Physiological and biological predictors of length of stay and recovery in adults with acute asthma

Introduction: Asthma remains a significant risk to patients and costs to healthcare systems. Data on length of stay and time to recovery is important for prognosis, management of inpatient beds and follow up. Objective: We assessed physiological and biochemical factors affecting length of stay (LOS) and time to recovery on admissions for acute asthma. Methods: Adults admitted with asthma exacerbations were studied from 2 hospitals in Hampshire, UK. Patients were assessed at admission for symptoms, observations, exhaled NO and blood tests including blood count, coagulation (APTT, PT) and cytokines (IL5, IL6, IL8, IL12, IL13, IL17A, IFNg, TNFa, RANTES, eotaxin). Results were explored using correlation coefficients and subsequently analysed in a multivariate regression model. Results: 126 patients were recruited of which 75.4% were female. Mean age was 40.0 (SD 14.4) and mean length of stay 3.98 (SD 2.65) days. In multivariate analysis, length of stay was significantly associated with increasing age(p=0.003), symptoms of wheeze(p=0.006), lower APTR(p=0.003) and increased oxygen requirement on arrival(p=0.01). Delayed recovery was associated with serum IL-12 over 1pg/mL on admission(HR for recovery 0.36, p=0.005) . Conclusion: These results demonstrate that older, wheezing patients with oxygen requirements are likely to remain in hospital longer. Markers of increased coagulation in the intrinsic pathway also correlate with increased length of stay. Detectable IL-12 in serum, favouring a Th1 response,correlates with slower recovery, possibly due to poor response to corticosteroid therapy.