BANGKOK - The Thai king's health appears to have deteriorated further, according to royal medical bulletin that says he underwent a procedure to purify his blood amid other physiological complications related to the heart.

A statement issued late Sunday said doctors performed a hemodialysis on King Bhumibol Adulyadej to purify his blood. It said the doctors also changed a tube that drains excess cerebrospinal fluid during a 2- 1/2 hour procedure.

"The medical team are watching his symptoms and giving treatments carefully because the overall symptoms of his sickness are still not stable," the statement said.

Previous statements have said the king's kidneys are not functioning properly.

The world's longest reigning monarch, who will turn 89 on Dec. 5, has been hospitalized for much of the past decade. Because Bhumibol has been king since 1946, there is great concern about his eventual succession by Crown Prince Vajiralongkorn, who has not earned the same respect as his father.

Sunday's statement said that the hemodialysis procedure and the replacement of the tube were carried out on Saturday.

After that procedure, his blood pressure dropped, which was brought back to normal after he was put on a ventilator and administered medicines.

Early Sunday, the king's pulse was faster and an inspection found higher levels of acid in the blood, the statement said. An echocardiogram found a sharp drop in blood injected into the lower left chamber of his heart as a result of high blood pressure in the lungs.

Subsequently medicines were administered to enlarged blood vessels in the lungs, which led to the improvement of the pulse and blood pressure, it said.

While Bhumibol is a constitutional monarch with no formal political role, he has generally been regarded as Thailand's unifying figure. However, as his health has deteriorated, his participation in public affairs has sharply declined in recent years.

Concern about succession has been entwined with Thailand's political turmoil in the past decade, as royalists have sought to ensure that they control the process instead of certain politicians whose fealty to the monarchy they doubt.