Use of intravenous isoproterenol for status asthmaticus in children.

The use of continuous drip iv isoproterenol was studied to determine its efficacy and indications in lower doses in severe asthma. Thirty-seven patients (6 months to 16 yr) received iv isoproterenol with asthma score of 6 (mean 6.8) or greater indicating PCO2 of 60 torr or higher or a PCO2 of 55 (mean 58.4) torr or greater without response to therapeutic levels of aminophylline, corticosteroids, and aerosolized isoetharine as well as appropriate oxygen. The initial dose of isoproterenol was 0.05 microgram/kg X min; if there was no response in PCO2, the continuous drip was increased by increments of not more than 0.05 microgram/kg X min every 15-20 min; iv aminophylline was continued by continuous infusion at therapeutic levels. The isoproterenol was infused until the PCO2 less than or equal to 40 torr and maintained at that dose for an equal time, then decreased over an interval equal to the response and maintenance time. There was complete response in 34 patients (mean dose 0.2 microgram/kg X min; mean response time 1.3 h, range 0.2-3.2 h). One patient had a partial response but the isoproterenol was discontinued with reversal of an arrhythmia; a 2nd patient had initial resolution but had rebound bronchospasm when the isoproterenol was abruptly discontinued. Thus, iv isoproterenol at lower initial and responding dose is effective for reversing increased PCO2 and impending respiratory failure in status asthmaticus in children, but the limitations and complications must be closely monitored.