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Abstract

Introduction: Asthma is a common reason for admission to the pediatric intensive care unit (PICU). Children who present with acute severe asthma often have blood drawn initially for complete blood counts (CBC) and chemistry panels despite any data correlating this common practice with patient outcomes. Methods: This is a retrospective analysis of all children admitted to a tertiary PICU from 1/2009 through 6/2012 with a diagnosis of severe asthma. We evaluated the association of any blood tests (CBC,basic metabolic panel) drawn within the first 24 hours of patient presentation and clinical variables (age, gender, temperature) with poor outcomes, specifically the need for positive pressure ventilation (PPV), and PICU and hospital length of stay (LOS). Results: 356 patients were admitted to the PICU with severe asthma and had blood drawn within the first 24 hours of presentation, of whom 230 had a full set of labs sent during the study period. 78 patients (22%) required some form of PPV. Age, WBC, eosinophil, neutrophil, and platelet (PLT) counts were associated with PPV on univariate screen (Mann Whitney U, p<0.25), while only WBC (p<0.001) and PLT (p<0.001) were significantly associated with PPV on multivariate logistic regression analysis. However, the receiver operating characteristic area under the curve for the model was only 0.66, demonstrating a poor discriminatory characteristic of the lab tests for predicting the need for PPV. The median PICU LOS was 1.9 days (IQR 1.8, 2.1) and hospital LOS was 3.3 days (IQR 3.0, 3.5). Age, sodium, WBC, and PLT count were associated with hospital LOS on univariate analyses (p<0.25), while age was the only variable found to be significantly associated with hospital LOS on multivariate analysis (p<0.0001). With each 6 month increase in age, the likelihood of hospital discharge at any point in time decreased by 2.4% (HR=0.976 95% CI: 0.965, 0.988). Age, sodium, WBC, and hemoglobin were associated with PICU LOS on univariate analysis (p<0.25), while WBC was the only variable significantly associated with PICU LOS in the final multivariate model (p<0.014). With each unit increase in WBC, likelihood of being discharged from the PICU at any point in time decreased by 2.4% (HR= 0.976, 95% CI: 0.957, 0.995). Median PICU LOS was 1.8 for those with WBC <15, and 1.7 days for those with WBC >/= 15 (p=0.64). There was no difference in hospital or PICU LOS or need for PPV based on gender, being febrile, HCO3, or if a CBC was drawn or not. (p>0.05). Conclusions: CBC and chemistry panels upon admission do not help predict severity of illness in children presenting with severe asthma. Routine sampling of blood in this population should not be considered.