Joan Rivers with her daugher Melissa Rivers, who is at her mother's side and consulting with doctors this weekend. (Photo: Getty)

Joan Rivers with her daugher Melissa Rivers, who is at her mother’s side and consulting with doctors this weekend. (Photo: Getty)

Joan Rivers is expected to undergo further medical treatment over the weekend that may include efforts to bring her out of a medically induced coma. But the prognosis is poor for someone her age, and the survival rate overall is not encouraging, according to reports and medical studies.

The procedure to induce a coma through drugs, lowering body temperature or a combination of both remains controversial.

Although it’s been an accepted procedure for several decades, not all neurosurgery doctors considered it effective.

According to studies and medical references, it’s considered a “last ditch” therapy.

While it seemingly works miracles in some cases, the mortality rate remains high, above 60 percent, according to the Journal of Neurology, Neurosurgery & Psychiatry.

Neurologists usually induce a coma only after other procedures have failed. “Coma is a last-ditch approach,” Dr. Stephan A. Mayer, then director of the neurological intensive care unit at the Columbia University Medical Center told The New York Times in a 2006 article.

Although Rivers’ doctors have released no information on the reasons for inducing a coma, the 81-year-old comedian most likely suffered what’s known as a “Hypoxic-ischemic brain injury.”

Also known as an “anoxic brain injury,” the condition most often results from cardiac arrest. The brain is deprived of oxygen, causing damage to cells.

Damage can begin after two minutes without oxygen. After five to ten minutes, serious and possibly irreversible brain damage can occur, according to medical references.

Rivers stopped breathing during a medical procedure on her vocal chords and went into cardiac arrest, according to authorities. Doctors do not know how long she was without oxygen.

In one study of 210 patients in the United States and Great Britain who suffered the same injury, 52 who had no response to eye stimulus died within 24 hours. By the seventh day, 96 patients with no spontaneous eye movements also died, according to the Journal.

But the study found some clinical signs that predict a good outcome. Involuntary eye movement, the ability of the eye’s retina to fix on an object, or the vocalization of any word suggested a 50 percent chance for a good recovery.

Even though the study was large, researchers cautioned that the predictive value of any single sign is limited. And, every patient is different.

Israeli Prime Minister Ariel Sharon, West Virginia miner Randal McCloy Jr. and Mexican boxer Ruben Contreras, all were put in a medically induced comas following a brain injury.

Sharon died in January after eight years in a vegetative state. McCloy, who was injured in a mine explosion, was able to go home after three months. And, Contreras was back on his feet in four months.

Rivers also faces other dangers from being in a coma, including pneumonia and blood clots. They can be fatal if clots move to the heart or lungs.

The hospital’s most recent report states that her “condition remains serious” although she is “stable.” The next 48 hours will be critical to her ability to recover.

Be sure to follow IM on Twitter for the latest updates.