Mechanical ventilation may prompt severe hallucinatory or delirious symptoms for patients in the ICU, who even as long as two years later might experience symptoms associated with post-traumatic stress disorder.
That's the finding from Johns Hopkins University researchers, who followed 186 patients hospitalized with acute respiratory illness. The researchers found that 66 of them, or more than one-third, experienced episodes of mentally traumatic delirium, and two thirds of those still reported frightening sensations or visions 24 months later.
"One woman I remember in the study reported that she was pretty distressed… she thought her husband and her nurse were talking about her and plotting to kill her, but if she had the right lucky number she might be spared," says O. Joseph Bienvenu, MD, associate professor of psychiatry and behavioral sciences and the study's principal investigator.
"Or maybe they believe someone is trying to poison them, when of course they are not."
Bienvenu's study, with colleagues at Johns Hopkins, was published online in the journal Psychological Medicine. Patients were recruited from 13 intensive care units within four Baltimore-area hospitals between October, 2004 and October, 2007. Patients with neurologic disease or head trauma were excluded, as were patients with less than six months to live.
None of the patients had dementia or psychosis before their acute respiratory illness, and nearly all were discharged to their homes, not skilled nursing facilities, after their acute illness subsided.
A complex chemical reaction may be occurring in the brain that causes incorrect impressions to be made on the part of the brain where memory is stored, scrambling the details of reality.
It's like people "remember bits and pieces and then incorporate things from dream-like states," he says. "A person with a Foley catheter being inserted might remember the experience as being raped."
Bienvenu says that primary care physicians, geriatricians, and other providers who see these patients need to recognize these symptoms for what they are, and not think that the patient is exhibiting psychosis, or treat with anti-psychotic drugs.
"If we just say, 'Oh right, this patient is psychotic,' we really would be missing a chance to explain these occurrences for these patients," Bienvenu says. "Many patients have told me how relieved they are to find out how common these experiences are, and that even though they seem very real, they're the result of delirium" and that [they] will pass.
"We need to tell them that these experiences will seem vivid and real, like they really did occur, it's just our brain playing tricks on us when we were critically ill." Some of the medications doctors now give such patients to calm them, Bienvenu says, can make the situation worse.
Other solutions include reducing the amount of sedation and making sure patients get up out of bed, even when they're critically ill, and walk around. Helping them sleep at night and be awake during the day may also reduce PTSD.
Another potential solution is the use of what Bienvenu called "ICU diaries, which involve nurses and family members writing down, in plain language, what has been happening to the patient while they're in the ICU, and maybe taking pictures of the patient.
"When the patient is feeling better, they can look back and make sense of some of their experiences and memories and see, for example, 'No, I wasn't being raped, but I was tied down, because I was fighting people and tried to remove my tubes.' "
Bienvenu stressed that these patients were extremely sick from the start, and of the 520 mechanically ventilated patients with acute lung injury who were originally observed for this study, 47% of them did not survive their hospitalization.
Patients who had been depressed prior to their hospitalization, and those who were in the ICU longer, were more likely to experience symptoms. Other apparent factors associated with a greater likelihood of a PTSD experience were those given high doses of opiates and those who developed bloodstream infections.
In fact, Bienvenu says, sepsis, or infections of the bloodstream, may play an important role in causing chemical confusion in the brain, perhaps in the amygdala, an area "important for fear conditioning," he says.
Infection may lead to an inflammation cascade that breaks down the blood brain barrier, and produces a bolus of noradrenaline. This somehow may allow traumatic memories of the hospital experience to be implanted, yet distorted, and that is what is recalled in subsequent delusions of what actually took place.
"Everyone remembers where they were on 9/11," Bienvenu explains. "We have a tendency to remember things that were emotionally arousing. These patients were on the verge of death, by definition, so a lot of experiences would be remembered vividly" except for the chemical reactions underway.