Three-time world boxing champion Camacho was gravely injured in a drive-by shooting in Puerto Rico on Tuesday night.
"This is the toughest fight in the life of Macho Camacho," said Ernesto Torres, director of the Rio Piedras Medical Centre.
"We are keeping him alive with medicine. He is a strong guy," Mr Torres added. "The prognosis is very poor."
Camacho, 50, was a passenger in a car driven by his friend, Alberto Yamil Mojica. They were sitting outside a bar when someone opened fire on them, killing Mr Mojica.
The shooting occurred near a popular shopping centre on Highway 167 in Bayamon, a suburban town west of the capital of San Juan.
Police have yet to make arrests or determine a motive for the attack.