You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Abstract: Some patients converted from ventricular fibrillation to organized rhythms by defibrillation - trained ambulance technicians(EMT - Ds) will refibrillate before hospital arrival.The authors analyzed 271 cases of ventricular fibrillation managed by EMT - Ds working without paramedic back - up.Of 111 patients initially converted to organized rhythms, 19(17 % ) refibrillated, 11(58 % ) of whom were reconverted to perfusing rhythms, including nine of 11(82 % ) who had spontaneous pulses prior to refibrillation.Among patients initially converted to organized rhythms, hospital admission rates were lower for patients who refibrillated than for patients who did not(53 % versus 76 % , P = NS), although discharge rates were virtually identical(37 % and 35 % , respectively).Scene - to - hospital transport times were not predictively associated with either the frequency of refibrillation or patient outcome.Defibrillation - trained EMTs can effectively manage refibrillation with additional shocks and are not at a significant disadvantage when paramedic back - up is not available.
Solution: Ventricular Fibrillation
Why? This term is directly present in the abstract and it is one of the main topic in it. So can be chosen as the medical subject heading.

New input: Abstract: Studies evaluating adverse effects of oral theophylline on learning and behavior have been performed on children with asthma receiving long-term theophylline therapy. To further differentiate the effects of asthma itself from the drugs used, we evaluated 20 asthmatic children (6 to 12 years of age) who had not received oral bronchodilators for at least 6 months. A double blind, placebo-controlled, parallel format was used with a 4-week theophylline or placebo period preceded by a 2-week baseline. Theophylline serum levels were maintained between 10 to 20 micrograms/mL. During baseline and treatment periods, the child's home and school behavior/performance were monitored independently by their parents and teachers using standardized report forms. A battery of psychologic tests was administered at the end of baseline and treatment periods. Seven children receiving theophylline were noted to have a change in school behavior and/or performance during their 4 weeks on drug compared to baseline, whereas none of the children receiving placebo were noted to be different (P = .004). Thus, the short-term administration of theophylline to asymptomatic asthmatic children not receiving oral bronchodilators can adversely affect school performance and behavior. Because this population represents the majority of asthmatic children, one needs to use theophylline cautiously in this age group, monitor school performance closely, or seek other treatment modalities.
Solution:
Achievement