Outcomes of children with life-threatening status asthmaticus requiring isoflurane therapy and extracorporeal life support

Abstract

Background: Severe, refractory asthma is a life-threatening emergency that may be treated with isoflurane and extracorporeal life support. The objective of this study was to describe the clinical response to isoflurane and outcomes after discharge of children who received isoflurane and/or extracorporeal life-support for near-fatal asthma.

Methods: This was a retrospective descriptive study using electronic medical record data from two pediatric intensive care units within a single healthcare system in Atlanta, GA.

Results: Forty-five children received isoflurane, and 14 children received extracorporeal life support, 9 without a trial of isoflurane. Hypercarbia and acidosis improved within four hours of starting isoflurane. Four children died during the index admission for asthma. Twenty-seven percent had a change in Functional Status Score of three or more points from baseline to PICU discharge. Patients had median percent predicted FEV1 and FEV1/FVC ratios pre- and post-bronchodilator values below normal pediatric values.

Conclusion: Children who received isoflurane and/or ECLS had a high frequency of previous PICU admission and intubation. Improvement in ventilation and acidosis occurred within the first four hours of starting isoflurane. Children who required isoflurane or ECLS may develop long-lasting deficits in their functional status. Children with near-fatal asthma are a high-risk group and require improved follow-up in the year following PICU discharge.

Keywords: Isoflurane; extracorporeal life-support; functional status score; pediatric intensive care unit; pulmonary function tests; status asthmaticus.

Figure 1.. Boxplots of A) pH, B) pCO2, and C) PaO2/FiO2 ratio at baseline, 1 hour, 4 hours, 12 hours, and 24 hours after starting isoflurane.

The median (middle line in box), 25^th and 75^th percentiles (lower and upper bound of box), and whiskers (95% confidence interval) are shown. All blood gas data, regardless of arterial, capillary, or venous type were used for the pH and pCO₂ plots. Comparisons were made to baseline values for each time-point using a two-tailed paired t-test for those patients with blood gas values at subsequent time points. The number of children per time point was: n = 53 at baseline, and n = 43 (pH) and n = 41 (pCO₂) (1 hour), n = 43 (4 hours), n = 38 (12 hours), and n = 28 (24 hours) after starting isoflurane. For the P_aO₂/F_iO₂ ratio plot, only arterial blood gases were used; there were n = 26 at baseline, n = 23 (1 hour), n = 23 (4 hours), n = 20 (12 hours) and n = 14 (24 hours). ****p < 0.0001

Figure 2.. Boxplots of Functional Status Scores (FSS).

A) Total FSS at baseline (prior to hospital admission (n = 54), pediatric intensive care unit (PICU) discharge (n = 51), and inpatient rehabilitation discharge (n = 17), B) change in FSS (Δ FSS) from baseline to PICU discharge (dotted line at a Δ FSS of 3 is the minimally significant change indicating new morbidity (n = 51), C) baseline FSS scores by domain (n = 54), and D) PICU discharge FSS scores by domain (n = 51). Wilcoxon matched-pairs signed rank test was used to test the difference between baseline and PICU discharge FSS scores, baseline and inpatient rehabilitation discharge FSS scores, and PICU and inpatient rehabilitation discharge FSS scores, **p < 0.01, ***p < 0.001, ****p < 0.0001.