BRASILIA Eunicio Oliveira, president of Brazil's Senate and a leading member of President Michel Temer's party, was being treated in the intensive care unit of a hospital in Brasilia after fainting during the night, the Senate said in a statement on Thursday.
Oliveira, who was elected head of Brazil's upper house of Congress in February and is one of 24 senators under investigation for corruption, was in stable condition.
Examinations showed no evidence of a stroke, which was initially suspected, according to a medical note released by the hospital.
Oliveira, 64, is a key Temer lieutenant in the drive to pass a series of key pension and labor code reforms aimed at trimming a swelling budget deficit and reviving investor confidence in Brazil's ailing economy.
He fainted after a long Lower house vote on a landmark labor reform late on Wednesday.
Earlier in the day, senators passed a bill that many prosecutors and judges say curbs their ability to carry out probes targeting politicians.
(Reporting by Ricardo Brito; Writing by Guillermo Parra-Bernal and Silvio Cascione; editing by Richard Lough and Pritha Sarkar)