Introduction
In sickle cell disease (SCD), acute chest syndrome (ACS) is a major
cause of significant mortality and morbidity. It is responsible for an
estimated 25% of sickle cell disease-related deaths, and is associated
with prolonged hospitalization, increased risk of respiratory failure,
future lung disease and 25% mortality in hospitalized
patients1,2. ACS has a 40% incidence in the SCD
population and is most commonly caused by infection and pulmonary
infarction. Pediatric patients with SCD frequently present to the
pediatric emergency department (PED) with complaints of fever, chest
pain, and cough, all of which may or may not be associated with ACS.
Other studies have been conducted to evaluate the differences between
adult and pediatric sickle cell patients in their presentation of ACS.
Findings include a lower prominence of extrapulmonary findings in
pediatric patients as compared to adult patients. Factors such as low
hemoglobin (Hb) and oxygen tension fraction were predictors of ACS in
pediatric patients3. Madhi et. al., also noted that
oxygen saturation (SpO2) level was significantly lower
at admission for children with ACS when compared to
adults.4 Certain co-morbidities, such as asthma, have
been shown to increase risk of ACS in pediatric
patients.5 Boyd et al. found that children with both
asthma and SCD experienced almost twice as many ACS episodes vs.
children with SCD without asthma.6 Other risk factors
for ACS include young age, severe SCD genotypes, low fetal Hb levels,
high steady-state Hb levels, high steady-state leukocyte count, history
of asthma, and a previous history of ACS1.
Despite growing research in the field, it remains challenging for PED
providers to determine which patients are at highest risk of ACS. In
fact, a national hospital ambulatory medical care survey evaluated
almost two-hundred thousand yearly emergency department (ED) visits by
SCD patients from 1999-2007 and found that 37% of those aged 0-19 years
ended up hospitalized7. This high frequency of ED
visits and hospitalizations increased pediatric SCD patient exposure to
nosocomial infections, radiation, and was associated with higher
mortality.
Chest x-rays (CXR) are frequently ordered, increasing radiation exposure
and healthcare costs. A Dallas Newborn cohort from 1996-2009 found that
SCD patients had greater than 25 radiographic tests before age 18, and
5% of these patients had greater than 100 tests.8This is concerning since one CXR has an average effective radiation dose
of 0.01-0.02 millisievert (mSv), comparable to 10 days of natural
radiation exposure9,10. While there is currently no
set limit on an acceptable radiation dose for pediatric patients,
providers should make every effort possible to reduce unnecessary
radiation exposure based on the principle of “as low as reasonably
achievable” (ALARA).
Therefore, the objectives of this study were: 1) to identify incidence
of CXR performance and ACS diagnosis in SCD patients, both with and
without fever, presenting to our PED, and 2) to identify significant
clinical and demographic predictors of ACS in this population in order
to implement a diagnostic algorithm for PED providers with the goal of
minimizing unnecessary CXR performance in this population.