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.

Example input: 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.
Example output: Ventricular Fibrillation
Example explanation: 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.
Q: Abstract: Two patients had heavy metal intoxication resulting from industrial exposure to mercury vapors. One patient remained asymptomatic despite high urinary mercury levels. The second presented with a documented toxic reaction, including abnormal electromyograms and hematuria. Treatment was begun with 2,3-dimercaptopropane-1-sulfonate, and investigational drug used under Food and Drug Administration guidelines (IND 19,276). Use in both patients resulted in a dramatic change in excretion half-life of the mercury, from 33.1 days before treatment to 11.2 days during therapy. No significant toxic effects related to drug therapy were observed. Clearing of hematuria and reversal of electromyographic abnormalities were prompt in the symptomatic patient. Therapy with 2,3-dimercaptopropane-1-sulfonate was effective in these two patients.
A:
Adult