation [1, 7].
Immunizations are known to produce a number of adverse events that theoretically could predispose to sudden compromise. Routine immunizations—in particular pertussis vaccine—can produce fever, irritability, and local skin reactions. The incidence of fever exceeding 100.4°F has been reported to occur in 26% of subjects receiving Infantrix (Chiron Biocine, Siena, Italy), one of the commercially available DTaP vaccines. However, the incidence of fever is much lower with initial dose than with subsequent booster doses.
Analysis of a combined DTaP, Haemophilus influenzae type b, inactivated poliovirus vaccine reported a risk of fever of greater than 38.0°C in less than 10% in high-risk low-birth-weight neonates receiving their first dose. A fever necessitating hospital admission was uncommon in our series, which may have been related to acetaminophen pretreatment [8]. It is also possible that the infants had a fever within the first 48 hours that did not come to the attention of the caregiver.
In developed countries, the greatest benefit of DTaP immunization is protection against pertussis. Pertussis outbreaks have continued to increase in the United States in recent decades. Infants have the highest mortality rate associated with pertussis infection among all age groups [9, 10]. One would imagine that infants or young children with single-ventricle congenital heart defects would be at particular risk.
Routine immunizations are administered to preterm infants as part of standard care in neonatal intensive care units [11, 12]. These immunizations have been found to be safe in these high-risk neonatal populations [13, 14]. In addition, newer conjugate DTaP vaccines now include Haemophilus influenzae type B conjugate and pneumococcal vaccine. As such, the decision to defer administration of DTaP would likely result in delays in administration of these other important infant vaccinations.
The study does have several important limitations. The study population size is relatively small, and sudden, unexpected deaths were rare; hence, we may have insufficient power to detect an association between immunizations and adverse events. It is not known whether the findings of this study are generalizable to institutions with different referral patterns or a less centralized system of pediatric heart care. In addition, the study lacks hemodynamic data concerning the response of an infant with a single-ventricle heart defect to immunization. One would like to have additional patient information such as heart rate, respiratory rate, or oxygen saturation in the hours immediately after immunization to support the notion that immunization is a relatively benign event in this patient population.
In summary, although routine infant immunizations have been associated anecdotally with sudden death, we could not find an association between routine immunization and adverse events in infants with single-ventricle defects. As such, we believe that such patients should receive immunizations according to published guidelines [15].
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