Abstract 261 Pulmonary: Reactive Airway Diseases I Poster Symposium, Monday, 5/3

β-2 adrenergic agonists are commonly used to treat children with severe asthma exacerbation. Some patients develop chest pain, significant tachycardia, or diastolic hypotension during therapy with these drugs. It is unclear whether the hemodynamic changes impair myocardial perfusion sufficiently to warrant limitation of β-2 adrenergic therapy. The purpose of this study was to determine whether there was evidence of myocardial ischemia and to identify the mechanisms underlying inadequate myocardial perfusion in children treated with β-2 agonists for severe asthma. Methods. Thirteen patients admitted to the pediatric intensive care unit for status asthmaticus were enrolled and followed for the initial 24 hours of care. The presence of ischemia was assessed by determining the ratio of myocardial oxygen supply to demand using the diastolic and systolic pressure time indices and the arterial oxygen content, measuring CPK-MB fractions, and following serial ECG. In addition, 24-hour Holter monitoring and an echocardiogram were obtained during the study period. Results. Four of 13 patients received continuous inhaled albuterol; 9 of 13 received continuous inhaled albuterol and intravenous terbutaline infusion. We found the following: a) 12 of 13 patients had a critically low oxygen supply:demand ratio (<12.5); b) 5 of these 12 had significant ST-T wave changes by ECG; c) 3 of these 5 showed reversal of ECG changes with support of the diastolic blood pressure by α-agonist infusion; 1 patient reversed with discontinuation of the terbutaline; 1 patient reversed without intervention; d) 2 of 11 patients had CPK-MB >5%, but only 1 of these had ECG changes; all patients had elevated total CPK; e) 4 of 10 patients had dysrhythmia by Holter monitoring; f) no patient showed echocardiographic evidence of wall motion abnormality. Conclusions. Children receiving β-2 agonists for treatment of asthma are at risk for myocardial ischemia. The reversibility of ischemic ECG changes with improved diastolic aortic tone implies that the inadequate oxygen supply is secondary to decreased driving pressure through the coronary circulation. Understanding of this mechanism allows for a rational approach toward therapy.

This work supported in part by the Yale CCRC Grant MO1-RR06022, NIH.