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: We evaluated the role of portasystemic shunts in the hyperkinetic circulatory state in rats with portal hypertension. Cardiac output and regional blood flow were measured by the radioactive microsphere technique in rats with portal hypertension caused by portal vein stenosis, in rats with end-to-side portacaval shunts, and in sham-operated rats. Cardiac output was significantly higher in rats with surgical shunts than in those of the two other groups and was significantly lower in sham-operated rats compared with portal hypertensive rats. Portal tributary blood flow and hepatic arterial blood flow expressed in absolute flow as well as in percentage of cardiac output were significantly increased in rats with surgical shunts compared with other groups. These blood flows were also significantly higher in portal hypertensive rats than in sham-operated animals. A significant correlation was found between cardiac output and portal tributary blood flow in rats with portal vein stenosis and in rats with surgical shunts; this correlation was absent in sham-operated rats. This study shows that the hyperkinetic circulatory state in rats with portal hypertension and a normal liver is related to the presence of portasystemic shunts but not to portal hypertension per se.
A:
Animal