Is Secondhand Smoke Exposure Associated With Increased Exacerbation Severity Among Children Hospitalized for Asthma?

DISCUSSION

Our study suggests that SHS exposure may contribute to asthma exacerbation severity among children admitted to the hospital. At CHCO, we found a statistically significant 20% increase in LOS among patients who report SHS exposure. In the overall cohort, we found a 60% greater likelihood of receiving IV steroids, and a trend toward an increased rate of PICU admission, both of which suggest more severe exacerbation. These data represent a previously undescribed health risk to children with asthma who are subjected to SHS exposure.

Previous research has shown that children with asthma who are exposed to SHS are more likely to experience acute exacerbations and require ED treatment, admission, and even intubation.^5,6,8 Our study contributes to the literature by showing that even once an exacerbation is triggered in a child with asthma and he or she requires hospitalization, those with SHS exposure may require longer hospitalization in some circumstances. Additionally, we found that SHS-exposed patients have a higher likelihood of receiving IV steroids, a more aggressive treatment typically reserved for the more acutely ill patients. Although there is no evidence that IV steroids are more effective than oral steroids, they can be used in patients with higher respiratory rates who cannot tolerate oral medications, and the National Heart, Lung, and Blood Institute Guidelines for the management of asthma recommend consideration of IV steroids for patients with an incomplete or poor response to therapy delivered in the ED.¹¹ The trend toward significance in the relationship between SHS exposure and PICU admission found in our data is consistent with findings published by van den Bosch et al in 2012.¹² In this multicenter retrospective case control study of 66 cases, the authors found that active or passive smoke exposure was independently associated with increased risk for PICU admission among children with asthma.¹² However, Lyell et al¹³ found in a retrospective case control study of 52 cases in Australia that parental-reported smoking was not associated with PICU admission. It appears that the relationship between SHS exposure and risk for PICU admission has yet to be fully elucidated through these retrospective analyses. A prospective study that includes cotinine measurement would be an ideal way to answer this question.

Unlike other risk factors for severe asthma exacerbation, such as race/ethnicity, socioeconomic status, and history of prematurity, SHS exposure is a modifiable risk factor. Other modifiable risk factors include lack of usual source of care, noncompliance, and other environmental exposures. Children with asthma who require hospitalization are known to be high risk. They are more likely to require subsequent oral steroid bursts, ED visits, and hospitalizations.^14,15 If we can intervene while a child is in the hospital and decrease future SHS exposure, we may be able to significantly affect the disease course of the child with asthma. Winickoff et al¹⁶ and Ralston et al¹⁷ previously demonstrated the feasibility of smoking cessation interventions at the time a child is hospitalized for a respiratory illness. Our study provides further evidence that providers should consider capitalizing on this “teachable moment” when a parent is in the hospital with his or her child by delivering smoking cessation interventions.

The 20% increased LOS seen in patients exposed to SHS in the CHCO cohort equates to an ∼10-hour longer hospital stay for each child with SHS exposure admitted for acute exacerbation. Although some may question the clinical significance of this finding, in the era of cost containment when many hospitals are focusing on discharge efficiency and early morning discharges, every additional hour in the hospital counts, and costs. The difference seen between patients at CHCO in Aurora, CO, and patients at MUSC in Charleston, SC, is likely, in part, because of differences in altitude and partial pressure of oxygen; 97% of the children admitted to CHCO required supplemental oxygen, whereas only 24% of children admitted to MUSC had the same requirement. It is plausible that the time it takes to wean children back to room air in Colorado contributes to the overall longer LOS and to the significant effect SHS exposure seems to have on LOS in that cohort that was not found in the MUSC cohort. There are institutional practice pattern differences that also may contribute to the LOS difference seen between the 2 institutions. Albuterol delivery is primarily via metered dose inhaler at CHCO and is given more often by nebulizer at MUSC. Additionally, albuterol weaning is driven by respiratory therapists at CHCO and by resident and attending physicians at MUSC. MUSC also has a step-down unit, whereas CHCO does not, which may affect PICU admission criteria and therefore may have affected our findings regarding the relationship between SHS exposure and PICU admission. However, both institutions use an albuterol-weaning pathway and prescribe prednisone/prednisolone (rather than dexamethasone) as their primary systemic steroid, and have the ability to give IV magnesium outside of the PICU. Other unmeasured variations in care also may contribute to the difference in LOS observed between these 2 institutions.

Our finding of increased likelihood of IV steroid receipt and a trend toward a significant increased risk of PICU admission among children with SHS exposure provides further evidence that among children who are hospitalized for acute asthma exacerbation, those who are exposed to SHS are at higher risk for more severe exacerbation.

There are several limitations to this study. We relied on caretaker reporting of SHS exposure, which is not as reliable as cotinine measurements. A recent study by Howrylak et al¹⁸ found high levels of underreporting of SHS exposure among hospitalized children when compared with serum and saliva levels. We were not able to assess for various exposure levels that may uniquely affect our outcome variables. This may have contributed to an underestimation of the actual effect of SHS exposure on exacerbation severity. However, a study that requires hair or blood sampling would be expensive and time-consuming. We feel that a retrospective chart review is an appropriate way to address our specific research question. In the future, researchers may wish to examine this relationship in further detail, and cotinine measurements would be an appropriate next step to advance knowledge in this area. Home inhaled corticosteroid use was included as a surrogate for disease severity. A more accurate measure of disease severity would have strengthened our analysis. Data on whether a patient had a usual source of care, which could contribute to disease control and exacerbation severity, was not available. Hospital system factors (eg, team availability to write discharge orders, families waiting for rides, or other barriers to patients physically leaving the hospital after discharge criteria are met) may affect discharge time and thus affect our primary outcome of LOS. These factors also may vary by institution, thus affecting our results. Of note, information on exact admit and discharge time is recorded electronically at both institutions, making this variable accurate and reliable. Our regression analysis should control for some of the variation in discharge time due to transportation issues by the inclusion of insurance status as a covariate. Future prospective studies may consider using the time a patient is medically ready for discharge as the primary outcome rather than actual discharge time. Additionally, as previously mentioned, asthma treatment practice patterns will vary by institution and therefore could contribute to the differences in LOS seen by institution. Because the medical records at the 2 institutions were different (paper versus electronic medical record), certain variables might be more accurately recorded or more easily discoverable at 1 institution when compared with the other. For example, oxygen supplementation was documented in several different areas of the MUSC charts, calling into question the accuracy of this variable at MUSC. On the other hand, information regarding oxygen supplementation was readily available in CHCO’s electronic medical record.

In this study of children at 2 children’s hospitals, there is a significant association between SHS exposure and LOS among children admitted for asthma at 1 institution. IV steroid use was more common among children exposed to SHS at both institutions, suggesting more severe exacerbation. Efforts to eliminate SHS exposure among children with asthma are needed, and smoking cessation interventions during the hospitalization may be a way to target parents of children at high risk with asthma.