Lamar Odom was rushed to hospital on Tuesday after being found unconscious in a Nevada brothel.
Doctors have told his ex-wife Khloe Kardashian - who is keeping a vigil at his bedside -that the longer he remains in the condition he is in, the less likely he is to recover.
Although Lamar reportedly squeezed the 'Keeping Up With the Kardashians' star's hand on Wednesday night, medics believe it could have been an involuntary reaction as he is showing no signs of consciousness or improvement.
According to TMZ, four of the sportsman's organs, including his kidneys and heart, are failing.
A source told the website: "The doctors are concerned it has been too long that he's been in this condition and now it's not looking good."
News of Lamar's condition has drawn messages of support from celebrities.