Well-intentioned efforts to save lives can also cause serious complications.

Many doctors put patients who are on mechanical ventilators into a deep sleep to prevent them from pulling out their breathing tubes, which would kill them, said Dr. Pratik Pandharipande, chief of anesthesiology and critical care medicine at Vanderbilt University School of Medicine in Nashville, Tennessee.

Both the disease itself and the use of sedatives can cause hallucinations, delirium and memory problems, said Dr. Jaspal Singh, a pulmonologist and critical care specialist at Atrium Health in Charlotte, North Carolina.

Many sedated patients experience terrifying hallucinations, which may return in recovery as nightmares and post-traumatic stress disorder.

Research shows 70% to 75% of patients on ventilators traditionally develop delirium. Delirious patients often “don’t realize they’re in the hospital,” Singh said. “They don’t recognize their family.”

In the French study in the New England Journal of Medicine, one-third of discharged COVID-19 patients suffered from “dysexecutive syndrome,” which can be characterized by inattention, disorientation or poorly organized movements in response to commands.

Research shows that patients who develop delirium — which can be an early sign of brain injury — are more likely to die than others. Those who survive often endure lengthy hospitalizations and are more likely to develop a long-term disability.

Under normal circumstances, hospitals would invite family members into the ICU to reassure patients and keep them grounded, said Dr. Carla Sevin, director of the ICU Recovery Center, also at Vanderbilt.

Just allowing a family member to hold a patient’s hand can help, according to Dr. Lee Fleisher, chair of an American Society of Anesthesiologists committee on brain health. Nurses normally spend considerable time each day orienting patients by talking to them, reminding them where they are and why they’re in the hospital.

“You can decrease the need for some of these drugs just by talking to patients and providing light touch and comfort,” Fleisher said.

These and other innovative practices — such as helping patients to move around and get off a ventilator as soon as possible — can reduce the rate of delirium to 50%.

Hospitals have banned visitors, however, to avoid spreading the virus. That leaves COVID-19 patients to suffer alone, even though it’s well known that isolation increases the risk of delirium, Fleisher said.

Although many hospitals offer patients tablets or smartphones to allow them to videoconference with family, these devices provide limited comfort and companionship.

Doctors are also positioning patients with COVID-19 on their stomachs, rather than their backs, because a prone position seems to help clear the lungs and let patients breathe more comfortably.

But a prone position also can be uncomfortable, so that patients need more medication, Pandharipande said.

All of these factors make COVID-19 patients extremely vulnerable to delirium. In a recent article in Critical Care, researchers said the intensive care unit has become a “delirium factory.”

“The way we’re having to care for patients right now is probably contributing to more mortality and bad outcomes than the virus itself,” said Dr. Sharon Inouye, a geriatrician at Harvard Medical School and Hebrew SeniorLife, a long-term care facility in Boston. “A lot of the things we’d like to do are just very difficult.”