M Karunanidhi was admitted in hospital owing to breathing difficulties due to throat and lung infection.
DMK chief M Karunanidhi today underwent tracheostomy at a private hospital in Chennai to optimise breathing. His condition is stable now.
The 92-year-old leader was readmitted to Kauvery Hospital in Chennai late last night with breathing difficulties due to throat and lung infection.
"Karunanidhi is stable," Dr S Aravindan, Executive Director, Kauvery Hospital said, adding that the former chief minister is being treated with antibiotics and being monitored by a team of doctors.
Karunanidhi was readmitted to the hospital a week after he was discharged after a week-long treatment for drug-induced allergy on December 7.
On October 25, DMK had announced that Karunanidhi was suffering from allergy "caused by a medicine he has been using" and has been advised rest by doctors.
The DMK chief, who has of late not been seen regularly in public, has confined himself to his home, although he has been issuing statements and reacting on key matters such as demonetisation.
He had also skipped campaigning during the by-election to three state Assembly seats last month. Ruling AIADMK won all three constituencies.
On December 5, former Chief Minister and AIADMK chief J Jayalalithaa died at a Chennai hospital after a massive cardiac arrest.