What began as a simple urinary-tract infection triggered a cascade of medical problems that ultimately left Pope John Paul clinging to life in the Vatican.
By last night, the 84-year-old pontiff's breathing was shallow, his kidneys were failing and he had suffered massive heart problems.
According to Rob Fowler, critical-care physician at Sunnybrook and Women's College Health Sciences Centre in Toronto, infections are "underrecognized as a cause of death."
"This scenario of an infection in a predisposed patient leading to more widespread infection is a very common pathway to death in many of our hospitalized patients," Dr. Fowler said in a telephone interview yesterday.
Although most people can bounce back easily from a urinary-tract infection, it can be life threatening for someone such as the Pope, who is not only elderly but suffering from Parkinson's disease, a brain disorder characterized by the impairment or death of neurons.
"Most are able to fight those [infections] off with their own immune system and antibiotics," Dr. Fowler said. "The Pope is much, much less able to do so. A rather innocuous urinary infection is life-threatening for him."
Elderly people can be more prone to such infections because they may not empty their bladder as frequently, which could result in less fluid flushing their system. Bacteria multiply within the bladder, then after reaching a critical level, spill into the bloodstream, where they are carried to all the body's organs, Dr. Fowler said.
"It's the systemic inflammation that then mediates this organ failure."
John Paul's health took a turn for the worse on Thursday, after he developed a high fever brought on by the infection, which then triggered septic shock and heart problems. An infection such as his can trigger a profound loss of blood pressure, which would deprive organs of their blood supply and put a massive strain on the heart.
Despite being critically ill, the Pope was reported to be "fully conscious and extraordinarily serene," Vatican officials said yesterday. He had participated in mass and received some top aides in the morning, one of whom said he had been receiving oxygen.
As time passes and the Pope's health continues to fail, he is likely to become drowsier and less aware of those around him, but he is not likely to be in pain, said Larry Librach, director of the Temmy Latner Centre for Palliative Care at the Mount Sinai Hospital in Toronto.
"They might give him some morphine if his breathing is a problem. They might give him a mild tranquilizer if he's agitated," Dr. Librach said. "Most people don't need a lot of that. Most people just need somebody being beside them or being with them."
Indeed, the final hours before death are not usually agonizingly painful, as many people fear, but quiet, with shallow or irregular breathing. "Usually dying people don't show a lot of signs of distress," Dr. Librach said. "Breathing will become shallower, then very irregular, then things will just shut down."
Although the exact mechanisms that cause death are unknown, it "almost seems like, one by one, the system shuts down," Dr. Librach said. "The kidneys shut down, electrolytes go all out of whack and then there's a cardiac arrest. If he still has that significant infection, those are toxins to the heart and brain, and people will die because of that."
And, as many who are dying do, the pontiff may give a last look or shed a final tear.
"Toward the end, people often open their eyes, look around and then things stop," Dr. Librach said. "People have talked about the final tears, but if you actually stand by somebody who is dying, they open their eyes, some people smile; they just look very placid and calm."